Influence of marine microalgal metabolites on the feeding behavior of the blue mussel Mytilus edulis

Effects of microalgal ectocrines on the feeding behavior of the blue mussel Mytilus edulis L., collected from Delaware Bay, Lewes, USA, were studied. Unialgal cultures of six species of marine microalgae were grown to the end of their exponential growth phase. Cells were removed by gentle filtration, leaving dissolved microalgal ectocrines in culture filtrates. Filtrates were then tested in filtration rate and particle selection bioassays. In filtration rate bioassays, dissolved ectocrines were delivered to mussels in a flow-through apparatus and removal of beads (6 m) used to determine rates. Filtration rates were significantly reduced by dissolved ectocrines from two of the microalgal species tested (Olisthodiscus luteus Carter and Dunaliella tertiolecta Butcher). None of the microalgal filtrates stimulated filtration rates of mussels. In particle selection bioassays, ectocrines were adsorbed onto either reverse phase (lipophilic) or normal phase (hydrophilic) microparticles (10 m) and delivered to mussels with an equal concentration of control treated particles. Mussels showed significant selection, either rejection or preferential ingestion, for ectocrine treated spheres depending upon microalgal species and sphere type used. This research shows that pre-ingestive chemical cues from microalgae can influence mussel feeding behavior. We suggest that epicellular ectocrines are more important in mediating this behavior than dissolved ectocrines.