The red-necked newt is an amphibian that looks like a toothy worm. With no limbs, smooth and shiny skin, it’s reminiscent of a snake, but it may not be just the appearance that looks like it. A new study has found that some of them may contain poison in saliva.
Scientists are surprised at this discovery. If it is true, “poison to saliva” is the first in amphibians. Nearly 200 species of red-necked newts live in the tropics of the world. They range in size, from Idioclium russeli, about 9 centimeters long, to Cacilia thompsoni in Colombia, which is nearly 1.5 meters long. “The Asian newt may be the least known group of vertebrates,” said Carlos Jarage, an evolutionary biologist at the Butantin Institute in Sao Paulo, Brazil.
Some species adapt to life in the dark and have completely degenerated eyes. This paper was published in the journal iScience on July 3. There are a total of three rows of the tipped teeth in the upper jaw and one row in the lower jaw, and the worm and arthropods are preyed on. It was already known, but when Jarerge was observing the red-necked newts captured in Brazil, he discovered secretory glands near its teeth that had never been reported before. In addition to saliva, it is a gland that may secrete toxic enzymes.
However, he cautioned that further analysis was needed to determine whether the saliva was actually toxic. If this were poison, it would be a breakthrough, said Emma Sherat, an evolutionary biologist at the University of Adelaide in Australia. One is that the poison used in the attack (distinguished from the poison for dangerous defenses when touched) has evolved independently in amphibians and reptiles.
There is a possibility that the conventional theory about the evolution of poison will be rewritten. At the same time, another question emerges about why the saliva of frogs and salamanders is not poisoned.
The only other known amphibian with attacking poison is a frog called Clethomints greeningi, which still lives in Brazil and stabs the opponent with the poison glands and sharp projections on his face. Scientists have recorded that there is a secretion gland around the teeth of a rhine-billed newt called Hypogeophis rotratus as of 1935.
However, they thought of it as a common mucus secretory gland. According to Jarage, for example, the secretory gland in the head of the red-necked newt secretes a lubricant that makes it easier to move around the ground.
On the other hand, the tail has a secretory gland that produces a defense poison, it is thought to prevent predators from chasing through the ground. Pedro Ruiz Mailho-Fontana, an evolutionary biologist at the Butantin Institute, who also led the study, took saliva samples from two Asian newts (Siphonops annutus) adults for this study and analyzed what chemicals were contained and found that it contained an enzyme group called “phthholipase A2.” It is widely found in animals with poisons for attack, such as wasps, scorpions, and snakes. According to the paper, the study team examined the physical structure of the secretory glands for four animals, two of which were observed with electron microscopy.
Mailho Fontana says she wanted to investigate with more individuals, but finding the red-tailed newt is not easy. They say it can take 20 hours to catch a newt, which is good at digging holes and diving. If more samples can be obtained, Mailho Fontana hopes to work with biochemistry and pharmacology researchers to investigate the true function of the secretory glands. Still, he believes that the saliva of the red-billed newt should help neutralize and digest the other party when preying on giant worms.
Many people think of bee needles and snake fangs when they hear that they are the venom of living things, but according to Mailho Fontana, there are many poisons that have evolved from saliva. The liquid in the mouth may have initially played the role of lubricant. It helped digestion, and eventually, it also acquired the ability to harm other organisms. Organisms with poison in saliva include snakes and beetles, as well as rats, slow loris, and bats in mammals.