Abstract
The ocean quahog Arctica islandica (L.) has been the focus of extensive research due to its commercial value and extreme longevity. However, little is known about its natural trophic behavior. In a feeding experiment that used plankton and clams collected from the White Sea coast, Arctica cleared a wide spectrum of particles, ranging from picoplanktonic cyanobacteria and nano-cryptophytes to diatom chains. Diatoms and heterotrophic dinoflagellates formed the bulk of Arctica ration, which equaled ~ 1% of its tissue carbon per day. The estimated prey selectivity increased with particle size, but the clams also discriminated between prey of similar size and taxonomy. The measured Arctica mass-specific filtration rates corresponded to those published earlier for intertidal mussels. Implications for Arctica growth are discussed.