Abstract
A sponge associated mysid crustacean, Heteromysis komaii Fukuoka, 2004, infecting in the gastral cavity of sponge, Callyspongia confoederata (Ridley, 1884), is reported based on the specimens from the northeastern coast of Izu-Ohshima Island, Sagami Sea, central Japan. The host sponges are distributed between 10 to 45 m in depth in our field observation. Eighty-four sponges were found in the region of about 6000 m², and H. komaii infected in the gastral cavity of 6 colonies of the sponges. In this case, 25 individuals of H. komaii composed of several stages of both sexes infected in a gastral cavity of C. confoederata. This finding is the second record of H. komaii.
