Abstract
A new cyclopoid copepod, Lichomolgus nakaii, was found in the branchial cavity and the intestines of the edible simple ascidian Halocynthia roretzi collected from the Pacific coast of northern Honshu, Japan. The new species is the fourth with four claws on the second antenna and the first associated with ascidian. It can be clearly distinguished from congeners by the possession of the shortest caudal rami, the form of genital segment, and the presence of one outer denticulate projection on the second segment of the fourth endopod.
