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The hydromedusae of Monterey Bay:
 Vertical distributions, behaviors, 
and species interactions

Kevin Raskoff, Ph.D.
Monterey Bay Aquarium Research Institute

Wednesday, May 2, 2001
3:00 p.m.–Pacific Forum

Cnidarians are frequently the dominant members of the gelatinous fauna, and hydromedusae are often the most common sub-group. Although hydromedusae have been well studied in some epipelagic areas, there is little known about the ecology of mesopelagic species. This is primarily due to the fact that nets, which were the principle methods of collecting and studying the organisms, were typically unable to sample these fragile, gelatinous animals without destroying them. It was not until the advent of blue water diving techniques, specialized nets, submersibles, and remotely operated vehicles (ROVs) that the role of gelatinous organisms in the mesopelagic ecosystem could be clarified. However, much remained to be learned. Questions of distribution, trophic interaction, and behavior were unanswered for most of the mesopelagic cnidarian taxa. This research used MBARI’s ROVs to collect both high-quality video footage and animals in pristine condition to study the ecology of the mesopelagic hydrozoans in Monterey Bay.

This talk will provide a broad range of ecological information on hydromedusae. The vertical distributions, seasonal and yearly variations, and the abundance of many common mesopelagic hydromedusae in Monterey Bay will be discussed. Novel forms of predation by medusae will be described with information on gut contents and foraging behavior. Lastly, a description of the first known cnidarian-pelagic tunicate mutualistic interaction will be presented, with a description of a unique tentacle-based asexual reproduction strategy.

Next: Microsatellite profiles of the genetic mating systems and reproductive natural histories of some fascinating fishes and turtles