The composition of fatty acids and stable isotopes in the detritophage Acila insignis (Gould, 1861) (Bivalvia: Nuculidae): Searching for markers of a microbial food web

The fatty acid composition and stable isotope ratios of carbon, nitrogen, and sulfur were analyzed in the protobranch bivalve Acila insignis, a selective detritophage inhabiting subtidal sand sediments of Vostok Bay (Sea of Japan). Soft tissues of A. insignis contained abnormally high concentrations of the polyunsaturated arachidonic acid, 20: 4(n-6), and a rare monounsaturated fatty acid 20: 1(n-13), which distinguishes this species from other bivalves. The high concentrations of these fatty acids in A. insignis, together with the low values of σ³⁴S and the high values of σ¹³C and σ¹⁵N, are probably a result of feeding on the microbial food web.