Opisthobranch of the Week Data
Bosellia sp. 1 is considered to be very rare in the waters of Okinawa's main island as I have seen and collected only the above single individual. This animal was collected from a clump of Halameda algae located in a surge channel between a rocky coast line and a live stony coral reef. The above photo has the animal on a blade of the Halameda upon which the specimen was collected.
Bosellia sp. 1 would seem to have a broad distribution; on the Sea Slug Forum it's reported from Hawaii, Kagoshima (Japan), and Okinawa. Ono (1999) also includes photos of this species in his book Opisthobranchs of Kerama Islands. Rudman (2004) commenting on Jun Imamoto's Kagoshima animals in the Sea Slug Forum, points out a discussion with Kathe Jensen as follows:
This is indeed an interesting find. I have checked with Kathe Jensen [#12346] who agrees that it is a species of Bosellia. There are only 'hints' at Bosellia being found in the Indo-West Pacific. Marcus (1978) mentioned specimens from the Red Sea and Burn(1998) mentions that Sherman Bleakney found specimens in Hawaii. It is interesting that Kathe Jensen mentions a sighting from Hawaii as well, in her message. As she says, until we know more it is difficult to say whether your animal is the same as one of the Atlantic species. If it is, it would be a very unusual 'natural distribution'.
Perhaps of interest is that two of Jun Imamoto's (Imamoto, 2004) photographs on the Sea Slug Forum have the small red mid-dorsal spot much the same as the single Okinawa specimen.