Re: Unknown translucent dorid from Brazil

Dear Vinicius,
One of the problems with the Halisarcida is that often they don't look like sponges at all - they often look like a thin layer of rubbery plastic over a rock. Actually I once took a rock to a sponge expert - who I won't embarass by naming - who insisted that what I was showing him was a compound ascidian, and only changed his mind a few months later when he examined it microscopically. There might not have been any sponge on your rock, but it is also possible there was a small colony of a halisarcid which didn't look like a sponge. There is a good photo of the Atlantic species, Halisarca dujardini on Bernard Picton's site at:
http://www.habitas.org.uk/marinelife/species.asp?item=C9100

and have a look at the Fact Sheet for Hallaxa chani where the photo shows the animal on another species of Halisarca. I also have a photo of another half-eaten colony of Halisarca which I'll post in a day or so
Best wishes,
Bill Rudman