Mussels Mytilus edulis: significant consumers and destroyers of mesozooplankton

This study tested the hypothesis that mesozooplankton, particularly crustaceans, inhaled by mussels Mytilus edulis (L.) would be killed by ingestion, or by incorporation into pseudofaeces. Crustaceans were expected to be vulnerable because they cannot rid themselves of mucus. Field and laboratory evidence is presented to show that mussels ingest most mesozooplankton present in inhaled sea water, that some of the material is triturated in the stomach between crystalline style and gastric shield, and that energy can be extracted from a diet of Artemia sp. indicating a degree of carnivory. Gastric processing of 'prey' animals is rapid (<40 min at 15 to 20 degrees C). Molluscs and crustaceans are commonest 'prey'. Animals <3 to 6 mm length are ingested. Inhaled but non-ingested crustaceans become mucus-bound and are expelled in pseudofaecal particles; such animals are dead or moribund.