Hallaxa michaeli on food sponge

March 23, 2007
From: Nicholas Missenden

Concerning message #17219:

Hi Bill,

Just thought I would send you some pictures that I took today of Hallaxa michaeli. I have taken pictures of them feeding on the yellow keratose sponges. As you can see from the full picture of the sponges there are a number of Hallaxa michaeli and their egg ribbons visible.

Locality: Bare Island, 22 m, NSW, Australia, Botany Bay, 21 March 2007, Sand bottom, broken reef . Length: from 10 mm to 20 mm. Photographer: Nicholas Missenden.

Regards
Nick

njmpm@iinet.net.au

Missenden, N.J., 2007 (Mar 23) Hallaxa michaeli on food sponge. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19734

Dear Nick,

Thanks for this great series of photos. It illustrates the close relationships these three species have to each other - Hallaxa michaeli feeding only on the sponge Halisarca laxus, and the sponge being found only on the stalked ascidian Pyura. For those of you not familar with Pyura, it is a stalked solitary ascidian, often found in groups or quite large beds. In Nick's photo the whole ascidian, stalk and body, are covered in a layer of sponge.

In your photo we can see the Hallaxa can burrow quite deeply into the sponge tissue, and its almost transparent mantle renders it almost invisible on its prey. In an earlier message [#17219] you mention finding Hallaxa on different coloured sponges. From you photo here it seems that the one colony of the sponge can range in colour through cream, brown, yellow and pink - which is new information on the sponge Halisarca laxus.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Mar 23). Comment on Hallaxa michaeli on food sponge by Nicholas Missenden. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19734

Factsheet

Hallaxa michaeli

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