ABSTRACT
Ophiarachnella gorgonia (Müller &Troschel) (Ophiurida, Ophiodermatidae) is widely distributed in the shallow water of Indo-West Pacific Area. Two color types have been recognized for a long time: dark brown-colored type found in Japanese mainland and Korean temperate waters and pale-colored or dull red-colored type found from subtropical and tropical region. These two color types have been identified to the single species since H. L. Clark (1909) synonymyzed them into O. gorgonia because he recognized no morphological difference other than color. However, the detailed morphological observation showed that these two are different forms.We examined micromorphology of external and internal ossicles by using SEM. Morphological differences were observed between the two forms in disk granules, disk scales, radial shields, dental plates, vertebral ossicles, but not in stomach wall ossicles nor peristomial plates. These results suggests O. gorgonia may be actually two cryptic species, temperate and tropical forms, but further studies should be required.
