Abstract
A copepod, Pseudanthessius chuukensis Uyeno, n. sp. (Cyclopoida: Pseudanthessiidae), is described based on the type specimen obtained from the grouper Epinephelus sp. (Actinopterygii: Perciformes: Serranidae) caught in Chuuk Lagoon (North Pacific Ocean), Federated States of Micronesia, North Pacific Ocean. The copepod differs from its congeners in the following female characters: the urosome is 5-segmented; caudal rami are five to six times longer than wide; the distal endopodal segment of leg 1 carries three spines and three setae; leg 4 endopod has two setae, without proximal swellings, and as long as about two-third of that of the exopod. This finding of the copepod is the first record of the family Pseudanthessiidae from the actinopterygian fish.