Supplementation of the protist Chilomonas paramecium with a highly unsaturated fatty acid enhances its nutritional quality for the rotifer Keratella quadrata

We tested whether a fatty acid supplementation technique using bovine serum albumin (BSA) as a carrier, previously developed for autotrophic protists, is also appropriate for supplementation of Chilomonas paramecium—a flagellated heterotrophic protist. Chilomonas paramecium was successfully enriched with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both known to be essential for crustacean zooplankton. Preparing C. paramecium enriched with EPA and DHA in concentrations similar to those found in Cryptomonas phaseolus, an alga known to support high growth and reproduction of Keratella, allowed us to test the direct nutritional effects of EPA and DHA on population growth and reproduction of the rotifer Keratella quadrata. Growth rates and egg production were highest when K. quadrata was fed with C. phaseolus. Compared to non-supplemented C. paramecium, egg production of K. quadrata was significantly enhanced on a diet of C. paramecium enriched with DHA, whereas no significant effects could be attributed to EPA enrichment. We conclude that DHA is important for reproduction of K. quadrata but cannot explain the majority of the difference in food quality between C. paramecium and C. phaseolus.