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Brains, behaviour, and evolution.
If ever there was a time to be careful about who you were going to mate with, it would probably be when there was a good chance you were going to die in the attempt.
And we’re not talking about some sort of heroic situation where the male has to endure hardships to get to the female. We’re talking about situations where the female herself is the threat.
“Fair princess, I have arrived to...”
CHOMP. Nom nom nom.
A lot has been written about the cannibalistic tendencies of praying mantises. Indeed, a recent New Scientist article called male mantids “the poster boy of risky sex.” Why the female tend to eat their mates seems to have a lot to do with them being aggressive hunters that pretty much try to eat anything. But we’re more concerned with the males’ response to that behaviour, rather than worrying about what causes it in the first place.
Barry tests the hypothesis that males pick what females to mate with in part by sensing chemical cues that the female gives off. In part, this is a replication of a previous study in the lab in more natural settings.
To give the males something to choose between, Barry split the females into two groups: one got fed three times as much as the other, so you would expect these would be attractive to males for two reasons. First, they should be in better condition, and second, they should be less hungry, and hopefully less likely to strike out at males.
To prevent the males from using visual cues, the females were placed in cages that were covered. Barry also put out empty control cages (which never attracted males). As expected, the males were significantly more likely to end up in cases containing well fed females.
After the males chose, Barry examined the number of eggs in the ovary to determine fecundity. This is a bit tricky, as you would expect that there’s going to be a correlation between feeding and fecundity, which was the case. But, Barry did find that when males did choose the poorly fed females, they picked ones that had mature eggs. When exposed to eggs alone, however, the males never ended up in those cages.
I suppose one question raised here is: How expensive is it to make a pheromone? Insects are famous for being able to detect and respond to small quantities of pheromones; if so, it may not take much to bring in a mate. Does food restriction shut down the chemical pathway, or are the males very sensitive to concentration levels of pheromones?
Barry KL. 2010. Influence of female nutritional status on mating dynamics in a sexually cannibalistic praying mantid Animal Behaviour. 10.1016/j.anbehav.2010.05.024
Photo by cskk on Flickr. Used under a Creative Commons license.... Read more »
Barry KL. (2010) Influence of female nutritional status on mating dynamics in a sexually cannibalistic praying mantid. Animal Behaviour. info:/10.1016/j.anbehav.2010.05.024
Victoria Braithwaite’s Do Fish Feel Pain? is not a technical book. The type is large and the prose is easy to understand.
I had to read this book, because many of the issues around fish pain are the same as those raised for invertebrate pain (Puri and Faulkes 2010; this post). Fish researchers are about five years ahead of the invertebrate researchers.
Braithwaite’s answer to the question posed in her title is...
Spoiler alert! Click the heading of the post to read more.
Her arguments will probably not convince everyone, however.
For Braithwaite, a defining aspect of pain is that pain is a conscious experience. She repeatedly distinguishes pain from nociception on the grounds that nociception is unconscious and reflexive. Her views on these definitions seem idiosyncratic. My impression is that for many researchers, nociception is a description of a behavioural response, with nothing said about consciousness one way or the other.
By recasting that the question of whether fish feel pain into the question of whether fish are conscious, Braithwaite’s arguments become harder to assail, but lose some of their force. Consciousness is a very tricky subject. We don’t have a good scientific theory of human consciousness, let alone animal consciousness.
Given her definition, a large chunk of her book is aimed at proving fish have consciousness; that they are, as she puts it“sentient beings.” For the last bit of evidence she needs to say fish are conscious, sentient beings, Braithwaite draws almost exclusively on one example of cooperative hunting that can occur between individuals in two species, groupers and moray eels. (Irritatingly, this key reference is nowhere to be found in the bibliography! It’s Bshary et al. 2006.)
Now, I realize that a single exciting, detailed story is more compelling than a compilation of statistics. Braithwaite may have chosen to use just a few case studies because this is a popular book. But a lot hinges on those specific examples. And she never says, “This is just one example, but there are loads more I could describe.”
She follows up her chapter on fish consciousness up with a chapter arguing that there is not yet evidence for consciousness in invertebrates. She focuses on the evidence for cephalopods and crustaceans, and I can’t help but wonder if her choices of examples are influenced by those two groups being lumped together with fishes as “seafood.” The strongest evidence of invertebrate nociception there is right now (Tracy et al. 2003) is nowhere to be seen. Similarly, I wonder if Braithwaite considered Portia spiders for evidence of complex cognition in an invertebrate (Wilcox and Jackson 1998). They are very clever wee beasties.
It is a little worrying that the spectacular diversity of fishes and invertebrates doesn’t seem to factor into the argument. If one fish can do it, they must all be able to do it, it seems. The notion that perhaps some fish species might experience pain more than others is never entertained. Again, there’s no way to tell if she just left this out because she wanted to have the broadest appeal or for some other reason.
The book ends with an exploration of applying animal welfare standards more strongly to fishes, and you get the sense that this is what matters most to Braithwaite. She talks about fish harvesting, aquaculture, angling, and more. Considering how degraded so many wild fisheries have become, I do hope that this book gets people to take stock of the way they harvest and use fish.
Another review is here (paywall).
Bshary, R., Hohner, A., Ait-el-Djoudi, K., & Fricke, H. (2006). Interspecific communicative and coordinated hunting between groupers and giant moray eels in the Red Sea PLoS Biology, 4 (12) DOI: 10.1371/journal.pbio.0040431
Brathwaite V. 2010. Do fish feel pain? Oxford University Press: Oxford. ISBN 978-0-19-955120-0
Puri S, Faulkes Z. 2010. Do decapods crustaceans have nociceptors for extreme pH? PLoS ONE 5(4): e10244. DOI: 10.1371/journal.pone.0010244
Tracey Jr., W., Wilson, R., Laurent, G., & Benzer, S. 2003. painless, a Drosophila gene essential for nociception Cell 113(2): 261-273. DOI: 10.1016/S0092-8674(03)00272-1
Wilcox RS & Jackson RR. 1998. Cognitive abilities of araneophagic jumping spiders. In: Animal cognition in nature: 411-434. Balda RP, Pepperberg IM, Kamil AC (eds). San Diego: Academic Press.
Photo by anikaviro on Flickr. Used under a Creative Commons license.... Read more »
Bshary, R., Hohner, A., Ait-el-Djoudi, K., & Fricke, H. (2006) Interspecific communicative and coordinated hunting between groupers and giant moray eels in the Red Sea. PLoS Biology, 4(12). DOI: 10.1371/journal.pbio.0040431
Brathwaite V. (2010) Do fish feel pain?. Oxford University Press, 1-194. info:/978-0-19-955120-0
Tracey Jr., W., Wilson, R., Laurent, G., & Benzer, S. (2003) painless, a Drosophila gene essential for nociception. Cell, 113(2), 261-273. DOI: 10.1016/S0092-8674(03)00272-1
Distinguishing your own species from other species is useful: for one thing, it prevents a lot of potentially embarrassing mating attempts.
“Um. You mean we don’t belong to, er... that is to say... you’re not my species? I am so sorry...”
But how fine a distinction can a species draw? Does it stop at, “You’re not my species,” or can it extend to, “You’re species B, not C or D”? And would species be able to distinguish other species outside of reproduction?
Schuchmann and Siemers tackled these questions by studying the echolocation calls of several related bat species that live in Europe.
Bats use echolocation for, well, location. They are not used in situations where animals are interacting with each other: they are used purely for the bat to get from point A to B without running into trees, and to find food. Even so, the sound that each bat species makes tend to be a little different in pitch. Might one bat species go, “That call is a bit to high to be Rhinolophus euryale, might be Rhinolophus ferrumequinum.”
These, I thought, were very interesting questions. But it wasn’t clear to me how they were going to test it.
The experimental set-up they use reminded me of one that is often used to test the cognitive abilities of babies. Bats, like babies, are easily bored. If you keep presenting the same thing over and over, they stop looking at it. When they detect a change, they react and look towards the new and much more interesting stimulus.
They recorded the echolocation calls of four bat species, and played them back to two (one of them, Rhinolophus euryale, pictured). They kept playing the same call from their own species over and over until the bat stopped responding, then swapped it for a new call.
Bats were very good at detecting when the call switched from their own species to a different species. That isn’t surprising, as it just tells you they can recognize their own species’ calls.
More to the point, when they first habituated the bat to a species different than themselves, and switched the call to yet a third species... the bats were still very good at detecting that difference. So the bats are not reacting with, “Meh. All those other species’ calls all sound alike. Not my species, have a nice day.”
It’s not clear what components of the call the bats are recognizing, although pitch is probably the major one. You could probably do some fun experiments seeing how much you could vary the calls and still have the bats responding. The authors also wonder if these different species might be able to benefit by eavesdropping on other species’s calls. If so, there might be some species that are more worth listening to at some times than others.
P.S. – Dart to the authors for using so many two letter abbreviations for species (Re) instead of writing out species names properly (Rhinolophus euryale)!
Schuchmann M & Siemers B. 2010. Behavioral evidence for community‐wide species discrimination from echolocation calls in bats The American Naturalist 176(1): 72-82. DOI: 10.1086/652993
Photo by by jasja dekker on Flickr. Used under a Creative Commons license.... Read more »
Schuchmann M, & Siemers B. (2010) Behavioral evidence for community‐wide species discrimination from echolocation calls in bats. The American Naturalist, 176(1), 72-82. DOI: 10.1086/652993
African rift lake cichlids are among the most famous subjects for the study of evolution. The rift lakes formed recently in geological time, but the cichlids that got in have radiated into a dazzling array of species in short order.
But there are cichlids and other similar recent geological events in the Americas, too, just as interesting!
This research by Elmer and colleagues takes advantage of a lake made by volcanic activity, in Nicaragua. The lake appears to have been formed about 1,800 years ago.
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This crater lake has been colonized by Midas cichlids and a few other fishes. The researchers have done a lot of DNA work here, and based on it, they think the Midas cichlids only got into the lake in the last hundred years or so. This population differs in several respects from the cichlids in the nearest neighbouring lakes.
There are two types of Midas cichlids in this lake: there's a common thin-lipped type (pretty sure this is what's pictured here), and a rarer thick lipped type. This difference in appearance is correlated with diet: the common thin-lipped guys have algae, fish and snails in their stomachs, while the thick-lipped one have arthropods.
Elmer and company argue that this could be a case of incipient speciation here. This is an attractive possibility, given that they seem to have two morphs that have different diets, which could leads to different ecological niches, which could lead to reproductive isolation. While plausible, they could not find any genetic distinction between the nuclear or mitochondrial genes between the two morphs (though they commit the crime of "but it's almost significant" for the mitochondrial DNA).
What needs to happen next? Someone needs to make this lake the focus of a career, and start documenting the populations year in, year out, much like Peter and Rosemary Grant did for the Galapagos finches. There need to be behavioural tests to see if fat-lipped females like fat-lipped males more than thin-lipped ones. There need to be ecological studies to see if these animals are inhabiting different locations in the lake.
If this population truly is this young, we have a great chance to watch speciation happen in front of our eyes.
Elmer, K., Lehtonen, T., Kautt, A., Harrod, C., & Meyer, A. (2010). Rapid sympatric ecological differentiation of crater lake cichlid fishes within historic times BMC Biology, 8 (1) DOI: 10.1186/1741-7007-8-60
Midas cichlid picture by Just Chaos on Flickr. Used under a Creative Commons license.... Read more »
Elmer, K., Lehtonen, T., Kautt, A., Harrod, C., & Meyer, A. (2010) Rapid sympatric ecological differentiation of crater lake cichlid fishes within historic times. BMC Biology, 8(1), 60. DOI: 10.1186/1741-7007-8-60
Making a clear visual signal is tricky. Consider this traffic signal:
(I totally thought I was going to have to photoshop a stop sign, but no.)
Whether this signal is effective depends on a lot of factors. What's the visual environment like? Some colours stand out better in some lighting conditions than others.
More critically for this discussion, what’s the experience of the person the signal is aimed at? And I mean the term broadly. Is the person colour blind? Has the person grown up in a place with blue stop signs everywhere?
Fuller and colleagues are interested in this question of colour signal, and are studying it in bluefin killifish (Lucania goodei). These fish live in lots of different habitats, ranging from water that is very clear, letting in lots of short-wavelength blue and ultraviolet light, to water that they describe as “tea-stained.” (In one of their experiments, they actually dump instant tea into an aquarium to make the water the right colour.)
The fish are quite brightly coloured, and the males vary in their colours. Fuller and company are trying to work out what factors influence those colours. Is it purely the physics of the environment – certain colours are just more visible in particular light regimes? Is it an innate preference of other fish (mainly females) that matter? Do all the ladies love red fins, say? Or do fish reared in a certain light environment develop a preference for one colour?
Rather than trying to sort this out one at a time, the researchers embarked on carrying out one of the most complicated experimental designs I’ve seen in a long time. Four genetic crosses of parents, two rearing environments, and two testing environments... 16 combinations of variables right there. They measured both the visual pigments expressed by the fish and a feeding-related behaviour: the tendency of the fish to pick at small coloured discs.
That’s not going to be easy to summarize, but let me try.
Visual pigments were affected by the environment the fish were raised in (i.e., clear or tea coloured).
Pecking was also affected by the environment: the fish were raised in; fish raised in clear water liked the yellow more than those raised in tea-stained water.
You’re probably thinking, “A-ha! The changes in the visual pigments explain the differences in behaviour!” Surprisingly, no. The differences in visual pigment expression explained a paltry 3% of the behavioural variation. The important changes are probably hidden somewhere in the visual centers of the brain.
There were also some effects of the setting the fish were tested in, which interacted with the rearing conditions. The authors say that the interactions between where the fish were raised and where the fish were tested is the “unique finding of this study” that is “striking.”
But there’s a problem for the reader in figuring this out. Here’s the graph they present plotting the behaviour (their Figure 5). Look for the open diamonds and the crosses.
That’s right: There aren’t any in the plotted data. D’oh! It snuck past the reviewers, editors, and proofreading authors! (Caveat: Hurricane Alex has curtailed my access to the paper, and it’s possible that the final version has been fixed.)
Of course, one of the problems with this experiment is that while part of the avowed reason for doing it is to explain mate choices, they didn’t measure mating preferences. I’m sure that’s coming. But you need these data on non-sexual stimuli to tell you whether females like certain colours all the time or just for mating.
For instance, human females are often thought to prefer pink. But will that enhance the dating opportunities for this man?
Fuller, R., Noa, L., & Strellner, R. (2010). Teasing Apart the Many Effects of Lighting Environment on Opsin Expression and Foraging Preference in Bluefin Killifish The American Naturalist 176(1): 1-13. DOI: 10.1086/652994
Stop sign ohoto by Chris Pirillo on Flickr. Man with cat by aBbYhaLO on Flickr. Both used under a Creative Commons license.... Read more »
Fuller, R., Noa, L., & Strellner, R. (2010) Teasing Apart the Many Effects of Lighting Environment on Opsin Expression and Foraging Preference in Bluefin Killifish. The American Naturalist, 176(1), 1-13. DOI: 10.1086/652994
Bermuda. Famous for its sun. Sand. Surf. Shorts. Triangles. Lizards.
Okay, maybe not the lizards. Not yet.
Islands and lakes hold a special place in the heart of evolutionary biologists (here’s a few examples from this blog: sticklebacks, crickets). As Jerry Coyne likes to say, island biogeography provides evidence for evolution so strong that most creationists simply ignore it.
View Larger Map
Bermuda formed about two million years ago. It’s small and a long way from the mainland, and has almost certainly never been connected to any other landmass. That Bermuda appeared very recently (in geologic terms) and that it is so far away from potentially invasive populations means that anything that lives only in Bermuda has probably evolved pretty darn fast.
Plestiodon longirostris is a skink that is found on Bermuda and nowhere else on earth. There aren’t many animal species living on this island at all, which is not surprising, given how remote it is. There are, however, other members of the genus, many of which live on the mainland of North America.
We’ve gotten fairly good at using DNA to generate hypotheses about relationships between species, and, to a lesser degree, the time of divergence. Using that, Brandley and company found that Plestiodon longirostris split from its closest relatives...
How old would you expect the Bermuda skink lineage to be? “Well, the island’s only two million years old, so it's got to be younger than that.”
That's a perfectly sensible answer. But wrong.
Brandley and company estimate that this lizard split from its relatives about 16 million years ago. This means that the line leading to this particular skink diverged way, way before Bermuda formed.
These data don’t, alas, give many clues to when the skink’s ancestors got to the island, or how. Nor do we know how its relatives on the mainland went extinct. But what it does say is that islands are not only important centers for evolutionary experimentation, they can also act as centers for preservation. Or, as the authors put it, islands can be a “life raft” for species that make it to their shores.
Brandley, M., Wang, Y., Guo, X., Nieto Montes de Oca, A., Fería Ortíz, M., Hikida, T., & Ota, H. (2010). Bermuda as an evolutionary life raft for an ancient lineage of endangered Lizards PLoS ONE, 5 (6) DOI: 10.1371/journal.pone.0011375
Lizard picture from here.... Read more »
Brandley, M., Wang, Y., Guo, X., Nieto Montes de Oca, A., Fería Ortíz, M., Hikida, T., & Ota, H. (2010) Bermuda as an evolutionary life raft for an ancient lineage of endangered Lizards. PLoS ONE, 5(6). DOI: 10.1371/journal.pone.0011375
You don't have to read this. You could stop at any time. Couldn't you?
Everyone is going to say "Yes" to that question. We love to think that we are masters of our fate, captains of our destiny, our choices are ours alone. That notion is crucial to the ethical concept of agency, legal matters of intent, and much more.
But I'm sure everyone has had a moment like in video below. It starts at 1:58 and runs to 3:00:
It's that moment where you stop yourself, and go, "What am I doing?"
We don't always know why we do what we do. This idea probably got its biggest push from Sigmund Freud. Freud has a lot to answer for, because so much of his psychology is wrong, but his notions about the unconscious were revolutionary . Two articles have recently appeared that both lend support, in broad strokes, to the important of unconscious decisions.
I'll start with the empirical, by Falk and colleagues, who looked at what happens in the brain when you try to persuade somebody of something. They took a bunch of volunteers, and tried to get them to use sunscreen every day. This research was done in sunny California, so it's relevant for the people there.
I'm not sure that was the exact material they used, but you get the idea.
While showing their educational material to 20 subjects, the authors took fMRI brain scans, paying particular attention to the medial prefrontal cortex. Falk and company also asked their subjects if they planned to used more sunscreen.
After a week, they asked the subjects back, and checked on their sunscreen use.
What people said they were going to do was not significantly correlated with what they did do. This might be called the "New Year's effect."
The fMRI signal in the medial prefrontal cortex (remember, taken beforehand) was significantly correlated with what people actually did. The brain scan was a better predictor of actual behaviour than people's own statements about their intentions.
The researcher do note that they are taking the subject's word that she or he used sunscreen. They argue, though, that people would probably tend to report using sunscreen consistent with their stated intention, so if anything, the relationship between the initial intention and sunscreen use - which was not significant in the first place - was inflated.
The brain scan explains about 25% of the behavioral variation, so the effect is not huge. But still, this experiment is important is that it's part of a larger emerging enterprise that chips away at the notion that our conscious decisions cause, or are independent of, neural activity. You can't argue that very well when the neural activity precedes conscious decision and predicts it better.
Along these lines, a new review by Custers and Aarts argues that everything a human being need to create and act towards a goal can all occur unconsciously. This paper deal more with psychology than neuroscience. Interestingly, it seems to suggest that subliminal messages - once oversold, now largely ignored - can have some effects on behaviour under some circumstances.
Falk, E., Berkman, E., Mann, T., Harrison, B., & Lieberman, M. (2010). Predicting Persuasion-Induced Behavior Change from the Brain Journal of Neuroscience, 30 (25), 8421-8424 DOI: 10.1523/JNEUROSCI.0063-10.2010
Custers, R., & Aarts, H. (2010). The Unconscious Will: How the Pursuit of Goals Operates Outside of Conscious Awareness Science, 329 (5987), 47-50 DOI: 10.1126/science.1188595... Read more »
Falk, E., Berkman, E., Mann, T., Harrison, B., & Lieberman, M. (2010) Predicting Persuasion-Induced Behavior Change from the Brain. Journal of Neuroscience, 30(25), 8421-8424. DOI: 10.1523/JNEUROSCI.0063-10.2010
Custers, R., & Aarts, H. (2010) The Unconscious Will: How the Pursuit of Goals Operates Outside of Conscious Awareness. Science, 329(5987), 47-50. DOI: 10.1126/science.1188595
The world is different for small animals and big animals. J.B.S. Haldane said it best:
To the mouse and any smaller animal (gravity) presents practically no dangers. You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes.
What does scale mean for neurons? As an animal gets bigger, it’s going to take longer for neural signals to get from one part of the animal to another – all other things being equal. But, typically, not all things are equal. You can speed up how fast a signal travels down the length of a neuron by making that neuron larger. just like water current can flow faster through a bigger pipe, an electrical current can flow faster down a larger axon.
There’s more going on in this paper by More and colleagues (so it’s literally More going on), but that gives you a starting point for the rationale here. If you take the teensiest mammal you can find, and one of the biggest mammals you can find, how different are those axons, and how fast they can send their signals, going to be?
To test this, they did neurophysiology and neuroanatomy on the neurons of a least shrew and an Asian elephant. These two animals are about as different in size as mammals can get. The shrew’s mass measures in milligrams, and the elephant’s measures in megagrams – tonnes!
But because you don’t want to draw a line using only two data points, they also went into the existing literature for mammalian neuroanatomy, and got equivalent measures for about nine other species of mammals.
The axon sizes scaled – bigger animals had bigger axons – but much, much less than the animal’s size. I mentioned mass before, but the more relevant, though less impressive, measure is going to be distance. An elephant’s is about 100 times longer than a shrew’s, but the elephant’s axons are only about twice as big. That’s about as close to scale-free a relationship in biology as you’re likely to find.
Okay, the neurons may be about the same size, but maybe there’s some other mechanism that might make the actual speed of the signals a better match to the animals’s proportions. Nope. A similar story held when they stimulated the nerves electrically and measuring the delay to the muscle twitch.
All of this means that big animals are going to be slower to detect and react to the world around them. It’s a real cost to being massive, which are no doubt compensated for by other factors. Like being able to sit anywhere you want.
Unfortunately, More and company point out that all this means that dinosaurs and other large creatures probably weren’t as as agile as they are often portrayed.
More, Heather L., Hutchinson, John R., Collins, David F., Weber, Douglas J., Aung, Steven K. H., & Donelan, J. Maxwell (2010). Scaling of sensorimotor control in terrestrial mammals Proceedings of the Royal Society B: Biological Sciences : 10.1098/rspb.2010.0898... Read more »
More, Heather L., Hutchinson, John R., Collins, David F., Weber, Douglas J., Aung, Steven K. H., & Donelan, J. Maxwell. (2010) Scaling of sensorimotor control in terrestrial mammals. Proceedings of the Royal Society B: Biological Sciences. info:/10.1098/rspb.2010.0898
Joshua Ward thinks scientists have to embrace social media.
Okay. As a blogger, someone on Twitter, and so on, I guess I can’t disagree with that.
But almost didn’t get to that point, because I just about did a spit-take when I read:
In the face of basic scientist shortages in many of the leading fields(...)
Shortage? What shortage? I rarely read about institutions unable to find good people. I read a lot about institutions with bona fide research positions that are swamped by applications.
Creating many high quality job opportunities is what will convince students to enter a scientific career, not having a Facebook page.
Ward, J. (2010). Recruiting future talent in ecology and evolutionary biology Trends in Ecology & Evolution. DOI: 10.1016/j.tree.2010.06.002... Read more »
Ward, J. (2010) Recruiting future talent in ecology and evolutionary biology. Trends in Ecology . DOI: 10.1016/j.tree.2010.06.002
How does one species get a bigger brain than another?
A while ago, I wrote about a paper that argued that genes that define boundaries in the nervous system seemed to be responsible for differing brain structures in cichlid fish. This seemed to explain the data better than a competing hypothesis, which was that the differences in brain size were caused by the length of time the brain spent forming neurons (neurogenesis). A forthcoming paper by Charvet and Striedter suggest a third possibility.
Bobwhite quails (pictured) have kind of small brains. But that’s okay, because they’re kind of small birds; they’re smaller than a chicken.
But despite the chicken having a bigger brain, the chicken goes from fertilization to hatching faster than the bobwhite quail.
Proportionately, both the quail and chicken start neurogenesis at about the same time. The chicken has a slight edge, but the extra 5% of time the chicken spends doing neurogenesis isn’t enough to explain that the chicken’s brain ends up being 100% bigger than the quail’s. When neurogenesis starts, the chicken’s brain is already 100-200% bigger than the quail’.
Before neurons form, the chicken’s cells are diving great guns. The whole cell cycle, everything mitosis related, is ramped up and going at a much faster clip in chicken than quail. They tested this using bromodeoxyuridine (BrdU), a chemical that cells incorporate into themselves if they’re actively dividing. The more a cell divides, the more BrdU it takes in. They couldn’t test all the way through development, but at around 11% development, chicken are showing cell division going about 100% faster than quail. After neurogenesis begins, though, that difference is almost nil.
To sum up: The chicken makes a mess of cells real fast, real early.
The other two mechanisms are more about changing the relative proportions of regions within a brain: enlarging over here, shrinking over there. This mechanism allows you to make brains that are different sizes, but that are otherwise structurally similar.
The unanswered question, though, is why do chickens need such large brains?
Ever wonder what chickens do when you’re not looking?
Charvet, C., & Striedter, G. (2010). Bigger brains cycle faster before neurogenesis begins: A comparison of brain development between chickens and bobwhite quail Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2010.0811
Photo by leshoward on Flickr, used under a Creative Commons license.... Read more »
Charvet, C., & Striedter, G. (2010) Bigger brains cycle faster before neurogenesis begins: A comparison of brain development between chickens and bobwhite quail. Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2010.0811
Sometimes, the scientific literature sucks at getting information to you.
I was looking at the table of contents of a new issue of The Journal of Crustacean Biology and saw an article about how to photograph soft-bodied crustaceans. Hm, I wonder why photographing soft-bodied crustaceans is difficult, I thought.
And the abstract mentioned software to deal with short focal planes by merging several pictures. The software is Helicon Focus.
Yes, I should be happy that I have found something useful, but... dagnabbit, why didn’t I know about this years ago?
For instance, here’s part of Figure 3 from a paper a few years back (Espinoza et al. 2006) on the left, compared to a new picture processed with Helicon Focus (click to enlarge).
These are neurons stained through a technique called backfilling. The best backfills are really superb, and you can see a lot of detail. But they’re often in thick tissue, and neurons go all over the place through it, making it hard to see all the relevant detail. The way people usually got around this was to get a camera lucida attached to a drawing tube through a microscope, then trace the axons as you focused up and down.
I was actually very pleased with the pictures in Figure 3 as published, which had dark cells against a very clear background. But the one shown here on the left shows the problem of getting all the relevant detail in the shot. The cell bodies on the right are okay, but the ones down a little deeper in the ganglion on the left and their axons are already blurring out.
The processed version on the right is better.
Having played with this a bit, sometimes there are things you can see in the individual frames that do get lost in the processed version. The biggest problem is when there is some detail underneath something else. You can often see it under the scope and in the individual frames, but not so well in the composite image.
This was so startling and so useful to me, I briefly entertained the thought of trying to turn this into a neuroscience methods paper. Then I looked and found short references that it had been used in the invertebrate neurobiology literature a couple of years ago (Scanell et al. 2008) in a journal I read. D’oh! Another shrewd Faulkes scheme bites the dust.
But at least I can spread the word through a blog post. A slightly more recent paper by Berejnov and company (2009) has nothing whatsoever to do with biology, but gives a better example of what you might get from this kind of software.
As I was writing this, I read an interview with Neil Gaiman, where he said this, mostly in relation to book publishing in particular genres:
Information used to be gold: hard to find, expensive, the equivalent of going off into the desert and coming back with a perfect lump of gold. Now, it’s the equivalent of going off into the jungle, in which there is information everywhere and what you are trying to find is the piece that is useful, while ignoring the noise.
I do wish the process of finding useful things was a little less jungle-like.
Berejnov, V., Sinton, D., & Djilali, N. (2010). Structure of porous electrodes in polymer electrolyte membrane fuel cells: An optical reconstruction technique Journal of Power Sources 195 (7), 1936-1939. DOI: 10.1016/j.jpowsour.2009.10.050
Espinoza SY, Breen L, Varghese N, Faulkes Z. 2006. Loss of escape-related giant neurons in a spiny lobster, Panulirus argus. The Biological Bulletin 211: 223-231. http://www.biolbull.org/cgi/content/abstract/211/3/223
Hegna, T. (2010). Photography of Soft-Bodied Crustaceans via Drying, Whitening, and Splicing Journal of Crustacean Biology 30(3): 351-356. DOI: 10.1651/09-3253.1
Scannell, E., Dell'Ova, C., Quinlan, E., Murphy, A., & Kleckner, N. (2008). Pharmacology of ionotropic and metabotropic glutamate receptors on neurons involved in feeding behavior in the pond snail, Helisoma trivolvis Journal of Experimental Biology 211(5): 824-833. DOI: 10.1242/jeb.011866... Read more »
Berejnov, V., Sinton, D., & Djilali, N. (2010) Structure of porous electrodes in polymer electrolyte membrane fuel cells: An optical reconstruction technique. Journal of Power Sources, 195(7), 1936-1939. DOI: 10.1016/j.jpowsour.2009.10.050
Hegna, T. (2010) Photography of Soft-Bodied Crustaceans via Drying, Whitening, and Splicing. Journal of Crustacean Biology, 30(3), 351-356. DOI: 10.1651/09-3253.1
Scannell, E., Dell'Ova, C., Quinlan, E., Murphy, A., & Kleckner, N. (2008) Pharmacology of ionotropic and metabotropic glutamate receptors on neurons involved in feeding behavior in the pond snail, Helisoma trivolvis. Journal of Experimental Biology, 211(5), 824-833. DOI: 10.1242/jeb.011866
A bite from a Komodo dragon would take you down. They have large teeth that are very sharp. And their salivary glands secrete venom.
For a long time, people sort of overlooked those two factors. The teeth were obvious, but the venom wasn’t. Instead, people suggested that one of the ways that the slow moving monitor lizards were able to take down large prey was because their mouths contained so many bacteria, that the bitten prey animal got infected, quite quickly, and went down from the bacteria.
The discovery of venom seemed to put the kibosh on that particular story – the prey die too fast for bacteria to be the cause of death. But it doesn’t change the fact that the mouths of Komodo dragons are loaded up with very nasty bacteria.
Bull and colleagues take a totally different approach to this question. Rather than asking what the bacteria do for the Komodo dragons, they ask what the Komodo dragons do for the bacteria.
They hypothesize that the way to view the relationship is using a disease model. Bacteria are spreading from dragon to dragon in an epidemic fashion. The bacteria spread from dragon to dragon by growing on the large kills that dragons make, which are often fed on by several different individuals. The dragons’ prey almost becomes an intermediate host; a means of spreading from dragon to dragon.
They are not suggesting that the bacteria are harming the Komodo dragons or causing them to become sick, which seems a bit of a strange bending of the word “disease,” but at least they warn us.
It’s an interesting way of looking at the problem. There’s no experimental evidence presented here that it allows you to make better predictions about the bacteria or the dragons, though.
The birth of dragons
Bull, J., Jessop, T., & Whiteley, M. (2010). Deathly Drool: Evolutionary and Ecological Basis of Septic Bacteria in Komodo Dragon Mouths PLoS ONE: 5(6): e11097. DOI: 10.1371/journal.pone.0011097... Read more »
Bull, J., Jessop, T., & Whiteley, M. (2010) Deathly Drool: Evolutionary and Ecological Basis of Septic Bacteria in Komodo Dragon Mouths. PLoS ONE, 5(6). DOI: 10.1371/journal.pone.0011097
You might expect a paper whose title starts with “Neural control” to include neurons.
This new paper by Liden and collegues doesn’t. It’s straight behaviour paper in the style of classic neuroethology. It starts by explicitly trying to tie itself to a hot new field: neuroeconomics. Neuroeconomics is about value assessment and decision making in humans. In many cases, this means doing brains scans of people while they play with experimenter’s money.
Liden and company argue that humans are far too complicated (which is true), and the way to go about understanding how you make decisions is by looking at an escape system. Escape systems are reasonably simple in terms of neurons, and they definitely control a decision: Fight or flight? Or, in the case of crayfish, freeze or tailflip?
When crayfish see a large dark object looming over them, they can freeze, or perform an escape tailflip. The experimenters put crayfish in a tank, and passed shadows over them. They did record from the giant pair of escape neurons that trigger visual escape responses, but they way they used those recordings was as a marker for whether an escape tailflip occurred.
Not surprisingly, when you change the stimulus the crayfish gets, the behaviour changes. Speed the shadow up, and the crayfish is more likely to freeze. But if the crayfish does tailflip, it “decides” to do so in less time.
The big finding that has the authors tooting the neuroeconomics horn is that if you put a strong smell of food in the water, the animal is more likely to freeze than if there’s very little smell of food. This, the researchers argue, means that the crayfish moderating the use of its escape behaviour due to the presence of the food, because the escape would be costly in that it would take the animal away from the food it wants.
But. This effect happens only at one of two shadow speeds that they tested. The effect does not appear to be very robust.
There are two problems with integrating this sort of study into the fold of neuroeconomics: The neurons and the economics.
As for the neurons, the title of this paper implies that it’s found how these neurons make decisions, but this paper suggests what to look for. It doesn’t give new discoveries at the neuronal level. There are no new neurons or synapses or neurotransmitters described here.
And the search isn’t going to be easy. The main neurons that make the escape decision in these cases are medial giant (MG) neurons. While the MG axons are well known, the bit where all the interesting integration is going on – the place where sensory neurons and interneurons are connecting with the MGs – are nearly a complete mystery, tucked away inside the crayfish’s brain. A while ago, I went looking in the scientific literature for any good picture or diagram of the MG cell bodies and dendrites in the brain – and came up empty handed.
I’m glad that the authors are working with the MG-mediated escape responses; they’re overdue for attention. But make no mistake, the low level of information about them is a bug, not a feature, for crayfish escape as a neuroeconomics model.
As for the economics, it seems difficult to assign values in this situation. Human economics is pretty easy: $20 is better than $10, but not as good as $50. Having a standardized interval scale makes some of the most interesting neuroeconomics research possible.
But what is the value of the smell of food? What is the cost of tailflipping? An escape tailflip is very brief, and it doesn’t take the animal very far from the food. The authors point out that crayfish who win fights gain access to food – which is true – to argue how important food resources are to crayfish. What they don’t mention is that will crayfish fight in the complete absence of food or any other resource. The advantages that crayfish gain through fighting are subtle enough that it took several decades of research before people figured out that there were any resource advantages gained by winning fights.
It’s also worth noting that these experiments are very similar to some theoretical models about the regulation of crayfish behaviour. Don Edwards (a former supervisor of senior author Jens Herberholz) wrote a paper discussing how a crayfish might choose between different behaviours (getting food, escaping a predator) back in 1991. The results of that computer model feel very much like the results presented here.
Indeed, thinking back to the 1990s, there were a lot of important papers on how crayfish escape responses were modulated via changes to the lateral giant (LG) interneuron circuit (e.g., Yeh et al. 1996). The changes were caused by social interactions, so this was pitched as a model for... human aggression!
All these little moments of “spin” in this paper seem to have carried through to how the paper has been promoted. This press release, from the interesting (albeit sometimes dodgy) Science Direct is a testament to good marketing. There’s another press release here. Here’s a snippet from one:
(A) new line of research that may help unravel the cellular brain activity involved in human decisions.
Yeah, and if I don’t clean out my fridge, I may help develop a new antibiotic.
This is good research. But to say that it’s going to help us understand human decision making? Not yet. Not by a long shot.
P.S. – I have to bust the authors and reviewers’ and editor’s chops for letting this get into the paper:
(D)ifferences were not statistically significant although only marginally(.)
A p value is either significant, or it is not. It is not legitimate to treat the p value as some sort of direct indication of the “reality” or the size of an effect; see Schmidt (2010) for more.
Shameless self-promotion! For those who might want more information on the crayfish escape system, I wrote a review on this, focusing on the evolution and diversity of the behaviour and the underlying neurons responsible for it (Faulkes 2008).
Edwards DH. 1991. Mutual inhibition among neural command systems as a possible mechanism for behavioral choice in crayfish. The Journal of Neuroscience 11: 1210-1223. http://www.jneurosci.org/cgi/content/abstract/11/5/1210
Faulkes Z. 2008. Turning loss into opportunity: The key deletion of an escape circuit in decapod crustaceans. Brain, Behavior and Evolution 72(4): 351-361. http://dx.doi.org/10.1159/000171488
Liden, William H., Phillips, Mary L., & Herberholz, Jens (2010). Neural control of behavioural choice in juvenile crayfish Proceedings of the Royal Society B: In press. 10.1098/rspb.2010.1000
... Read more »
Liden, William H., Phillips, Mary L., & Herberholz, Jens. (2010) Neural control of behavioural choice in juvenile crayfish. Proceedings of the Royal Society B. info:/10.1098/rspb.2010.1000
Yeh, S., Fricke, R., & Edwards, D. (1996) The Effect of Social Experience on Serotonergic Modulation of the Escape Circuit of Crayfish. Science, 271(5247), 366-369. DOI: 10.1126/science.271.5247.366
Now this is wild:
It’s a fish. It jumps.
This picture was not taken in an aquarium filled with water; it’s in air.
The fish is a blenny, Alticus arnoldorum, and a new paper introduced me to this fish that barely deserves to be called a fish. According to the author, Shi-Tong Hsieh, this fish spends so much time on land that it actively defends territory on land. It can stay out of water indefinitely, as long as it stays moist.
That blows my mind.
Hsieh was interested how blennies were able to be so agile on land, so he recorded high speed video of several species and did detailed analysis of the movement. The leaping blenny above is the most active on land.
The big finding is that these terrestrial blennies are able to rotate their tail. That it, they can move it clockwise or counterclockwise relative to the axis of their bodies, not simply move it back and forth. When these fish jump, they are pushing off with the side of their tails, not the bottom.
The terrestrial blennies are able to jump about twice as far as their aquatic relatives, which can’t twist the tail. Although there isn’t enough evidence to say that this ability to rotate the tail caused the performance increase, it certainly is mighty suspicious.
Hsieh suggests that this jumping behaviour may be related to C-starts, which are fish escape responses I’ve mentioned before here and here. This would be tricky to test: the neurons are huge, but active behaviours like jumping make it difficult to record the activity.
An easier follow-up would probably be to start looking closely at the musculature and innervation of these terrestrial blennies to figure out exactly what has changed in the skeleton and / or muscles that allow them to do the twist.
Hsieh, Shi-Tong Tonia (2010). A Locomotor Innovation Enables Water-Land Transition in a Marine Fish PLoS ONE, 5 (6) : 10.1371/journal.pone.0011197... Read more »
Hsieh, Shi-Tong Tonia. (2010) A Locomotor Innovation Enables Water-Land Transition in a Marine Fish. PLoS ONE, 5(6). info:/10.1371/journal.pone.0011197
I saw this and could think of nothing but the alien from the movie Predator.
This is a frontal view of the head of a male Branchinecta brushi. This species of fairy shrimp is interesting in several ways. First, it is a species new to science, having just been described in a paper last week.
Second, this is one of the two highest crustacean species on the planet. There is one other crustacean found in the same pools that B. brushi is found in.
I also have to give this paper credit for the best opening line for a Materials and Methods section I may have ever read:
Dr. Charles F. Brush collected our specimens on 13 December 1988 during a successful bid to break the world record for high altitude SCUBA diving.
And yes, the species was named after the record holder who discovered and collected them.
The location of this successful world record bid was Cerro Paniri, a mountain in Chile. This image of the crater pond where this species was found gives a sense of what you have to do to break a world record in altitude, either for SCUBA or finding new species:
That’s 5,946 metres above sea level. This means crustaceans in these kinds of environments tend to have eggs that encyst, and can remain dormant for long periods until water returns, or be taken up and dispersed by birds. That this is particular species reproduces sexually also suggests that several cysts were introduced to the area by birds.
What’s slightly nerve wracking is that, as you can imagine, pools like this tend to come and go. This particular species is known only from the one collection in the one pool, and the authors suggest it might have evolved and speciated only in that pool. That makes it a good thing that it’s so high up, humans are unlikely to mess with it.
Hegna, T., & Lazo-Wasem, E. (2010). Branchinecta brushi n. sp. (Branchiopoda: Anostraca: Branchinectidae) from a Volcanic Crater in Northern Chile (Antofagasta Province): A New Altitude Record for Crustaceans Journal of Crustacean Biology 30(3): 445-464 DOI: 10.1651/09-3236.1... Read more »
Hegna, T., & Lazo-Wasem, E. (2010) Branchinecta brushi n. sp. (Branchiopoda: Anostraca: Branchinectidae) from a Volcanic Crater in Northern Chile (Antofagasta Province): A New Altitude Record for Crustaceans. Journal of Crustacean Biology, 30(3), 445-464. DOI: 10.1651/09-3236.1
The problem with writing about sea slug colouration is that they are so spectacular, so lovely, that you are tempted to turn the whole post into a photo gallery just to show off the pictures.
The bright colours are not there for just the benefit of lucky SCUBA divers. As I've noted before, sea slugs mollusks are perhaps the most appealing targets imaginable for a predator. When your entire body plan is essentially a predator’s “meals on wheels,” you might think the last thing you would want to do would be to draw attention to yourself.
Except that seas slugs are not as helpless as they might seem. They use chemicals extracted from the food they eat to make fairly nasty new chemicals. Predators do not like ingesting these chemicals, and some may well be toxic enough that if you ate one of these slugs, the predator might die.
Of course, making a predator sick after you’re in said predator’s digestive gland doesn’t do the slug any good, either. And that’s the problem with deterrents: they only work when everyone knows about them. Corollary: If you ever develop a doomsday device, don’t keep it a secret.
The theory that these bright colours are honest signals is more often intuited that tested. Just because SCUBA divers find sea slugs easy to see doesn’t mean that other animals do. Every animal has different sensory abilities, a different umwelt than humans. For instance, some fish see ultraviolet; many crustaceans are insensitive to red. And just because they seem very bright in an aquarium doesn’t mean they’ll stand out in the wild, where shade of the rainbow drop out the deeper you go.
You also have to reckon that at some point, there is going to be a point of diminishing returns. Even if you have a deterrent, there’s a point where you will draw so much attention to yourself that predators will attack either because they’re naive or starving or in error. Corollary: Don’t go around being an ass even if you know kung fu, because sooner or later someone will wail on you anyway for being a jerk.
Cortesi and Cheney keep quite a few of these balls in their air in this paper to figure out if, in fact, sea slugs’s bright colours are warning signs as predicted. They collected twenty sea slug species from their natural habitats, and took high quality images, including the ultraviolet, of both the slug and the environment it was found in.
To test whether this combination of colours of the slug on the background were conspicuous to fish, they used models of the kinds of colours that a couple of different fish species can see. The triggerfish (here) sees in the blue-green range; another species tested sees up into the ultraviolet. The authors admit that these species were chosen because we know about their visual systems, not because we know for certain that they eat all twenty of these sea slug species. Somewhere down the road, it would be nice if someone did behavioural tests with known sea slug predators.
The theory is that the most conspicuous sea slugs should be the ones that are the most toxic. To test toxicity, the authors ground up slugs, and put the extract in with brine shrimp eggs. Brine shrimp are pretty tough little creatures, but development is fairly fussy, and shrimp will be killed off by sea slug chemicals.
One of the most toxic is Sagaminopteron ornatum, shown here. Hypselodoris obscura, below that, is near the bottom of the toxicity list; the very bottom one I couldn't find a picture of searching the photo database as I usually do. I guess it’s just that plain-looking that nobody can be bothered to take a picture of it.
There is a correlation between conspicuousness and toxicity, regardless of what fish visual system they used to model this. There is a lot of variation, though, with the correlation explaining only about 7-12% of the variance.
The authors talk about several explanations to the rest of the variance. They talk about sexual selection, developmental variation, and the necessary simplification of the rampantly wild colour patterns into a more tractable measure of contrast. They also point out that while they measured toxicity, toxicity may not be as relevant a measure as palatability. There are plenty of foods that wouldn’t kill me or even make me sick, but I sure wouldn’t choose to eat voluntarily.
One of the other factors that they don’t raise is that there may be mimicry going on. Typically mimicry is considered to be between a pair of, or small number of species. But maybe there’s an element of bluffing that could be effective.
The authors also don’t discuss the possibility of individual variation. The methods are a bit vague on just how many individuals they used to test the toxicity. Considering that the chemical defenses are diet based, it’s entirely possible that toxicity fluctuates not only between individuals, but within an individual over time, as well.
Cortesi, F., & Cheney, K. (2010). Conspicuousness is correlated with toxicity in marine opisthobranchs Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2010.02018.x
Chromodora splendida picture by taso.viglas on Flickr.
Chelidonura varians by Allerina & Glen MacLarty on Flickr.
Rhinecanthus aculeatus picture by zsispeo on Flickr.
Sagaminopteron ornatum by saspotato on Flickr.
Hypselodoris obscura by doug.deep on Flickr.
All photos used under a Creative Commons license.
Video link I want to embed, but can't.... Read more »
Cortesi, F., & Cheney, K. (2010) Conspicuousness is correlated with toxicity in marine opisthobranchs. Journal of Evolutionary Biology. DOI: 10.1111/j.1420-9101.2010.02018.x
I was imitating Jean Chrétien a while ago to tell an anecdote to one of my students.
I could have done the greatest, most perfect, most spot-on, hysterical impersonation of Chrétien ever.* It all would have been lost on this student. An American undergraduate would be unlikely to recognize a Canadian prime minister, no matter how distinctive his speaking style was. (And it was. Oh, how it was.)
That’s the problem with imitation: it only works if both parties recognize what’s being imitated.
There’s imitation in the natural world, too, although it’s better known as mimicry. Almost everyone knows the example of the viceroy butterfly: tastes fine, but looks like the monarch butterfly, which tastes awful, so birds leave both alone because they can’t tell them apart. Thus, the viceroy gains an advantage. This is Batesian mimicry, named after Henry Bates. (Sean Carroll has a great bio of Bates in his book Into the Jungle.)
What if the viceroy butterfly and the monarch butterfly never met? Imagine that there was no overlap in their distributions at all? Now that would be a puzzle.
Those two butterflies do overlap, but a new review paper by Pfennig and Mullen argues that there are many cases where a mimic species occurs where the species its imitating does not. There are no cases where the mimic is completely isolated from the species it is mimicking, but the range of the mimic is often much greater than those of of the species being mimicked.
Pfennig and Mullen give examples of mimicking snakes that occur hundreds of kilometers away from the range of the model species. For the most part, there are only able to give crude estimates of how often the mimic is found without the model: basically, at this point, we’re unable to say little more than, “It happens.”
The paper lists several ways that we might be able to explain these distributions.
The first possibility is that mimicry really isn’t Batesian mimicry. For example, a species thought to be harmless might turn out not to be harmless (Müllerian mimicry). Alternately, both species have hit upon some sort of signal independently that predators avoid (convergent evolution).
Second, distributions of species are very dynamic. Just because the two species don’t overlap in some location now doesn’t mean that they have never done so. I like this idea, because it reminds us that things have a history.
Third, they discuss the possibility of hybridization leading to expansion for genes related to mimicry into new populations. Hybridization seems to occur quite a bit in butterflies, which are important models for mimcry, but this may not happen much in other species.
Fourth, the authors note that if a mimic is rare in arts of its ranges away from the model, it may not incur much of a cost, because many predators avoid feeding on unfamiliar foods. If anything, this paper underestimate the role that the predators could play in establishing the mimicking situation. If a long-lived, fairly smart predator feeds on the distasteful model at site A, it may remember that even if it encounters the mimic at site B very much later.
This review paper is a nice example of a review that tries to push the state of the art forward, and not just summarize.
Pfennig, D., & Mullen, S. (2010). Mimics without models: causes and consequences of allopatry in Batesian mimicry complexes. Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2010.0586
Photo by ~K~ on Flickr, used under a Creative Commons license.
* It wasn’t, but it could have been. Work with me here.... Read more »
Pfennig, D., & Mullen, S. (2010) Mimics without models: causes and consequences of allopatry in Batesian mimicry complexes. Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2010.0586
Everybody makes mistakes. But the peer-reviewed scientific literature tries to reduce mistakes by having fairly rigorous rules for citation. Citing original sources increases transparency and greatly facilitates fact-checking.
For instance, in one of our recent papers, we pointed out that a reference given in another paper did not support the point being made (as far as we could tell). Probably most practicing scientists have a story like that. But how common is that sort of error?
A new paper by Todd and company claims that the error rate for peer-reviewed scientific journals in marine biology is about one in four.
That’s a bit of a surprise.
To come up with this number, they looked at one reference given in support of a claim from three articles of two issues of 33 journals (198 references total – pity they couldn’t have found a way to squeeze in two more to make it an even number). The authors say the reference was selected at random, but they didn’t really, because they only picked assertions that were supported by one reference, so a bit of selection is going on.
Although the title of the article claims one quarter of citations is “inappropriate,” the picture is not as bleak as the title suggests. In fact, only 6% of references did not support the claim being made; a figure closer to one in twenty than one in four.
The “one in four” comes from their claim that 75% of reference support the claim in the paper making them. The remaining 25% that they deem “inappropriate,” however, fall into several categories, and not all of those categories are equally problematic.
About 10% of citations are ambiguous, although the Todd and colleagues say they tended to give benefit of the doubt to those doing the citing. Annoying, but perhaps not damaging to the scientific literature.
The remainder of citations (7.6%) they deem “inappropriate” are cases where the claim is not supported by original data in the paper being cited, but in another paper that the cited paper itself cites. These are almost certainly people citing review articles. Todd and company argue that this is “inappropriate,” but this is surely debatable. Off the top of my head, here are some positive reasons to cite reviews:
Review articles often more cohesive than original articles
Easier to read text with a single citation than a long list of citations
Can save time and effort for readers to track down only one article instead of a long series
Todd and company did look at impact factor of the journal the original paper doing the citing appeared in, with the unstated hypothesis being that “good” journals (i.e., higher impact factors) would have fewer inappropriate citations than “bad” journals. No relationship, which I think goes to show reviewers, and the review process, is a pretty homogeneous lot. (Every journal has a reviewer 2 who hates the paper.)
When initial discussion of this broke out on Twitter, Carin Bondar’s initial response was, “Impact factor is screwed!”
I don’t think so. Impact factor would screwed only if there was some sort of systematic bias in which journals are being inappropriately citated. As far as I can tell, everything in this paper seems to suggest the errors are occurring at random. (Impact factors can be abused, but they provide a rough measure for authors to figure out if a journal has any credibility, which is a major problem in this day of experimentation in scientific publishing.)
Journal editors and reviewers should be the gatekeepers here. Reviewers should have some understanding of the relevant literature for the paper they are reviewing. But there are too few people to review too many papers, and it may be unreasonable for reviewers to do more than just a spot check. Maybe journals, particularly those of published by some of the extremely profitable academic publishers, could hire professional fact checkers. That a journal that had full-time fact checkers could easily be a selling point as a good impact factor.
That this article shows how easy it is to go and fact check these things shows, more than anything else, that the citation system works. We just don’t take enough advantage of the opportunities.
Todd, P., Guest, J., Lu, J., & Chou, L. (2010). One in four citations in marine biology papers is inappropriate Marine Ecology Progress Series, 408, 299-303 DOI: 10.3354/meps08587
Photo by gadl on Flickr, used under a Creative Commons license.... Read more »
Todd, P., Guest, J., Lu, J., & Chou, L. (2010) One in four citations in marine biology papers is inappropriate. Marine Ecology Progress Series, 299-303. DOI: 10.3354/meps08587
It’s good to be omniscient.
Only a few natural studies have been able to approach that level of knowledge. Peter and Rosemary Grant come fairly close in some seasons studying finches on the smaller Galapagos Islands. A new paper must must surely be a contender for god-like knowledge of a population of animals.
Rodríguez-Muñoz and colleagues basically became all-seeing and all-knowing to figure out what evolutionary pressures were being brought to bear on a population of crickets (Gryllus campestris). In other words, who’s getting it on with whom? Who’s being eaten? Those sorts of things.
To do this, they pulled off a rather astonishing video recording set-up of over 60 infra-red cameras that allowed them to monitor between 150-200 crickets all the time.
Let me say that again.
Every. Single. Cricket.
All. The. Time.
And lest you think this is in a controlled lab setting? No! This is a field in Spain! And lest you think this is just a series of snapshots of the population? No! They tagged each individual so they were able to identify them by name! And lest you think was some a few days? No! This was over two summers! And, just to top put a cherry on top, they did DNA work to identify parents and offspring.
And some say they did it while keeping six plates on rods spinning simultaneously and telling jokes.
Once you’ve got thousands of hours of video of crickets... what do you want to know?
A classic prediction in evolution and ethology is that most females have some reproductive success, but males tend to vary wildly in their success, with some being “super winners” and some being “super losers” (It’s rather like research.)
They did indeed find this pattern, but a surprise was that the female success was not as uniform as expected: many females had no offspring. They also found that the females had more offspring when they mated with multiple males. This is an effect that has been suggested in other research, but the comprehensive nature of this study makes this one of the best examples for the phenomenon to date. Indeed, females tended to have as many mates as males.
Another surprise was that dominant males had fewer offspring than subordinate males. The authors don’t have a ready explanation for why this is, more or less shrugging and saying, “Dominance doesn’t always predict mating success.”
Are there similar surprises waiting in survivorship? The story doesn’t seem to be as well fleshed out as the mating story. For instance, there’s not a major breakdown of the causes of death; mostly it’s just lifespan information.
The main behaviour that appeared to be linked to lifespan was singing in the males. Longer-lived males had sung more over their lives. This suggests that the ability to sing a lot is a good indicator of general health. And, for short-lived males, this was also correlated with more offspring. Oddly, though, there was no correlation between the amount of singing and amount of offspring for long-lived males.
With so many surprises, I’m sure there will be other papers to emerge from this massive recording session. And it will be interesting to see if other researchers can apply this high level of surveillance to other species that are larger or more mobile.
Rodriguez-Munoz, R., Bretman, A., Slate, J., Walling, C., & Tregenza, T. (2010). Natural and sexual selection in a wild insect population Science 328(5983): 1269-1272. DOI: 10.1126/science.1188102
Third picture by Gilles San Martin on Flickr, used under a Creative Commons license.... Read more »
Rodriguez-Munoz, R., Bretman, A., Slate, J., Walling, C., & Tregenza, T. (2010) Natural and sexual selection in a wild insect population. Science, 328(5983), 1269-1272. DOI: 10.1126/science.1188102
Walter Garstang famously said that ontogeny creates phylogeny: you need to understand the development of a structure to understand the diversity of that structure across species.
There are a few different ways to change the way a structure is put together. Research on the development of limbs has tended to view morphological changes as being caused by changing boundaries that delineate different regions of the embryo. If you want a bigger forebrain, shift the boundary between the forebrain and the midbrain backward.
Neurobiologists, however, have sometimes suggested that brains differ due to the amount and duration of neurogenesis that goes on during development. If you want a bigger forebrain, make neurons for a longer time in the forebrain than in the midbrain.
A new paper by Sylvester and colleagues tries to look at the relative importance of these two developmental mechanisms in brain evolution. To do this, they looked at the brains of cichlid fishes. Cichlids are renowned among evolutionary biologists for their diversity and the speed at which it was achieved, and this diversity extends to their brain morphology. They chose six species to study; Cynotilapia afra and Copadichromis borleyi are shown here (click to enlarge). The former is a mbuna, a rock-dwelling fish, and the latter is a sand-dweller; the authors had three species of each.
The brains of the mbuna and non-mbuna differ in their proportions: the mbuna have smaller forebrains (strictly speaking, purists would say the telencephalon) than the non-mbuna.
Sylvester and colleagues visualized the cichlid brains using several that are well-known to be involved in development, like sonic hedgehog (shh), and Wnt and found that the pattern of expression of these did indeed differ in these species, typically following the mbuna / non-mbuna split.
To test whether these genes caused the differences in brain sizes, the authors exposed embryos of the mbuna species Labeotropheus fuelleborni (right) to lithium chloride, which affects the Wnt pathway. When they did this, they found that the L. fuelleborni brains were looking rather more like non-mbuna brains, which proportionately larger telencephalons.
Sylvester and company argue that this suggests the very early expression of genes that lay out patterns in the nervous system are key regulators of brain evolution. Considering that they sort of set up timing of neurogenesis as an alternate hypothesis in their introduction, however, it’s worth pointing out that they didn’t actually measure neurogenesis or try to manipulate it in a manner similar to what they did for these patterning genes and proteins. It’s possible that neurogenesis is playing a role in shaping diversity of brains in other ways than tested here.
Sylvester, J., Rich, C., Loh, Y., van Staaden, M., Fraser, G., & Streelman, J. (2010). Brain diversity evolves via differences in patterning Proceedings of the National Academy of Sciences 107(21): 9718-9723. DOI: 10.1073/pnas.1000395107
Photo of Cynotilapia afra by Calwhiz on FLickr; photo of Labeotropheus fuelleborni by Lee Nachtigal on Flickr; photo of Copadichromis borleyi by Petrichor on Flickr. All used under a Creative Commons license.... Read more »
Sylvester, J., Rich, C., Loh, Y., van Staaden, M., Fraser, G., & Streelman, J. (2010) Brain diversity evolves via differences in patterning. Proceedings of the National Academy of Sciences, 107(21), 9718-9723. DOI: 10.1073/pnas.1000395107
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