Hydrichthys pietschi, New Species, (Coelenterata) Parasitic on The Fish, Ceratias holboelli

Abstract

A new hydroid. Hydrichlhys pietschi, was found on a myctophid fish, Ceratias holboelli Kroyer, collected off the leeward shore of Oahu, Hawaii. The basal plate of the hydroid erodes the pigmented epidermis and underlying tissues of the host. The literature on commensal and parasitic hydroids is reviewed.