LOCKHART, S.J.; MOOI, R.; JONES, C.D.; California Academy of Sciences; California Academy of Sciences; AMLR, Southwest Fisheries Science Center: Benthic imagery of echinoids living in Antarctic shelf habitats

In March of 2003, the US Antarctic Marine Living Resources (AMLR) program conducted a benthic trawl survey of demersal fish and associated invertebrates in the regions around the South Shetland Islands, Antarctica. In conjunction with the survey, more than 2,400 images were taken of the sea bottom in depths from 50 to about 500 meters. The majority of these photos contain images of echinoderms, most of which have seldom, if ever, been seen in situ. Consequently, the images have a great potential to enhance our understanding of how these poorly understood animals live, and with which other components of the biota they are associated. Our studies focused on the echinoid component of the benthos, notably cidaroid (pencil spine) and irregular sea urchins. We were able to record differing behaviors among several species of cidaroids, and several frames show cidaroids such as Notocidaris gaussensis actively feeding on sponges. Specimens of Rhynocidaris triplopora and of a new species of Notocidaris are also shown in the photos, but can be easily missed due to cryptic coloration. Irregular urchins in the family Schizasteridae are clearly epifaunal, and can often be found at the ends of trails on the substrate surface. The most notable and easily recognized of these is Brachysternaster chesheri. In spite of the importance of these qualitative observations, quantitative analysis of such photos to obtain population densities or abundance measures should be treated with extreme caution, not only because of the cryptic nature of even relatively conspicuous forms, but because of the great difficulty in making positive and accurate identifications.