Energy content and chemical defense of the articulate brachiopod Liothyrella uva (Jackson, 1912) from the Antarctic Peninsula

Abstract

Energy levels ( x ̄ ± 1 SD) of whole soft body tissues and shells of the antarctic brachiopod Liothyrella uva (Jackson, 1912) were 9.0 ± 1.0 and 1.1 ± 0.4· kJ· g −1 dry wt, respectively. The majority of the energy in the soft body tissues was attributable to NaOH-soluble protein (17.4% dry wt) and in the shell to lipid (2.6% dry wt). An intact individual with a shell length of 3.4 cm and a wet and dry wt of 5.8 and 2.9 g, respectively, contained a total of 9.6 kJ. As dense populations of L. uva occur in the Southern Ocean, this species represents a considerable potential energy resource for predators, including sea stars and fish (ca 10 3kJ·m −2 in some areas). Total crude extracts of whole brachiopod soft tissues caused significant retraction of sensory tube-feet in 6 species of sympatric sea stars. Control assays employing whole crude extracts of the fresh soft tissues of the antarctic limpet Nacella concinna (Strebel, 1908) or seawater alone did not elicit significant sustained tube-foot retraction. Bioactivity was diminished in frozen extracts of brachiopod soft tissues exposed to the sensory tube-feet of the sea star Odontaster validus (Koehler, 1906), but was not diminished in the tube-foot retraction response of the sea star Neosmilaster georgianus (Studer, 1885). Lyophilized brachiopod soft tissues ground into a fine powder and embedded at a concentration of 2% (wt:vol) in agar pellets containing 5% krill caused significant feeding deterrence in an allopatric fish (the sheepshead minnow Cyprinidon variegatus Lacepede 1803). These findings suggest that, similar to temperate zone and tropical brachiopods, body tissues of this antarctic brachiopod are unpalatable to potential predators.