Feeding and metabolism of the siphonophore Sphaeronectes gracilis |
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Authors: | Purcell, Jennifer E. Kremer, Patricia |
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Affiliation: | Department of Biological Sciences and the Marine Science Institute, University of California Santa Barbara, CA 93106 3Allan Hancock Foundation, University of Southern California Los Angeles, CA 90007, USA |
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Abstract: | The in situ predation rate of the siphonophore Sphaeronectesgracilis was estimated from gut content analysis of hand-collectedsiphonophores and from laboratory data on digestion rates ofprey organisms. At daytime prey densities of 0.25 copepods 11,S. gracilis was estimated to consume 8.1 15.4 prey day1siphonophore1. From data on abundances of siphonophoresand copepods, S. gracilis was estimated to consume 24%of the copepods daily. In laboratory experiments, ingestionrates averaged 13.8 prey day1 siphonophore1 atprey densities of 5 copepods 11 and 36.9 at 20 copeods11. This was equivalent to a specific ingestion rate(for both carbon and nitrogen) of 17% day1 and45% day1, respectively, while specific ingestion in situwas only 2% day1. Ammonium excretion averaged 0.095 µg-atsiphonophore1 day1 at 5 prey 11, and 0.162at 20 prey 11. The specific respiration (carbon) andspecific excretion (nitrogen as ammonium) were calculated tobe 3% day1 at the lower experimental food level, and5% day1 at the higher food level. 1Contribution from the Catalina Marine Science Center No. 66.2Present address: Dept. of Biology, University of Victoria,Victoria, B.C., Canada V8W 2Y2. |
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