Snakes swap toxic toads for fireflies but retain unique chemical defence

Chemical analysis has revealed that an ‘extreme’ dietary shift millions of years ago helped a group of snakes retain its unique chemical defence system.

Rhabdophis snakes, commonly found across eastern Asia, acquire defensive toxins from their prey, rather than producing it themselves, that makes them unpalatable to predators. However, one group of Rhabdophis species native to southern China has shifted its diet away from poisonous toads to harmless earthworms. Despite this, the snakes still seem to have the same class of defensive toxin that their relatives derive from amphibians. Chemical analysis has shown that the snakes now source it from the only other organism known to produce bufadienolide compounds – fireflies.