If a worm and a snake had a scandalous and slimy loving child, it could look like a cecilia: a legless creature that is not really a worm or snake, but an amphibian that lives in the ground and is found in the tropics all over the world. world.
Happy to spend most of their time below the forest floor, the caecilians are elusive and little known. That is why Carlos Jared, a biologist at the Butantan Institute in São Paulo, Brazil, has spent a good part of the last three decades on his way.
Packing a caecilian specimen, he said, often takes hours of painstaking digging, carefully executed so that a poorly-pointed shovel doesn’t split the creature in two. Once a specimen is seen, “you have to jump on it,” said Dr. Jared, and then fight the gnarled amphibian, which, depending on the species, can range in length from a couple of inches to five feet, in a sack. Many cecilias have wrung out of Dr. Jared’s grasp at the last moment, gleefully greased with a gelatinous substance gushing from his skin.
But Dr. Jared said the fascinating and sometimes mystifying biology of animals makes relentless pursuit worthwhile. Their team’s latest discovery, published Friday in iScience, shows that the mouths of the cilia are likely to be lined with venom-tipped teeth, unlike those found in some snakes.
The discovery would mark the first time that venomous glands have been found in the mouth of an amphibian, an evolutionary history prior to the appearance of snakes in more than 100 million years. That could make little-known Cecilies among the oldest poisonous mordants on Earth.
Like most other amphibians, Cecilias are believed to only produce poisons that, unlike poisons, are not actively injected into other creatures. Then Pedro Luiz Mailho-Fontana, a postdoctoral scholar who works with Dr. Jared, was puzzled when he discovered a series of fluid-filled canals lining the teeth of a Cecilian sample in the laboratory. “This is something very different here,” he recalled thinking.
After searching the mouths of newly hatched cilia, Dr. Mailho-Fontana determined that the glands that hold the teeth grow from the same tissue that gives rise to the teeth.
Dental tissue is also the point of origin for venomous glands in snakes, which could help explain the purpose of the new ducts, Dr. Jared said. With no legs or arms to dodge predators or prey, animals like snakes and cilia must rely on their heads.
Cecilies, like some snakes, are equipped with impressive teeth and can be quite “bitten,” said Emma Sherratt, an evolutionary biologist at the University of Adelaide who was not involved in the study.
If the caecilians also have a poisonous bite, they may have independently stumbled upon a strategy that worked well for many snakes. That would be “really interesting and remarkable,” said Shab Mohammadi, an evolutionary biologist at the University of Nebraska-Lincoln who was not involved in the study. Perhaps the lack of limb is an important impulse for the evolution of toxins transmitted by the teeth.
But Dr. Mohammadi also noted that it is still unclear how harmful the gland contents are, or how toxic they are to the insects and worms that the cilia make. Dr. Jared and his team have yet to perform an in-depth chemical analysis of the cecilium glandular gouple, although early tests show that it is packed with a protein that is also present in snake and insect venoms. The mouths of the cecilios appear to be full of slime at meal times, but the secretions have proven stubbornly slimy and difficult to remove, Dr. Mailho-Fontana said.
The researchers are also not sure how widespread the venom glands are among the species of Cilia, which currently number more than 200 (with many more likely unknown). If the ducts are found in ancient lineages, it could indicate that the cilices were among the first terrestrial vertebrates to bind their bites with poison.
Dr. Jared’s team plans to hook up a few more specimens, but even once they manage to get them, it won’t be easy.
A few years ago, during a visit to the laboratory of a collaborator in London, Marta Maria Antoniazzi, co-author of the study also from the Butantan Institute, picked up a small cecilio that quickly sank her teeth into her hand.
“It hurt a lot,” he said.
And it took a surprisingly long time for the wound to heal. Now, Dr. Antoniazzi wonders if she was an unintentional victim of poison.
“At the time, we could not have imagined,” he said.
