Thesis

Prey Selectivity In Utricularia Gibba

Suction feeding is one of the primary methods aquatic organisms use to capture prey. Suction feeding in aquatic organisms is well understood in adult fish, but poorly understood in fry. Hydrodynamic theory predicts that suction feeding is not effective in smaller organisms, where a minimum gape diameter is required for a successful suction event. This minimum gape diameter is the lower limit where suction feeding is still viable. Studies have shown that fish larvae have low capture success, but there are few data on similar sized plant suction feeders. Aquatic bladderwort species (Utricularia gibba, U. vulgaris) capture microscopic prey using suction feeding in underwater bladder-shaped traps at dimensions typically less than 1 mm. This project examines how bladderworts suction feed by quantifying the capture success, trap morphology and prey morphology to address the following questions: (1) do smaller traps catch smaller and fewer prey; (2) do smaller traps have a relatively larger gape (characterized as gape diameter relative to total trap size) than larger traps to limit the negative effects of being small on capture success. Bladderwort traps capture prey relative to gape diameter, with smaller bladders catching smaller-sized and fewer prey overall compared to larger bladders. Smaller bladderwort traps display isometric allometry, with smaller traps having relatively same gape length as larger traps.

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