How does aggregation influence filtration and particle encounter in the sea anemone Metridium senile?*

Metridium senile reproduces sexually or asexually, influenced by prey availability and size in the habitat. Asexual reproduction occurs when prey is abundant and intermediately sized. This could lead to clone aggregation, which may alter the fluid dynamics within the colony, thereby impacting flow and particle transport at different colony positions. This study hypothesizes that solitary anemones may feed more than aggregated counterparts. We tested this by creating spatial configurations of an individual within an aggregation, using a live model with physical model clonemates. Flow within the live model’s tentacle crown was measured under different continuous background flow conditions to examine filtration and prey encounter chances using leakiness and Peclet number (Pe). Findings suggest solitary anemones feed more efficiently under low-flow conditions, but feeding drops as background flow speed increases. Feeding by aggregated anemones was found to significantly improve as the background flow speed was increased. Under high flow speeds, both solitary and aggregated anemones have similar feeding opportunities, though solitary ones experience significant drag. Finally, we note that Pe could serve as a potential indicator of prey selectivity among passive suspension feeders.