UPPER LEFT: Healthy animal showing cerata and ramifications of the digestive gland across dorsal body surface. UPPER RIGHT: animals starved, in dark, for 5 days, showing almost complete absorption of cerata and breakdown of digestive gland. Animals 5-6cm long. PHOTOS: B.Goldman.
A-C. Transverse sections through healthy animal showing: A digestive gland duct(d) running into cerata; B zooxanthellae (z) in cells of the digestive gland: C zooxanthellae in digestive gland. Scale = 40 microns. PHOTOS: Bill Rudman.
For general discussion on zooxanthellae symbiosis in nudibranchs see page on Solar-powered Sea Slugs.
Pinufius is always found on colonies of the coral Porites. It feeds on the coral tissue and retains symbiotic zooxanthellae from the coral, and keeps them alive in ducts of its digestive gland. There are a number of nudibranchs feeding on Porites, each species apparently utilising a differnet part of the coral tissue. In a preliminary experiment to see whether Pinufius actually required the zooxanthellae for its survival 5 freshly colected animals were kept in the dark, without Porites. After 5 days the cerata had been absorbed, and on histological examination, the digestive gland cells were disintegrating and the zooxanthellae expelled into the lumen of the digestive gland ducts. Earlier observations of mine showed that when Pinufius was kept on Porites colonies in an aquarium with insufficient light for photosynthesis, they did not grow or reproduce, but did not absorb their cerata even after 8 weeks. These preliminary observations suggest that Pinufius requires both coral tissue and zooxanthellae for adequate nutrition.
•Rudman, W.B. (1981) Further studies on the anatomy and ecology of opisthobranch molluscs feeding on the scleractinian coral Porites. Zoological Journal of the Linnean Society 71: 373-412.
•Rudman, W.B. (1982) The taxonomy and biology of further aeolidacean and arminacean nudibranch molluscs with symbiotic zooxanthellae. Zoological Journal of the Linnean Society 74: 147-196.
Rudman, W.B., 1999 (October 4) Pinufius rebus Zooxanthellae symbiosis. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/pinurebu2