Strange snake-like animals have venom in their mouths

The researchers describe special glands along the teeth of the ringed caecilian species (Siphonops annulatus) with a biological origin and function similar to the venom glands of snakes in a study published July 3 in the journal iScience. If further study helps confirm those glands contain venom, the caecilian could become the oldest terrestrial vertebrate with oral venom glands.

Siphonops annulatus curled up on the forest floor.

Caecilian are strange creatures, they are almost blind, using a combination of facial tentacles and mucus to find their way in underground burrows. "This animal secretes two types of compounds, the tail secretes poison while the head produces mucus to help them crawl on the ground," said biologist Carlos Jared, director of the Laboratory of Structural Biology at the Butantan Institute in São Paulo, Brazil, said. "Since caecilian are one of the least studied vertebrates, their biology is a black box full of surprises."

Pedro Luiz Mailho-Fontana, postdoctoral fellow in the Laboratory of Structural Biology and lead author of the study, found a series of small fluid-filled glands in the upper and lower caecilian jaws, accompanied by long tubes. at the root of the tooth. Through analysis of embryos, Mailho-Fontana found that the oral glands originate in a tissue distinct from the toxic glands and the caecilian skin mucus.

Mailho-Fontana et al. suspect that caecilian can use secretions from glands in the mouth to incapacitate prey. Since caecilian have no legs, their mouth is the only tool they have for hunting. According to Marta Maria Antoniazzi, an evolutionary biologist at the Butantan Institute and co-author of the study, caecilian can activate glands in the mouth when biting, and integrate specialized biomolecules in secretions.

Preliminary chemical analysis of secretions from caecilian oral glands revealed increased activity of phospholipase A2, a protein common in animal poisons, and even higher levels than in some species of rattlesnakes. It is possible that the caecilian represent a more primitive form of venom gland evolution. Snakes appeared from the Cretaceous period about 100 million years ago but the caecilian date back much longer, about 250 million years.

This also suggests that it represents a more primitive evolutionary form of the venom gland. Scientists still do not know how toxic the glandular mucus is, pending further chemical analysis.

Caecilian is the only amphibian that fertilizes internally

Males have a penis-like organ that is inserted into the female's vagina during copulation, a process that lasts two to three hours. About 25% of the caecilian are egg-laying animals and 75% are egg-eaters, the eggs they lay are crystal clear. Like snakes, this animal also uses its mouth to hunt for prey, worms, mollusks, small snakes, frogs, lizards, etc. are their food.