Leeches, parasitic on bivalves, came to the rivers of Primorye from China and Japan.

Leeches B. kasmiana inside the shell of the bivalve. (Photo by press service of the Northern Federal University.)

Researchers from Northern (Arctic) Federal University together with colleagues from the Federal center for integrated study of the Arctic, RAS found in Primorye clam leech Batracobdella kasmiana.

By itself, this view is not new, but previously it was only found in Japan and China. Now it turns out that it is a lot in the basin of the Razdolnaya river near Vladivostok, and also in the Smooth river in the Khasan district of Primorsky Krai. According to experts, it should be also in the rivers of North and South Korea, but it has not yet been found.

Leeches Batracobdella belong to the family flat leeches that spetsializiruyutsya amphibians and aquatic reptiles, but some feed on the hemolymph of invertebrates worms and mollusks. B . kasmiana just refers to the latter: it prefers large freshwater bivalves – mussels and perlovits.

One clam can live over fifty leeches, but since leech hide in your shell, find them quite difficult. New information about the habitat of B. kasmiana you can see from the article in the journal Zootaxa. Most likely, the leech came into the South Primorye rivers of Japan, Korea or northeast China during the glacial period (about 20 thousand years ago), when sea level was much lower and rivers of these regions could be interconnected.

What B. kasmiana is in the rivers of Primorye – is actually not very good news. Bivalves, on which it is parasitic, it is very important for the self-purification of rivers and lakes. They feed on silt and algae which are filtered from the water; a single clam can filter more than 10 gallons of water per day.

However, due to human activities the number of clams in fresh water is strongly reduced, and the leech then becomes quite inappropriately – it may happen that filter out excess organics in rivers and lakes will become no one.