The role of hyperiid parasites as a trophic link between jellyfish and fishes

The trophic interactions between the scyphozoan medusa Chrysaora plocamia and the palm ruff Seriolella violacea were investigated off northern Chile and showed that large numbers of hyperiid amphipods parasitizing the medusa may channel energy back to the fishes, which feed on the parasites. The biomass of hyperiids eaten by the fish was a function of the biomass of hyperiids parasitizing the medusa. This temporally available food supply may enhance fish recruitment. The large number of hyperiids parasitizing diverse jellyfish species represents a missing trophic link in current efforts to understand the effects of jellyfish blooms on marine food webs.     

ISOLATION AND FLOW CYTOMETRIC CHARACTERIZATION OF PROTOPLASTS FROM MARINE MACROALGAE

Protoplasts were isolated from Ulva rigida C. Agardh (Chlorophyta) and two species of Rhodophyta , Gracilariopsis lemaneiformis ( Bory) Dawson, Acleto et Folvik and Gracilaria tenuistipitata Chang et Xia var . liui with minor modifications (the inclusion of 0.01% agarase in the set of cell-wall-degrading enzymes for the two red algae). Flow cytometric characteristics of freshly isolated protoplasts were determined on a FACScan flow cytometer (FC). The most useful parameters for characterizing protoplasts from marine algae were forward angle light scatter (FSC), orange fluorescence (FL2) and red fluorescence (FL3). Protoplasts from all the species were easily distinguishable when their FSC, FL2, and FL3 signals were combined in the bivariate plots FL3 vs. FSC and FL3 us. FL2. Two alternative techniques to help identify protoplasts from debris in the FC computer screen were developed (for FC without sorting capability). Both techniques were based on the ability of new FCs to record time. The first one was based on the induction of rapid changes of cell volume in response to osmotic stress. Only intact protoplasts responded to changes in the osmotic pressure. The second one was based on the uptake and hydrolysis of fluorescein diacetate by intracellular esterases. Viable protoplasts showed a hyperbolic accumulation of fluorescein with time. Semimaximal fluorescein accumulation was attained in 30.5 ± 9.5 s. Debris was easily recognized since, contrary to protoplasts, it did not show a time-dependent accumulation of fluorescein .