PRATT, M.C.; Bowdoin College: Consequences of coloniality: the effect of flow on feeding and form in a bryozoan

Colonial animals can grow in a wide variety of shapes, but certain forms have apparently evolved several times in different taxa. Various hypotheses have been put forth to explain patterns in the evolution of colony form, but most of these have focused on spatial limitation or risk of dislodgement, while only more recently has the potential selective role of food acquisition been explored. Previous work has shown that one species of bryozoan, Membranipora membranacea, has a higher ingestion rate, grows faster, and survives longer than other species tested from the same habitat. The question remains why Membranipora outperforms these other species. I tested some potential reasons why Membranipora captures food so effectively including how water flow interacts with the shape and size of the colony as well as the spacing of feeding zooids within the colony to affect feeding success. The size and shape of the colony as well as the spacing of zooids within the colony all affect feeding rate; however, the advantage of spacing feeding zooids closely together to create an efficient and integrated colony current is most likely what gives Membranipora a feeding advantage over other species.