Opisthobranch of the Week Data
Cratena lineata is considered to be rare in Okinawan waters; I've not personally seen this very attractive aeolid in the waters of Okinawa's main island and Atsushi Ono reports the above featured animal is one of six which he has seen in the Keramas* (per. com.). The animal was collected by Atsushi in February of 1999 from a rope-supported buoy within the confines of a Zamami Island bay. Another attractive Cratena sp. from the Kerama Islands was featured earlier, Cratena simba.
Rudman (2000) describes the species as follows:
This species usually has white longitudinal lines on the body and cerata. Sometimes the lines on the cerata are restricted to the tip and sometimes the body can lack any pigmentation. The digestive gland duct in each ceras ranges in colour from bright red, green or dull brown to black. Often the basal section of the ceratal digestive gland duct is red, and the rest a brownish colour, perhaps reflecting a change in diet. Normally there is one large orange patch on each side of the head but in some specimens this can be replaced by a bent line or divided into two spots on each side.
Marshall & Willan (1999) point out the similarity between C. lineata and another closely related aeolid, Phidiana bourailli. The following is taken from their publication:
C. lineata is most similar to Phidiana bourailli because the cerata also have white streaks in that species. However in P. bourailli the rhinophores have ring-like extensions (annuli) and there are short vermilion dashes down either side of the body.
* Keramas = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.