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Associate Professor of Biology at The University of Texas-Pan American.
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- September 1, 2010
- 01:33 PM
- 43 views
Eat ‘til you can’t eat no more: Evolution of the pig-out
by Zen Faulkes in NeuroDojo
Eating food is a wonderful activity. Without it, you’d die.
But have you ever gone overboard? Got to the end of a meal and thought:
“I ate too much.”
In the natural world, we’re so used to thinking of food as scarce for animals that we don’t often think about issues associated with animals that eat and eat and eat until they do not eat any more. It probably is fairly hard to hit that satiation point for many species.
On the other hand, some species are well known for infrequent but huge meals. They have to eat as much as they can when they can, because their food source is unpredictable. But how do you get to the ability to eat those large meals? We know the “I ate too much” sensation can be uncomfortable, but could it be costly in evolutionary terms?
Pruitt and Krauel decided to look at these issues of gorging in wolf spiders (Schizocosa ocreata). They collected many young female spiders in Tennessee, and reared them in the lab. To test how much the females could eat in one go, they fed them crickets.
A lot of crickets.
After the spiders were not taking any more crickets, they measured the just how much mass the females had taken on in all that feeding. The females varied quite a bit in how much food they could take on, and there is a clear advantage to doing so: their eggs developed faster and they had more of them.
As I alluded to before, Pruitt and Krauel mated their females. They took the offspring and measure how gluttonous they were compared to their mother, and it turns out that the winners of the eating contest tended to have daughters who could also wolf down a lot of food, too. Eating large meals is heritable.
Now we get to the coolest part.
The researcher took those spiders into the wild, and let them loose.
But they didn’t just turn them loose because the experiment was done, oh no. They let them out in to locations in the Tennessee forest. One was covered with nets so that birds – likely the major predators of these spiders – were unlikely to be able to get in.
All their released spiders were marked so they could be identified. Every day for two weeks, they tried to recapture the spiders they released.
When it was all over, they estimated that their eating champions were more likely to survive and have reproductive success but only in environments where the predators had been excluded. In the more naturalistic settings, where birds were free to zip down and conduct their own experiments in how much birds can eat, the heavy eaters suffered: they more likely to have been picked out of the population.
And the moral of the story is: Life is all about trade-offs. Sure, you can take in a lot of energy in one go... that will make you so slow that you can escape when you need to.
Swings and roundabouts, as they say.
Reference
Pruitt JN, & Krauel JJ. 2010. The adaptive value of gluttony: predators mediate the life history
trade-offs of satiation threshold Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2010.02070.x
Top photo by robstephaustralia on Flickr; bottom photo by dishevld on Flickr; used under a Creative Commons license.... Read more »
Pruitt JN, & Krauel JJ. (2010) The adaptive value of gluttony: predators mediate the life history trade-offs of satiation threshold. Journal of Evolutionary Biology. DOI: 10.1111/j.1420-9101.2010.02070.x
- August 31, 2010
- 08:00 AM
- 29 views
Neurons in the wild
by Zen Faulkes in NeuroDojo
Anyone who’s thought about science knows the promise and perils of simplification. People joke about physicists who begin working on an applied problem by saying, “Assume the cow is a perfect sphere...”
Working on an animal in a lab is a little like assuming a cow is a perfect sphere. You can get a pretty long way by simplifying the situation. But as I’ve talked about before, you often get many unexpected and delightful findings when you let an animal be an animal, in the environment and setting that its ancestors have navigated more or less successfully for millions of years.
A new paper by Kostarakos and Römer looks how neurons work in a natural setting, using a favourite critter for this blog: crickets. Although females of many crickets species can fly, they normally walk along the ground a calling male. There can be a lot of “stuff” in the way of that song: grass, rocks, trees, and more. And just being close to the ground is acoustically “bad” (that’s the technical term).
Kostarakos and Römer decided to look into all this by taking their recording equipment out doors.
One of the things this comes out from such experiments, although the authors don’t emphasize it, is how sensitive cricket ears to cricket sounds. It would be easy to miss this little aside, to which I’ve added some emphasis:
(A)t greater distances, the AN1 neuron still responded to the chirps even when the microphone recordings revealed no signal.
The AN1 neurons they mention appears to be critical for the cricket to recognize and find the song of another cricket. The AN1 neurons are so key their firing patterns are probably very good indicators of the behaviour of the intact animal. A cricket has two AN1 cells: a right and a left one, thus obeying the law of bilateral symmetry.
From recording the AN1 neurons, we find out that these little guys can pick up songs from another cricket on the order of 10 meters away. Considering that the animal is only a few centimeters long, that’s a substantial distance.
One of the surprises, though, is that it seems that every cricket has some “dull spots,” where as the animal gets closer to the signal, the neural response drops a bit. (The authors call these “silent spots,” although the AN1 response probably rarely goes to zero.) Some crickets will hear the song better at 10 meters away than they will at 8 meters away, though it picks up again when the sound gets to 6 meters away. But it was very variable from case to case, and it’s not clear if that is due to the individuals, or some peculiarities of the individual recording session. Remember, this is all out in the field, with breezes, grasses, all kinds of things happening.
Although the animal can hear the song at 10 meters away, another bit of a surprise is that at that distance, it can’t tell where the sound is coming from, that is. In a lab situation, it is laughably easy for a cricket to locate a sound 30° off center. In the field, though, with a speaker placed 30° to one side or the other, but there’s no difference in spiking activity of the left and right AN1 neurons when the sound is about 5 meters away.
Again, though, there’s a lot of variation from individual to individual. And it even fluctuates over the course of several minutes. And it fluctuates with temperature. Neurons are very temperature sensitive; you can double the firing rate of AN1 by making it about 10°C warmer.
All of which suggests that crickets are performing the important job of finding a mate with a hearing system that is a little bit wonky and unreliable. There’s dull spots, you can hear a sound but not be sure of the direction, and what you hear depends on the temperature.
One thing that might be interesting would be to use a real calling male, rather than using a “canned” song played through a speaker. Might the caller somehow tweak the song to to maximize the physiological changes in the receiver?
Some people have to go and do some more field experiments to watch the song finding behaviour of females very closely. I think I might now just the people to call.
Given this, and some of the talks I saw at the International Congress of Neuroethology at the start of the month, recording out of doors could yield lots of new findings to work with. The science of ethology always prided itself on its emphasis of animals in their natural setting; I’m looking forward to neuroethologists reclaiming a little more of that ground truth you get from taking things into the field
This is real life, baby.
Reference
Kostarakos K & Römer H. 2010. Sound transmission and directional hearing in field crickets: neurophysiological studies outdoors Journal of Comparative Physiology A 196(9): 669-681. DOI: 10.1007/s00359-010-0557-x
Picture by Gilles San Martin on Flickr, used under a Creative Commons license.
Related posts
Let your neurons relax, the predators are gone!
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Kostarakos K, & Römer H. (2010) Sound transmission and directional hearing in field crickets: neurophysiological studies outdoors. Journal of Comparative Physiology A, 196(9), 669-681. DOI: 10.1007/s00359-010-0557-x
- August 30, 2010
- 08:00 AM
- 29 views
Yummy mummies
by Zen Faulkes in NeuroDojo
When you think of cleaner fish, you probably think of those dramatically coloured little fish on tropical coral reefs, dancing in and out of the jaws of moray eels and other large predators. But coral reef fish aren’t the only ones that pick up parasites.
Pacific salmon get lice. Sea lice, to be exact. And you have to think these are about as unpleasant as human lice. Obviously, since salmon are heavily exploited, biologists are going to be interested in ways to control potentially harmful parasites that could hurt the salmon.
Losos and colleagues discovered something, apparently quite by chance: sticklebacks were picking parasites off the salmon and eating them. Good for the salmon, who gets a parasite removed, and good for the stickleback, who gets a meal. The salmon don’t seem to solicit cleaning, like some coral reef fish do, but they don’t swim away from the sticklebacks, either. And as you can see from the picture, the sticklebacks used in the experiments are about the same size as the salmon.
But that’s not the cool part.
The cool part is that the stickleback were selectively picking off female sea lice. The sticklebacks are also doing something the authors called “cropping.” Because the eggs of a pregnant sea louse are not attached to the salmon, the stickleback can grab on to the eggs alone and pull them off without removing the louse. Even if the louse isn’t killed, “cropping” probably exerts a pretty strong damping effect on the overall population of the parasites.
This is the first time cleaning has been seen in the family that sticklebacks belong to, and the first time it’s been seen in the relatively cool waters of the Canadian Pacific.
Reference
Losos CJC, Reynolds JD, & Dill LM (2010). Sex-selective Predation by Threespine Sticklebacks on Sea Lice: A Novel Cleaning Behaviour Ethology : 10.1111/j.1439-0310.2010.01814.x
Related post
It pays to advertise, even on coral reefs... Read more »
Losos CJC, Reynolds JD, & Dill LM. (2010) Sex-selective Predation by Threespine Sticklebacks on Sea Lice: A Novel Cleaning Behaviour. Ethology. info:/10.1111/j.1439-0310.2010.01814.x
- August 27, 2010
- 10:28 AM
- 72 views
Please explain the end of kin selection
by Zen Faulkes in NeuroDojo
As an evolutionary biologist, I’m very familiar with the idea of kin selection. When I saw a paper titled “The evolution of eusociality” in the table of contents of Nature, and read the abstract saying, “Kin selection? Don’t need it,” I thought to myself, “Ooooh, this is big.”
I’ve read blog posts about it on Plektix and Wired. I listened to first author Martin Novak being interviewed on the Nature podcast.
Novak does a good job of explaining why kin selection is invoked to invoke the evolution of sterile castes. I’ll also buy his argument that kin selection needs special conditions to work. But I have yet to read or hear a decent summary for how natural selection can pull off this feat. Novak seems to be saying that mathematically, they are the same.
The Wired article suggests that they are resorting to revived form of group selection. Third author, E.O. Wilson, has certainly been suggesting that group selection should be revived for some time (his co-author on that piece, David Sloan Wilson, is quoted in the Wired article.)
I understand that it can be hard to convey mathematical propositions verbally. But I am currently very unsatisfied with the explanations I’ve heard so far. I may not be along in this.
I am not going to have a chance to read the full paper for a while yet. The first day of our fall semester is Monday, and our library only has a subscription to the print edition of Nature.
So here is a challenge to you, fellow science bloggers! Can anyone explain the gist of this paper and how it shows natural selection explains eusociality – and do it without resorting to equations?
Reference
Nowak M, Tarnita C, Wilson E. 2010. The evolution of eusociality Nature 466(7310): 1057-1062. DOI: 10.1038/nature09205... Read more »
Nowak, M., Tarnita, C., & Wilson, E. (2010) The evolution of eusociality. Nature, 466(7310), 1057-1062. DOI: 10.1038/nature09205
- August 26, 2010
- 10:59 PM
- 39 views
Lose the ears, but keep the neurons
by Zen Faulkes in NeuroDojo
Bigger. Better.
When thinking about the evolution of nervous systems, there is sometimes a tendency to think of a sort of manifest destiny of nervous systems. It’s part of a larger tendency to see everything in evolution as part of a “march of progress,” but somehow, I think there’s a greater tendency to think about neural evolution as a tale of ever increasing complexity.
Examples of simplification are nice examples of exceptions. Vestigial organs have always been seen as powerful examples indicating that structures have an evolutionary history. A new paper by Lehmann and colleagues looks at simplification of grasshopper ears.
They examined four species, which ranged from animals with full wings to hoppers that are flightless. (A wingless species, Peripodisma tymphii, is shown.)Wings matter for hearing, not directly, but because one of the major selective pressures on flying insects is the desire to not be eaten by a bat – and many bats echolocate. So if you give up on flying, you are less likely to be eaten by a bat.
Perhaps the biggest difference between the four species is in the size of the eardrum: or, to use the more precise name, the tympanum. The authors claim in the discussion that there seems to be a relationship between wing length and tympanum size, which you would predict based on the considerations above. But they don’t plot it anywhere in the results.
The sensitivity of the ears differs in the four species. Slightly. All tend to be most sensitive to sounds in the 4-5 kHz range, and can usually hear sounds at higher and lower frequencies if they’re loud enough. As might be expected, though, the wingless species shown above, P. tymphii, was the least sensitive to ultrasound – the range that bats use to echolocate.
The sensory neurons, however, do not seem to be noticeably different across the four species. This suggests that differences in sensitivity is probably caused by tweaking the physiology of the neurons, not by loss of cells (although they don’t do close counts of the neurons).
Given that neurons are often thought of as being energy hungry, it’s perhaps a little surprising that the periphery changes more then the neurons do. It will be hard to judge these kinds of evolutionary tales until we get a better handle on what the costs of developing and maintaining small neural circuits is.
Reference
Lehmann G, Berger S, Strauß J, Lehmann A, & Pflüger, H. 2010. The auditory system of non-calling grasshoppers (Melanoplinae: Podismini) and the evolutionary regression of their tympanal ears Journal of Comparative Physiology A. DOI: 10.1007/s00359-010-0560-2... Read more »
Lehmann, G., Berger, S., Strauß, J., Lehmann, A., & Pflüger, H. (2010) The auditory system of non-calling grasshoppers (Melanoplinae: Podismini) and the evolutionary regression of their tympanal ears. Journal of Comparative Physiology A. DOI: 10.1007/s00359-010-0560-2
- August 25, 2010
- 10:53 PM
- 49 views
Magic for dogs
by Zen Faulkes in NeuroDojo
At the recent International Congress of Neuroethology, one of the keynote talks was by Susana Martinez-Conde about the psychology of magic. She’s written a few article on illusions, and has a book on the subject coming out soon.
It was great, but it was a little unusual for a neuroethology meeting. It was all humans, so there wasn’t much ethology. And there really wasn’t a lot in the way of neurons. I wondered, “Are there magic tricks for animals?”
Maybe there is.
If you’ve played fetch with a dog for a while, you can “psych them out” by pretending to throw the ball. They’ll tear off after it... and then stop.
The essence of human illusions, psychologically, revolves around attention and expectation. To emphasize how important attention is and how unimportant concealment is, check Penn and Teller’s version of the classic cup and ball trick.
That’s right: you can have everything out in the open, and in many cases, the illusion still works.
Similarly, people’s expectation of what should happen is so strong, they will swear something happened during a magic show that did not.
It seems to me that the “fake throw” plays upon those same elements of attention and expectation in exactly the same way. I can’t help but wonder if the dog experiences this as an illusion very much like humans experiencing an illusion at a magic show. Do they actually “perceive” or “misremember” the ball being thrown? I don’t know, and more frustratingly, I can’t think of a way to test it.
And while I was preparing this, I found a great post on Talking Brains about how the “fake throw” might tell us something about mirror neurons. It might be a bit difficult to use it as a model system.
Can anyone think of any other cases where animals might get fooled and experienced by some of the same tricks as humans?
Reference
Macknik, S., King, M., Randi, J., Robbins, A., Teller, ., Thompson, J., & Martinez-Conde, S. (2008). Attention and awareness in stage magic: turning tricks into research Nature Reviews Neuroscience, 9 (11), 871-879 DOI: 10.1038/nrn2473
Photo from here.... Read more »
Macknik, S., King, M., Randi, J., Robbins, A., Teller, ., Thompson, J., & Martinez-Conde, S. (2008) Attention and awareness in stage magic: turning tricks into research. Nature Reviews Neuroscience, 9(11), 871-879. DOI: 10.1038/nrn2473
- August 19, 2010
- 08:00 AM
- 41 views
Why is a spider like a Derringer?
by Zen Faulkes in NeuroDojo
The Derringer pistol:
Pros: Easy concealment. Stylish.
Con: You’ve only got one shot.
Argiope bruennichi of the male variety are rather like Derringer pistols. Because, you see, their sex organs tend to break during mating.
Yes. Break off.
You almost can’t help but wonder if being eaten by the female – which is the fate for a large percentage of them – isn’t almost a relief to the poor boys at that point.
When you only one shot at genetic glory, you would expect to aim at the target carefully. You might expect the males to be incredibly selective about what females they mate with. In many invertebrates, there’s an easy measure of female quality: size. Bigger bodies mean more eggs.
Shulte and colleagues tested this by experiments in the field and the lab. The males had a choice between two females that differed in size. They didn’t just measure which female was mated with, but the level of the male’s interest, from “Just looking” (male comes to female’s web) to “Sure I’ll come in to see your etchings” (male enters web) to fake yawn (male courts female) to squeaking bedsprings (copulation).
The prediction is that as the differences in the two females get bigger, so too should the differences in the males’ behaviours.
The reality was... not much difference in the males’ behaviour. The males tended to go to one female very quickly and stay with that female regardless of the size, particularly in the lab. In the field, there’s more evidence for choosiness: half the males
What’s going on here? It’s not terribly clear. Maybe the cost of searching for females is so high (predation, maybe?) that the pressure is on for males to mate with the first female they meet. Maybe the male of this species doesn’t have the sensory ability to discriminate sizes, but it would be darned unusual, because lots of arthropods can do such tasks.
The males aren’t complete oblivious to the females, though. Males select quite strongly for unmated females. Because, you see, if there had been a previous male... well, let’s just say that working around the broken sex organs of a previous suitor can really cramp your style. The likelihood of siring any little spiderlets goes way down for previously mated females. But even then, some males would reject unmated females, and it’s not clear why.
Reference
Schulte, K., Uhl, G., & Schneider, J. (2010). Mate choice in males with one-shot genitalia: limited importance of female fecundity Animal Behaviour DOI: 10.1016/j.anbehav.2010.07.005
Derringer photo by remixoverdrive on Flickr. Spider photo by Joachim S. Müller on Flickr. Both used under a Creative Commons license.
Related posts
Life and death and sex choices in mantids... Read more »
Schulte, K., Uhl, G., & Schneider, J. (2010) Mate choice in males with one-shot genitalia: limited importance of female fecundity. Animal Behaviour. DOI: 10.1016/j.anbehav.2010.07.005
- August 18, 2010
- 08:00 AM
- 46 views
Dude looks like a lady? Male lizards courting males
by Zen Faulkes in NeuroDojo
Oh, mistaken gender identity. Are you ever not funny?
Sudden change creates uncertainty. This is as true in evolution as it is in financial crises. Evolutionarily speaking, the eastern fence lizard, Sceloporus undulatus is in a moment of sudden and fast chance – some of them, at least.
These lizards find themselves in a situation rather like some mice I’ve talked about before (here and here). A couple of thousand years ago, a new habitat opens up with very light coloured sand. Humans, in a fit of cleverness a few thousand years later, name it White Sands, New Mexico. The lizards see an opportunity and move in. For those that do, the darkest animals tend to have a hard time of it, because their high contrast make them easy pickings for predators. Lightly coloured animals get the advantage.
The rest of the population, though, in a more normal habitat, are being not picked on for having a darker hue. So the colour of the individual in the two habitats get more and more different over time.
What happens when you put members from these two divergent populations together in the same room? Will there be any behavioural differences, or will it just be as though one lizard thinks, “Oh, my brother, though we are long separated by the shifting sands, yet I still recognize you as a member of my kind, my tribe, my species!”
It didn’t quite work out that way. When they put together two males, a male from the White Sands habitat tended to react to a darkly coloured male from another habitat with:
“Whoa. Who’s the hottie?!”
The light coloured males gave courtship displays to those dark coloured males more than half the time. This is not usual behaviour: more typically, males who get introduced to another male will usually react aggressively, because these guys are territorial.
Although the colour of the lizards’s back is the most obvious cause to point to, the authors say it’s probably not the major difference between the populations that is driving this odd behaviour. When animals are displaying to each other, they do so in such a way as to show their undersides, not their backs.
The colouring of the lizards’ undersides also varies between the white sands and the dark soils. Lizards from the white sands tend to have bigger display patches on their undersides, and this is true for both males and females. Because the display patches of females from the white sands are larger, they tend to be fairly close in size to those of the males from the dark soil environments.
Extract from Figure 4. WS = white sands, DS = dark soil.
While this seems a plausible explanation, it is an untested hypothesis at this point. And it’s not clear right why larger patches might have had a selective advantage in a light sand environment.
But you could see how anyone could make that sort of mistake. Right?
Reference
Robertson JM, & Rosenblum EB. 2010. Male territoriality and ‘sex confusion’ in recently adapted lizards at White Sands Journal of Evolutionary Biology. DOI: 10.1111/j.1420-9101.2010.02063.x. http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2010.02063.x/abstract
Photo by TrombaMarina on Flickr, used under a Creative Commons license.... Read more »
Robertson JM, & Rosenblum EB. (2010) Male territoriality and ‘sex confusion’ in recently adapted lizards at White Sands. Journal of Evolutionary Biology. info:/
- August 17, 2010
- 08:00 AM
- 53 views
Celebrate diversity: Old female salamanders
by Zen Faulkes in Marmorkrebs
Imagine, if you will, a line of ancient females, who trick males into having sex with them, so that the females can continue living indefinitely.
I know, you’ve seen it before in a dozens of movies, books, and television episodes. Who hasn’t seen a vain sorceress stealing youth, particularly from young men?
Something like this goes on in some salamanders, except that no one salamander is living unusually long. The evolutionary line of salamanders, though, is showing surprisingly longevity.
Some salamanders are all female... but they are not, strictly speaking, asexual or parthenogenetic. These unisexual female lineages engage in a little sperm “theft” from several sexual salamanders species (Ambystoma laterale is pictured), a process known as kleptogenesis. Genetically, these unisexual females are all over the map. Some unisexuals have a paired set of chromosomes like the more typical sexual species (i.e., they are diploid); others have three, four, or five sets of chromosomes.
This unusual mode of reproduction is interesting, because it might allow a unisexual species to avoid genetic stasis. In theory, sexual species have the edge in a changing environment because more genetic variations are possible through sexual reproduction. Having every individual be genetically identical is great as long as the environment never changes.
But environments do change, so it’s generally though that parthenogenetic species tend to go extinct at much higher rates than sexual ones.
This new paper by Bi and Bogart tries to settle how old this odd lineage of female salamanders is. One previous study suggested millions of years; another estimated tens of thousands of years. Bi and Bogart come down on the side of millions of years; a little over 5 million years, to be precise.
The reason for the discrepancy comes down to an issue concerning the wrong bit of DNA being amplified and analyzed. Most animal cells have DNA in two places: the cell nucleus (where most people think of it being), and in the mitochondria (the cell’s power plant). In normal sexual species, nuclear DNA comes equally from both parents, while mitochondrial come from mom.
Because these all-female salamanders get nuclear DNA from the sperm they “steal,” you can really only try to trace relationships using mitochondrial DNA in these animals.
The problem is that nuclear DNA sometimes has some bits in it that are extremely similar to mitochondrial DNA. These sequences, called numts, are probably derived from the mitochondria. Bi and Bogart argue that the previous research that suggested that these female salamanders split from the sexual salamanders about 25,00 years ago probably sequenced a numt instead of a mitochondrial gene.
That DNA. It’s tricky.
Parthenogenesis in Marmorkrebs is blessedly simple in comparison.
Reference
Bi, K., & Bogart, J. (2010). Time and time again: Unisexual salamanders (genus Ambystoma) are the oldest unisexual vertebrates BMC Evolutionary Biology, 10 (1) DOI: 10.1186/1471-2148-10-238
Photo by whiteoakart on Flickr, used under a Creative Commons license.... Read more »
Bi, K., & Bogart, J. (2010) Time and time again: Unisexual salamanders (genus Ambystoma) are the oldest unisexual vertebrates. BMC Evolutionary Biology, 10(1), 238. DOI: 10.1186/1471-2148-10-238
- August 16, 2010
- 08:00 AM
- 61 views
Song memes
by Zen Faulkes in NeuroDojo
Over thirty years ago, Richard Dawkins coined the term “meme” in his classic book The Selfish Gene. A meme was analogous to a gene. A gene is a physical replicator that multiplied itself (but with variations), in such a way that permitted selection and evolution. A meme, Dawkins wrote, was an intellectual replicator that could also multiple itself, creating variants as it did so, allowing evolution.
About two years ago. Susan Blackmore complained that people weren’t taking mimetics seriously, and I argued that mimetics is nowhere near being serious science.
A new paper by Cardoso and Atwell uses the meme concept in describing birdsong. On the face of it, bird song is not a bad model to use the meme concept. Some songs are easily measured; and there are distinct varieties, that are subject to some variation as they are learned.
Cardoso and Atwell looked at the songs of dark eyed juncos (Junco hyemalis) in California, where there has only been a population for about 30 years. In that time, their songs have gotten higher in pitch, which is something that tends to happen to birds in environments with lots of human created sound. They compared those to an older, more established population further from urban centers.
They’re trying to figure out if the number of modifications the birds introduce is enough to explain the change in the songs (like mutation for a gene). If it isn’t, that suggests there is another process going on, like a selective process as birds discard some songs.
If I’m understanding the authors right*, the birds change their songs slightly, but those modifications are only enough to account for about half the difference between the two populations.
The remaining difference between the two populations, they argue, came because the high frequency songs “outcompeted” the low frequency songs. But I think* they are also arguing that no selection for high pitched songs is going on right now. They say this because they reckon that if there was selection going on right now, it would be expressed by more males learning, and singing, higher-pitched songs than lower pitched songs – which isn’t the case.
In other words, the song situation appears to have stabilized. This is slightly frustrating for me as a reader, because I was hoping to get a sense of the process of song change, but it seems most of the action happened decades ago.
What I am not seeing is how characterising songs as memes leads to distinctly different hypotheses or explanations than plain old learning and communication theory does. Cardoso and Atwell are able to couch their descriptions in terms of mimetics, but I would be more impressed if they were about to use mimetics to make a explicit prediction that differed from some theory.
I haven’t changed my mind about mimetics yet.
* I have to put in that caveat that I may be getting it wrong, because this paper assumes a lot of background knowledge. For instance, me being a novice in birdsong, it’s not clear how you would group over 1,000 sound recordings into about 100 song types, or memes. There several points like that in this paper.
Reference
Cardoso G, & Atwell J. 2010. Directional cultural change by modification and replacement of memes. Evolution. DOI: 10.1111/j.1558-5646.2010.01102.x
Photo by pheanix300 on Flickr, used under a Creative Commons license.... Read more »
Cardoso, G., & Atwell, J. (2010) DIRECTIONAL CULTURAL CHANGE BY MODIFICATION AND REPLACEMENT OF MEMES. Evolution. DOI: 10.1111/j.1558-5646.2010.01102.x
- August 6, 2010
- 08:00 AM
- 63 views
Nothing but the finest...feces
by Zen Faulkes in NeuroDojo
There comes a moment in every biology blogger’s life when he or she must write about poop.
This is one of those moments.
When a paper’s title includes phrase, “fecal particle size,” sometimes, one just thinks, “Okay, I really should read that, if for no other reason than it was clearly a lot of unpleasant work for someone.”
The intellectual issue here relates to the difference digestive strategies of mammals and reptiles. Mammals chew; reptiles generally don’t. This has a lot of consequences. It means mammals can spend a lot less time digesting food. This, in turn, helps to make the high-energy endothermic lifestyle that mammals enjoy possible. And it means that mammals should have feces that are more... fine-grained, if you will. You’re not likely to find something like this in the droppings of a mammal:
The authors recovered this particular leaf from the feces of a common iguana.
But this is science, damnit, not a schoolkid’s joke! We need quantifiable data on the particles in poop! We need to test those turds!
So, Julia Fritz and her four co-authors collected a lot of samples from fourteen reptiles species held in European zoos. Then, they started sieving all those feces. They had a few predictions about what they’d find. The major one, that the reptiles’ feces would have large particles, was confirmed. They had also predicted that large bodied animals would also tend to have coarser feces, probably due to bite size.
They also predicted that animals fed prepared food would tend to have larger particles, reasoning that those feeding on plants in the ground would be able to manipulate the plant in ways that allowed the reptiles a chance to regulate the size of the bites they took. They tested two tortoise species, and found the effect in one, but not the other. So the story is a little equivocal here.
Now, you may think that you’ve heard about reptiles using stones in their stomach to break down their food. Fritz and company find no evidence of that at all. It’s a little surprising, as I would have thought this would be something that would have been settled long ago.
As an outsider to the digestive physiology field, it’s a bit difficult for me to figure out what the next logical set of questions to ask is. The authors, however, say that one thing they would like to do is get a lot of excrement from free-ranging reptiles. They modestly note that this is “a major logistical challenge.”
Reference
Fritz, J., Hummel, J., Kienzle, E., Streich, W., & Clauss, M. (2010). To chew or not to chew: fecal particle size in herbivorous reptiles and mammals Journal of Experimental Zoology Part A: Ecological Genetics and Physiology DOI: 10.1002/jez.629... Read more »
Fritz, J., Hummel, J., Kienzle, E., Streich, W., & Clauss, M. (2010) To chew or not to chew: fecal particle size in herbivorous reptiles and mammals. Journal of Experimental Zoology Part A: Ecological Genetics and Physiology. DOI: 10.1002/jez.629
- August 5, 2010
- 08:00 AM
- 63 views
Eyes on the edge: How archerfish see in and out of water
by Zen Faulkes in NeuroDojo
Archerfish rock.
These little sharpshooters are famous for being able to spit water at an insect, not on the surface of the water, but a good ways above it. And these insects are often camouflaged to boot. Then, they have to catch the insect when it hits the water before other fish get it, or it gets swept away by any water currents.
In other words, archerfish have to calculate, perform precision maneuvers, and anticipate the outcomes of their actions.
This paper, though, looks mainly at the visual problem. Anyone has probably noticed that light behaves differently when it moves through water than when it moves through air. The famous example that every kid has probably asked his parents about is why a spoon in a glass of water looks like the two halves are broken apart.
The authors here looked at the properties of the photoreceptors in the archerfish eyes. Something to remember is that the top of the retina looks down, which for the archerfish means into the water, and the bottom part of the retina looks up, which for the archerfish means looking up and out of the water. Now, it gets a bit sticky because fish have more complicated eyes that we primates do. We have rods and three kinds of cones. The archerfish has rods, single cones and double cones.
First, they found that the three general areas of the eye they looked at, the light-sensing cells of the ventral part of the retina had rather different light absorbing properties than the rest. This correlates with the fish’s visual task: the bottom part of the eye looks up, out of water.
As light goes through the water, the colours change. At the top of the water, the light tends to have shorter wavelengths than the light being reflected from the bottom of the water. The sensitivity of the photoreceptors in those regions matched quite well with the different kinds of light these animals would be seeing.
The highest density of cones is also right in the “sweet spot” where the fish will be looking at its target. The authors don’t use the term “fovea,” but it seems to me that is exactly what it is. And the resolution the archerfish is probably capable of is estimated to be about 8 minutes of arc; by comparison, arthropods eyes tend to be only able to resolve several degrees of arc, and I think humans in fractions of a second of arc.
They interpret these differences across the retina as adaptations to living at the interface, which is perfectly reasonable. The authors suggest that it something that other fish living near the surface have, although one might expect it to be particularly enhanced in the archerfish.
Next steps for this group is to start doing a bucket of behavioural tests to see how well the fish is able to discriminate different colours, shades, and so on. Since the fish has a nice behaviour of spitting at things they see, it should be possible to train them to spit at objects they can see, then tweak the visual stimuli until they can’t do the task any more.
Reference
Temple, S., Hart, N., Marshall, N., & Collin, S. (2010). A spitting image: specializations in archerfish eyes for vision at the interface between air and water Proceedings of the Royal Society B: Biological Sciences, 277 (1694), 2607-2615 DOI: 10.1098/rspb.2010.0345... Read more »
Temple, S., Hart, N., Marshall, N., & Collin, S. (2010) A spitting image: specializations in archerfish eyes for vision at the interface between air and water. Proceedings of the Royal Society B: Biological Sciences, 277(1694), 2607-2615. DOI: 10.1098/rspb.2010.0345
- July 27, 2010
- 08:00 AM
- 74 views
North American crayfish diversity threatened
by Zen Faulkes in Marmorkrebs
When I recently attended the International Association of Astacology meeting, it was ground into my face how bad things are for crayfish.
In Europe, crayfish are being beaten up by exotic North American species. If competition doesn’t get them, the crayfish plague that the exotics carry will.
In North America, the home to the greatest diversity of crayfish species in the world, non-indigenous species are playing a role in some regions, but habitat degradation is the bigger concern. At the Astacology meeting, we were treated to scenes like this:
Mountains are being flattened to remove coal.
Strangely, the same factors that lead to the wonderful high diversity of North American crayfish are the same factors that make them vulnerable, mainly geographic isolation. Because crayfish need to stay wet, and are not terribly mobile, they often don’t disperse very well on their own. Consequently, many species have a limited range, often falling within a few locations in a single American state.
Taylor and colleagues provide a summary of just how bad things are in North America. The take home message that every crayfish biologist and every crayfish pet owner should have burned into their brain is this:
Almost half of North American crayfish species are under threat.
I don’t use the phrase “under threat” in any sort of technical way, but just indicating some sort of conservation concern.
On a per species basis, crayfish are the second most threatened kind of animal in North America, behind freshwater mussels, which obviously have many of the same issues as crayfish: small geographic ranges, limited mobility, vulnerable to competition and habitat degradation.
Taylor and colleagues provide other useful information, including a list of all known species and a standard common name. The article is rather nicely illustrated with a few crayfish pictures, too (not for every species, however).
All of this makes the prospect of Marmorkrebs being introduced into North American waters a veritable nightmare scenario. Competition between Marmorkrebs and a local species could be enough to push a species into extinction.
Reference
Taylor, C., Schuster, G., Cooper, J., DiStefano, R., Eversole, A., Hamr, P., Hobbs, III, H., Robison, H., Skelton, C., & Thoma, R. (2007). A Reassessment of the Conservation Status of Crayfishes of the United States and Canada after 10+ Years of Increased Awareness Fisheries 32(8): 372-389. DOI: 10.1577/1548-8446(2007)32[372:AROTCS]2.0.CO;2
Photo by ddimick on Flickr. Used under a Creative Commons license.... Read more »
Taylor, C., Schuster, G., Cooper, J., DiStefano, R., Eversole, A., Hamr, P., Hobbs, III, H., Robison, H., Skelton, C., & Thoma, R. (2007) A Reassessment of the Conservation Status of Crayfishes of the United States and Canada after 10 Years of Increased Awareness. Fisheries, 32(8), 372-389. DOI: 10.1577/1548-8446(2007)32[372:AROTCS]2.0.CO;2
- July 22, 2010
- 08:00 AM
- 87 views
Drugs in the water affecting crustaceans’s precious bodily fluids?
by Zen Faulkes in NeuroDojo
You shouldn’t be able to call a species anything you want.
Yes, biologists switched to using Latin names for species because we recognized that common names were too variable and imprecise. Still, that doesn’t mean that common names are infinitely flexible.
A crustacean story has been making the rounds in the news, and alas, the news stories are often botching the basics. I wish I could be surprised. News stories based on journal articles seem to be a never ending well of things to correct.
The first time I saw the article was at New Scientist. Then I spotted it on the front of The Age here. Then I saw it again time here, which was what finally set me off. But before this post went up, it also got featured on National Geographic and Improbable Research.
I had looked at the article abstract, and I thought, “Wait. The headline said this was a shrimp. The abstract says nothing about a shrimp.”
The sometimes interesting but often irritating Science Daily has a picture of the senior author, Alex Ford (right), holding something I would not call a shrimp. It’s an amphipod. I can only find one other picture of this species on the web, on Ford’s home page here. In fact, the title of the Science Daily blurb was exactly that of the journal article – except that the word “amphipod” had been replaced by “shrimp.”
The Age referred to this beast as a “prawn”, and showed a picture of something normally called a prawn, Penaeus monodon, which is an entirely different beast. And it gave it the lurid title referring to crustaceans “getting high.”
The third article showed a picture of another species (Crangon crangon) that is not even close to the one studied in the paper. And this time, the article referred to the animals becoming “suicidal”!
Does calling an amphipod a “shrimp” or a “prawn” matter? Yes! People eat shrimp and prawns, but not amphipods. Bu changing the common name, you introduce a whole new set of worries and fears about the safety of people’s food. It’s made worse considering that the third article is at a website called “Fish2Fork,” which strongly suggests they think it’s a seafood story.
The paper is actually quite interesting, but it shows neither animals “seeing the light” (title and article 1), “getting high” (article 2) or “becoming suicidal” (article 3).
The behaviours that the authors are testing are the tendency of amphipods to swim towards a light (phototaxis) or tendency to swim up or down (geotaxis). I am guessing the former is where “seeing the light” comes from, but “seeing the light” doesn’t capture the actual behaviour well at all. I would expect “seeing the light” to mean that the amphipods gained some ability to see something they couldn’t before.
The authors didn’t just test the effect of Prozac, but two other drugs, and the neuroactive chemical serotonin (which Prozac interacts with and which is often important to crustaceans), and a natural parasitic infection (acanthocephalans).
Amphipods that were infected with parasites, given serotonin, or given Prozac all tended to be more likely to be attracted to light, and more likely to be swimming upwards. Thus, amphipods are more likely to be out in the water in bright light, where they would be more susceptible to being eaten by predators. This, of course, is what parasites “wants” so that they can infect the next host in their life cycle. Still, this is hardly “getting high” or “suicidal” in the way people think of those phrases.
Further reading of the paper reveals a less straightforward interpretation than the headlines say. Guler and Ford didn’t measure the drug concentrations in the water where they collected their animals. They argue that their values are within the ballpark that other researchers have recorded in “STP effluent”. (I don’t know what “STP” means, because the authors don’t define it. A little help here? You know, for those of us who don’t speak acronym.)
Complicating matters further is that the authors tested five concentrations for the drugs they tested, ranging from 0 to 10 µg per liter, but it seems only one concentration of Prozac (0.1 µg per litre) caused a significant difference in the amphipods’ behaviour. So if we’re taking enough anti-depressants, there may not be a problem?
Finally, only used males in this experiment, and there is no explanation why.
This paper is interesting, but it’s yet another case of the researchers and press release writers working too hard.
For more fun with headlines, see the stuff I’ve written with Carin Bondar!
Additional: Deep Sea News also got to this one.
Reference
Guler Y., & Ford A. (2010). Anti-depressants make amphipods see the light Aquatic Toxicology. DOI: 10.1016/j.aquatox.2010.05.019... Read more »
Guler Y., & Ford A. (2010) Anti-depressants make amphipods see the light. Aquatic Toxicology. DOI: 10.1016/j.aquatox.2010.05.019
- July 21, 2010
- 08:00 AM
- 103 views
Snake eyes
by Zen Faulkes in NeuroDojo
To many, “snake eyes” is a bad bet at the craps table. To some, it’s a GI Joe character. To a very small, select group, it’s a minor addition to the oeuvre of Brian De Palma. *
Today, I want to look at the most literal meaning of the term imaginable. But, since this is a biology blog, you could probably guess that I was going to end up talking about the eyes of snakes.
I’m willing to bet that when most people visualize snake eyes, they think of something with a vertical slit for a pupil, like the animal shown here. Such eye look a little scary to humans, because we have circular pupils. Snakes aren’t the only animals to have such pupils; many cats do, too. Why do some animals have vertical pupils, and some have circular pupils?
Brischoux and colleagues set out right away to correct one idea that many people have about vertical eyes that is wrong: it’s not for night vision. They set out to test other hypotheses about the function of pupil shape using snakes as their subjects. One reason for using snakes is that the pupils vary considerably, so compare the animal above to the one below (click to enlarge).
Admit it: it looks friendlier with circular pupils, doesn’t it?
The pupil shape appears to be related to day and night, but in a different way: You can close a slit pupil much tighter than a circular pupil. The yellow snake above has its pupils shut down quite far. This might be advantageous to an animal that normally moves around at night to prevent it from being temporarily blinded by bright light in the day.
The authors also suggest that a vertical pupil may be less recognizable then a round one, making it advantageous for ambush predators who use camouflage. The authors don’t mention that many prey species also use camouflage, and following that logic, might also be expected to have slit pupils.
Brischoux and colleagues coded out about 100 snake species, categorising their pupil shape, type of foraging, and time when the animals were most activity. They found that most snakes fell into a fairly small number of positions in the possible range of values: sit and wait ambush predators that hunted at night tended to have vertical pupils; snakes that actively foraged during the say tended to have circular pupils.
What I don’t get about their figure above, though, is why the data points are scattered. Look at the trio of dots on the lower right corner. Why are they separated? If these are categorical values, all three should be right on top of each other. That implies that they’ve measured something quantitatively, not by category... and if so, where are the value labels for the axes?
Having done all that, the authors admit they still can’t definitively tie pupil shape to any particular adaptive advantage. They suggest some good experiments, such as manipulating pupil shape to see if this affects how readily detectable an potential predator is. They also point out that many other species vary in their pupil shape, and that similar analyses could be done for those groups, too.
Reference
Brischoux F, Pizzatto L, & Shine R (2010). Insights into the adaptive significance of vertical pupil shape in snakes Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2010.02046.x
Yellow snake photo by MrClean1982 on Flickr. Garter snake photo by C. A. Mullhaupt on Flickr. Both used under a Creative Commons license.
* The film has a special place in my heart, because it was filmed in Montréal when I was living there, and I was able to look in and see the set they had built in the old Montréal Forum when I walked to and from McGill University.... Read more »
Brischoux F, Pizzatto L, & Shine R. (2010) Insights into the adaptive significance of vertical pupil shape in snakes. Journal of Evolutionary Biology. DOI: 10.1111/j.1420-9101.2010.02046.x
- July 19, 2010
- 08:00 AM
- 78 views
Neural plasticity isn’t new
by Zen Faulkes in NeuroDojo
A recent post on neuroscience of learning got me thinking about how several people are talking about brain plasticity as though it is a huge revelation of the last couple of decades. From the post:
Only twenty years ago most people in the world of neuroscience believed that the connections between the neurons in your brain were fixed by the time you were a teenager (or even younger)
This is a distortion of history, I think. Ideas about neural plasticity were bubbling around well before 1990s. For instance, Merzenich and Kaas did many experiments published in the early 1980s that showed that if you cut a sensory nerve in a monkey, you saw a major reorganization of the representation of that body in the cortex.
It is true that people thought mammalian nervous systems did not generate new neurons until probably the min-1990s. But then, adult neurogenesis was yesterday’s news to people studying neuroethology, who had been hearing about how new neruons were added to the brains of adult songbirds, like canaries, for years before that (Goldman and Nottebohm, 1983).
Invertebrate neurobiologists had been on the trail of synaptic changes associated with learning and memory a decade earlier (Castellucci and Kandel, 1974).
And, if you think about it, in order for learning to occur and memories to be formed, some kind of change had to be happening at the neuronal level. Psychologist Don Hebb was thinking about how such changes at the neural level might occur back in 1949 (reviewed here).
Previously, people argued about whether those changes were presynaptic or postsynaptic, as though there were only two possibilities. I could make a very long list of ways that neurons might change in response to experience now, and that list shows no sign that it’s reached its limit yet. In fact, less than a month ago, Kuba and colleagues showed yet a new way that neurons can change their propensity to fire: by changing the place on the cell where action potentials start.
We did not suddenly discover plasticity two decades ago. I think the surprise has been not that nervous systems can change, but the number of mechanisms by which they can change.
References
Castellucci VF, & Kandel ER (1974). A Quantal Analysis of the Synaptic Depression Underlying Habituation of the Gill-Withdrawal Reflex in Aplysia Proceedings of the National Academy of Sciences of the United States of America, 71 (12), 5004-5008
Goldman SA, & Nottebohm F (1983). Neuronal production, migration, and differentiation in a vocal control nucleus of the adult female canary brain Proceedings of the National Academy of Sciences of the United States of America 80(8): 2390-2394
Hebb DO. (1949). The organization of behavior. New York: Wiley.
Kuba H, Oichi Y, & Ohmori H (2010). Presynaptic activity regulates Na+ channel distribution at the axon initial segment Nature, 465 (7301), 1075-1078 DOI: 10.1038/nature09087
Merzenich M, & Kaas J. (1982). Reorganization of mammalian somatosensory cortex following peripheral nerve injury Trends in Neurosciences 5: 434-436. DOI: 10.1016/0166-2236(82)90235-1
Canary picture by meophamman on Flickr, used under a Creative Commons license. ... Read more »
Castellucci VF, & Kandel ER. (1974) A Quantal Analysis of the Synaptic Depression Underlying Habituation of the Gill-Withdrawal Reflex in Aplysia. Proceedings of the National Academy of Sciences of the United States of America, 71(12), 5004-5008. info:/
Kuba H, Oichi Y, & Ohmori H. (2010) Presynaptic activity regulates Na channel distribution at the axon initial segment. Nature, 465(7301), 1075-1078. DOI: 10.1038/nature09087
Merzenich M, & Kaas J. (1982) Reorganization of mammalian somatosensory cortex following peripheral nerve injury. Trends in Neurosciences, 434-436. DOI: 10.1016/0166-2236(82)90235-1
- July 14, 2010
- 08:00 AM
- 74 views
Life and death and sex choices in mantids
by Zen Faulkes in NeuroDojo
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?
Reference
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
- July 13, 2010
- 08:00 AM
- 102 views
Asexual species identifications
by Zen Faulkes in Marmorkrebs
Marmorkrebs are difficult beasts. As I’ve mentioned before, there is no species name for them yet, partly because of how people define species. At the practical level, most crayfish are identified by the sex organs of the males (which Marmorkrebs don’t have). At the conceptual level, many people define species by interbreeding populations (which parthenogenetic organisms don’t do).
Birky and colleagues recently proposed a way to define species for parthenogenetic organisms. As near as I can understand it, their argument runs like this.
First, they’re going to define species using DNA. They just think morphology is too subtle and too prone to mislead.
Second, the criteria that they’re going to use to separate species is going to revolve around two key concepts: genetic drift and adaptation to a niche.
For any organism, even parthenogenetic clones like Marmorkrebs, there is a certain probability that mutations will occur each generation. Even when there is no selection pressure for that mutation, the frequency of the mutation in the population will change just due to chance over time, even becoming fixed or eliminated. That’s genetic drift.
Birky and company define a species as a group of organisms that show genetic changes that are too large to be accounted for by drift alone. They argue that this is indicative of a population that has undergone adaptation to a specific ecological niche.
The details of their proposal involve a fair amount of math, which, for the purposes of writing a blog post, I didn’t feel the need to become intimately acquainted with. At first glance, however, this approach seems generally fruitful. They apply their methods to six different asexual groups, and seem to make some headway on defining them. I think they could also apply their approach to sorting defining an asexual species that is derived from sexual ancestors, although they don’t discuss this.
Some potential glitches in their approach are that they effectively rule out the possibility that two species could be created by drift alone, which I think many evolutionary biologist would be uncomfortable with. They also mention briefly the idea of “higher taxa,” but how to define those higher taxa was not laid out nearly as clearly as for species.
But they do provide hope that Marmorkrebs, and many other asexuals, can get recognized as species, as they should be, in my opinion.
(Note: I wrote most of this before learning that there is a paper coming out that should shed some new light on the identity of Marmorkrebs. Stay tuned!)
Reference
Birky C, Adams J, Gemmel M, & Perry J. 2010. Using population genetic theory and DNA sequences for species detection and identification in asexual organisms PLoS ONE 5(5): e10609. DOI: 10.1371/journal.pone.0010609... Read more »
Birky C, Adams J, Gemmel M, & Perry J. (2010) Using population genetic theory and DNA sequences for species detection and identification in asexual organisms. PLoS ONE, 5(5). DOI: 10.1371/journal.pone.0010609
- July 12, 2010
- 08:00 AM
- 160 views
Book review: Do Fish Feel Pain?
by Zen Faulkes in NeuroDojo
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.
“Yes.”
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).
References
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
- July 9, 2010
- 08:00 AM
- 117 views
“You’re not my type!”, echolocation edition
by Zen Faulkes in NeuroDojo
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...”
Awkwaaaaaaaaaaaaaaaaaaaaard.
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)!
Reference
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
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