Substrate-dependent bacterivory by intertidal benthic copepods
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The trophic importance of bacteria to harpacticoid copepods in intertidal areas remains poorly understood, and so do the mechanisms of bacterial feeding. It is, for instance, unclear whether harpacticoids directly target bacterial cells or merely co-ingest them with substrates to which bacterial cells may be attached. Here, we investigate bacterial uptake and substrate requirement for four mud intertidal species (Microarthridion littorale, Platychelipus littoralis, Delavalia palustris and Nannopus palustris) by means of 13C-labeled bacteria and biomarker fatty acids (FA). Bacterial uptake strongly depended on grazing on a primary food source but bacterial ingestion rates were low, and no clear indication of copepods directly targeting bacteria was found. Delavalia was the only species that accumulated bacteria-derived FA and gained in polyunsaturated FA (PUFA) probably through bioconversion of bacteria-derived FA. In general, however, our results suggest that bacteria represent a relatively minor and low-quality food for intertidal harpacticoid copepods.
KeywordsCopepod Species Harpacticoid Copepod Total Fatty Acid Content Harpacticoids Bacterial Uptake
The first author acknowledges a PhD grant of IWT (Institute for the Promotion of Innovation through Science and Technology in Flanders). MDT is a postdoctoral researcher financed by the Special Research Fund at the Ghent University (GOA project 01GA1911 W). Financial support was obtained from the Flemish Science Foundation through project 3G019209 W and from the research council of Ghent University through project BOF09/24 J/148. Special thanks go to Ir. Dirk Van Gansbeke (Marine Biology, UGent) for analyzing the fatty acids and Annick Vankenhove for her help with sorting the copepods. The authors thank two anonymous reviewers for their constructive remarks that contributed to the improvement of the manuscript.
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