Some observations on the diet and distribution of nudibranchs at Signy Island, Antarctica

Observations were made on the diet and distribution of eight species of nudibranchs found in Borge Bay, Signy Island, Antarctica. Specimens from seven sites were examined in situ on four separate occasions during 1992 and 1993 using SCUBA. A small collection for identification was also made. Six of the eight species present were identified, and the first ecological data for at least one species (Charcotia granulosa) were recorded. Notaeolidia gigas was feeding principally on hydroids of the genus Tubularia over the entire depth range surveyed (3-36 m), and was most abundant in shallow water, whereas Tritoniella belli was only found at deeper sites, mostly on an octocoral of the genus Ascolepis. Charcotia granulosa and Pseudotritonia gracilidens appeared to be specialist bryozoan feeders and, as has been found at other locations, Austrodoris kerguelenesis specialised on the demosponge Dendrilla antarctica. Two unidentified aeolid species occurred almost entirely on particular hydroids and the prey of Tritonia antarctica was not apparent. The physical size of Antarctic nudibranchs may have important implications to the type of prey and feeding strategy used by different species.