Opisthobranch of the Week Data
Glossodoris hikuerensis was originally described, as Rosodoris hikuerensis, from the Tuamotu Archipelago (French Polynesia.), in the central Pacific, and it has a wide distribution from East Africa to Fiji and Queensland. This species is similar in color and shape to G. cincta. The following is taken from Rudman (1986) in reference to the similarity of G. hikuerensis to that of G. cincta:
. . . both species being a brownish colour with whitish speckling. In colour, G. hikuerensis differs in having a distinct brown, white and black border to the mantle and in shape it differs in the relatively wide, thin mantle overlap and the soft feel of the body, which is much more rigid in G. cincta. Internally, the radula of G. hikuerensis differs markedly from that of G. cincta. In specimens of similar size there are twice as many rows of teeth in the radula of G. hikuerensis and approximately twice as many teeth in each row. The individual teeth of G. cincta are only two-thirds the size of similar teeth in G. hikuerensis. The most obvious difference is the complete absence of denticles on the teeth of G. hikuerensis which distinguishes this species from all other species of Glossodoris.
Glossodoris hikuerensis is known to grow to a relatively large size; Scott Johnson (2000) reports in the Sea Slug Forum finding a 135mm individual from Enewetak and Atsushi Ono has seen an animal in the Kerama Islands in excess of 150mm. The species is considered to be very rare in the waters of Okinawa's Kerama Islands. I've not personally seen any of these animals in the waters of the main island of Okinawa, and Atsushi Ono reports photographing, in addition to the above featured animal, one 20mm individual as well as a 150mm specimen (per. com.).
The above animal was found on the surface of a rock in the waters surrounding Zamami Island, one of a series of islands in the Kerama Islands Group, which are located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.