Meeting Abstract
8.10 Sunday, Jan. 4 Palatability and anti-predatory chemical defenses in a suite of ascidians from the Western Antarctic Peninsula. KOPLOVITZ, G*; MCCLINTOCK, JB; AMSLER, CD; BAKER, BJ; University of Alabama at Birmingham; University of Alabama at Birmingham; University of Alabama at Birmingham; University of South Florida gilkop@uab.edu
Fourteen species of colonial and solitary ascidians were collected from hard and soft bottom habitats at depths ranging from 0 to 40 m near Palmer Station, Antarctica (64 46 S, 64 03 W) on the Western Antarctic Peninsula. Palatability was evaluated in laboratory bioassays using the sympatric omnivorous fish Notothenia coriiceps and the omnivorous sea star Odontaster validus. When compared to a control food, small bite-sized pieces of outer body tissue of all 14 ascidian species were unpalatable to fish (spit out), while 9 of the 14 species tested were unpalatable (rejected from the ambulacral feeding groove) to sea stars. Eleven ascidian species were collected in sufficient quantity to prepare lipophilic and hydrophilic extracts and incorporate these at tissue level concentration into alginate food pellets. Control (no extract) and experimental alginate food pellets tested in fish and sea star bioassays indicated that only the lipophilic extract of the colonial ascidian Distaplia colligans was deterrent, and in this case to both predators. Similarly, the omnivorous sympatric amphipod Gondogeneia antarctica was fed ascidian extracts (10 species) in alginate food pellets and only one species (the colonial Distaplia cylindrica) deterred feeding, while extracts in 7 species actually stimulated feeding. Thus, while Antarctic ascidians are unpalatable to sympatric consumers, their lack of palatability appears to be rarely based on organic chemical defenses, but rather be related to one or more of the following: 1) inorganic acids, 2) structural defenses (e.g., tunic toughness), or 3) low nutritional value. This research was supported by NSF grants # OPP-0442769 and OPP-0442857.
