Opisthobranch of the Week Data
Flabellina bicolor is considered to be common on Okinawa; I've seen and collected a total of twenty individuals (the initial two specimens were collected on the 3rd of July, 1987), although numerous others have been seen but not collected. This small attractive aeolid is the most common nudibranch seen in the upper three meters on live stony coral reefs here.
A translucent white or bluish-white body and the presence of a subterminal golden or orange band on each cerata characterize Okinawan specimens. F. bicolor is one of a group of species having lamellate rhinophores, and oral tentacles with a flattened terminal lobe. As the animal crawls, the flattened paddle-like oral tentacles continuously flap up and down. This behavior is apparently being done to test the crawling surface of the substrate.
F. bicolor is a widespread species found throughout the Indo-Pacific. Gosliner & Willan (1991) point out the great amount of pigment variability associated with the species and apparently this variability has been responsible for a great deal of confusion between this and previously described species of closely related members of the family.
The initial report of the animal's occurrence from Japan (Baba, 1936, Pl. 2, fig. 4 as Coryphella ornata) came from Ishigaki (an island of the Ryukyu Archipelago, approximately 450km Southwest of Okinawa).