A new mesopelagic larvacean, Mesochordaeus erythrocephalus, sp. nov., from Monterey Bay, with a description of its filtering house

A new species in the genus Mesochordaeus is described from 25 specimens collected by a remotely operated vehicle at mesopelagic depths in Monterey Bay, California.Mesochordaeus erythrocephalus is a large species (tail length up to 50 mm, trunk length up to 7 mm) characterized by large crescent-shaped spiracles, digitate lips, a bifurcate tail and bright red pigmentation of the digestive system.The filtering 'house' is large, 4-5 times the tail length of the animal, and its structure is most similar to that of another large mesopelagic larvacean, Bathochordaeus.This description confirms the distinctness of this recently erected genus, but raises questions as to its taxonomic affiliation.