Hallaxa michaeli - feeding record

Dear Nick,
This is a very interesting find. I have found this animal a few times in New South Wales and it was named Hallaxa michaeli about 10 years ago. Little is known about it, the original description being based on one 6 mm long animal. Many species of Hallaxa appear to feed on keratose sponges of the genus Halisarca, so I was excited to see your animal on this pink sponge which is Halisarca laxus (Lendefeld), a species known only from New South Wales. The identity of that species remained a mystery for over 100 years until a living specimen was examined by Pat Bergquist, who published a photo of an almost identically shaped and coloured colony as the one in your photo (Bergquist,1996). Also Bergquist stated that the sponge seemed to grow commmensally on the ascidian Pyura. By coincidence, the specimen whose photos I am using for the species Fact Sheet, was found on cunjevoi, the local name here for a stalked ascidian of the genus Pyura.

I only wish all my attempts at finding feeding information fell into place so well.

• Bergquist, P.R. (1996) The marine fauna of New Zealand. Porifera: Demospongiae Part 5. Dendroceratida and Halisarcida. New Zealand Oceanographic Memoir, 107: 1-53.

Best wishes,
Bill Rudman