Opisthobranch of the Week Data
Cratena sp. 1 is considered to be very rare in the waters of Okinawa's main island as I have seen and collected a total of only two individuals over a period of many years of diving here. The above featured animal was collected toward the end of a SCUBA dive while on a long decompression; it was found in a narrow cut near shore. Specifically, the animal was found on a "feather hydroid" (thecate hydroid) amid a dense growth of red algae species. I've added an additional page illustrating the only additional specimen I've collected here. Gosliner (1987, p. 127) reports what appears to be the same animal as Cratena sp. 1 from Southern Africa.
Cratena sp. 1 is quite similar to Baba's animal from Sagami Bay (Hervia affinis), and may turn out to be a color variation of Cratena affinis (Baba, 1949). The two large flattened rings on the rhinophores are distinctive, as are the inflated cerata which abruptly end in a thin tapering papilla at the tip. Cratena sp. 1 is missing the two large red spots seen in the drawing from Baba. I've added a page with the original drawing from Baba of Cratena affinis (as Hervia affinis).
I've also added the following links to the two described species of Cratena from Okinawan waters. These two are: