Meeting Abstract
Upside-down jellyfish (Cassiopea) and pulsing soft corals (Xenia) generate water flows by contracting their bells and polyp arms, respectively. This pulsing behavior is thought to increase nutrient flow to the organisms and allow for increased photosynthetic rates by the symbiotic zooxanthellae that both organisms harbor. Upside-down jellyfish are typically found in groups from 2 to over a hundred individuals of varying sizes. These groups are dynamic, with individuals changing their position within the group. Similarly, pulsing soft corals form colonies in which the stalked polyps can adapt their position relative to other polyps and to the background flow. The fluid dynamics of these groups and colonies might have an important role in the development and growth of individual jellyfish and polyps. Choosing a certain position or neighbor in the group, or adjusting one’s position relative to one’s neighbors, might benefit individuals and increase their fitness. In the lab, individual upside-down jellyfish have showed different pause lengths between pulses. When two jellyfish are put close together, their pulsing patterns change, often to reveal one individual to be more active and pulse more often than the other. The fluid dynamic effects of short vs. long pauses and of individual vs. pairs of jellyfish have been investigated using particle image velocimetry (PIV). Similar PIV experiments will be conducted with the pulsing corals, comparing the behavior and fluid dynamics of individual vs. pairs of polyps. Our results will shed light on the potential fluid dynamic advantages of group behavior in pulsing marine invertebrates.
