Coloration/toxicity question

D

drew

Guest
For the experts (Tim, Paul, Henk, Apples, et al...):

Since the "fire-belly" coloration in Cynops pyrrhogaster is a "warning" to predators of the newts' toxicity, is there any deviation in level of toxicity which correlates to the deviation in red/orange coloration between the C.pyrrhogaster races or locations of origin? For instance, is sasayamae race less toxic than the newts from Yaku-shima? Have there ever been any studies on this?

Just curious...please don't lick any of your newts to find out!
 
Hi Drew,

indeed an interesting question.
But sorry I do not know any study to this problem, and I do not want to try it.
But I think there is a difference, because some smell of different.
By the way!
I think the red coloration is more than warning. Perhaps also for "communication" between the newts. Color must be important - see breeding coloration!

Paul
 
As far as I know this does not follow in some of the dendrobatids (as an example).

Ed
 
I've been thinking more about this topic....

If the "fire belly" coloration was brought about through the process of natural selection as a favored mutation that resulted in the warding off of predators, does the lack of bright coloration in the sasayamae "race" indicate a lack of predation in that geographic region? Or maybe, at least, the predators in that region were not deterred by coloration ("colorblind?"), so natural selection for that particular trait did not take place in that region. Or would that make the case for sasayamae being a separate species?

Or, if like you mentioned, Paul, the "fire belly" was a selection based on a mutation favorable for mating/attraction/communication within the species, what environmental phenomenon might cause such a different coloration in the different geographic areas?


meanwhile, the newt is thinking...."where are the worms?"
 
One of the items that always needs to be taken into consideration is that many predators are colorblind (particuarly mammalian predators).
Also, with regards to avian and reptile predators, the actual colors may be less important than how the pattern reflects UVA as this appears to be an important recognition for more and more species.
I do not think this has been studied in fish as of yet.

Ed
 
I've always thought it was fascinating that so many of the bright colors/patterns displayed by animals that we humans find so attractive are really just happy accidents, because we are probably the only animals that actually perceive the colors in that way.
 
Hmm,
I'm depending on what you mean by accident I'm not sure I agree with you on that statement.
Actually many animals can percieve the color patterns but it appears that many of them may not interpret them the same as we do.

Ed
 
Color perception is different from species to species. Assuming that the coloration in newts developed in response to predation by species that perceive that coloration differently than humans, it seems fortuitous that we are rewarded with newts that are so pleasing to human eyes.
 
Drew, you pose an interesting question but since I'm no expert
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I can't really answer it with any confidence.

I'd just point out that the red ventral coloration in C.pyrrhogaster is caused by the consumption of foods high in carotenoids, which are not synthesized by the newts themselves. Indeed, some are redder than others, and some are not red at all but instead more orange like C.ensicauda or Taricha granulosa. It's a good assumption but I'm not sure we can conclude with any certainty that the ventral pigmentation is biologically intended to ward off potential predators -- though it may have that effect. It's interesting to note that C.p morphs and juvies don't develop their full red coloration until they become aquatic. Since they're on land for a couple of years, their bellies are not exposed to potential predators so I guess they don't need to be red-bellied during that phase if the red indeed is meant as a warning to predators. Maybe the yellow dorsal/tail coloration that appears during their juvenile phase and generally disappears during their aquatic, adult phase serves the same purpose? Anyway, I'd be interested in knowing the toxicity levels of juveniles compared with adults
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What's the case with dart frogs? Do they retain their bright colors through successive generations in captivity or are their colors also dependent on carotenoids? I have heard that F2 dart frogs have no or only minimal toxicity. I wonder if this is the case with F2 pyrrhogaster....
 
For both Cynops and Taricha, the larvae are non-toxic and then the juveniles begin to become toxic after metamorphosis. I think they gradually increase in toxicity as they move towards adulthood. Larvae of Notophthalmus are also non-toxic, but the efts have a much higher toxicity than the adults do, and are obviously more brightly colored. Interestingly, the eggs of C. pyrrhogaster and T. granulosa also contain the toxin TTX, presumably deposited there by the females.

As for dart frogs, they get their toxins from their diet--primarily the ants they eat--which is why the lose toxicity in captivity. I'm not sure about their colors in captivity, but I think they retain them.
 
There is some color loss in certain species of poison arrow frogs (Epidobates tricolor for example) but as far as I know most do not exhibit this tendency.
The accumulation of the red/yellow/orange pigment in the ventral surface of Cynops as a antipredator warning is consistant with other animals such as Bombina even to the point where cb animals do not develop the same intensity of color. I beleive that these species also have an antipredator display via an arched body that displays the ventral colors.

I would argue that pigmentation in many species is the result of antipredator pressure. There are many species that coloration is at least partly due to mate recognition and I would argue that Cynops and Triterus are two families that demonstrate this quite well.

Ed
 
Ed: Does, then, the courtship display display the ventral side ever?


I guess that this would require some "sacrifices" of CB newts...something I doubt people would be willing to do.

so is there a verdict to preserving the color in successive generations? Also, if it was selected for, would a percentage of the young retain the fiery colors of the WC?
 
Hi Joseph,
You would need to look in the literature for the actual courtship displays to see if there is any components that include the ventral colors but in the families I mentioned, the colors of the males become much more pronounced during the breeding seasons and include colors not normally associated aposematic colorations (such as blue).
The ventral colors can be maintained through successive generations by feeding the larva on a caretenoid rich diet (such as crustaceans).
Ed
 
Thanks for that input, Liz and Ed
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Earlier today, I found myself pondering the differences between Cynops pyrrhogaster and its European kin (?) Triturus marmoratus. With the genus Cynops, the vivid coloration is generally on the bellies (with the exception of certain C.ensicauda in the possession of a certain hobbyist
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), while with Triturus, the dorsum is the most colorful. What might account for this? From a predators' viewpoint, a waterbird seeking prey in a pond would probably be less deterred by the red belly of a C.pyrrhogaster than by the green-red dorsum of a T.marmoratus, whereas a predatory fish might be more deterred by the red belly of a C.pyrrhogaster rising for air than by the brightly colored dorsum of a T.marmoratus, when seen from below.

But this comparison may not be a good one since I assume that T.marmoratus is more terrestrial in the wild than is C.pyrrhogaster...

I still suspect that coloration in these species is not solely to do with predator deterrence
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Ed, would mysis shrimp be considered rich in caretenoids?
 
Does anyone know if there are any snakes that eat (or at least attempt to eat) Cynops or Triturus? I don't know anything about their vision, but garter snakes are pretty much the only predators capable of taking Taricha, and even then not all of them are resistant to the toxin and capable of actually eating one. It would be interesting if there were similar predator examples with other species of newts.
 
Hi Tim,
Don't forget the coloration in the tails of courting male C. cyanureus, and even C. orientalis for your comparision.

Mysids should contain plenty of the pigments as these will color flamingo feathers. (however I'm not sure that these have been fed to larva to see if the adults are more colorful as of yet, but it was a point I was pondering after I read this thread).

Ed
 
Liz, the frog-eating Pryer's keelback snake (Amphiesma pryeri) has been reported to prey occasionally on C.ensicauda adults and larvae.

Ed, yes, and the tails of courting male C.pyrrhogaster can get pretty colorful as well
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(Message edited by TJ on August 17, 2004)
 
Ed. C. o displays breeding colors?


I think T. marmoratus's dorsal coloration may be camouflage more than warning colors(green and black)....it just looks bright away from its element.
 
Hi Joseph,
On the tails, more color develops during the breeding season. Its no where near as pronounced as some of the other Cynops (or Triterus) but it is there.

Ed
 
Mind describing it? I remember asking a question on the same topic(breeding colors in C. o) and someone said they showed no change.
 
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