Meeting Abstract

54.5  Saturday, Jan. 5  Trade-offs between propulsion and filter feeding among three species of pelagic tunicates RAKOW, K.C.; MIT/WHOI Joint Program in Oceanography krakow@whoi.edu

Salps are pelagic, barrel-shaped, jet-propelled swimmers that have higher filtering rates of small particles (1 µm- 1 mm) than almost any other planktonic grazer. The coupling of feeding and locomotion by salps during jet propulsion results in trade-offs between these two life processes. This group of animals is characterized by a diversity of morphologies that corresponds to a range of swimming styles and speeds. To begin to understand linkages between morphology and ecological function we are focusing on three species: Salpa cylindrica, a fast-swimming, streamlined form, Pegea confoederata, a slower swimming form and Cyclosalpa spp., a slow swimming form with wheel shaped aggregates. High definition video sequences of swimming salps are digitized in order to measure the body volume over several pulse cycles. An upper limit for filtration efficiency can then be calculated based on these volume flow rate data. Jet velocities produced by swimming salps are quantified using two dimensional DPIV (Digital Particle Image Velocimetry) and then used to estimate whole-cycle propulsive efficiency. Volume flow rate and propulsive efficiency data provide a mechanistic basis for variations in swimming speeds and filtering efficiencies among species of salps.