30 October 2025

A new species of marine turbellarian has been discovered in the Sea of ​​Okhotsk

A new species of marine turbellarian (polycladid)—Pseudoceros japonicus—was discovered in Aniva Bay in the Sea of ​​Okhotsk.
 
In September, during a hand-collecting operation, specialists from the Sakhalin branch of the Russian State Research Center "All-Russian Research Institute of Fisheries and Oceanography" (VNIRO) discovered seven specimens of the flatworm Pseudoceros japonicus in the offshore intertidal zone near the village of Prigorodnoye.
 
Previously, these animals were not thought to inhabit the waters of the Sea of ​​Okhotsk, and the only confirmed sightings of the worm in Russian waters were in the Sea of ​​Japan.
 
Pseudoceros is a genus of free-living marine flatworms of the order Polycladid, belonging to the class Ciliated worms, primarily found in the warm waters of the Pacific and Indian Oceans.
 
The discovery of these individuals in Aniva Bay expands our understanding of the species' distribution within its range.
 
The collected specimens were photographed and preserved in ethyl alcohol for further study.
 
VNIRO Press Service