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Brains, behaviour, and evolution.
Let me try to apply one of the suggestions in Don’t Be Such a Scientist and practice a little concision:I love this book. I devoured it in one evening.Whew. Now, I can go back to my normal science mode.Randy Olson has been working in Hollywood for over a decade, but he’s still one of us. He gets what being an academic scientist does to you: you become literal, critical, and absolutely focused on destroying error – and it never goes away. He gets us. But he also gets how other people see us, and Olson has a message for us, his former colleagues: For other people, it’s not just about the data, guys.Olson isn’t the first person to say that persuading non-scientists about the truth of things requires more persuasion than just evidence. This has not been a popular message, particularly among a lot of my fellow science bloggers.* These kinds of messages get characterized as weak-kneed capitulation, compromising the truth.For that reason, Olson will probably face his strongest criticism for suggesting that scientists not be unlikeable. It sounds a lot like admonitions of other writers never to offend, which has generated a growling response that there are some people that we scientists want to offend: the people who deal out lies, errors, and untruths.Olson has not cracked that hard problem: how to communicate with those nice people who are just like you and me, except for a few beliefs that are divorced from reality. You know the ones: the creationists, the climate change deniers, the anti-vaccine campaigners, the moon landing conspiracy theorists, the birthers, and so on. Olson’s tips and suggestions won’t matter when dealing with those people, but that’s not Olson’s book. It’s a book that somebody needs to write – badly – but Olson’s approach shouldn’t be dismissed because of that. He’s pointing out that when you launch a full out assault on your enemies, you risk inflicting a lot of casualties on people who might have been on side.Part of what convinced that Olson is on the right track were uncomfortable moments reading this book when you recognize yourself, and think, “Oh, damn, he’s right.”For instance, Olson talks about how being an academic means being critical. We academics forget that even honest and correct criticism can be very deflating.Have you ever walked out of a movie that you loved, and you’re replaying some of those favourite moments and lines in your head... and one of the people you’re with points out something that’s completely illogical? Do you happily respond to that honest and correct criticism, “Wow, I’m so glad you pointed that out!” If so, you’re a better person than me, because my response was an irritated, “That’s not the point.” **And yet, we scientists are routinely praised for pointing out those annoying little untruths. On the very day I received my copy of Olson’s book, one of my blog posts was picked as an editor’s choice specifically because it was critical.On that note, I don’t think it’s any accident that the words highlighted in the blurbs on the back are the ones that say how critical this book is. After all, this book is aimed at scientists and academics, so if you want their respect, you’ve got to show them that you’re criticizing! In fact, the tone here is very amiable and affable. The most critical sections of the book seem more exasperated than stinging.On a similar note, Olson also talks about how scientists are extremely literal. Here again, you don’t have to look further than recent stuff on the blogosphere. The new film Creation is starting to get reviews, and here’s Eugenie Scott’s review on Panda’s Thumb.As someone with a stake in how the public understands evolution and it’s most famous proponent, the bottom line for me was that the science be presented accurately. The second was that the story of Darwin’s life be presented accurately.Her bottom line is not whether the movie has a good story, is emotionally powerful, well acted, or any of the other dozens of things that most people look for in a movie. Her bottom line is accuracy. Such a scientist. For many, looking for that first is missing the point of why they watch a movie.Finally, Olson has something in common with Adam Savage. It’s not just that they do science-y stuff on film. MythBusters host Savage was quoted as saying recently:I realized that my humiliation and good TV go hand in hand.Olson is not afraid to make a point at his own expense. Don’t Be Such a Scientist starts with Olson on the receiving end of a truly terrifying bawling out by an acting teacher. Those four pages alone are near worth the price of admission, but it’s not the lowest or most embarrassing moment for Olson in the book. This is self deprecation taken to a new high, and it’s an illustration of one of Olson’s key tactics for communication: don’t “rise above,” as he puts it. In other words, don’t be high and mighty. Audiences tend not to like such people.*** I’ve tried to avoid righteous indignation on this blog, there are occasions where I bet someone reading it thought, “Boy, is he full of himself.”There is more about this book that I’d like to comment on and explore, but I’ll leave them for later. I’m teaching a class on biological writing this semester, and I hope I can bring some of the issues Olson raises into the class. Don’t Be Such a Scientist is a rich source of ideas, and I’ll be riffing off them for some time to come.ReferenceOlson, R. (2009). Don't Be Such a Scientist. Island Press, 1-216 ISBN: 9781597265638* That Olson mentions the tenor at scienceblogs.com as something damaging rather than helpful... let’s say I’ll be interested to read the response.** For me, the movie was Edward Scissorhands.*** I do have to wonder what Olson makes of the success of House, a show that has a character that seems to violate almost single suggestion that Olson has. The character is unlikeable, always rising above...... Read more »
Olson, R. (2009) Don't Be Such a Scientist. Island Press, 1-216. info:other/9781597265638
“We’re going to have some problems getting this under the microscope...”There are just times you’d like to be a fly on the wall when certain science projects are being planned. I can’t quite imagine the conversations that led up to this paper. “Let’s look at the brain of the biggest fish in the world.” (I suppose the fish start small and have to grow up big. But still.)The brains of sharks are interesting, in part because they much larger than people would think. People tend to think of sharks as primitive (how many shark documentaries have used the phrase, “unchanged for millions of years”?), and primitive means small brains. But compared to body size, shark brains are often as big as birds’ and mammals’.And when thinking about evolution of brains, extremes are often very informative. The whale shark (Rhincodon typus) is not only extreme in its size (as noted, they’re bigger than any other fish in the world), but extreme in its diet: it’s a filter feeder, which is not the first thing that comes to mind when people hear the words, “giant shark.”This paper is not only interesting because the species is unusual for neurobiology, it’s interesting because it applies a technique that is used a lot for humans, but quire rarely for other beasties: magnetic resonance imaging (MRI). Now, this is not fMRI, which is constantly in the science headlines: this is purely anatomical data, not imaging the brain of a live shark.Although the whale shark has a massive brain in absolute terms, it turns out that it isn’t very large relative to its body mass compared to other sharks. In fact, it’s small. In a situation like this, there are two hypotheses that come to mind. The first is that the feature was inherited from a common ancestor, in which case, you6d predict that the whale shark’s relatives also have small brains. The second is that the feature may be an adaptation to the particular ecology of the species, and the prediction there would be that species with the most similar lifestyle would have small brains.In this case, the whale shark has a small brain in common with other large filter feeding sharks, like the basking shark (compared using previously published data). It’s easy to think that filter feeders can afford to have small brains, but the authors caution that social behaviours in sharks and allies is another factor that is often strongly correlated with brain size.When looking at individual regions of the brain, the whale sharks also had something in common with other oceanic, pelagic sharks, but not their relatives: a very large cerebellum. Cerebellum is usually described as being involved in motor coordination. Why would these open ocean sharks need such a large cerebellum? The authors suggest that perhaps the use of that open ocean is more complex than you might expect. The sharks are not just lazing around at the top of the water, but making significant vertical migrations and travel for very long distances. These possibilities seem a bit foggy, however, based on the traditional notions of cerebellar function. Usually, the cerebellum is involved in coordinating fine movements, not long range navigation. There may be some other undiscovered ecological or behavioural force in play shaping the brains of these massive animals.ReferenceYopak, K., & Frank, L. (2009). Brain Size and Brain Organization of the Whale Shark, Rhincodon typus, Using Magnetic Resonance Imaging Brain, Behavior and Evolution, 74 (2), 121-142 DOI: 10.1159/000235962Photo by user TANAKA Juuyoh (田中十洋) on Flickr, used under a Creative Commons license.... Read more »
Yopak, K., & Frank, L. (2009) Brain Size and Brain Organization of the Whale Shark, Rhincodon typus, Using Magnetic Resonance Imaging. Brain, Behavior and Evolution, 74(2), 121-142. DOI: 10.1159/000235962
The best cartoon shows – like Rocky and Bullwinkle, ReBoot, or Avatar: The Last Airbender – work on two levels. There’s one layer of meaning that kids pick up on, and another layer that their parents watching beside them pick up on. The same signal has different meanings to different audiences. This new paper by Moosman and colleagues investigates how one signal might do double duty in the animal kingdom.Fireflies (which in this case are beetles rather than flies) light up to attract mates. But this is a conspicuous signals, and a conspicuous signal has its downsides: eavesdroppers can pick up on those signals, and even imitate them to lure in prey. Moosman and colleagues suspected this flashing light had yet a third effect: to be a warning sign.This particular firefly, Photinus pyralis,is thought to have chemical compounds that make it distasteful to come predators. Another firefly, Photuris, eats these smaller Photinus, and gain the same defensive chemical compounds from their prey.In that case, is it possible that predators might come to recognize their flash as a warning colouration, like the bright colours of poison dart frogs or some venomous snakes? This paper ran several tests of this hypothesis.First, the authors confirmed that the three species of insect-eating bats they were examining and fireflies overlapped in both space and time: fireflies were signaling at times and places where bats were flying.Second, they examined a lot of bat poo for traces of firefly remains, and found none. They found plenty of other insects, including others that were firefly sized, suggesting that bats avoided these particular insects.Third, they gave captive bats food pellets containing portions of fireflies. Bats rejected food significantly more often if it contained traces of fireflies.At this point, all this is pretty strong evidence that bats don’t like to eat these bugs. But is it because the bats recognize the flashing light signal? The authors tested this capturing several wild bats, and exposing them to artificial lures that flashed... or not. If the lights were a warning sign in the bat’s mind, you’d predict more attacks on the non-flashing lures than the flashing lures.The behavioural results don’t strongly support the idea. Of the three bats species, only one, Eptesicus fuscus (shown), preferentially attacked the non-flashing lures, and the only the larger, Photuris-sized lures. The authors do point out that E. fuscus is the species that overlaps with the fireflies the most, and thus may be the bat that has the most to gain by recognizing a flash as a danger sign.Another potentially problematic aspect of their experimental design was that they presented the bats not with a natural, intermittent rate set of flashes, but with a super-firefly, continuous set of flashes. This might be okay, because greater stimuli often generate greater responses, but it’s also possible that the unnatural stimulus is getting an unnatural response.Given that only one of the six combinations of three bat species and two sizes of lures showed evidence of flashes being warning signs, this sentence in the conclusion paints the situation with far too wide a brush:In conclusion, bioluminescence of adult fireflies should indeed be considered in the context of a warning signal against bats(.)Although it is often important to show that something can happen, that this happens in only one out of six cases tested raises real questions about whether this does happen with regularity. The authors risk overreaching just a little past the data they have.ReferenceMoosman, Jr, P., Cratsley, C., Lehto, S., & Thomas, H. (2009). Do courtship flashes of fireflies (Coleoptera: Lampyridae) serve as aposematic signals to insectivorous bats? Animal Behaviour DOI: 10.1016/j.anbehav.2009.07.028... Read more »
Moosman, Jr, P., Cratsley, C., Lehto, S., & Thomas, H. (2009) Do courtship flashes of fireflies (Coleoptera: Lampyridae) serve as aposematic signals to insectivorous bats?. Animal Behaviour. DOI: 10.1016/j.anbehav.2009.07.028
As many know, this is the 150th anniversary of the publication of On the Origin of Species. If I may be so bold, one of the things that might distinguish our thinking about evolution in the last 50 years from the first hundred years might be the speed at which natural selection can operate. For a long time, we thought of evolution taking long times: millions of years would be needed to see the gradual accumulation of changes. We learned in the past few decades that we can see the effects of selection over the course of a few decades.
There are a few fast changing situations that press should press the fast forward button on natural selection. Invasions are one. That’s why they’re invasions, not slow expansions. Boronow and Langkilde look at how the invasion of red fire ants are affecting fence lizards.... Read more »
Boronow, K., & Langkilde, T. (2009) Sublethal effects of invasive fire ant venom on a native lizard. Journal of Experimental Zoology Part A: Ecological Genetics and Physiology. DOI: 10.1002/jez.570
This paper on mice evolving a new coat colour has been making a big splash in science news. It’s being touted as a new textbook example of evolution. Actually, not just an example, but an “icon.” I’m not sure what to think about that, given that Icons of Evolution is a notorious creationist book. Plus, the last time someone was touting “it’ll be in all the textbooks” were the promoters of the breathlessly over-hyped Darwinius / Ida fossil.
Reading the technical paper is very frustrating. I hate to say, but I don’t think the story is as complete or as impressive – yet – as the press releases indicate.... Read more »
Linnen, C., Kingsley, E., Jensen, J., & Hoekstra, H. (2009) On the Origin and Spread of an Adaptive Allele in Deer Mice. Science, 325(5944), 1095-1098. DOI: 10.1126/science.1175826
Smell is the oldest and most basic sense. Smell is the detection of external chemicals, which bacteria, without even having neurons (because they are one-celled), are able to do with ease. Taste is a mere spin-off of smell, as it is also about detection of chemicals, just those in a little higher concentrations a little closer to the body.
A new paper by Shah and colleagues blurs the already fuzzy line between small, taste, and even nociception (detection of tissue damaging stimuli). They examined skin cells in the interior of the throats and lungs of humans.... Read more »
Shah, A., Ben-Shahar, Y., Moninger, T., Kline, J., & Welsh, M. (2009) Motile Cilia of Human Airway Epithelia Are Chemosensory. Science, 325(5944), 1131-1134. DOI: 10.1126/science.1173869
Yesterday, I wrote about ankylosaurs’ clubbed tails. Today, I get another new paper on another group of vertebrates to have clubbed tails, the massive armored mammals called glyptodonts. To the best of my knowledge, these two groups may be the only vertebrates to have massive bony clubs on their tails. This paper is also concerned with whether glypotodonts could use their tails as weapons, but takes a decidedly different approach.
Blanco and company are trying to characterize a feature in the glypotodonts’ clubbed tail that we are familiar with in our own clubs: the center of percussion. ... Read more »
R. Ernesto Blanco, Washington W. Jones, & Andrés Rinderknecht. (2009) The sweet spot of a biological hammer: the centre of percussion of glyptodont (Mammalia: Xenarthra) tail clubs. Proceedings of the Roayal Society B. info:/10.1098/rspb.2009.1144
I’m going to dare to step way outside my research expertise on this post, and look at a paper because I love me some dinosaurs. I particularly love ankylosaurs; there’s one within arm's reach in my office. Ankylosaurs are often depicted in art locked in combat with a savage meat eater like Tyrannasaurus rex, mainly relying on its armor, but wielding one massive weapon: a huge bony club at the end of its tail.I was disappointed to learn that the ankylosaurs I had as a kid (and that I still have on my desk) didn’t really exist, but were composites of many different species. Now, will Victoria Arbour destroy another childhood memory with her analysis of whether ankylosaurs could really use their clubbed tails as weapons?The first couple of paragraphs made me quaver in my decision to try understanding this paper. I have no idea what “postzygapophyses” are, except that they’re some part of skeletal anatomy. But I march on to the descriptions of the X-rays slices they did of some skeletons.Arbour estimated of the placement of tail muscles by looking at tendons that fossilized, and using crocodiles as a model. She suggests that the tail could be bent sideways, but says nothing about swinging it up, as is often depicted in art.To figure out the forces the animal might have been able to generate by swinging the tail, Arbour crunches some numbers using estimates of muscle mass, inertia, and so on. Unfortunately for a casual reader like me, the number presented are not linked to anything that I might reasonably be able to relate to. That comes in the discussion, fortunately, where the $64,000 question starts to take shape.: COuld these clubbed tails do damage?For some of the ankylosaurs with small clubs, Arbour argues, probably not. But some of the animals with larger clubs probably could. Since the shear forces needed vary from bone to bone, Arbour suggests future studies might try to quantify the strength of leg bones of meat eating dinosaurs as well as ribs of ankylosaurs. Arbour is more interested in the latter possibility, in fact: she suggests that the size of the clubs is such that juveniles probably did not have very large clubs, which she argues means they are unlikely to be defensive weapons. Instead, she thinks the clubs may have been used in ankylosaur on ankylosaur competition. This may be testable. Recent research on ceratopsian dinosaurs (like Triceratops) showed injuries consistent with the horns being used for competition. If ankylosaurs were clubbing each other, the breaks in the bones should be preserved.So the notion of ankylosaurs using their tails as weapons may not be completely wrong, the hypothesis has taken a bit of a beating here. (Pun fully intended!)ReferenceArbour, V. (2009). Estimating Impact Forces of Tail Club Strikes by Ankylosaurid Dinosaurs PLoS ONE, 4 (8) DOI: 10.1371/journal.pone.0006738... Read more »
Arbour, V. (2009) Estimating Impact Forces of Tail Club Strikes by Ankylosaurid Dinosaurs. PLoS ONE, 4(8). DOI: 10.1371/journal.pone.0006738
Why do animals living in different regions show different behaviours? One possibility is that animals have a big behavioural repertoire, and that they tweak their behaviour to suit the particular conditions they find themselves in. Alternately, animals might be somewhat more stereotyped in their behaviour, and different populations have been selected to perform different behaviours over evolutionary time.
This new paper by Zayasu and Wada looks at this question in a little crab, Ilyoplax pusilla. ... Read more »
Zayasu, Y., & Wada, K. (2009) A translocation experiment explains regional differences in the waving display of the intertidal brachyuran crab Ilyoplax pusilla. Journal of Ethology. DOI: 10.1007/s10164-009-0177-5
Weird things happen when organisms get cut off into small areas. Look at islands. Homo floresiensis, the Flores Island “hobbit,” was a very small human that probably evolved on an island. On the other hand, you’ve also got wetas, which are the biggest crickets you’ll ever see, which also evolved on an island. It seems that big things get small and small things get big on islands. I guess the perfect size for any animal on an island is a rabbit.Ponds and small lakes are also islands. They’re wet instead of dry, but from the point of view of evolution, you have a lot of the same factors that come into play: small populations, sometimes few competitors or predators, and new niches to exploit.This paper looked at evolutionary body size changes in nine-spined stickleback. These hardy fish are sometimes the only fish in small ponds and lakes in their range in northern Europe, but in larger lakes, rivers, and the ocean, they are one among many fishes – often bigger, with large appetites.Although the title refers to “giantism,” giant is a relative thing. The largest fish they found had a length of about 7 cm; palm of the hand kind of size. But when you consider that many other populations where had lengths of about 4 cm, you have to admit that almost twice the size probably counts as giant for that species.Those largest fishes were found in the isolated ponds, as suspected. The pond fish sorted out into two groups. The smallest sticklebacks were in ponds also contained three-spined sticklebacks or trout.When they reared eggs from fish collected from these various ponds in the lab, they found the “giants” were on a completely different growth trajectory almost from the get go. So it did not seem to be the case that the large fish were large just because they were living longer because there were few predators around. Turned out the big ones also lived longer, giving those populations a double whammy to reach their large size. These two points suggest that these size differences are genetically controlled, and thus heritable, and are not due to increased food availability, say, or other environmental effects.The authors rightly refer to the all of their lakes and rivers as “natural experiments.” Still, a natural experiment is still not as clean as a lab experiment, and perhaps there could be some manipulations to test some of the hypotheses coming from their data. And although this paper supports the idea that islands are hotbeds for evolution of body size, it doesn’t seem to help move forward in predicting if a species in isolation is going to get bigger or smaller.ReferenceHerczeg, G., Gonda, A., & Merilä, J. (2009). EVOLUTION OF GIGANTISM IN NINE-SPINED STICKLEBACKS Evolution DOI: 10.1111/j.1558-5646.2009.00781.x... Read more »
Herczeg, G., Gonda, A., & Merilä, J. (2009) EVOLUTION OF GIGANTISM IN NINE-SPINED STICKLEBACKS. Evolution. DOI: 10.1111/j.1558-5646.2009.00781.x
Bowerbirds are one of those fascinating species that you just have to love. The male constructs elaborate structures (bowers) to lure in females, going to great lengths to find just the right pieces. Some say that such structures are analogous to human artwork.This new paper is the first to test an hypothesis that has been around for a few years that general cognitive ability may affect reproductive fitness. Kaegy and colleagues list a few ways that this could happen. Good cognitive skills may:Be indicative of good genes.Allow a parent to be a better provider.Allow one individual to trick another into mating (similar to an idea in this paper).Let one individual to attune courtship and mating behaviour to the desires of a wider variety of partners.Curiously, in three of these four, they list the male as being the one that benefits from good cognitive performance. Why enhanced cognition should be an advantage for males, but not females, in providing for offspring (say) is not at all clear.They tested the bowerbirds’ problem solving ability by exploiting the birds’ colour preferences. Males love having blue objects in their bowers, and they hate having red objects in their bower. The team somewhat evilly conspired to place a bunch of red objects in males’ bowers... but made them rather difficult to remove. In one case, they covered the red objects with a container. Birds had to removed the cover before they could get to the offending red bits. Males differed in how long it took them to solve this task, so there is variability that could be subject to selection. Males who solved the problem faster tended to have more mating success.In the second test, the authors placed three tiles (one blue, one greed, one red) near the bower in a triangle. All were bolted down, so the bird literally could not remove them. The solution is not to take the red objects away, but to cover the red tiles with other materials. Here, the outcome is more complicated. The amount of red tile covered was not correlated to mating success until some statistical jiggery-pokery is done to correct for the males’ age. The position of the red tile in the triangle was also having an influence. The amount the red tile was covered did correlate with mating success, if the tile was in the position closest to the nest.Somewhat strangely, getting a good score on the one test (clear covering) was not correlated with a good score on the second test (bolted objects). Again using some statistical procedures I am not really familiar with, the authors say when both results are considered, that problem solving correlates well with mating success.The females didn’t see any of these males’ mental gymastics, as they rarely visited the bowers.In this species, these results suggest that general cognitive skills are not due just to being a good provider, because since the males’ success was just in getting more copulations, not rearing offspring. It also seems unlikely that cognitive ability is being directly assessed by the females, since they weren’t around to see all this.The discussion returns to a very strangely male-centric point of view. For instance, let me add some emphasis to this quote:One prediction is that species with more intense sexual selection, such as polygynous species, should have enhanced cognitive abilities because of more intense selection for males with better cognitive performance.It seems odd to argue that selection pressure on males specifically. Many of these hypotheses include the notion that females are constantly assessing males – and assessment is a cognitive task, just like problem solving is. You have to remember, compare, and so on. (There are some sections of the paper that are a little more nuanced, but still.) If New Scientist can be chastised for its “geeks get the girls” line on this story, the authors could also do with a little egalitarian editing.Media coverage here and here. I confess to being a bit disappointed because I had planned to blog about this before those articles came out, but I was too slow this time.ReferenceKeagy, J., Savard, J., & Borgia, G. (2009). Male satin bowerbird problem-solving ability predicts mating success Animal Behaviour DOI: 10.1016/j.anbehav.2009.07.011Picture by user bdonald on Flickr and used under a Creative Commons license.... Read more »
Keagy, J., Savard, J., & Borgia, G. (2009) Male satin bowerbird problem-solving ability predicts mating success. Animal Behaviour. DOI: 10.1016/j.anbehav.2009.07.011
ResearchBlogging.orgIt is an obvious fact to most humans that finding a mate is a difficult thing. Now trying doing that without moving.
Of course, this is the problem faced by many plants. Some of the most successful, flowering plants, use animals to overcome this. But the addition of pollinators into the reproductive mix doesn’t change that there are differences in the interests of male and female plants. As in many animals. males are thought to be capable of producing more gametes, so gain greater reproductive success by dispersing as much pollen as possible.... Read more »
Waelti, M., Page, P., Widmer, A., & Schiestl, F. (2009) How to be an attractive male: floral dimorphism and attractiveness to pollinators in a dioecious plant. BMC Evolutionary Biology, 9(1), 190. DOI: 10.1186/1471-2148-9-190
Animals compete in all sorts of way, even right down to the cellular level. Sperm competition became a prominent idea in ethology in the early 1980s, driven by theoretical considerations coming from sociobiology and the technical innovations of early DNA fingerprinting. It’s been long enough that you’d expect some fairly clear generalizations about sperm and genetics in the context of sperm competition, but Mossman and colleagues indicate there’s still work to do.Mossman and colleagues argue that when you look across species and compare them, long sperm are faster – and you’d predict sperm competition would favour fast sperm. When you look within a single species, they claim, the pattern is not so obvious. They decide to look at this in zebra finches (Taeniopygia guttata), a well studied bird.They had a colony of birds in which they knew all the relationships (for the genetics), they got sperm samples to look at the morphology of known individuals, and to measure the speed of the sperm.The measurements of sperm are actually fairly complex. For instance, which sperm do you measure? They measured the speed of all sperm, the top 20%, and the fastest single one they measured. They took all those measures and ran them through stats to get a single value that incorporates information from all three measurements. Similarly, the authors didn’t just measure sperm length, but several features.When you correlate all those features, the longest sperm turn out to be the fastest ones.But in order for either sperm length or speed to be important evolutionarily, it has to be heritable. This involved looking at the relationships of hundreds of birds and linking those with the sperm characteristics they’d examined, and sperm length and speed are very heritable. Of course, since each is correlated with the other, heritability would be a package deal.Nevertheless, as every researcher knows, correlation does not imply causation. Follow-up research might focus on an experimental test of the relationship between sperm length and speed. One way might be to see if breeding experiments, perhaps using an animal that’s a little faster breeding than zebra finches, could generate fast-and slow-swimming strains. There’s also a prediction that males with large, fast-swimming sperm should have a selective advantage over other males if females are able to mate with multiple males. This seems to be true in “domestic fowl,” as the authors put it (I think that means “chickens”), but testing in zebra finches would be a logical thing to do.ReferenceMossman, J., Slate, J., Humphries, S., & Birkhead, T. (2009). SPERM MORPHOLOGY AND VELOCITY ARE GENETICALLY CODETERMINED IN THE ZEBRA FINCH Evolution DOI: 10.1111/j.1558-5646.2009.00753.xPicture by user marj k on Flickr, used under a Creative Commons license.... Read more »
Mossman, J., Slate, J., Humphries, S., & Birkhead, T. (2009) SPERM MORPHOLOGY AND VELOCITY ARE GENETICALLY CODETERMINED IN THE ZEBRA FINCH. Evolution. DOI: 10.1111/j.1558-5646.2009.00753.x
What do you do when you’re trying to get somewhere, and you get conflicting information? The person in the passenger’s seat swears he knows which way to turn, but the GPS unit in your car tells you to go the opposite direction. Problematic. Indeed, possibly relationship-changing depending on who’s in the passenger seat.
Still, humans generally have it easy when it comes to navigating. Our decisions are usually “turn left” or “turn right.” We are close to flatlanders when we are moving around our environment. Animals animals that fly, climb, or swim have to take the vertical dimension into account when getting around much more than humans do.... Read more »
Holbrook, R., & Burt de Perera, T. (2009) Separate encoding of vertical and horizontal components of space during orientation in fish. Animal Behaviour. DOI: 10.1016/j.anbehav.2009.03.021
One of the most famous findings in animal behaviour is that the dance of honeybees in the hive is correlated with the location of their food. The dance depends on the distance of the food, the direction of the food, the quality of the food, and, according to a new paper by Abbot and Dukas, how dangerous the food is.... Read more »
Abbott, K., & Dukas, R. (2009) Honeybees consider flower danger in their waggle dance. Animal Behaviour. DOI: 10.1016/j.anbehav.2009.05.029
You think snakes on a plane are crazy? Bats! On the ground!
Before humans arrived on New Zealand, the only mammals living there were bat species. One of only two remaining native Kiwi mammals is Mystacina tuberculata, the lesser short-tailed bat.
This bat’s second claim to fame is that it walks. Only one other bat, the vampire bat, does this, and vampire bats don’t spend anywhere near the same amount of time on the ground as M. tuberculata does. That there are no other land mammals in New Zealand has been suggested as a reason that these bats are such ground huggers. This was suggested by analogy with birds, which are often flightless on islands that don’t have large predators. Indeed, New Zealand provides an example here with the kakapo, which Douglas Adams famously described as the world’s largest and least able to fly parrot.... Read more »
Hand SJ, Weisbecker V, Beck RMD, Archer M, Godthelp H, Tennyson ADJ, Worthy TH. (2009) Bats that walk: a new evolutionary hypothesis for the terrestrial behaviour of New Zealand's endemic mystacinids. BMC Evolutionary Biology, 169. DOI: 10.1186/1471-2148-9-169
In old Disney comics, Scrooge McDuck would often be shown swimming in his money bin, diving through the coins like an exuberant dolphin. Leading many young minds to wonder, “How does he do that?” Coins don’t move like water; they’re arguably closer to something like dry sand.A new paper shows that one lizard may not be able to get through McDuck’s nine cubic acres of money, but it comes a lot closer than anything else we know about so far. Scincus scincus is a cute little lizard a few winches long, whose common name, “sandfish,” tells you a lot about its behaviour. These lizards dive through sand like Unca Scrooge dives through silver dollars. Previously, people had suspected they paddled though the sand using their legs, much like some fish might use their pectoral fins in addition to their trunk. The problem with testing an hypothesis like this is that sand has this irritating property of being opaque – a problem I had significant personal experience with, I might add. I solved it using wires and recording from muscles.Maladen and colleagues went to high speed X-ray videography. I suspect that they probably spent a long time trying to find a combination of materials with the right combination of transparencies to X-rays, but they did it. And they found that the sandfish might better be described as a sand eel. The swimming that these lizards did (rather fast, about 10 cm per second) was entirely driven by the trunk. The legs were simply held in position and didn’t play a part after the animal got under the sand. There are some fantastic movies of this in the supplemental material.From here, the paper looks into the physics of the situation. To be entirely honest, it’s fairly difficult stuff for me. When they write:It is remarkable that η does not change significantlyfor different φ...I have to take their word for the remarkable nature of those Greek letters. I am rather hoping that some physics blogger out there can walk through the granular materials math in this paper.Maladen and company end by noting that they have helped to show how organisms can exploit the alternately solid-like and fluid-like properties of sand to move through it. And this is indeed a substantial achievement, but what if you turn that around? If animals can do this, why haven’t more done so? To the best of my knowledge, no animals besides other lizards swim through sand like sandfish do. And I doubt that this is due to visibility problems; I think it is just that digging organisms are relatively rare.There is so much nice stuff in this paper that I might forgive them for citing a sand crab digging paper from the 1970s instead of more recent and more detailed articles.ReferenceRyan D. Maladen, Yang Ding, Chen Li, & Daniel I. Goldman (2009). Undulatory Swimming in Sand: Subsurface Locomotion of the Sandfish Lizard Science, 325 (5938), 314-318 DOI: 10.1126/science.1172490Sandfish photo by user thew...g's on Flickr. Used under Creative Commons license.... Read more »
Ryan D. Maladen, Yang Ding, Chen Li, & Daniel I. Goldman. (2009) Undulatory Swimming in Sand: Subsurface Locomotion of the Sandfish Lizard. Science, 325(5938), 314-318. DOI: 10.1126/science.1172490
If you know a little bit about neurons, even really basic stuff, you probably know that neurons send signals with action potentials (a.k.a. spikes). What fewer people know is that there is great diversity in how neurons signal. There are many sensory neurons and interneurons that work entirely without action potentials. I once asked my Ph.D. supervisor, Dorothy Paul, “Is there such a thing as a non-spiking motor neuron?” Dorothy did most of her research working on non-spiking sensory neurons in the west coast mole crab, Emerita analoga. She didn’t give me the answer, but told me it was an excellent question and I should think about it. Some time later, I heard another student asking the same question to another researcher at a poster at a Society for Neuroscience poster, and the person said, “No.”This paper says the answer is, “Yes.” There are non-spiking motor neurons. Qiang Liu and colleagues did their research on the little nematode worm, Caenorhabditis elegans, and were able to take advantage of the huge knowledge of the genetics of this beast, and our ability to manipulate this animal’s genes. They recorded the output of muscle cells using standard electrical recordings, but instead of using electricity to stimulate the motor neurons controlling those muscles – the classical way of doing things – they genetically engineered the worm.The authors were able to make the worms express a protein called channelrhodopsin in certain neurons. Rhodopsin is a visual pigment that responds to light. When you flash a light on these worms (did I mention they’re transparent?), the channelrhodopsin opens up a channel that allows electrical current to flow into the neuron. Thus, you can use a flash of light to fire neurons of your choosing.In neurons with action potentials, activity is like a light switch: flipping the switch harder doesn’t make the light from the bulb any brighter. A key set of data is to increase the light intensity stimulating the motor neurons (shown by different line colours in the figure here), and record the response of the motor neurons. If there was a classic action potential in the motor neuron, you’d expect there to be no response until you hit a threshold, and always the same response in the muscle. But the effect is more like a dimmer than a switch: the greater the light intensity to the motor neurons, the more the muscles responded. This is just what you would as expect for a non-spiking neuron.There rest of this paper revolves around characterizing the synaptic connections between motor neuron and muscle in much more detail. It mainly looks at how the strength of connections between the cells change with repeated stimulation of the motor neurons.This is not the first demonstration of non-spiking motor neurons. Another nematode, Ascaris, probably claimed that honor two decades ago (Stretton and Davis 1989). So while I did learn quite a bit from this paper (I didn’t know about the Ascaris work) and am impressed with the techniques in this paper, I am still a bit puzzled as to why it’s in Proceedings of the National Academy of Science (PNAS). PNAS is one of those exclusive high profile journals, sometimes disparagingly called a “glamour mag,” that publishes on what it considers to be “high impact” science. I guess this paper made it in because C. elegans has become such an important model organism, because this paper doesn’t show any previously unknown or unexpected kind of phenomenon.But considering that the Ascaris work was published before I asked my supervisor about non-spiking motor neurons, I suppose that the phenomenon could stand to be much better known in the neurobiology community.ReferencesLiu, Q., Hollopeter, G., & Jorgensen, E. (2009). Graded synaptic transmission at the Caenorhabditis elegans neuromuscular junction Proceedings of the National Academy of Sciences, 106 (26), 10823-10828 DOI: 10.1073/pnas.0903570106Davis RE, Stretton AO. 1989. Signaling properties of Ascaris motorneurons: graded active responses, graded synaptic transmission, and tonic transmitter release. J Neurosci 9(2):415-425. http://www.jneurosci.org/cgi/content/abstract/9/2/415... Read more »
Liu, Q., Hollopeter, G., & Jorgensen, E. (2009) Graded synaptic transmission at the Caenorhabditis elegans neuromuscular junction. Proceedings of the National Academy of Sciences, 106(26), 10823-10828. DOI: 10.1073/pnas.0903570106
Cleaner fish are undeniably photogenic. They are colourful little fish that much larger fish will sit still for and allow the cleaner to dart all around them, even into the waiting jaws of their “clients,” while the cleaners feast of many small surface parasites. Cleaner fish provide one of the classic examples of mutualism in the animal kingdom, proving that evolution does not always mean bloody competition.How do “client” fish recognize cleaner fish from a quick snack, particularly given that there are many different species of cleaners? Karen Cheney and colleagues tackle the problem not just from many different angles, but from many different lighting conditions.First, they found all cleaner fish had either blue or yellow in their colouration, compared to only about 2/3 of a control group of fishes. They also confirmed a previous finding that all cleaner fish had a long stripe on the side.But why blue and yellow? Is there any particular reason for these particular colours? It is just evolutionary happenstance, where one random colour became established, and later, all the others without it were selected against?Cheney and colleagues hypothesized that these colours are used because they stand out strongly against the background. Demonstrating this is tricky, because what we see as a colour in a nice, brightly lit aquarium is not necessarily what another fish will see in the natural habitat, for several reasons. First, fish may not see colour like we do. Second, water filters out different wavelengths of light, so the colours change as you descend. Third, the major light source is overhead, whereas aquaria let in light from all sides.To test this, they did some computer modeling using the known visual properties of several fish species, and seeing how they responded to different colours in front of an average coral reef background. Blue, of almost any shade, came out as the most conspicuous for all species for fairly long distances. Yellow was particularly conspicuous against black – such as the long black stripes that cleaner fish have. It was also highly conspicuous against blue water, the other major visual element in a coral reef habitat.To top this all off, Cheney and company took some fish models, painted with different colours and patterns, into coral reefs. One was a realistic representation of a local cleaner fish, and the others had some variation of colour pattern. Just knocking out blue from the model significantly dropped the response of client fish (figure shown; click to enlarge). Blue alone is not enough to attract clients, as several models with blue colours in the wrong places fared no better than the blue-less but otherwise realistic models. The ever more radical departures from the realistic colour scheme showed even more declines in client responses, but none of the “duds” were significantly different from each other.The authors suggest that cleaner probably evolved before the conspicuous colouration, which is a sensible hypothesis. Just because something is conspicuous does not guarantee a client’s appropriate response. In fact, it is difficult to imagine a scenario where a highly visible colour preceded the evolution of the cleaning behaviour.This research does a very clean job of examining the signaling end of partnership between cleaner and client. Hopefully, someone will pick up with this on the receiver end, and start examining the sensory capabilities of the client fish that enable them to recognize cleaners and react appropriately to those signals.ReferencesCheney, K., Grutter, A., Blomberg, S., & Marshall, N. (2009). Blue and Yellow Signal Cleaning Behavior in Coral Reef Fishes Current Biology DOI: 10.1016/j.cub.2009.06.028Picture: New Scientist gallery... Read more »
Cheney, K., Grutter, A., Blomberg, S., & Marshall, N. (2009) Blue and Yellow Signal Cleaning Behavior in Coral Reef Fishes. Current Biology. DOI: 10.1016/j.cub.2009.06.028
Some males just don’t know when to quit.When you think of guppies, you probably think of pretty little fish in the pet store. But male guppies are notorious sexual harassers. They are so bad that they don’t even respect species boundaries, the cads! Male guppies will try to mate not only with a different species of guppy, they will try to mate with fish in an entirely different genus.Picky they ain’t.Of course, trying to mate with a female in the wrong genus is unlikely to yield any offspring, so it’s not really worth it for the males to try mating with the wrong genus. So while male guppies have the proverbial “one thing on their brain,” it is to their advantage to use their brain to try to learn which females to stop chasing.In this experiment, Valero and colleagues tested male guppies’ responses to Skiffia bilineata females (pictured below). They had three conditions.In one, two male guppies were put in a tank with female guppies for 2 weeks, then repaired in a new testing tank with either the same, familiar female guppies or new, unfamilar female guppies.In the second, the set up was the same, except the females were Skiffia bilineata.In the third, critical test, males were paired with females of both species, and then repaired with familiar or new females of both species (guppies and Skiffia bilineata). Half the time, the female guppy was new and the Skiffia bilineata) was familiar to the males; the other half of the time, the female guppy was familiar and the Skiffia bilineata) was new.In the tests with two species of females, the males increased the proportion of times they tried to mate with the unfamiliar Skiffia bilineata females. Valero and coauthors suggest this means that the males had learned not to try to mate with females that had previously encountered.When there was only one species, the guppies showed no changes towards females regardless of which species they were and regardless of whether they were familiar or not. The authors suggest that for the males to learn, they have to make a comparison between the different species.Oddly, though, they did not change how often they displayed to those Skiffia bilineata females. Just the attempted copulations changed. This is surprising, as you might expect that learning would generalize across related sexual behaviours. The authors discuss the costs of sexual displays, but as far as I can see, have nothing to add that might explain why displays are unaffected but attempted copulations are.Or maybe it’s just more proof that some males don’t know when to quit.ReferencesValero, A., Magurran, A., & Garcia, C. (2009). Guppy males distinguish between familiar and unfamiliar females of a distantly related species Animal Behaviour DOI: 10.1016/j.anbehav.2009.05.018... Read more »
Valero, A., Magurran, A., & Garcia, C. (2009) Guppy males distinguish between familiar and unfamiliar females of a distantly related species. Animal Behaviour. DOI: 10.1016/j.anbehav.2009.05.018
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