The saliva of the shrew living in Poland contains venom that damages red blood cells. The results of the study on this animal were reported by scientists in the journal Zoological Letters.
Venomous insects, spiders, scorpions, jellyfish, fish, frogs, toads and snakes are well known. However, among mammals, the production of venom is rare. For example, male Australian platypuses have venomous spines on their hind legs. The North American short-tailed blarina (a species of the shrew) kills insects with venom contained in its saliva. Small insectivorous mammals from Cuba and Haiti called almics also have venomous saliva. Finally, the Eurasian water shrew (of the shrew family) living in Poland can kill an animal larger than itself with its venomous saliva. Its venom has a strong paralysing effect, which allows it to immobilise its prey and “store” it in a state of coma. The Mediterranean water shrew is also a venomous mammal.
Until now, they have been considered the only venomous mammals living in our country. However, Krzysztof Kowalski from the Nicolaus Copernicus University in Toruń and Paweł Marciniak and Leszek Rychlik from the Adam Mickiewicz University have discovered that the common shrew (Sorex araneus), a small mammal weighing between 5 and 15 grams, is also venomous. Since the shrew feeds around the clock, eating almost as much as it weighs (mainly insects and other invertebrates), additional hunting opportunities are badly needed. If it cannot eat, it dies within 10 hours.
As early as 400 years ago, there were suggestions in the literature that shrews were venomous (Topsell RE. Historie of Foure-footed Beasts. London: Jaggard; 1607), but later researchers found them to be unjustified.
Now, Polish scientists have taken a salivary extract from the salivary glands of the river shrew and the common shrew to test the effect of the venom in the sample on red blood cells (erythrocytes) of frogs of the genus Peophylax.
As it turned out, when exposed to the shrew’s saliva, severe haemolysis occurred, i.e., the passage of haemoglobin into the plasma as a result of the destruction of the erythrocytes. With their venom allowing them to hunt larger prey (such as small frogs, young mice and even other shrews), velvet shrews find it easier to avoid starvation.
“It is likely that venom production among shrews and other eulipotyphlans may be more widespread than it has previously been assumed,” – comment the authors of the publication.
(https://doi.org/10.1186/s40851-022-00191-5)