Meeting Abstract
Bladderwort are among the smallest suction feeders, with both terrestrial and aquatic species trapping microscopic prey in underwater traps or underground traps in waterlogged soils. In this study we compare the suction performance of a small terrestrial species (Utricularia praelonga), a small aquatic species (U. gibba), and a large aquatic species (U. vulgaris). Our studies of U. gibba and U. vulgaris show, despite their small size, bladderwort traps feed in the inviscid flow regime: the flow in front of their mouths is predicted by inviscid suction models, the flow in their mouths by the unsteady Bernoulli equation. Maximum flow speeds are 5 m/s in U. gibba and 2 m/s in U. praelonga, two species with similar-sized traps (diameter 0.7 to 1.4 mm) but very different gape morphologies. Mouth morphology varies widely across our three species. While U. vulgaris has its trap door very close to the outer wall of the trap, U. gibba’s trap door is shielded by a vestibule. Both these aquatic species have few bristles around their mouth opening, while the mouth opening in the terrestrial U. praelonga is shielded by dense clusters of bristles. Our flow data show that the suction flows of these species all develop a central jet in the mouth, but differ in the inflow. For example, we observed several incidences of the U. praelonga flow forming a pulsed jet soon after the jet enters the main bladder, in contrast to the steady jet of U. gibba. We will explore the causes of these similarities and differences in the future using a robotic model of the traps.
