Meeting Abstract
Bladderwort are a genus of carnivorous plants that traps zooplankton of submillimeter size by active suction. They are among the smallest suction feeders, with gapes ranging from 0.18 to 1.2 mm in the species Utriculria vulgaris. Other suction feeders of similar size (larval fish) are relatively ineffective feeders, in contrast to adult fish. Both larval and adult fish capture predominantly prey that is considerably smaller than their gape; prey size and prey size range increase with increasing gape size. In fish larvae, the feeding apparatus grows positively allometrically; in adult fish, feeding apparatus and gape scale isometrically with body size. The aim of this study is to explore the size selectivity and feeding morphology of bladderwort. We found that the traps of U. vulgaris range over one order of magnitude from 0.3 to 3 mm and with gape scaling roughly isometrically with trap size (scaling coefficient 0.95). To explore prey size selectivity, we conducted laboratory feeding trials with ostracods (size range 0.07 to 0.86 mm). We found that larger traps catch larger and a wider size range of prey, consistent with findings in fish. However in bladderwort, prey size distribution is biased towards large prey. Capture rates (number of prey caught within a given time period) as a measure of capture effectiveness is considerably lower in bladderwort (up to 5/day) than fish, including first-feeding fish (more than 5/hour), reflecting that plants capture prey for nutrients, not for energy.
