Metasychis varicollaris sp. nov. and report of Metasychis gotoi (Maldanidae, Annelida) from the China Seas.

Polychaete species are widely distributed throughout Indo-Pacific and European waters. We collected Metasychis specimens from the China Seas to report on Metasychis varicollaris sp. n. and Metasychis gotoi (Izuka, 1902) in greater detail. Geographic analysis of the potential distribution areas of M. gotoi indicates that it may be found in most coastal areas of China. The newly discovered species, M. varicollaris and M. gotoi, have an overlapping distribution in the northern South China Sea. Metasychis varicollaris sp. n. is characterized by a crenulated cephalic rim, complete collar on chaetiger 1, a packet-shaped anal funnel, and a spirally-fringed notochaetae with spiral pectinate bands imbricated over the main shaft. Our study provides a taxonomic key to all species of Metasychis.