Meeting Abstract
Utricularia vulgaris, the common bladderwort, uses an active-mechanism suction trap to capture prey. This trap comprises a hollow bladder with a door and is set through continuously pumping water from the bladder to maintain a negative pressure. The trap is sprung when hairs at the mouth of the bladder encounter prey, releasing a door at the mouth and sucking in the prey. The traps appear to misfire on a frequent basis, forcing them to reset continually through pumping out water. This energetic cost of setting and resetting varies with the size of the traps. Due to this size effect on cost we hypothesize that there should be an increased success or payoff for larger traps. In addition to the energetic cost, the resource cost associated with trap formation also scales with size. To determine the activity and the volumes of water pumped by each trap we used UV fluorescent dye to measure the activity of U. vulgaris over 48 hours. Dye sucked into traps can’t escape and the dye concentration increases with each trap firing, allowing us to measure volume intake. Image analysis of full plants after the dye treatment allowed measurement of trapping activity and feeding success of the individual traps. We found that the youngest traps and recently matured traps trigger frequently yet are very unlikely to capture prey. Mature traps rarely trigger, but are likely to capture prey. The elevated firing rate of young traps has high energetic costs. Explanations for this possibly maladaptive trait could be either that the trap door is initially unable to withstand the bladder pressures, or that the bladder walls are initially unable to maintain subcritical pressures.
