Role of diet on population dynamics of the scale-worms Lepidonotus squamatus and Harmothoe imbricata(Polychaeta, Polynoidae) in the White Sea

Abstract

Under the harsh environmental conditions of the White Sea, the polynoid polychaetes Lepidonotus squamatus and Harmothoe imbricata coexist in the same habitats, often showing recurrent alternations in dominance. The present study focused on their diet and food preferences based on the analyses of gut contents (after dissection of preserved specimens) and faecal pellets (released by selected living specimens). Our results pointed out that the dietary regimes were significantly dependent on the collection site (and the respective dominant prey species) and not on the scale-worm species, suggesting that L. squamatus and H. imbricata are non-selective at the species level. There was also a significant overlap of their dietary regimes and our data support the existence of intra- and inter-specific aggressive behaviour, with H. imbricata being more aggressive than L. squamatus. These findings, combined with their life cycle strategies and other biological and environmental constraints, arose as significant driving forces explaining the population dynamics of the two studied scale-worms in the White Sea.