A group led by researchers at Butantan Institute in Brazil and supported by FAPESP has described for the first time the presence of venom glands in the mouth of an amphibian.
The legless animal is a caecilian and lives underground.
It has toot-related glands that, when compressed during biting, release a secretion into its prey earthworms, insect larvae, small amphibians and snakes, and even rodent pups.
A paper reporting the study is published in iScience.
"We were analyzing the mucus glands in the skin of the animal's head, which it uses to burrow down into the soil, when we discovered these structures.
They're located at the base of the teeth and develop out of the dental lamina, the tissue that typically gives rise to teeth, as is the case with snakes' venom glands," said Pedro Luiz Mailho-Fontana, first author of the paper and a postdoctoral intern at Butantan Institute with a scholarship from São Paulo Research Foundation FAPESP.
In the new report the researchers show that caecilians can be venomous, and indeed are the first amphibians to have an active defense system.
Biologists apply the term venomous to organisms that bite or sting to inject their toxins, such as snakes, spiders, and scorpions, whereas poisonous refers to organisms that deliver toxins when touched or eaten.
In these caecilians, the secretion released by the glands also serves to lubricate a prey so that it is easier to swallow.
Except for a group that lives in aquatic environments, caecilians spend their entire lives in burrows or underground tunnels.
As a result, they have very small eyes, which sense light but do not form images.
They are also the only vertebrates that have tentacles.
In caecilians, these are near the eyes and act as feelers equipped with chemical sensors that test the environment for sensory data.