Feeding on Halimeda

June 27, 2003
From: Oliver A. Gussmann

Dear Dr. Rudman,
In my PhD research I have come across 'curious zig-zag grazing traces' on the living segments of the calcareous alga Halimeda. I have read that some nudibranchs feed on the alga's chloroplasts, and wondered if they would leave such (any) a grazing trace. Any comments would be helpful.
Sincerely,
Oliver Gussmann
Department of Marine Science
University of Otago
Dunedin, New Zealand

gusol423@student.otago.ac.nz

Gussmann, O.A., 2003 (Jun 27) Feeding on Halimeda. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/10330

Dear Oliver,
If you look at the Solar-powered Sea Slugs Page you'll get some information on sacoglossan [not nudibranch] feeders and their retention of chloroplasts.

A number of species do graze on species of Halimeda. In the Indo-West Pacific the most common species to do this is Elysiella pusilla [see Page 1, Page 2]. You can find other examples on the Forum by using the search facility to search for halimeda

As to grazing marks. Although I have often found them on Halimeda I can't recall seeing grazing marks. This may be related to the nature of their teeth - they have a ribbon consisting of a single tooth in each row. In those grazing molluscs that leave recognisable traces, the radula ribbon is quite broad, usually with multiple teeth in each row. This doesn't mean your grazing marks aren't caused by a sacoglossan, but I would say it is unlikely.
Best wishes
Bill

Rudman, W.B., 2003 (Jun 27). Comment on Feeding on Halimeda by Oliver A. Gussmann. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/10330

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