Description of two species of Peniculus von Nordmann, 1832 (Copepoda: Siphonostomatoida: Pennellidae) parasitic on commercial fishes from Korea, including a new species.

Two pennellids of the genus Peniculus von Nordmann, 1832 (Copepoda: Siphonostomatoida: Pennellidae), including a new species, are described based on adult post-metamorphosis female specimens collected from commercially important fishes off Chuja Island, Korea. Peniculus quadratus n. sp. was collected from the surface of the mouth palate of the surfperch Neoditrema ransonnetii Steindachner (Perciformes: Embiotocidae). The new species can be differentiated from its congeners by a combination of the following features: the shape of the cephalothorax is relatively quadrangular, the fourth pedigerous somite is incorporated into the anterior end of trunk, and the trunk is bottle-shaped, narrowing slightly towards anterior extremity. Peniculus fistula von Nordmann, 1832 was collected from the dorsal fin and body surface of the pearl-spot chromis Chromis notata (Temminck & Schlegel) (Perciformes: Embiotocidae). A close comparison of the specimens of P. fistula collected from Korea with the original description revealed some differences in the shape of the cephalothorax and the length/width ratio of the trunk. These discrepancies are considered to represent intraspecific variation or observational errors. The finding of P. fistula represents not only a new record from the Northwest Pacific but also from a new host.