PETERS, K.J.*; AMSLER, C.D.; MCCLINTOCK, J.B.; BAKER, B.J.; Univ. of Alabama at Birmingham; Univ. of Alabama at Birmingham; Univ. of Alabama at Birmingham; Univ. of South Florida: Palatability and chemical defenses of Antarctic Peninsula sponges

One of the major benthic taxa in terms of biomass along the western side of the Antarctic Peninsula is Demospongiae. These sponges, which are primarily found at depths greater than 30 meters, are predominantly preyed upon by spongivorous and omnivorous sea stars with the most abundant sea star in our study area being the omnivorous sea star, Odontaster validus. In the current study, demosponges were collected from the shallow waters (<40 meters) around Anvers Island, Antarctica. Out of the 51 sponge species collected, 33 (65%) were collected in great enough numbers to have at least three replicates available for live tissue feeding assays. The fresh outer tissue from 24 of the 33 (73%) sponge species was rejected when presented to O. validus. There were 22 unpalatable species amenable to separation of inner and outer layers. Using only fresh sponge tissue, 36% of the unpalatable species had the outer layer rejected while the inner layer was not rejected. Crude organic extracts were made of the species that showed any rejection when fed to O. validus. The extracts from 13 unpalatable species were used in feeding assays and the lipophilic and/or hydrophilic extract was rejected in all of them. This provides evidence that chemical defenses are an explanation for all of the unpalatability observed in the present study. This research was supported by National Science Foundation awards to CDA and JBM (OPP-0125181) and to BJB (OPP-0125152).