Opisthobranch of the Week Data
Cratena simbais an attractive member of the genus and is considered to be very rare in Okinawan waters; I've not personally seen nor collected any specimens and it is unknown from Okinawa Island, but it has been photographed and collected by Atsushi Ono in the Kerama Islands. The close proximity of the main island of Okinawa to the Kerama Islands, as well as the similar opisthofauna to that of the Kerama Islands, suggests the possibility that it is also present here on Okinawa proper. The above featured animal is one which was photographed in the waters of Gahi Island, one of a series of islands in the Kerama Islands Group, which are located 30 ~ 40 kilometers west of the Okinawa capitol, Naha. This featured animal was photographed by Atsushi Ono on 1 August, 2000, from the waters off the SE Area of Gahi Island, in 8m of water. Atsushi's beautiful photograph is used here with his kind permission; it should be noted that Atsushi considers the species to be rare in the Kerama Islands in as much as this is the only representative of the species he has seen (per. comm.).
Marshall & Willan (1999) point out the close similarity between Cratena simba and that of some specimens of Phidiana bourailli. Unfortunately I do not yet have the original species description by Edmunds (1970) and will use, in part, the following description from Marshall & Willan (1999):
This is a very small aeolid nudibranch with a long and slender body. The dorsum is high and rounded in profile. The anterior foot corners are enlarged into pointed tentacles, and thus prominent. The tail is exceptionally long and the tip is pointed. The oral tentacles are very long and slender. The rhinophores are slender and have weak annuli. The cerata are slender and smooth, and they taper evenly to a rounded tip with a constriction immediately below the apex which is thus like a nipple. The cerata are arranged in five discrete clusters in symmetrical pairs.
The general body color is translucent white with narrow, wavy, vermilion lines and scattered opaque white spots. The basal half of the oral tentacles and rhinophores is translucent with white spots and the distal half is uniform opaque white. There is a pale orange ring half way up the rhinophores. The cerata are translucent with fine longitudinal opaque white lines and the digestive diverticulum, which occupies the entire space of the ceras, is pale brown.