Opisthobranch of the Week Data
The above image of Rostanga sp. 2 is the only specimen seen and collected here and it's considered to be very rare in the waters of Okinawa's main island. It was collected in an area of mixed coral rubble and rock from 190 feet of water from beneath rock rubble during a mid-morning SCUBA excursion. The majority of the described species of Rostanga apparently feed on orange or reddish-orange sponges from which the dorids retain the color of the host. The majority of described species are orange or a reddish orange color. Rostanga risbeci described by Baba (1991) from Japan however is black and is known to feed on a black sponge (Baba, 1991). The above featured animal was not found associated with any specific food sponge.
I've previously featured an additional unknown Rostanga on these pages from Gahi Island, one of a series of islands in the Kerama Islands Group *, Rostanga sp. 1.
* Keramas = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.