Tissue-specific palatability and chemical defenses against macropredators and pathogens in the common articulate brachiopod Liothyrella uva from the Antarctic Peninsula

The punctate terebratulid brachiopod Liothyrella uva is the most common brachiopod species in Antarctica. Whole brachiopods, either live or freeze dried and ground into a powder and suspended in alginate, were unpalatable to the sympatric macropredators Odontaster validus (an abundant, omnivorous sea star) and Notothenia coriiceps (an abundant, omnivorous, epibenthic fish). The unpalatability of these ground tissues coupled with that of lipophilic extracts of whole L. uva presented in alginate pellets to O. validus, suggests an involvement of chemical defenses. Several isolated brachiopod tissues were also unpalatable to O. validus after being freeze dried, ground and suspended in alginate, but only the pedicle was unpalatable in such preparations to both O. validus and N. coriiceps. This observation is consistent with the Optimal Defense Theory since the pedicle is the only tissue not protected inside the brachiopod shell. There was, however, no correlation between the energetic content and unpalatability of any of the individual tissues. Organic extracts of tissues involved in feeding (lophophore and intestine-stomach) had relatively strong antimicrobial activity when assayed against several strains of Antarctic bacteria. However, the lophophore was palatable to both macropredators, suggesting nonoverlapping chemical defenses are involved in protection against predators and pathogens.