Re: Feeding in Ceratosoma brevicaudatum

October 27, 2000
From: Des Paroz

Hi Bill

Your response has got me wondering.

Firstly, I am 100% about the critter being a dorid nudibranch. Absolutely certain of that. And I did take quite some time to study the aspects (having followed the forum in detail, I'm learning what to look for in features and behaviour). Based on that, and comparing that with photos in Debelius and WA books, and your site, I am 95%+ sure of the identification of it as C. brevicaudatum.

Not sure if you know Bushrangers Bay at all, but the nudi was found in the shallows of the inner bay. This part of the bay is predominantly sand bottom, with large clumps of sea grass. There are some rocky areas, with small amounts of sponge growth.

Inner Bushrangers Bay is not a great spot for sub-tidal nudis.

This particular individual was found in a small clump of green sea grass on sand, with no visible sponge growth in the immediate vicinity. Maybe at least 10m away. I will certainly check this spot next time I dive the bay and look for any sponge growth. I know the bay reasonably well (at least 150 dives there), and can get back to the same spot easily. Being a large nudi I was able to pay close attention. It was curling around arms of sea grass, and really appeared to be feeding.

A mystery - I wish I'd had the camera.....

Best regards
Des

des@paroz.com

Paroz, D., 2000 (Oct 27) Re: Feeding in Ceratosoma brevicaudatum. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3216

Dear Des,
It's pretty hard to mistake Ceratosoma brevicaudatum for anything else so I guess the puzzle is to find what it is doing. Not all sponge-feeding nudibranchs stay on their food sponges and often sponges may form a thin layer over rocks and other hard surfaces and then become partly overgrown themselves making it extremely difficult to see them.

These dorids can live for some time without feeding so it could be travelling, and looking for a new sponge colony, or its food could be close by but very cryptic. A good example is the common intertidal dorid Rostanga arbutus in New South Wales, Australia. Any visitor to rock platforms is likely to see this bright orange-red nudibranch crawling busily along in rockpools. And yet it took me about 10 years to find what sponge it ate. One time with a hammer and chisel I broke off a slab of sandstone to expose a thin layer of the sponge Clathria aceratoobtusa which had been living in the crack, a millimeter or so wide, in the sandstone. Rostanga, apparently living in an environment devoid of any potential sponge food was in fact living in a place where its food was abundant, but just not visible.

Not that I suggest that you attack Bushrangers Bay with a jackhammer in search of sponges, its just that sometimes an answer, which seems so simple with hindsight, is very difficult to find.

Best wishes,
Bill Rudman.

Rudman, W.B., 2000 (Oct 27). Comment on Re: Feeding in Ceratosoma brevicaudatum by Des Paroz. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3216

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