Osezaki Suruga Bay, Japan, 9 Nov. 2002. Approx 7mm long. Depth: 9m. Photo: Jun Imamoto.
This photo fits the painting in Baba (1949) of Hervia affinis in all major respects. In particular the two large flattened rings on the rhinophores are very distinctive, and so are the inflated cerata which abruptedly end in a thin tapering papilla at the tip. Baba notes the body is covered in white spots, as is in this photo, and describes the cerata as having fine, longitudinal, opaque white lines and a dark digestive gland. It also has the red patches on the sides of the head the Baba describes. The onky major difference is that the ceratal digestive gland is not black, but that colour is most probably determined by the stage of the feeding cycle and the colour of the food. Described as Hervia affinis, the most appropriate genus for this species must wait until more material is examined.
Note added 2 Dec 2002: Photos of a very similar looking animal, also from Japan, were initially thought to be a colour variation of this species. They have the same characteristic ceratal shape and arrangement, and red patch at the base of the cerata, but they lack white lines on the cerata and the flattened rhinophore rings appear to be in the form of radiating papillae. See message below. I have placed photos concerning this 'form' or 'species' on a separate page as Cratena cf. affinis until their relationship to each other is clarified.
• Baba, K (1949) Opisthobranchia of Sagami Bay collected by His Majesty The Emperor of Japan. Iwanami Shoyen, Tokyo. 194pp., 50 Pls pages.
Rudman, W.B., 2002 (November 25) Cratena affinis (Baba, 1949). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/crataffi