Meeting Abstract
Bladderwort Utricularia vulgaris is an aquatic carnivorous plant that catches zooplankton in small underwater traps. The trapping mechanism is active: when prey touches the trigger hairs on the trap door, it is sucked into the trap. Active mechanisms are energetically costly, hence we predict that the traps have a high capture efficiency (captures per feeding strike). Bladderwort is a rootless, free-floating primary stolon with a growing and a senescing end. In this study we explore the effects of trap size and trap age on capture efficiency. We fed the plant ostracods to study capture success as a function of trap diameter and age. We recorded capture events acoustically (traps make a popping sound when triggered) to characterize the time course and to calculate capture efficiency as the ratio of capture success (total number of prey items captured) to suction events (number of events in the sound recording). We found that capture behavior can be modelled as a first-order reaction with prey density declining exponentially over time. Traps mature within 10 days. Capture success is steady at 30 to 40% for mature traps and then gradually declines to zero as a traps senesce. Presented with ostracod prey (300 to 600 micron diameter), traps smaller than 1.3 mm were unable to catch prey. Overall, our results show that bladderwort are effective suction feeders with success rates (ratio of successful versus total number of strikes) higher than those of fish larvae with a similar gape size (e.g. Sparus aurata at age 6 days: gape 200 microns, capture success: 20%).
