What is Solenodon poison

Poisonous mammal surprises researchers

Poison is a weapon that many vertebrates have in their quiver. However, it is distributed very differently: Poison is widespread among bony and cartilaginous fish as well as amphibians. The group, which used to be called reptiles, is limited to snakes and lizards - there are no poisonous turtles or crocodiles. And the birds drop out completely, apart from one or the other species that accumulate so much toxins in the body through ingesting poisonous food that it becomes inedible itself.

And the mammals? There are only a few examples, and they are spread across the family tree. The platypus, for example, has a poisonous spur on its heel and the kayan slow-paced lorikeet, an ancient primate, has a poisonous bite, which, however, comes about in a rather cumbersome way: the poison gland sits on the arm, so the lory has to lick it first to get the poison distributed in saliva. This is far from the elegance and effectiveness of venom injection as practiced by snakes.

Where the use of poison is a bit more common

The largest "concentration" of poisonous mammals can be found among the insectivores, specifically with the shrews and the weevils that only occur in the Caribbean. Researchers from the Liverpool School of Tropical Medicine and the Zoological Society of London have now taken a closer look at the latter and presented their results in the journal "PNAS".

Slot weevils (Solenodontidae) look a bit like shrews themselves, but in XL format. Including the tail, they can be over half a meter long. The neurotoxin that they produce in their salivary glands flows through a groove on one of their incisors into the victim's wound. It is not used against predators - of which there were hardly any until the arrival of humans and their domestic animals in the Caribbean. Its sole purpose is to paralyze the prey: insects, worms, and small vertebrates.

The team led by Liverpool researcher Nick Casewell focused on the Dominican sand weevil (Solenodon paradoxus), which only occurs in the forests of the island of Hispaniola. On the one hand, they carried out DNA analyzes of the animal and comparisons with other mammals; on the other hand, they took poison from wild weevils and analyzed it in the laboratory. Variants of kallikrein, an enzyme from the group of serine proteases, turned out to be the central components. According to the researchers, these have a blood pressure lowering effect - to put it mildly, this lowering can be severe enough to kill a mouse.

Kallikrein occurs in its basic form in the salivary glands of many mammals, including humans. What surprised the researchers is the fact that the sand weevil has developed into a poisonous form that is very similar to that of poisonous shrews. According to genetic analyzes, these two animal groups went their separate ways 70 million years ago, so the poison apparatus is a case of convergent evolution. According to the study, insectivore species have become poisonous four times independently of one another. Casewell calls it "a fascinating example of how evolution can lead new adaptations along repeatable paths".

Samuel Turvey of the Zoological Society of London describes the Dominican weevil as "one of the most fascinating animals in the world". Neither that nor his poison system help him in his current emergency. In both states that share the island of Hispaniola - Haiti and the Dominican Republic - it is suffering from the destruction of its habitat and feral domestic animals such as cats, dogs and mongooses. It has been on the Red List as critically endangered for decades. (jdo, November 27, 2019)