RUI: Patterns of Prey Capture by Mnemiopsis leidyi and other Lobate Ctenophores

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9820172CostelloLobate ctenophores are well known as important predators in marine planktonic communities. Based primarily on previous research involving members of the lobate genus Mnemiopsis, lobate ctenophores are commonly thought to impact marine plankton communities via consumption of late stage (late copepodite and adult) copepods. Quantitative estimates of lobate ctenophore impact have relied upon combining the functional relationship between copepod density and ctenophore ingestion rate with field densities of ctenophores and copepods. However, late stage copepods may not be the primary prey of most lobate ctenophores. Preliminary evidence suggests that Mnemiopsis utilizes two parallel and simultaneous mechanisms for capturing prey. The first depends upon ciliary flow generated by the auricles to entrain slow or inactive prey which are sieved through oral tentacles. The second is an ambush mechanism which depends upon collision of rapidly swimming prey such as copepods with the ctenophore's outstretched oral lobes. A very limited group of in-situ data supports the contention that the lobate body design is optimized for feeding on small and weakly swimming prey and that stronger swimmers such as late stage copepods are a secondary nutritional source, both from a numerical and biomass perspective. If the latter is true, then the trophic role of lobate ctenophores may be commonly misunderstood and their predatory impact substantially underestimated. However, resolution of this issue is not currently possible due to the limited information available detailing the actual prey capture process and in-situ gut contents of lobate ctenophores. This research has two major goals. First, to develop an appropriately detailed description of the mechanical processes underlying prey capture in the laboratory for several representative genera of lobate ctenophores. Second, to quantitatively compare this mechanical description with in-situ selection patterns and feeding rates of these ctenophores. Both laboratory and field studies need to be integrated to fully understand the role played by these predators in marine planktonic communities.