Résumé
The natural diet and the feeding selectivity of the harpacticoid copepod Canuella perplexa T. & A. Scott, 1893 were studied in submerged muddy sediments of artificial lagoons in Arcachon Bay (SW France). This study focused on the role of phototrophic microorganisms as food sources. Therefore, chlorin and carotenoid pigments in copepods were compared with those present in the top 3 cm of the sediment. High performance liquid chromatography with on-line measurement of absorption spectra was used for separation, identification, and quantification of pigments. Diatoms, purple phototrophic bacteria, cyanobacteria, and green microalgae contributed to the benthic phototrophic community. C. perplexa ingested diatoms and infrequently cyanobacteria and/or green microalgae in preference to purple phototrophic bacteria. Ingested chlorophyll a was converted into phaeophytin and phaeophorbide-like compounds. Moreover the copepod synthesized astaxanthin and a related isomer most likely from ingested β-carotene.