There are many poisonous snakes. But how many species of snakes use the poison of their prey to attack? Just one. The snakes Rhabdophis, originally from Southeast Asia. Instead of producing their own poison they borrow it from their food, the toads. They store it in their own body to paralyze the heart of possible predators. Interestingly, researchers have realized that some species of the same genus do not devour toads. But they have found another source of toxicity, hitherto unknown and completely unexpected: fireflies. The snake that borrows the poison is amazing.
Toads … and fireflies
These snakes wear glands in the skin where they store bufadienolides. A class of lethal steroids they get from the toads, their toxic prey of choice. «They bend their necks in a defensive posture. Surprise unfortunate predators with a bite of toxins, ”says Utah State University herpetologist Alan Savitzky. Raptors and small carnivorous mammals can end tragically.
Snakes get sus toxins from the toads they devour. But not all members of the genus derive their defensive toxin from the same source. Some of them exchanged their main toad diet for earthworms. As these are harmless, snakes have added a dessert that produces the same class of toxins as toads. Firefly larvae. The findings appear in the PNAS magazine.
"It is the first documented case of a vertebrate predator that changes from a vertebrate dam to an invertebrate dam because of the selective advantage of obtaining the same defensive toxin," says Savitzky.
There is a distant relationship between toads and fireflies. The drastic change in diet probably involved a chemical signal shared by both. Maybe the toxins themselves. They are the only animals currently suspected of synthesizing these compounds. "This represents a remarkable evolutionary example of adaptation," says Savitzky.
Changing the diet
Researchers do not know what caused this change in diet. There is also no information to suggest that toads are not available in regions where snakes eat worms. It is possible that the change in diet occurred in response to a higher density of earthworms compared to toads, ”he explains. “It is possible that a diet of earthworms is richer in energy. At least compared to the cost of catching worms versus frogs. But that is simply speculation, ”clarifies the researcher.
The snake that borrows the poison is a notable example of how species adapt in the survival game.