Sperm from 2 males (red and green) competing inside a female fruit fly. Image by Scott Pitnick via futurity.org

Every species has some genes that never existed before in evolutionary history, but where do new genes come from? Many new genes are made by copy-and-paste: old genes get copied, rearranged and pasted together with parts of other genes, plus some good ol’ junk DNA. The result: a piece of DNA that usually gets tossed out as an experiment gone bad. But sometimes, those new genes give their owners a competitive edge and they become part of the genome of an entire species.

More often than you might expect, new genes become male-specific and play important roles in male fertility. These genes get fast-tracked, becoming quickly “fixed” in the population because of the advantage they give to the boys in that age-old competition: who can make the most babies. New research into a group of newly evolved sperm genes in Drosophila melanogaster shows just how quickly new genes can become indispensable. The research was published last week in Proceedings of the National Academy of Sciences (see link at bottom).

Evolution is usually a frustratingly slow process, but sex has a way of speeding it up. The “goal” of any gene is to get made into as many copies as possible. A gene that helps its owner get a little bit more food than its neighbor may or may not actually lead to more babies, so it’s not going to spread all that fast. On the other hand, if a gene has a direct effect on how many offspring get made, it can spread very quickly. And what could be more direct than boosting the competitive ability of sperm?

In the fruit fly Drosophila melanogaster, a group of at least 4 male-specific genes have rapidly evolved together in the last 5.4 million years. The genes are called Sperm dynein intermediate chain (Sdic) 1 through 4. Dyneins are motor proteins that can move things around inside cells or that help to move cell flagella (like the tail of a sperm). The Sdic genes are located next to each other on the X chromosome. They evolved from a mixture of two other genes, plus some “junk” DNA, creating the first Sdic gene about 5.4 million years ago. After that, they quickly spread through the fruit fly population. After the first Sdic gene was formed, the copy-and-paste events that created the other 3 happened within the last 102-180 thousand years ago and also spread super-quickly. This is pretty much the blink of an eye in evolution terms. The authors of the study wanted to know why these genes were important enough to get fast-tracked through evolution.

Biologists have a tried-and-true method for figuring out why genes are important: break them and see what goes wrong. The authors deleted all of the Sdic genes (not an easy feat!) and tested these mutant males’ fertility. At first, they saw no defects: the males had normal testes and their sperm seemed happy enough.

Photo credit: T. Chapman in PLoS Biology; Vol. 6, No. 7, e179; July 29, 2008.

Next, they looked at whether the sperm could actually fertilize eggs normally. All of the males with Sdic deletions (mutant males) could fertilize eggs. Even more surprising: there was no difference in the number of offspring from mutant males vs. normal males.

So, why are the Sdic genes so important? The first set of experiments only looked at the number of offspring when one male mates to one female. But in nature, female fruit flies will mate with more than one male, so the ability to outcompete other males is extremely important.

To find if Sdic genes are involved in sperm competition, the authors pitted mutant males against normal males. They first mated a female to a standard male. Three days later they mated the same female either to a mutant male or a normal (control) male and counted how many of the offspring were from each male. This is easy in flies, because you just have to look at the eye color of the offspring.

This experiment measures the ability of the second male’s sperm to displace sperm from the first male. Normally, the second male has a huge advantage and sires most of the offspring. But even a small defect in the ability to knock the first male’s sperm out of storage could have dire consequences for the second male.

The bottom line: mutant sperm were worse at displacing the first male’s sperm.

The result was consistent between experiments, but not huge. The second male still always has the advantage. But, mutant sperm performed worse than normal sperm by a few percentage points. Also keep in mind that this was a controlled experiment in the lab. Males were only mated when at their peak fertility. Females only had to mate with 2 males. In the wild, females will mate with many males, and some males may have less sperm available at mating because they’ve also mated many times. So, finding even a small difference in the lab suggests these genes are very important for fertility in the wild.

Altogether, these results show that the Sdic genes are important for fertility. Natural selection drove the evolution of these genes because they gave males a competitive edge. These results are important because they clearly demonstrate that male-male competition can drive new genes to become very quickly integrated into existing pathways like sperm development. In other words, sex leads to new genes.

Reference

Yeh, S., Do, T., Chan, C., Cordova, A., Carranza, F., Yamamoto, E., Abbassi, M., Gandasetiawan, K., Librado, P., Damia, E., Dimitri, P., Rozas, J., Hartl, D., Roote, J., & Ranz, J. (2012). Functional evidence that a recently evolved Drosophila sperm-specific gene boosts sperm competition Proceedings of the National Academy of Sciences, 109 (6), 2043-2048 DOI: 10.1073/pnas.1121327109

Sitting on a rickety homemade bookshelf in my living room are the fifty volumes of my Great-Grandfather’s Harvard Classics. Once a teenaged political refugee from the Russian revolutionary turmoil of 1905 and later an accomplished bacteriologist with Merck, my Great-Grandfather exemplified Harvard President Charles Eliot’s American middle class, “twentieth century idea of a cultivated man,” the kind of person for whom Eliot’s “five foot shelf of books” was intended. A respected Mr. among professional scientific peers of Drs., my Great-Grandfather was fiercely committed to self-education. I never met him, but I imagine that my Great-Grandfather would have subscribed to Eliot’s notion of individual and civilizational progress, progress that is the result of “man observing, recording, inventing, and imagining.” The Harvard Classics were selected to be a survey of how this process has played out over the millennia.

Eliot’s words, “observing, recording, inventing, and imagining,” describe several thousand years of human intellectual activity by invoking the process of science. This is appropriate because Eliot, and my Great-Grandfather, were living when the modern scientific view of the world was well on its way to world domination, becoming a new belief system with as much cultural heft as the major religions, and one whose conquest occurred even more rapidly than the spectacular rise from obscurity of Christianity, Buddhism, and Islam over the last two thousand years. The modern scientific take on the world has not displaced religious views, just as Islam became a global player without displacing Christianity. But science has become as influential as any of its social competitors, with its chronicle of our earth’s history, of the creation of volcanic islands and the erosion of canyons, its story of the solar system with its central principle of gravitation that explains the shapes of the planets as well as their orbits around a central furnace of nuclear fusion, its tale of colliding atoms and molecules that make up the material world, and perhaps the most disturbing account of all, of our deep genetic history that connects without discontinuity into a pre-human, evolutionary past during which our modern DNA has been sculpted by the brutal work of natural selection.

The one volume among the entire Harvard Classics that most prophetically anticipates the coming cultural influence of scientific thought is Darwin’s The Voyage of the Beagle. But too often the Voyage has been given second billing among collections of Great Books. Adam Kirsch, in an insightful essay on the Harvard Classics, gently chides Eliot for the excessive enthusiasm that led him to devote two of the fifty volumes to Darwin; Kirsch suggests that a modern edition of the Classics should “doubtless” keep On the Origin of Species and ditch the Voyage for James Watson’s Double Helix. Harold Bloom, whose selection of non-fiction for his Western Canon is unforgivably erratic and unprincipled, recommends Matthew Arnold’s essays and John Stuart Mill’s On Liberty and Autobiography, but nothing by Darwin. There is a common (and, let’s face it, usually correct) idea that great scientific writing is valuable for its intellectual importance, but of marginal literary value. Darwin’s Origin is often included in collections of great books by default, because it is one of the very few important primary scientific documents that can be read without specialized training. But the Origin is an argument for a specific scientific theory, while the Voyage is a much more general foreshadowing of science’s cultural force in the modern world. If you are going to read one book by Darwin before you die, or one Great Book on any of the sciences, it must be The Voyage of the Beagle, because this book is a genuinely great work of literature, a compelling account of a then-embryonic vision of the world that has now come into its own in modern society, told in an expressive and beautiful language which is exactly suited to its subject.

I. Observations

The Voyage of the Beagle is Darwin’s account of those five formative years abroad that transformed him into the scientist who would discover natural selection. The book is a hybrid, a scientific account fused to the ever-popular travel narrative, because Darwin was writing to explain his scientific findings, and to sell books to the reading public eager for accounts of the world that most would never visit. Darwin returned from his voyage in 1836, and his account was first published in 1839 as the most popular part of a multi-volume record of the Beagle’s exploits, and later in 1845 as the definitive edition that we read today.

What strikes you most immediately on reading the Voyage of the Beagle are Darwin’s remarkable powers of observation that would make Sherlock Holmes weep with shame. It is no wonder that Darwin came up with the idea of natural selection. His observations are fanatically precise and carefully filtered for emphasis, because like a good scientist, Darwin is using his observations to infer the story behind what he sees. To infer the story successfully, it is not sufficient to simply to collect vague impressions and general outlines; it is necessary to capture the small, but high-information details that allow you to rule out alternative narratives, to narrow the space of possible explanations so that you can be confident in the story you settle on.

Imagine yourself arriving at the chaotic scene of a severe earthquake, the city around you devastated, not a building left intact, an entire population’s wealth and physical security wiped out, misery coming at you from every direction. How do you make sense of this disorder? Here is Darwin, cool as an FAA investigator at a crash scene, discussing the 1835 earthquake that devastated the Chilean city of Concepcion. What he sees are the patterns in the surviving walls. He observes their orientation, down to the angles of the ornamental bricks, and infers the behavior of the earthquake:

The town of Concepcion was built in the usual Spanish fashion, with all the streets running at right angles to each other; one set ranging south-west by west, and the other set north-west by north. The walls in the former direction certainly stood better than those in the latter; the greater number of the masses of brickwork were thrown down towards the north-east. Both these circumstances perfectly agree with the general idea of the undulations having come from the south-west; in which quarter subterranean noises were also heard; for it is evident that the walls running south-west and north-east which presented their ends to the point whence the undulations came, would be much less likely to fall than those walls which, running north-west and south-east, must in their whole lengths have been at the same instant thrown out of the perpendicular…

The different resistance offered by the walls, according to their direction, was well exemplified in the case of the Cathedral. The side which fronted the north-east presented a grand pile of ruins… The side walls (running south-west and north-east), though exceedingly fractured, yet remained standing; but the vast buttresses (at right angles to them, and therefore parallel to the walls that fell) were in many cases cut clean off, as if by a chisel, and hurled to the ground. Some square ornaments on the coping of these same walls were moved by the earthquake into a diagonal position.

Darwin’s observations are focused and precise because his goal is not merely to record his feelings and impressions of a scene (although he does that too, as we’ll see); Darwin’s aim is to discover answers to questions that with hindsight might seem obvious, but which others had not even realized could be asked. How is it, for example, that wasps are able to subdue spiders without killing them, in order to serve them up as live food to their larvae?

I was much interested one day by watching a deadly contest between a Pepsis and a large spider of the genus Lycosa. The wasp made a sudden dash at its prey, and then flew away: the spider was evidently wounded, for, trying to escape, it rolled down a little slope, but had still strength sufficient to crawl into a thick tuft of grass. The wasp soon returned, and seemed surprised at not immediately finding its victim. It then commenced as regular a hunt as ever hound did after fox; making short semicircular casts, and all the time rapidly vibrating its wings and antennae. The spider, though well concealed, was soon discovered, and the wasp, evidently still afraid of its adversary’s jaws, after much manoeuvring, inflicted two stings on the under side of its thorax. At last, carefully examining with its antennae the now motionless spider, it proceeded to drag away the body. But I stopped both tyrant and prey.

Darwin has counted the number of times the spider has been stung, where it has been stung, and has noted the method behind the wasp’s motion that others (such as myself) would have taken to be a random walk. Behind Darwin’s focus is a belief that the world has an underlying rationale, one that can be inferred if we look closely enough. The behavior of wasps and spiders is not unfathomable; it is the result of a careful survival strategy. Earthquakes don’t just randomly knock down walls; they travel in waves and exert forces on buildings at particular angles. Darwin’s observations are precise because the world is precise, locked into very tight constraints of cause and effect, and therefore we use the tools of reason and observation to understand why the world behaves the way it does.

Many find this approach to the world puzzling, or maybe just exhausting, both in 19th century Chile and the 21st century United States. Darwin often had difficulty convincing people that he didn’t have some less ethereal reason for his efforts, that he wasn’t secretly prospecting for valuable ores:

I found the most ready way of explaining my employment was to ask them how it was that they themselves were not curious concerning earthquakes and volcanos?–why some springs were hot and others cold?–why there were mountains in Chile, and not a hill in La Plata? These bare questions at once satisfied and silenced the greater number; some, however (like a few in England who are a century behindhand), thought that all such inquiries were useless and impious; and that it was quite sufficient that God had thus made the mountains.

Science depends upon a restlessness, an intellectual dissatisfaction that leads to questions that probe not only the conventional wisdom but one’s own clever or deeply held ideas. It was this dissatisfaction that drove Darwin to brave thousands of miles of discomforts, seasickness, earthquakes, severe thirst, cold nights on beds of rocks, vile food, and even violent political upheaval with an energy that would have put Crocodile Hunter Steve Erwin to shame. You can feel the fierceness of this drive behind Darwin’s keen observations, in their rigor and their relentless grasping towards the story behind Nature’s surfaces.

II. People

It would be wrong to assume that Darwin’s scientific instincts make him a passionless observer of the world. In fact, much of the power of the Voyage comes from Darwin’s ability to find emotional resonance in the targets of his scrutiny. His knack for seeing precisely works with his sense of humanity to make Darwin particularly skilled at rendering people, and describing their poignant and ironic moments as they respond to their natural and social environments. These results do not come without tension as Darwin relates after his description of the aftermath of the quake at Concepcion:

I have not attempted to give any detailed description of the appearance of Concepcion, for I feel that it is quite impossible to convey the mingled feelings which I experienced. Several of the officers visited it before me, but their strongest language failed to give a just idea of the scene of desolation. It is a bitter and humiliating thing to see works, which have cost man so much time and labour, overthrown in one minute; yet compassion for the inhabitants was almost instantly banished, by the surprise in seeing a state of things produced in a moment of time, which one was accustomed to attribute to a succession of ages. In my opinion, we have scarcely beheld, since leaving England, any sight so deeply interesting.

But Darwin’s affinity for the interesting strengthens the humane accounts of the people he describes. This is because the sharp, lucid descriptions of behaviors, appearances, and environments naturally reveal the underlying human story, largely free of Darwin’s authorial impositions. Instead of imputing thoughts and reinventing forgotten dialogue, Darwin largely describes people’s actions. He steps out of the way and pulls off the classic writer’s trick of bringing characters to life by showing, not telling. He generally observes people in much the same way he observes animals, usually without moral judgment or condemnation, and driven by a desire to understand.

This is perhaps most vividly seen in Darwin’s account of his encounters with the natives at the end of the world in Tierra del Fuego. The crew of the Beagle, on a previous voyage, had more or less kidnapped several Fuegians, and now the Beagle’s captain wanted to bring them back home. One of these natives was purchased as a boy for the price of a pearl button. Now a young man, Jemmy Button (as he is affectionately, or maybe cruelly known) is about to return to his stone age culture, after having spent three years within one of the world’s most technologically sophisticated civilizations. He hardly remembers his native language and speaks broken English, but, like any teenager, is very impressed with the fact that he can make himself look sophisticated:

He was of a patriotic disposition; and he liked to praise his own tribe and country, in which he truly said there were “plenty of trees,” and he abused all the other tribes: he stoutly declared that there was no Devil in his land. Jemmy was short, thick, and fat, but vain of his personal appearance; he used always to wear gloves, his hair was neatly cut, and he was distressed if his well-polished shoes were dirtied. He was fond of admiring himself in a looking glass; and a merry-faced little Indian boy from the Rio Negro, whom we had for some months on board, soon perceived this, and used to mock him: Jemmy, who was always rather jealous of the attention paid to this little boy, did not at all like this, and used to say, with rather a contemptuous twist of his head, “Too much skylark.”

Clearly Jemmy is struggling with acutely ambiguous feelings about his background; he is defensive of his people, yet he wants to prove that despite his family roots, he can be at least as civilized as any of his British shipmates. Even worse, he’s about to be unceremoniously dropped back among his naked kinfolk. In the mid-nineteenth century, many probably thought nothing of treating Jemmy like this; there was a natural order to things, and Jemmy was best off in his place. But Darwin manages, almost inadvertently, to poignantly render the ambiguity of Jemmy’s reunion with his family:

We had already perceived that Jemmy had almost forgotten his own language. I should think there was scarcely another human being with so small a stock of language, for his English was very imperfect. It was laughable, but almost pitiable, to hear him speak to his wild brother in English, and then ask him in Spanish (“no sabe?”) whether he did not understand him.

Some time later, when the Beagle briefly returns to the region before leaving for good, Jemmy turns up again in a canoe, unclothed, scrawny, and long-haired. His first action is to turn his back on his former shipmates in embarrassment.

The chapter on the Fuegians is unforgettable because Darwin appears to have been more unsettled by his encounters with these people than with any others during his five year voyage. He is honest about his rattled feelings and the difficulty he has making sense of what appear to be lives of unnecessary misery:

A woman, who was suckling a recently-born child, came one day alongside the vessel, and remained there out of mere curiosity, whilst the sleet fell and thawed on her naked bosom, and on the skin of her naked baby! These poor wretches were stunted in their growth, their hideous faces bedaubed with white paint, their skins filthy and greasy, their hair entangled, their voices discordant, and their gestures violent. Viewing such men, one can hardly make oneself believe that they are fellow-creatures, and inhabitants of the same world. It is a common subject of conjecture what pleasure in life some of the lower animals can enjoy: how much more reasonably the same question may be asked with respect to these barbarians! At night five or six human beings, naked and scarcely protected from the wind and rain of this tempestuous climate, sleep on the wet ground coiled up like animals. Whenever it is low water, winter or summer, night or day, they must rise to pick shellfish from the rocks; and the women either dive to collect sea-eggs, or sit patiently in their canoes, and with a baited hair-line without any hook, jerk out little fish. If a seal is killed, or the floating carcass of a putrid whale is discovered, it is a feast; and such miserable food is assisted by a few tasteless berries and fungi.

It would be easy to chalk up Darwin’s discomfort and his comments about savages to the sensibility of his less-enlightened era, but this is not really fair. I can imagine myself, removed from my wired-up home, my laptop, Trader Joe’s, running water and flush toilets, and dropped into the midst of a stone age culture that somehow manages to contemporaneously exist on the same planet as the Large Hadron Collider. Even free from racial prejudices, value judgements of alternative lifestyles, and so forth, who would not be uncomfortable, if not deeply disturbed? Confronted with such beings who are thoroughly alien, but nonetheless clearly human, in their intelligence, their desires, and their needs, how would we react? Darwin is honest about his discomfort and his opinions, and his method of observing and then inferring the story serves him well, because he does not try to fit the Fuegians into some morality tale. Instead, recognizing them as fully human, he attempts to understand how it could be that they exist in such an apparently miserable condition.

Whilst beholding these savages, one asks, Whence have they come? What could have tempted, or what change compelled, a tribe of men, to leave the fine regions of the north, to travel down the Cordillera or backbone of America, to invent and build canoes, which are not used by the tribes of Chile, Peru, and Brazil, and then to enter on one of the most inhospitable countries within the limits of the globe? Although such reflections must at first seize on the mind, yet we may feel sure that they are partly erroneous. There is no reason to believe that the Fuegians decrease in number; therefore we must suppose that they enjoy a sufficient share of happiness, of whatever kind it may be, to render life worth having. Nature by making habit omnipotent, and its effects hereditary, has fitted the Fuegian to the climate and the productions of his miserable country.

III. Language

One of the primary reasons you should read the Voyage is for its style. In this book, more so than in the Origin, Darwin is a scientific stylist, using language matched to the pursuit of his scientific aims while simultaneously creating a work of expressive power. The result is compelling because the practice of science is not an impersonal, algorithmic process, but is instead a human act of imagination. Despite Francis Bacon’s fussy admonition not to substitute the dreams of our imaginations for patterns in the world, scientific theories, however mind-bogglingly well-constrained by observations and experiments, are mental constructs. Richard Feynman described the process of creating these constructs as putting your imagination in a straightjacket, which is not a constricting process, but one that becomes a scaffold for science’s imaginative successes. Darwin’s style in the Voyage is powerful because it exhibits, at the fine level of sentences and paragraphs, a scientific imagination churning away, observing, sifting, and finally inferring the story of nature’s driving forces. As Darwin puts it, “The limit of man’s knowledge in any subject possesses a high interest, which is perhaps increased by its close neighbourhood to the realms of imagination.”

Here is how this method plays out in a slapstick scene relating Darwin’s attempt to understand why Galapagos marine iguanas are sometimes afraid of the water. Preceding the inferred storyline are the observations, along with some experiments that today would require an institutionally approved vertebrate animal protocol:

When frightened it will not enter the water. Hence it is easy to drive these lizards down to any little point overhanging the sea, where they will sooner allow a person to catch hold of their tails than jump into the water… I threw one several times as far as I could, into a deep pool left by the retiring tide; but it invariably returned in a direct line to the spot where I stood… I several times caught this same lizard, by driving it down to a point, and though possessed of such perfect powers of diving and swimming, nothing would induce it to enter the water; and as often as I threw it in, it returned in the manner above described. Perhaps this singular piece of apparent stupidity may be accounted for by the circumstance that this reptile has no enemy whatever on shore, whereas at sea it must often fall a prey to the numerous sharks. Hence, probably, urged by a fixed and hereditary instinct that the shore is its place of safety, whatever the emergency may be, it there takes refuge.

Darwin happened to be one of the great 19th century travel writers, a skilled renderer of vivid images in the days before photography. In this respect, Darwin compares favorably with another first-rate travel writer, Herman Melville. Both Darwin and Melville cut their writerly teeth producing best-selling accounts of their voyages to the exotic Southern hemisphere (in Melville’s case the accounts were lightly fictionalized), and both knew what features would sell with the travel-narrative-reading public.

Melville’s imagery is impressionistic and improvisational, as in this description of the Galapagos from The Encantadas:

In many places the coast is rock-bound, or, more properly, clinker-bound; tumbled masses of blackish or greenish stuff like the dross of an iron-furnace, forming dark clefts and caves here and there, into which a ceaseless sea pours a fury of foam; overhanging them with a swirl of gray, haggard mist, amidst which sail screaming flights of unearthly birds heightening the dismal din. However calm the sea without, there is no rest for these swells and those rocks; they lash and are lashed, even when the outer ocean is most at peace with, itself. On the oppressive, clouded days, such as are peculiar to this part of the watery Equator, the dark, vitrified masses, many of which raise themselves among white whirlpools and breakers in detached and perilous places off the shore, present a most Plutonian sight. In no world but a fallen one could such lands exist.

Darwin, while also drawing a comparison with iron-foundries, does not make vague observations about “blackish and greenish stuff.” His approach to imagery depends, of course, on observational precision and tight organization of his thoughts. This strategy can be just as successful as Melville’s more consciously literary style. Darwin’s words, while not always technical, are usually specific, and descriptions are often given in geometrical terms of symmetries, regularities, lines, and circles. Here is Darwin on the Galapagos, on Chatham Island:

The entire surface of this part of the island seems to have been permeated, like a sieve, by the subterranean vapours: here and there the lava, whilst soft, has been blown into great bubbles; and in other parts, the tops of caverns similarly formed have fallen in, leaving circular pits with steep sides. From the regular form of the many craters, they gave to the country an artificial appearance, which vividly reminded me of those parts of Staffordshire where the great iron-foundries are most numerous. The day was glowing hot, and the scrambling over the rough surface and through the intricate thickets was very fatiguing; but I was well repaid by the strange Cyclopean scene. As I was walking along I met two large tortoises, each of which must have weighed at least two hundred pounds: one was eating a piece of cactus, and as I approached, it stared at me and slowly walked away; the other gave a deep hiss, and drew in its head. These huge reptiles, surrounded by the black lava, the leafless shrubs, and large cacti, seemed to my fancy like some antediluvian animals.

Another strategy that Darwin uses to powerful effect is the shocking contrast between violence and beauty so commonly found in nature. In this case, the murder of a sea captain intrudes on a serene moment in the Galapagos:

The water is only three or four inches deep and rests on a layer of beautifully crystallised, white salt. The lake is quite circular, and is fringed with a border of bright green succulent plants; the almost precipitous walls of the crater are clothed with wood, so that the scene was altogether both picturesque and curious. A few years since the sailors belonging to a sealing-vessel murdered their captain in this quiet spot; and we saw his skull lying among the bushes.

Note that the lake is not fringed with generic green plants, but green succulent plants. The walls of the crater are “almost precipitous”; here precipitous means literally perpendicular, forming a 90 degree angle with the surface. And contrasting with this very specific, orderly scene is a messy reminder of human conflict.

Finally, there are the thick, nineteenth-century technical terms that have their own grand beauty, words like marl, calcareous, fissured, scoriae, concretions. The sounds of these word resonate with the processes and scenes they describe. The precise application of such terms, the constant movement of sentences towards arguments, inferences, and conclusions, and the knack for exotic and startling imagery aimed at armchair-bound, would-be explorers back on the home island, these features together would put Darwin’s Voyage in the Great Books Hall of Fame even if Darwin hadn’t later upended millennia of biological thinking with his discovery of natural selection.

IV. God

As you read the Voyage, and become absorbed its imagery its grand scope, it is easy to miss what is absent. Darwin, in all of his arguments, inferences, hypotheses, and narratives of natural history, quietly refuses to ever invoke God as an explanation. The geographical distribution of animals, the causes of extinctions, the composition of the rock on mountain ranges, the layout of the vast plains of the South American Pampas, are all explained exclusively in terms of natural processes. What is remarkable about these explanations is that they operate on vast scales of space and time, and therefore the actual stories of natural history themselves are not directly observable. They are inferred from the evidence that we can observe – raised beds of fossilized sea shells, thousands of miles from any ocean; folded layers of various types of rock exposed in the great mountains of the Cordillera; the resemblance of the skeletons of long-extinct, gigantic quadrupeds to those of living species. Wielding the method of observation and inference, Darwin and his fellow scientists infer majestic stories of our origin and that of the world around us, stories that have now largely supplanted the competing stories of other major belief systems in our society.

Here is Darwin inferring the thoroughly materialistic creation story of the tremendous mountain ranges of the Cordillera:

As the beds of the conglomerate have been thrown off at an angle of 45 degrees by the red Portillo granite (with the underlying sandstone baked by it), we may feel sure that the greater part of the injection and upheaval of the already partially formed Portillo line took place after the accumulation of the conglomerate, and long after the elevation of the Peuquenes ridge. So that the Portillo, the loftiest line in this part of the Cordillera, is not so old as the less lofty line of the Peuquenes. Evidence derived from an inclined stream of lava at the eastern base of the Portillo might be adduced to show that it owes part of its great height to elevations of a still later date. Looking to its earliest origin, the red granite seems to have been injected on an ancient pre-existing line of white granite and mica-slate.

Despite our arguments over whether to teach creationism in schools, and regardless of the fact that large majorities in all modern societies believe in God, the scientific stories of the world are what we overwhelmingly teach, what we research, and on these stories we base our businesses, our medical practice and our technologies. This was not the case in Darwin’s day, which is one reason why the Voyage is a prophetic document of the coming cultural consensus.

The Voyage makes it clear that scientists’ refusal to invoke Divine agency as a causal explanation does not arise from a desire to stand against religion or to promote atheism. At issue is what suffices as an explanation. Darwin refuses to settle for vagueness, and rightly considers statements like ‘it was born in nature’, or ‘God made it’ to be no better (or perhaps worse) than saying ‘I don’t know.’ This refusal to accept the unfathomable as an explanation is the first step in the scientific process, and it clears the ground for observation, hypothesis, inference, and experiment to operate. It is based on faith that the world, unlike God, is not inscrutable, and that our minds can comprehend the detailed links of cause and effect behind the scenes of the Universe. (This bedrock faith in causality is the source of much anguish among scientists over the potential breakdown of causality at nature’s smallest and largest scales.) And so, what you read in the Voyage is an almost fanatical demand for precision and rigor, a curmudgeonly insistence that we don’t fill in our stories with what scientists call ‘hand waving.’ Again and again Darwin rejects content-free explanations. Of petrified trees:

How surprising it is that every atom of the woody matter in this great cylinder should have been removed and replaced by silex so perfectly that each vessel and pore is preserved! These trees flourished at about the period of our lower chalk; they all belonged to the fir-tribe. It was amusing to hear the inhabitants discussing the nature of the fossil shells which I collected, almost in the same terms as were used a century ago in Europe,–namely, whether or not they had been thus “born by nature.”

Boiling water:

At the place where we slept water necessarily boiled, from the diminished pressure of the atmosphere, at a lower temperature than it does in a less lofty country; the case being the converse of that of a Papin’s digester. Hence the potatoes, after remaining for some hours in the boiling water, were nearly as hard as ever. The pot was left on the fire all night, and next morning it was boiled again, but yet the potatoes were not cooked. I found out this by overhearing my two companions discussing the cause, they had come to the simple conclusion “that the cursed pot (which was a new one) did not choose to boil potatoes.”

All scientists hand-wave, of course, but it’s supposed to be a temporary stop-gap. Often scientists are wrong (the batting average of new scientific ideas would probably not be competitive in professional baseball), but successful science begins not by stumbling on a correct idea, but as an attitude and a method, which over time enables us to bootstrap our way to successful explanations that succeed like no others. Its method has made science the game to beat. Intelligent design, herbal remedies, fad diets, ESP, basically any ideas that make a go at competing on science’s materialistic home turf, all of them end up measured in our public arguments by science’s standard. This is why pseudo-science exists: you have to dress your ideas in a lab coat, complete with pocket-protector and protective eyewear, if you want people to believe your ideas about the physical world.

It may have taken a few hundred years to get there, but, let’s face it, the eventual cultural success of science has been inevitable ever since Galileo, Newton, and their important predecessors hit upon the method to explain the material world that succeeds like no other. Beginning with explanations of the motions of the stars, and moving on to falling bodies closer to home, there should have been no reason to expect that the scope of science should stop there. By the time of the Voyage, science was making serious inroads into matter and earth’s history, and it was about crack open biology in a spectacular way. We don’t like to argue with success, and, one hundred seventy years after the publication of the Voyage, science’s influence within modern culture (and within those cultures that we today consider in the process of modernizing) rivals that of the major religions. Just as major religions coexist in our societies (with occasional discomfort), science has not displaced religion as a cultural influence. It has, however become an overwhelming presence in the stories we tell about our material world, a relentless current in our society that can be compared with the streams that Darwin observed in the Chilean Cordillera:

As often as I have seen beds of mud, sand, and shingle, accumulated to the thickness of many thousand feet, I have felt inclined to exclaim that causes, such as the present rivers and the present beaches, could never have ground down and produced such masses. But, on the other hand, when listening to the rattling noise of these torrents, and calling to mind that whole races of animals have passed away from the face of the earth, and that during this whole period, night and day, these stones have gone rattling onwards in their course, I have thought to myself, can any mountains, any continent, withstand such waste?

Pick up your own free, electronic copy of The Voyage of the Beagle over at Project Gutenberg.

The scientific literature indicates that there are at least two dozen adverse health effects linked to exposure to mineral oil, a crude oil derivative. New research indicates these fat-soluble hydrocarbons are accumulating to disturbing levels in our bodies, and affecting newborns by contaminating breast milk.

How did they get there? Mineral oil is legally allowed to be added to our foods, drugs and cosmetics, where they accumulate in our bodies over time, with the highest concentrations found in our fat deposits. One autopsy study performed in 1985, revealed that 48% of the livers and 46% of the spleens of the 465 autopsies analyzed showed signs of mineral-oil induced lipogranuloma (a nodule of necrotic, fatty tissue associated with granulomatous inflammation or a foreign-body reaction around a deposit of an oily substance), indicating just how widespread pathological tissue changes associated with exposure really are.

CLICK FOR FULL STORY

Drosophila melanogaster. Photo by Botaurus Stellaris via Wikipedia.

While I don’t doubt that you have all been eagerly awaiting an update to my ‘Publications’ page, some of you may not have noticed that it has finally arrived. After only about 5 and half years in graduate school, I finally have my very own first-author research article.

Why did it take so long? Believe me, I wish it didn’t. But it turns out that writing the paper takes about the same amount of time as doing all the experiments (I may be exaggerating here, but that’s certainly how it felt). After all the re-writes, peer-reviews, and more re-writes, the beautifully formatted, very sciency-looking version is finally online (in the wonderfully open-access journal PLoS Genetics).

If you’re curious what this paper is about, but have absolutely no desire to read it, you’re in luck! I’m not going to go through a play-by-play with this paper because, while I think the results are really cool, I also feel like I already wrote the thing. But I will summarize why the paper is an important step in our continuing quest to figure out what the hell is going on in the seminal fluid.

When flies, or worms, or cats, or people have sex, the male isn’t simply throwing a bunch of sperm into the female where one of them will hopefully reach an egg. Those sperm have a lot of help from other components of the seminal fluid, including tons of seminal fluid proteins (Sfps). You can’t exactly match up the proteins in flies to their counterparts in people; they have changed too much over time to do that. But, the types of proteins in flies are very similar to the types in humans. I have been working on a specific type of Sfps in my work: proteases.

Proteases are a pretty cool group of proteins. They seem simple enough: they chop up other proteins. But each one has a completely different job. Some turn on proteins by cutting them, others turn proteins off. Some only cut up a single target protein at a predetermined place. Others will chop up anything.

The proteases in my paper, CG11864 and one I’ve named ‘seminase’, appear to have really specific targets, but I still don’t know if they are activators or destroyers (possibly both).

The main points of the paper were these:

1. We found what we believe is the first protease cascade in insect seminal fluid.
2. Our earlier classification of Sfps into two groups based on when they act (short-term and long-term) is no longer as clear-cut as we thought.
3. Proteases might be an important way to quickly start the ball rolling on post-mating effects we see in flies.

Number 1: Protease cascades (where a proteases are used to turn on other proteases that eventually go on to do some job) are an important feature of lots of things that go on in your body that you care about. Blood clotting is a good example: when people are missing one of the proteases in the blood clot cascade, they have hemophilia, and usually bleed to death. At least one protease cascade also exists in human seminal fluid, turning it from a gelatinous goo to more of a liquid several minutes after ejaculation.

So much proteolysis going on in there. Image via Wikipedia.

Why do we need this cascade, and how exactly does it work? The answer is complicated (read: no one really knows). Many studies suggest it’s important for male fertility, and that sperm will be trapped if the protease cascade doesn’t work properly, though this is still controversial. Studying this protein network in people, or even mice, is a huge challenge. Wouldn’t it be nice if some easy-to-work-with animal, like a fruit fly, also had a protease cascade in the seminal fluid? That way, we could manipulate the cascade to understand how it works and why, and apply that knowledge to other seminal fluid protease cascades. Well, here you go. You’re welcome.

Number 2: This one is much more difficult to see why it’s important. Basically, we had a nice grouping system for our Sfps based on whether they affected the female soon after mating (ie: within 24 hours) or had a more prolonged effect (over many days). And this was working just fine until we found seminase. This protease activates a cascade that affects “short term” proteins, but it is also crucial for the long term usage of sperm in storage. Without this protease, the female will simply forget she still has sperm to use and will go mate with someone else after a few days. This is Not Good for whichever poor male was missing his seminase. So seminase is both short term and long term, suggesting there really aren’t two distinct phases of post-mating female responses.

LaFlamme, et al. 2012, Figure 6. This figure is the Cliff's Notes version of the paper. Left side is "short term" stuff. Right side is "long term". Check out the link to the paper for a full description of this figure.

Finally, number 3: Lots of stuff needs to happen after a mating in flies. The female needs to ramp up egg production, store sperm, use the sperm properly, eat more, sleep less, and lose her libido. All of these things rely on Sfps. Do all the Sfps work independently to do their jobs, or might they all be coordinated somehow?

Though I certainly did not prove this in the paper (there’s a ton more work that needs to be done), we are starting to see a suggestion that proteases (maybe my good friend seminase) might be used as a “switch” to turn everything on at once. Proteases can act really fast, and having a protease cascade means the signal can be quickly and easily amplified. More importantly, a single protease can turn on many different proteins, so you don’t need a separate switch for everything that needs to happen in the female.

Whether this might be applicable to other animals, like us, we’ll have to wait to find out. But I certainly wouldn’t be surprised if it turns out to be very common. All animals that anyone has bothered to look at so far have proteases in the seminal fluid. They’ve got to be doing something.

Related Articles

• Get in my spermathecae! 
• A protein in worm semen is an “on” switch for sperm.
• Love is (sometimes) a battlefield.

Reference

LaFlamme, B., Ravi Ram, K., & Wolfner, M. (2012). The Drosophila melanogaster Seminal Fluid Protease “Seminase” Regulates Proteolytic and Post-Mating Reproductive Processes PLoS Genetics, 8 (1) DOI: 10.1371/journal.pgen.1002435

Hunter–gatherers and other primates as prey, predators, and competitors of snakes:

Relationships between primates and snakes are of widespread interest from anthropological, psychological, and evolutionary perspectives, but surprisingly, little is known about the dangers that serpents have posed to people with prehistoric lifestyles and nonhuman primates. Here, we report ethnographic observations of 120 Philippine Agta Negritos when they were still preliterate hunter–gatherers, among whom 26% of adult males had survived predation attempts by reticulated pythons. Six fatal attacks occurred between 1934 and 1973. Agta ate pythons as well as deer, wild pigs, and monkeys, which are also eaten by pythons, and therefore, the two species were reciprocally prey, predators, and potential competitors. Natural history data document snake predation on tree shrews and 26 species of nonhuman primates as well as many species of primates approaching, mobbing, killing, and sometimes eating snakes. These findings, interpreted within the context of snake and primate phylogenies, corroborate the hypothesis that complex ecological interactions have long characterized our shared evolutionary history.

Hating snakes is deeply ingrained in our evolutionary past. I feel validated.

Egg spots on the anal fin of a male cichlid fish. Image via Wikipedia.

Cichlid fish are an evolutionary biologist’s dream. There are thousands of species of cichlids, and more seem to crop up every day. Evolution never truly stands still in any species, but if you want to see it in action, cichlids are a good place to start.

Cichlid fish live, and evolve, in the East African Great Lakes. Not only are they fun to study, they’re also extremely beautiful. The many different colors and patterns found in these fish are, at least in part, the result of sexual selection. Sexual selection can be driven by the preferences of the opposite sex. For example, peacocks have ridiculous (but pretty) tails because peahens think they look nice. On the other hand, sexual selection could be driven by the same sex: ornaments or pigmentation might be a signal to rival males that it’s time to fight.

The largest group of cichlid species is the haplochromine cichlids (roughly 1500 species). A feature of many haplochromines are the colorful “egg spots” on the anal fin of males. Tons of studies have been done trying to pin down exactly what these spots are used for. Some studies have suggested that females prefer males with more egg spots, for various potential reasons (including this now largely disproved one), but this is still an unsettled issue.

Male Astatotilapia burtoni, the species used in the paper. Image from Theis, et al. Figure 1A.

Now, a paper by Anya Theis, Walter Salzburger, and Bernd Egger from the Unviersity of Basel (published this month in PLoS One) argues that egg spots can be used for male-male competition. The jist: the fewer egg spots a male has, the more likely it is he’s going to be attacked by other males.

The authors performed two separate experiments to first test whether females preferred more or less egg spots on their guy. These experiments used a new method for testing preference. Usually, these experiments involve measuring how much time a female will spend in the vicinity of each male presented to her. In this paper, the authors instead counted how many eggs a female laid in front of each male (when given a choice of two males with different numbers of egg spots). You can check out Figure 2 of the paper to see how this was done.

In a separate experiment, females were able to move freely between 4 chambers, each of which held a different male, with different numbers of egg spots, and lay their eggs. Females of this species scoop up the eggs into their mouths and let the male fertilize them there. Once females were at this “mouth brooding” stage, the researchers removed them and did paternity tests to find out who the daddy was.

So many choices... (Image from Theis, et al. Figure 1)

The results of these two experiments were a little confusing and the graphs not extremely helpful (at least to me), but the take-away message was this: in this species, females didn’t seem to give a hoot how many egg spots a male had. At least, not in any consistent or predictable way. (Though, keep in mind, this may not be the case for other cichlid species).

So far, the experiments seemed to be a bust. They still had no idea what those egg spots were for. On to the final experiment: let the boys fight!

The set up for experiment 3 was simple enough: put a focal male in the middle of the tank and flank him by two “stimulus” males on either side, in transparent cylinders. The middle male was always territorial (so they knew he’d fight to protect his love-shack). One of the stimulus males had normal, intact egg spots, and the other male sadly had his egg spots removed by “freeze-branding” with liquid nitrogen.

The battle arena (Image from Theis, et al. Figure 2)

The researchers then presumably grabbed a bowl of popcorn and watched the battle of the fishes (no fish were harmed in the collection of these data). The total number of aggressive behaviors (“bites, butts, or quivers”) of the focal male toward the two stimulus males was recorded for 10 minutes.

In this case, the result was clear: males without egg spots induce rage in their rivals. This is the first time cichlid egg spots have been implicated in male-male competition. Perhaps lack of egg spots indicates that a male is weak and easy to fend off. This could be possible, since those pretty dots are costly to make. The authors point out that this may also explain the apparent lack of female preference for spots in this species. Females are only going to be courted by males with a territory. If all the egg-spotless males have been scared off by the spottier boys, a female doesn’t need to choose. The best males are the only ones left to shake a tail fin her way.

Reference
Theis, A., Salzburger, W., & Egger, B. (2012). The Function of Anal Fin Egg-Spots in the Cichlid Fish Astatotilapia burtoni PLoS ONE, 7 (1) DOI: 10.1371/journal.pone.0029878

Related articles

• New research into egg spots in cichlids (practicalfishkeeping.co.uk)
• Nature: Mouth-brooding cichlids (conservationreport.com)

Xenopus eggs

Female frogs (Xenopus laevis) release their eggs out into the water, where they wait for some lucky sperm to come along and fertilize them. But they don’t wait very long. Frog eggs are ticking time bombs that self-destruct after only a few hours if not fertilized. Previously, how this happened was a mystery. Now, new research from Kobe University and (in a separate paper) CNRS in France has found that the eggs die by a well-known mechanism: programmed cell death.

Nestled inside the female’s ovaries, frog eggs can hang out in a state of suspended animation for months. These eggs aren’t able to be fertilized yet, but they will be as soon as they’re laid. The hormone progesterone starts the clock during ovulation. (You may know progesterone from its role in menstruation and pregnancy in people). Progesterone brings the eggs briefly out of their suspended state, until they get to the next stopping point, from metaphase I to metaphase II of meiosis.

But even though these eggs are again frozen in time, developmentally, the countdown continues. After being laid, frog eggs start to deteriorate, and the chances a sperm cell will be successful in fertilizing it go way down. After 48 hours, the eggs are completely dead.

The finding that eggs deteriorate because of programmed cell death (called apoptosis) is not completely new. Eggs from other species, from starfish to humans, also die by apoptosis a short time after ovulation if not fertilized. But whether this also occurs in frogs was not known.

Why do we care about frogs? The frog is a very important model for development. They have huge eggs that can be studied by eye. Even extracts made from the eggs can be used to study important cellular processes that can have important consequences for understanding human diseases and causes of female infertility. Specifically in this case, if we can learn more about why frog eggs deteriorate, we can find out what goes wrong when they deteriorate abnormally fast. And in that sense, it’s pretty great that the mechanism of death seems to be conserved between us and frogs.

This little male will be ready to fertilize some fresh eggs before they go bad. Image via Flickr.

You might imagine that ovulated eggs could just sit around for an indefinite period of time, as long as they don’t get eaten or anything. After all, aren’t they stuck at a specific developmental stage for possibly months before ovulation? While this is true for the cell-cycle arrest inside the ovaries (metaphase I), it’s not true for the second block (at metaphase II, after ovulation).

The authors of the first paper (Tokmakov, et al.) surgically removed eggs from the ovaries, so that they wouldn’t be affected by progesterone. These progesterone-free eggs could hang out in the water for at least 72 hours (at which point, I assume the researchers got bored) without any signs of apoptosis. On the other hand, if treated with progesterone, the eggs returned to their normal suicidal selves.

Why aren’t the eggs safe in the second cell-cycle arrest? It turns out that the developmental block isn’t all that strong.

Both papers found that within 6-18 hours after ovulation, frog eggs will spontaneously escape from the block. At that point, the countdown really speeds up, since even if a sperm does come along, it won’t find the egg at the necessary stage for fertilization. As if it knows there’s no point to even trying anymore, the egg turns on the cell death program shortly after escaping arrest. Within 24 hours, the egg is dead. Interestingly, the second paper (Du Pasquier, et al.) also found that some eggs will stay inside the female after ovulation for over 24 hours. These eggs, too, will die a programmed death.

To test the hypothesis that early release from arrest jump-starts the cell death program, Tokmakov and colleagues treated newly laid eggs with a drug called roscovitine. Roscovitine interferes with the cell cycle machinery and causes the eggs to escape the developmental block much earlier than normal. Cell death was greatly accelerated in the drug-treated eggs, compared to eggs that weren’t treated. Similar results were seen in another experiment that used a different chemical.

However, the eggs didn’t start killing themselves immediately after their early escape from cell-cycle arrest. Though the drug sped things up, it still took many hours to see the signs of cell death (18 hours in the treated eggs versus 24 hours in normal eggs). So, while the authors show clearly that exiting the arrest comes before cell death, and that there may actually be a cause-and-effect relationship between the two, it can’t be the whole story.

By the way, why doesn’t evolution just find a way to make the second block stronger, so the eggs don’t have to kill themselves at all? The papers didn’t seem to offer any clues, but one guess is that, as in humans, the DNA inside the eggs will start to fall apart over time, and maybe this is more of a problem during the second block than the first. It may be in the female’s best interest to make sure only the best, freshest eggs are in the running for fertilization.

References

• Tokmakov, A., Iguchi, S., Iwasaki, T., & Fukami, Y. (2011). Unfertilized frog eggs die by apoptosis following meiotic exit BMC Cell Biology, 12 (1) DOI: 10.1186/1471-2121-12-56
• Du Pasquier, D., Dupré, A., & Jessus, C. (2011). Unfertilized Xenopus Eggs Die by Bad-Dependent Apoptosis under the Control of Cdk1 and JNK PLoS ONE, 6 (8) DOI: 10.1371/journal.pone.0023672

Related articles

Great prostrate silicified trunks of trees, embedded in a conglomerate, were extraordinarily numerous. I measured one which was fifteen feet in circumference: how surprising it is that every atom of the woody matter in this great cylinder should have been removed and replaced by silex so perfectly that each vessel and pore is preserved! These trees flourished at about the period of our lower chalk; they all belonged to the fir-tribe. It was amusing to hear the inhabitants discussing the nature of the fossil shells which I collected, almost in the same terms as were used a century ago in Europe,–namely, whether or not they had been thus “born by nature.” My geological examination of the country generally created a good deal of surprise amongst the Chilenos: it was long before they could be convinced that I was not hunting for mines. This was sometimes troublesome: I found the most ready way of explaining my employment was to ask them how it was that they themselves were not curious concerning earthquakes and volcanos?–why some springs were hot and others cold?–why there were mountains in Chile, and not a hill in La Plata? These bare questions at once satisfied and silenced the greater number; some, however (like a few in England who are a century behindhand), thought that all such inquiries were useless and impious; and that it was quite sufficient that God had thus made the mountains.

- Voyage of The Beagle, Chapter XVI

One of the remarkable features of this book is Darwin’s relentless commitment to a scientific point of view. He asks questions nobody around him thinks to ask, and he is unsatisfied with answers not based in observable evidence and reasoned thought.

My research, and the research of many people in the Wolfner lab, is geared toward understanding how proteins in semen help sperm do their job of fertilizing eggs. These proteins aren’t part of the sperm, and they’re made in a totally different organ, but they’re essential for male fertility (yes, even in people). In our favorite animal, the fruit fly Drosophila melanogaster, these “extra” proteins are needed for all three steps of sperm success: getting into storage (in the female), staying alive in storage, and being released so they can fertilize eggs.

We’re starting to understand a great deal about the male side of things (though there are still A LOT of questions), but we basically know nothing about the female side.

The secretory cells surrounding the spermathecae are shown here in glowy green. The coiled up seminal receptacle is in the top left (black arrow). From Schnakenberg, et al. 2011.

That’s where this paper by Sandra Schnakenberg, Wilfredo Matias, and Mark Siegal comes in. They focused on a few cells that surround two of the female’s sperm storage organs: the paired spermathecae. They discovered that these cells (called secretory cells) pump out proteins that tell sperm how to get into storage. Without the stuff from these cells, sperm get lost and can’t enter the spermathecae. The spermathecae are attached to the uterus and store about 100 sperm each after mating. Another structure, the long, coiled seminal receptacle stores the other 400-600 sperm.

Schnakenberg and colleagues found two proteins (my favorite kind: proteases!) that are made in these secretory cells and nowhere else in the fly (the cells are shown in green in the picture above). They then identified the part of the fly’s DNA–the regulatory sequence–that tells the fly to only make these proteins in those particular cells.

With the regulatory sequence in hand, they could turn on cell-killing genes in those secretory cells, essentially deleting them from the fly’s body. The point? To figure out what the hell those cells do, other than make some generic-looking proteases. If you want to know what something does, the best way to find out is to break it, then wait to see what goes wrong. In this case, without those cells, sperm lose their sense of direction. They can’t get into storage (at least, not into the spermathecae). But, what about the seminal receptacle, you ask? Don’t tons of sperm make it in there? Well, turns out they can get in, but they don’t stay alive in there for very long.

The fun part? Proteins from the secretory cells only need to be around right before/during mating to do their job. If you get rid of them after mating, everything is still okay. So, how do they keep sperm alive for long periods of time after mating? One possibility is that they’re needed to turn on some program in the storage organs right at the time of mating, and other proteins do the heavy lifting.

This egg had been stuck in the female until it was squeezed out by the researchers under a microscope. The green dots show the nuclei...things that shouldn't be there in a normal egg that hasn't even been laid yet. This egg is on its way to being a little larva already. From Schnakenberg, et al. 2011.

The weirdest result from this experiment is that the secretory cells are needed for the female to lay eggs like a normal female. Fruit flies usually lay a bunch of eggs every day after mating, for up to two weeks. But females without their spermathecal secretory cells will lay eggs normally for a day, then not lay any the next day, then be normal, and on and on.

What happens on those days when she isn’t laying any eggs? An egg is still released from the ovary, but for some reason gets stuck in the uterus. There, it can be fertilized and, amazingly, develop and hatch into a larva. This creates a situation where flies give live birth. Kinda gnarly.

Now that we have an idea of how female flies guide sperm into storage, we can start to study the interaction between semen proteins and female proteins. And we can finally ask questions that evolutionary biologists have been wanting to ask for a very long time. Do male and female proteins generally work together, or is the “battle of the sexes” a more common theme? Which kinds of proteins tend to be in conflict? And who’s really in control over fertilization success? My guess: it’s going to be a little of everything, depending on the context. And that’s why biology is so much fun.

Reference:
Schnakenberg, S., Matias, W., & Siegal, M. (2011). Sperm-Storage Defects and Live Birth in Drosophila Females Lacking Spermathecal Secretory Cells PLoS Biology, 9 (11) DOI: 10.1371/journal.pbio.1001192

Ivan Orasnky and Adam Marcus make a clarion call for greater openness about plagiarism and why papers get withdrawn, but …

The most alarming comments were around the paucity of access to scientific literature, which is (after all) there to increase knowledge, make R&D more efficient and provide the grist of scientific debate that drives progress.

Covered by William Heisel here the two say that, “most retractions live in obscurity in Medline and other databases.”

It’s not only retractions that are hard to find

The ‘innacurate science’ message is very important for the entire community. But isn’t the bigger issue that those who funded the retracted research – often taxpayers – aren’t particularly likely to find out about them. Nor are investors always likely to hear about retractions on basic science papers whose findings may have formed the basis for companies into which they pour dollars.”

When the valuable product of ‘good science’ – accurate observation and insightful observation – is not easily available to fellow scientists and innovators the rate of advancement of real knowledge creation is lower than the amount of effort applied.

If it’s easier for researchers to read their Twitter feed on last night’s episode of their favourite show than to access the information they need to make their next advance – then we have a big problem.

Surely in a hi-tech information age that is open to (almost) all, we must be able to make this invaluable science content easily available to researchers as a routine and regular part of their working day?

Wolbachia inside a host cell. Image via topnews.net

Wolbachia are a type of bacteria that live inside the cells of many animals, but mostly insects. They are passed on from mother to child through the mother’s eggs.

They can often be bad for the insect host: they might kill all male offspring, destroy the host’s gonads, or make it harder for the host female to make eggs with sub-par blood. This is why Wolbachia has been pursued as a potential tool for reducing mosquito populations that carry dangerous human pathogens like Dengue virus and malaria.

On the other hand, Wolbachia can be a good thing for the host. In some species, Wolbachia infection can protect the host from viral infections. And, as a new paper in the journal Science demonstrates, they can ramp up the host female’s egg production by increasing the activity of the germline stem cells. (This article does a very nice job of explaining the paper and its implications).

For this study, the authors used a relative of the common laboratory workhorse Drosophila melanogaster, known as D. mauritiana. D. mauritiana is a fruit fly that is only found on two little islands off the coast of Africa, Mauritius and Rodriguez. The flies are naturally infected with their own specific strain of Wolbachia.

The authors of the paper noticed that infected females produced about 4 times the eggs of uninfected females, apparently due to the presence of Wolbachia inside the cells that give rise to eggs. They found that the activity of these cells was increased in infected females–about 2-fold–but not enough to explain all the extra eggs being produced.

So, where do the extra eggs come from? Wolbachia is helping the flies out in two ways. The bacteria ramp up egg production and shut off the normal programmed cell death inside the ovary.

It appears that male D. mauritiana are out of luck, though. Even though Wolbachia were found in the germline stem cells of testes, they weren’t ramping up sperm production. Males can’t transmit the bacteria to their offspring, so Wolbachia really have no incentive to help the boys out (see: male-killing).

These tiny bacteria appear to have lots of different strategies for manipulating their host’s reproduction (and gene expression), but exactly how they do it is still a mystery. I’ll keep you posted if anyone figures it out!

Reference:
Fast, E., Toomey, M., Panaram, K., Desjardins, D., Kolaczyk, E., & Frydman, H. (2011). Wolbachia Enhance Drosophila Stem Cell Proliferation and Target the Germline Stem Cell Niche Science, 334 (6058), 990-992 DOI: 10.1126/science.1209609

Seminal fluid is kind of like a cocktail: lots of ingredients that all have to work together in just the right way to...well, this metaphor can only be stretched so far. Image via birthdayideasforyou.com.

If you’ve perused the other posts on this site, you may have noticed that I have a thing for seminal fluid. That’s because semen is awesome: it’s full of proteins, lipids, sugars, and who knows what else, all of which plays some role in fertility.

Exactly what all that stuff is doing is still a total mystery (except for a very few rare cases).

Unfortunately, just picking out one protein and asking, “what happens if I break this?” doesn’t seem to work in most cases. One reason for this could be that there are tons of fail-safes built in. After all, if destroying the function of any one protein could cause infertility, making babies would be a lot more difficult.

My own research is on a type of proteins, called proteases, in the seminal fluid of fruit flies. These proteases act very quickly during and after mating to cut up other seminal fluid proteins to do… something related to reproduction. Nailing down exactly what all these proteases do inside the female is definitely not easy.

C. elegans sperm (from Sam Ward lab website)

That’s why I was very excited to see this paper in PLoS Genetics recently. A protease called TRY-5 in male worms (C. elegans) activates sperm as they are transferred to a hermaphrodite. So, such an important protease must be required for fertility, right?

Wrong. The hermaphrodite uses a completely different (still unknown) activator for its sperm, and this can also activate male sperm if something were to happen to TRY-5. And if the hermaphrodite’s activator is broken? No problem, she can use TRY-5 from the male.

Of course, in the wild, most hermaphrodites probably never encounter a male, so I guess if their own activator was broken, they’d be screwed (or not, as the case may be). But males would be extremely unlikely to encounter a hermaphrodite with a broken sperm activation system. So why have TRY-5 at all?

This is the sort of question that pops up over and over again in seminal fluid research. The male goes through all the trouble to make tons of proteins that, individually, appear to do nothing all that important. But making all those proteins takes energy. And, if you look very closely at the evolutionary history of the proteins, you find again and again that they’re not lost over time. In fact, they seem to be picked out by natural selection to keep changing in ways that may affect their function, but never quite break them.

So, what is the answer? Why have TRY-5, or any of those little moochers hanging out in the seminal fluid? My best guess is that no matter how hard we try, we can never quite exactly mimic the natural environment of our favorite experimental animals in the lab. Worms (and flies, too, for that matter) experience situations in the wild that we probably can’t even imagine. In the lab, a difference of a couple of minutes may not affect anything, whereas in nature, it could be the difference between fertilizing eggs and being kicked out of the gene pool for good.

In the case of TRY-5, the authors suggest that it may be a more efficient activator of sperm and that this somehow works in the male’s favor. The difference in efficiency, though, if it exists, is too small to see under their laboratory conditions.  They speculate that a difference in efficiency could benefit the male by decreasing the chance that his sperm is lost before they can fertilize the hermaphrodite’s eggs:

“For example, activation by TRY-5 might occur more rapidly than that mediated by the hermaphrodite activator. If so, its transfer would decrease the chance that transferred sperm would be lost before they have the opportunity to migrate away from the vulva.” (Smith & Stanfield, 2011 PLoS Genetics)

It may seem silly to try to pick away at the functions of all these proteins in the seminal fluid, but I think it’s very important (though I may be biased). Everyone knows that you need a sperm and an egg to make a baby, but the process is much, much more complex than that. And we still have no idea how all of these proteins, genes, and the environment fit together to determine how and when a new life will be formed.

Reference: 

Smith, J., & Stanfield, G. (2011). TRY-5 Is a Sperm-Activating Protease in Caenorhabditis elegans Seminal Fluid PLoS Genetics, 7 (11) DOI: 10.1371/journal.pgen.1002375

I have been truly lucky to meet some incredible people within not only this industry but industries I never imagined myself becoming involved in. I have had the opportunity to meet some of my personal icons and people that I look up to and admire. In the last year I have been given the opportunity to broaden my horizons by encountering some people outside of the herpetoculture realm. With these meetings you the audience have spoke out and told me either personally or via email you wanted more of the same. I had every intention of bringing the audience what they wanted but as some of you may know I can be well, somewhat ‘anal’ for lack of a better term when it comes to certain things. I am not the best editor when it comes to writing and I am still learning.

In October of this year I was hospitalized with bacterial meningitis. A few of my close friends knew and were very supportive. Without becoming melodramatic about it. On the 3rd day when I was finally lucid enough to comprehend what was being said the doctor explained if I had not come in when I did I wouldn’t have made it. Those kinds of incidents put a whole new perspective on things. I am still recovering today, I still have some memory loss and bright sunlight hurts my eyes. I am retraining myself on words and things that I should remember. I don’t write this for a play on your sympathy. I like what my dad said about sympathy.

“You know where to find sympathy?”

“No, where?”

“Between shit and syphilis in the dictionary.”

As I said it changed my perspective on things. We recently brought on board a new Project Manager and she has been a huge asset in helping us organize the various aspects of The Reptile Apartment Group and its workings. Details are essential to any project and she is making sure that each project produced will have that attention to detail. (She’s still working on my editing skills and any mistakes in this post are to be squarely blamed on me).

With that said, I am relaunching reptileapartment.com as a new site. I’m keeping the original intent of the site but this growth will bring to light more of the scientific aspects of herpetoculture that you the audience have requested. We will still produce the in depth care articles that you have come to depend on us for; but we are now going to start writing more scientific articles looking into the natural history, physiology, and other aspects that are often ignored by herpetoculture at large. Now we will add the aim of crossing the boundary of herpetoculture and herpetology. With that being said we’re off to put the final touches on the new  site! Stay tuned right here for more.

When you enter a query in basic search, the query is sent to every individual data resource (database, collection, and portal) searched by the discovery tool. The individual data resources send back a list of results from the search query. Results are then ranked in relevance order. You can review the results and navigate to the host site of a particular result for more detailed information.

After the jump, we’ll look at four federated search portals, and we’ll see what features these search systems have in common.  We’ll also find which features make each federated search portal unique.

Science Accelerator

Science Accelerator is a free federated web search engine created by the U.S. Department of Energy’s OSTI. The tool allows users to search “key resources” from the Department of Energy’s collections, which are all listed on this page of the website.  Search features of the portal include:

• Quick search option (keyword search form) available on the site homepage and in the upper right corner of each page on the portal.
• Advanced Search form, where the user can search by keyword within the full record, title, or author fields. Within the advanced search form, the user can also select a date range and select which resources to search in (via checkboxes beside each resource name).
• Refine search results in hit list (through a keyword search within the result set).
• Re-rank the results (by rank, date, title, or author).
• View results from a specific resource.
• View results from Wikipedia and EurekAlert.
• View clusters of results sorted by topic or date.
• Select specific results from the hit list and e-mail the results.
• Create an alert based on the query (for registered users only).

Each result in the hit list displays the document title, relevance rank (illustrated by colored star icons), source, a brief snippet from the document, and any other important bibliographic data (title, publication date, etc). Selecting a search result will take the user to the document record (or full-text version, if available) on a third-party site.  A small PDF icon  below the result listing indicated that the users can download a full-text PDF version of the document.

Search results for Science Accelerator.

WorldWideScience.org

WorldWideScience.org is a federated search portal that searches international scientific and technical literature. The service is offered by the WorldWideScience Alliance, which is a “governance structure” for the search portal. The portal was created by the OSTI (like Science Accelerator).  WorldWideScience.org has a multilingual interface, accessible on the homepage or through the advanced search form, which allows the user to select a language to search in (translations are powered by Microsoft Translator).

Search features and results are very similar to the Science Accelerator portal, with quick or advanced search forms, all searchable resources listed below the advanced search form, results ranked by relevance,  result topics (and common authors, publishers, publications, and dates) listed in a sidebar on one side of the hit list, results from Wikipedia and EurekaAlert on the other side of the hit list, options to print or email results, and the option to turn the search into an automatic alert (for registered users).  WorldWideScience.org divides results into two lists (accessible through tabs at the top of the hit list): Papers and Multimedia.  An option at the top of the hit list also gives user the option to “Translate Results” (although this feature didn’t seem to be functioning correctly at the time of testing).

Search results for WorldWideScience.org.

Science.gov

Science.gov is a search system with access to over 50 databases and over 2100 selected websites, offering 200 million pages of authoritative U.S. government science information, including research and development results.  Science.gov is an inter-agency initiative of 18 U.S. government science organizations within 14 Federal Agencies, and Science.gov is also the U.S. contribution to WorldWideScience.org. The About Section of Science.gov lists some of the most recent features of Science.gov 5.0.  Most of these listed search features are similar to the features available through Science Accelerator and WorldWideScience.org (all resources listed below advanced search form, relavency-ranked results, topic/author/date clusters, options to email results and create an alert of the search, etc.) .

The Image Search feature (described in more detail in a previous blog post) seems to be a unique tool on Science.gov, which allows users to search by keyword and select from a list of image resources in which to conduct their search.

Search results for Science.gov.

Scitopia

Scitopia is the only federated search portal in this list that isn’t maintained by the federal government.  Scitopia runs on  Deep Web Technologies’ Explorit Research Accelerator federated search engine (Science.gov also runs on Deep Web technology), and the portal is maintained by a collaborating group of science and technology societies.  According to the site homepage, users can search over “3.5 million documents, plus patents and government date.”

Like the previously listed federated search portals, Scitopia features simple and advanced search forms (with all resources listed under the advanced form),  a side menu of topic/author/publication/publisher/affiliation/date clusters based on the search results,  relevance-ranked results, alert and email options for queries and results, and search results that appear on third-party sites when selected.

Like WorldWideScience.org, Scitopia divides its results into separate lists, organized under three tabs: Societies, Patents, and Government.  Scitopia additionally includes a “topic browse” index, which lists common topics in alphabetical order and links to search results for each topic (Science.gov also has a topic index).

Search results for Scitopia.org.

Conclusion

All four federated science search portals have very similar interfaces and search features, such as advanced search forms with all available resources listed below, search results ranked by relevance,  a side menu of topic/author/date/etc. clusters, options for emailing results and creating alerts from searches, and search results that open directly in third party sites when selected.  Some unique features exist on each portal, such as an image search feature on Science.gov or a multilingual search interface on WorldWideScience.org. The main differences between the portals, however, seem to be the databases which these portals search through.  All the portals may share some similar resources, but each portal seems to have a slightly different focus: Department of Energy resources for Science Accelerator, international scientific information on WorldWideScience.org, US scientific government information on Science.gov, and scientific data from both government and technical society resources on Scitopia.

All four portals seem to use very similar search technology (Deep Web specifically for Scitopia and Science.gov), and the OSTI played a large part in the creation of three of the portals (Science Accelerator, WorldWideScience.org, and Science.gov).  Despite these similarities, each portal searches some unique databases, so each portal will produce a different result set for identical queries.  Prior art searchers should therefore search all four portals, as well as other available subscription and free search systems, in order to locate all relevant non-patent literature prior art.

Have you used any of these federated search portals for prior art searching? Which portal do you think has the best search features?  Let us know in the comments!

This post was contributed by Joelle Mornini. The Intellogist blog is provided for free by Intellogist’s parent company Landon IP, a major provider of patent searches, trademark searches, technical translations, and information retrieval services.

Close-up of a diatom. Image via Wikipedia.

Did you know that diatoms have sex? I didn’t. You know diatoms, those microscopic, silicon-encased, sorta algae things that live in the ocean…and basically anywhere else there’s water. They’re single-celled organisms that hang out at the bottom of the food chain and their dead, decomposed bodies (called diatomaceous earth) are used by humans for many things (like making nitroglycerine safer to handle).

I mean, look at that thing. It looks like a piece of glass. How exciting could its life really be? It turns out, many species of diatoms need sex to survive. And one species, Pseudostaurosira trainorii, has a really funky way of getting it on. The sperm from male P. trainorii cast out little threads that can act as fishing lines for grabbing eggs. Males and females of this species can also communicate, letting each other know when it’s time for sex. The research describing the secret sex life of these tiny creatures was published online in the journal PLoS One.

There are hundreds of species of diatoms, but they basically fall into two groups: the centrics (which evolved first) and the pennates (which evolved later). Centrics can be “male” or “female”, making either sperm or eggs. The sperm have a flagellum (sperm tail) so they can swim toward eggs. Most of the pennates, on the other hand, do not have tails and don’t even make sperm and eggs. Their gametes all look the same and are basically pretty boring, as far as I can tell.

There are two groups of pennates, however, that do make sperm and eggs. These are species that are more closely related to the centrics. But even though they make sperm, the sperm don’t have tails.

An obvious question is, where did the sperm tails go? Were they lost before the evolution of the pennates, or after?

The problem: no one has really bothered to look at how ancient pennates reproduce.

The authors of this paper wanted to fill this gap in diatom knowledge by looking at an ancient pennate species, P. trainorii. What they found was a totally new kind of sperm.

Casting off

Sperm of P. trainorii extruding a "thread". Image from Figure 1 of Sato, et al. 2011.

The picture above looks like you might imagine most sperm to look. It has a head and a tail. But there are a couple of things that set this sperm apart from the rest.

First, that sperm has two nuclei instead of the normal one. Eggs also have two nuclei, so when an egg and sperm fuse, two nuclei have to be destroyed before a new diatom can be made. Why do it this way? I have no idea.

Second, that is no tail. Instead, the sperm extrude little “threads” that can’t actually move on their own. The sperm puts out a thread and then winds it back up to help itself move. The sperm put out threads in random directions, spinning around like tops, until they get near an egg. Check out movie S1 in the paper (scroll down after clicking the link).

If the sperm is lucky, it might hit the egg with its sticky thread and reel it in like a fish. The sperm and egg can then fuse and make a new diatomaceous baby.

Look at the bottom left of panel A. The top blob is a sperm that's sticking out a thread. To the right is an egg (labeled e). If you follow this pair through panels B and C, you can see the sperm reel in the egg. Image from Figure 1 of Sato, et al. 2011.

If the sperm doesn’t get lucky and hit an egg with its thread, don’t worry; it can still fertilize an egg. When a sperm gets close enough to an egg, it becomes ameboid and moves directly toward the egg. Sometimes, two or more sperm will gang up on an egg and try to fuse with it. But once a single sperm has fertilized an egg, the other sperm will instantly go back to randomly casting out threads and searching for love.

Sexy shrinking

I want to backtrack for just a minute. Why do diatoms even need to have sex? They seem perfectly happy floating along as single-celled, asexual glassy things. What makes them switch from making clones of themselves to dividing into either sperm or eggs?

Image via Flickr.

The answer: diatoms are constantly shrinking. Diatom shells are made up of two unequal halves. The big half overlaps the small one so that a tight seal is formed.

Each generation, the daughter cell that gets the smaller half has to make an even smaller new half. Eventually, the cells become so tiny they can’t divide that way anymore. To reset their size, they need to have sex. They do this by turning themselves in to sperm (if they’re male) or eggs (if they’re female).

P. trainorii clones can either make male or female gametes (sperm or eggs), but not both. That means, when they decide its time for sex, they have to find a suitable partner.

Sato and colleagues found out that each sex produces its own kind of signal, likely through a pheromone, that tells the other sex that its ready to get it on.

Sexy talk

The authors predict that this species makes at least three different kinds of pheromones, that are nicely summarized in the picture below.

The secret sex talk of diatoms. In pink, a female clone sends out a signal that she's ready for lovin'. A male clone picks up the scent and undergoes gametogenesis to make two sperm. He then sends out the blue signal to let the female know he's ready to go. She gets the message and makes two eggs of her own. It's then up to the male to find her and finish the job. The sperm sends out random threads until it gets close to the eggs. It then goes ameboid, after sensing the third pheromone, and moves directly to the egg. Image from Figure 11 of Sato, et al. 2011.

Male clones were able to detect the presence of a female from a distance, through a filter that they can’t cross. Even though they couldn’t touch or get to the female, male clones were stimulated by something in the water and started the process to make sperm.

Females, in turn, could detect that a male had gotten the message. Also through a filter, a female clone could detect a “sexualized” male (i.e.: one that had turned itself into sperm) and this was enough to get her to go through the process of making eggs.

The third predicted pheromone wasn’t detected in the experiments. Even though eau de female clone could convince a male to make sperm, it wasn’t enough to get him to form psuedopods and move directly toward the female. Eggs that had been killed by heat also couldn’t do it for a male. The authors predict that the third pheromone probably doesn’t last very long or go very far. Males might have to be very close to detect it.

I don’t know if this paper answered any questions about the evolution of pennate diatoms, since the threads described in the paper aren’t anything like the flagella of the centrics. But it’s still really cool. This is the first time threads like this have been shown to have a role in sex (a very distantly related type of algae, the Haptophytes, also send out threads, but these are used for catching prey, not for sex).

This is what I love about science. You never know what you’re going to find.

Reference:
Sato, S., Beakes, G., Idei, M., Nagumo, T., & Mann, D. (2011). Novel Sex Cells and Evidence for Sex Pheromones in Diatoms PLoS ONE, 6 (10) DOI: 10.1371/journal.pone.0026923

Yes, ladies, I *am* happy to see you! Image by Ria Tan (via Flickr).

Male fiddler crabs wave their giant claws to get the attention of females. Females prefer males that wave a lot, in line with a common theme in female choice: making the male work for it. Waving that big thing around is more than just an advertisement. The thing is heavy to lift, so the male has to be in good shape to keep up all that waving. It’s also dangerous. The more he waves that big sign saying, “Hey, look at me!” the more predators will take notice.

How do males determine how often to wave if too much waving will get them dead, and too little will keep them from getting mates? As we’ve seen before, many males in the animal kingdom have to walk this fine line between life and sex, and they all cope with it in different ways.

New research from Richard Milner, Michael Jennions, and Patricia Backwell at The Australian National University has found the answer for the fiddler crab, Uca annulipes. The more competition there is, the more a male will wave. The research appears in the Journal Biology Letters.

These are the things a female fiddler crab finds sexy:

• Males with a faster waving rate (the ones who wave most often);
• Males who wave slightly earlier than competitors. In this species, males tend to wave in sync with each other, though some may wave a little before the others. And it’s hot;
• Bigger claws. That’s right: size matters.
• An awesome bachelor pad (females make their final decision based on the quality of the male’s burrow).

Because the first item on the Lady Fiddler Crab’s Guide to Finding True Love is one most likely to get a guy killed, the authors focused on this one. They wanted to know how the trade-off was managed from the male’s point of view. Specifically, they asked whether males were more likely to put themselves at risk if they were up against competition.

They directly manipulated the level of competition experienced by a given male. Females were tethered in place by a piece of string in front of the test male. Then, the researchers created a situation with either low or high competition.

For the low competition scenario, other males in the vicinity were first cleared out. The researchers “startled all crabs into their burrows by standing up and approaching them.” I’m sure the other male crabs wished they also possessed these awesome powers to drive off their enemies. They then made sure males couldn’t come back out before the trial was over, by placing bottle caps over all the burrow entrances, except one.

When the lucky guy came out, they measured how often he waved at the female, over 30 seconds, once he had time to get started.

For high competition, only some burrows were closed off. They then measured the wave rate of the same male as in the low competition scenario. This whole process was repeated with 50 different males.

They found that males will wave more if they are surrounded by competition. In the high competition scenario, the median wave rate was 16.5 waves per 30 seconds. This was compared to about 11 in the low competition scenario.

All right, boys, let's see you shake it! (Image via Flickr)

Even without competition, males still want to put on a good show for the female, but they’re not going to go into overkill without more incentive. In fact, the wave frequency went up with increasing numbers of rival males. They save the really intense waving for the toughest situations. When only one rival is near the focal male, he waves about 16.5 times in 30 seconds. That goes up to over 2o when 4 rivals are present.

The results from this study weren’t necessarily the way it had to be. Males might benefit from putting their best claw forward, regardless of the competition. Receptive females are rare. For every 45 males, there is only one female with eggs ready to be fertilized.

Besides that, females don’t always pick the best male from a single group. She might shop around, looking at males in several groups before making up her mind. Males should therefore try hard to get her interested, even if no one else is around.

The finding that males save the good stuff for when they need to stand out from the immediate crowd suggests that it really is costly for males to always perform at their peak. After all, it’s no good being super sexy if you’re just going to die before cashing it in.

Reference:

Milner, R., Jennions, M., & Backwell, P. (2011). Keeping up appearances: male fiddler crabs wave faster in a crowd Biology Letters DOI: 10.1098/rsbl.2011.0926