They May Not Be Snakes, however These Amphibians Have a Venomous Bite

Oral Glands Close Up

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An amplified picture of the mouth of a ringed caecilian, Siphonops annulatus, exposes snake-like oral glands. Researchers from Brazil’s Butantan Institute and Utah State University state the glands might show an early evolutionary style of oral venom organs. Credit: Butantan Institute, Brazil

Utah State University and Butantan Institute researchers release evolutionary findings in iScience.

Utah State University biologist Edmund ‘Butch’ Brodie, Jr. and associates from São Paulo’s Butantan Institute report the very first recognized proof of oral venom glands in amphibians. Their research study, supported by the Brazilian National Council for Scientific and Technological Development, appears in the July 3, 2020, concern of iScience.

“We think of amphibians — frogs, toads and the like — as basically harmless,” states Brodie, emeritus teacher in USU’s Department of Biology. “We know a number of amphibians store nasty, poisonous secretions in their skin to deter predators. But to learn at least one can inflict injury from its mouth is extraordinary.”

Ringed Caecilian Siphonops annulatus

A ringed caecilian, Siphonops annulatus. Neither snakes nor worms, caecilians are serpent-like amphibians associated with frogs and salamanders. Researchers from Brazil’s Butantan Institute and Utah State University report the animals have poisonous oral glands — the very first recognized discovery of the snake-like glands in amphibians. Credit: Carlos Jared, Butantan Institute

Brodie and his associates found the oral glands in a household of caecilians, serpent-like animals associated with frogs and salamanders. Neither snakes nor worms, caecilians are discovered in tropical environments of Africa, Asian and the Americas. Some are marine and some, like the ringed caecilian (Siphonops annulatus) studied by Brodie’s group, reside in burrows of their own making.

In 2018, the group reported the types produced compounds from skin glands at both ends of its snake-like body. Concentrated at the head and extending the length of the body, the animal releases a mucous-like lube that allows it to rapidly dive underground to get away predators. At the tail, caecilians have actually glands equipped with a toxic substance, which serves as a last line of chemical defense, obstructing a quickly burrowed tunnel from starving hunters.

“What we didn’t know is these caecilians have tiny fluid-filled glands in the upper and lower jaw, with long ducts that open at the base of each of their spoon-shaped teeth,” Brodie states.

Amphibian Scientists

Researcher Pedro Luiz Mailho-Fontana of Brazil’s Butantan Insitute, left, and biologist Edmund “Butch” Brodie, Jr. of Utah State University, U.S.A., at USU’s Logan, Utah school. Credit: M. Muffoletto

His research study coworker Pedro Luiz Mailho-Fontana, who studied with Brodie as a checking out college student at USU’s Logan school in 2015, saw the never-before-described oral glands. Using embryonic analysis, Mailho-Fontana, very first author of the paper, found the glands — called “dental glands” — stemmed from a various tissue than the slime and toxin glands discovered in the caecilian’s skin.

“The poisonous skin glands form from the epidermis, but these oral glands develop from the dental tissue, and this is the same developmental origin we find in the venom glands of reptiles,” he states.

The scientists speculate caecilians, geared up without any limbs and just a mouth for searching, trigger their oral glands when they bite down on victim, consisting of worms, termites, frogs, and lizards.

The group doesn’t yet understand the biochemical structure of the fluid kept in the oral glands.

“If we can verify the secretions are toxic, these glands could indicate an early evolutionary design of oral venom organs,” Brodie states. “They may have evolved in caecilians earlier than in snakes.”

For more on this discovery, read Snake-Like Venom Glands Discovered Along the Teeth of Amphibians.

Reference: “Morphological Evidence for an Oral Venom System in Caecilian Amphibians” by Pedro Luiz Mailho-Fontana, Marta Maria Antoniazzi, Cesar Alexandre, Daniel Carvalho Pimenta, Juliana Mozer Sciani, Edmund D. Brodie Jr. and Carlos Jared, 3 July 2020, iScience.
DOI: 10.1016/j.isci.2020.101234

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