Opisthobranch of the Week Data
Doriopsis granulosa is considered to be rare in Okinawan waters; I've not personally observed this rare dorid in the waters of Okinawa's main island, however, Atsushi Ono reports the above featured animal is only one of two individuals (only the above animal was collected) which he has seen in the Keramas* (pers. comm.). The featured animal was collected by Atsushi in September of 1998 from beneath live coral in five meters of water. D. granulosa has a Tropical Indo-Pacific distribution and is known to feed on siliceous sponges (Marshall & Willan, 1999).
There is apparently a fair amount of confusion in the literature in terms of the number of Doriopsis species within the genus. The following are comments taken from the Sea Slug Forum (Rudman, 1999) in regards to some of the confusion:
Species of Doriopsis are characterised by the arrangement of the gills in a transverse line across the back rather than in the typical dorid circle. Specimens of Doriopsis are either deep blue, green or yellow and there has been considerable confusion in the literature concerning how many species there are in the genus. At one extreme 4 species, one each of green and blue and two of yellow have been suggested, while at the other extreme only one variably coloured species has been proposed.
Biological observations from throughout the Pacific suggest that there are at least two species, one yellow or green and one deep blue. It is also possible that the yellow New Zealand species, Doriopsis flabellifera Cheeseman, 1881, is a third valid species. The earliest name for the yellow/green species is D. granulosa and for the blue, D. pecten. Reports from Hawaii (Kay & Young, 1969; Bertsch & Johnson,1981), Japan (Hamatani, 1961, Baba & Hamatani, 1961), central Pacific (Young, 1967; Johnson, 1981) show that D. pecten feeds exclusively on a deep blue sponge Terpios, and D. granulosa on a yellow or orange sponge, identified by Young (1967) as Prianos phlox de Laubenfels, 1954. The eggs of D. granulosa are reported to be yellow, while those of D. pecten are cream, and the egg ribbon of D. granulosa is about four times as wide as that of D. pecten.
* Keramas = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.