Opisthobranch of the Week Data
I've not personally seen Baeolidia japonica here in the waters of Okinawa's main island, however, Atsushi Ono mentions (pers. comm.) seeing over 20 individuals in the Keramas*, but has collected only two specimens. Atsushi found the above featured animal in an area of mixed rock and dead coral. Atsushi considers the species to be uncommon in the Keramas.
Baba (1933) originally described the species from a single specimen found attached to Sargassum in Tomioka Bay. Baba's species description is taken from his 1933 publication as follows:
The body in life is small and measures about 12mm in length. The oral tentacles are slender and smooth, while the rhinophores are provided with small processes on the surface. The branchial papillae are somewhat compressed and arranged in 5 groups on either side of the back. The foot at its anterior margin is grooved transversely and the upper lip is notched in the middle; the antero-lateral corners are produced into horns.
The body including oral tentacles, rhinophores and branchial papillae are dark brown with whitish spots.
In addition to the above featured animal I've added a second image of B. japonica, also kindly furnished by Atsushi.
* Keramas = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.