Opisthobranch of the Week Data
Hallaxa iju is considered to be very rare on Okinawa as only four specimens have been collected and the above featured animal is the most recent of the four (22 March, 1997), as of early April, 2000. The animal was found crawling on the surface of silty-sand amid strewn oyster rubble beneath Tengan Pier. The original photograph of the above small animal was shot at 4:1 (four times life size, using bellows and a 105mm macro lens). This species has been found in several localities within the western Pacific; in addition to Okinawa, the animals are known from the Marshall Islands, Papua New Guinea, and the Philippines.
Hallaxa iju was described by Gosliner & Johnson (1994) and the chosen specific name is the Marshallese word for star, which has reference to the stellate appearance of the rhinophores as viewed from a dorsal aspect. Gosliner & Johnson (ibid.) point out that "H. iju can be immediately distinguished from all other members of the genus by the expanded margins of the rhinophoral lamellae." The broad white rhinophoral extensions are quite evident in the above animal. Most members of the genus are cryptic on their sponge prey, and H. iju is probably a sponge predator as well, although the four Okinawan specimens were not found associated with any discernable prey.
I've included a photograph of one of the paratypes from Okinawa used in the species description.