Abstract
Parasites, particularly crustaceans, are considered as an important limiting factor in the development of intensified fish culture. The parasitic copepod of the Arabian Gulf fish is poorly known. So, the current investigation aimed to record the caligid species infecting the rosy goatfish Parupeneus rubescens in the Arabian Gulf. One copepod species was identified belonged to family Caligidae and labeled as Lepeophtheirus salmonis Krøyer 1837 depends mainly on its morphological, morphometric, and ultrastructural characteristics. It is characterized by lacking lunules, the anterior margin of the cephalothorax is not folded, three-segmented exopod of the fourth leg and longer than the protopod, leg 4 with the middle terminal claw as long as the inner one, accessory processes on terminal elements II and III of the exopod of the first leg, a genital complex distinctly wider than being long, and a relatively short abdomen. Therefore, the present study demonstrated that the rosy goatfish represents a new host for Lepeophtheirus species and added locality records for this infection.