Rhabdophis subminiatus, Red-necked keelback – Kaeng Krachan National Park. Photo by Thai National Parks

LOGAN – Utah State University herpetologist Dr. Alan Savitzky is part of a multi-national research group of scientists who have documented an example of adaptation in the animal kingdom.

He said “keelback” snakes, found in southeast Asia, sport glands in their skin where they store a class of lethal steroids to protect them from predators. These snakes have derived the lethal poisons from eating toads.

This is where an evolutionary example of adaptation has been observed.

”The surprise from this most recent study is that a group of these snakes that have stopped eating frogs and started eating earthworms still have that same type of toxin in their skin,” Dr. Savitzky explained, “But in this case they’re not eating frogs and toads, they’re eating firefly larvae. And the fireflies also produce the same type of toxin the toads have in their skin.”

Savitzky said when the keel back snakes switched their diet it could have left them defenseless against their predators.

”In the process of switching from a diet of frogs, including toxic toads, to a diet of earthworms, the snakes would otherwise have been chemically unprotected except that they have been able to exploit this other source of toxins, which in this case is the firefly larvae.”

Savitzky said this represents a remarkable evolutionary example of adaptation to compensate for the absence of defensive compounds after the snakes shifted to a new class of prey.

Because of the distant relationship between toads and fireflies, he said, the dramatic dietary shift most likely involved a chemical cue shared by the toads and fireflies, perhaps the toxins themselves.



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