Bornella cf japonica Baba, 1949

This species, which we think is Bornella japonica, is known in the Marshalls from a single specimen found in a shallow ledge in the windward seaward reef's groove and spur system of Kwajalein Atoll. This is right in or just out from the zone where the ocean waves break on the reef and for most of the year, it is an extremely rough and surgy area. Only during the doldrums and when the swell is down are we able to dive there. It is amazing that these small nudibranchs can hold on during the normally surgy conditions. Yet this is not the only nudibranch found there. This zone is also the best area in the atoll for Glossodoris rufomarginata, G. atromarginata, Pteraeolidia ianthina, and Flabellina exoptata. Bornella cf japonica differs from the more common Bornella stellifer in that it has a much brighter red network of lines over a white body, and its dorsolateral processes are white and very slightly flattened. It matches Baba's original description pretty well. The dorsolateral processes form three pairs, plus a couple of small single processes near the posterior end. The processes could be described, as Baba (1949) does, as bifid at the tips with smaller points around the base (although Baba reported just two smaller points while our specimen has three or four). The rhinophore sheaths have 4 or 5 supra-marginal papillae, the posterior one of which is larger and bifid or trifid, much the same as Bornella japonica. The only reasons for not being more positive about the ID is that so far B. japonica is known only from Japan, and photos thought to be this species on the Sea Slug Forum, while similar, do look just a bit different

The small black eye is visible just below the rhinophore sheath in the specimen below.

Created 20 January 2007
Updated 31 May 2007

Reference:

Baba, K. 1949. Opisthobranchia of Sagami Bay. Iwanami Shoten. Tokyo.