Selectivity of the rotifer Brachionus plicatilis fed mixtures of algal species with various cell volumes and cell densities

The ability for food selectivity of rotifer Brachionus plicatiliswas studied in the laboratory by feeding mixtures of microalgae with various cell volumes. Chlorella sp. (≈22 µm³) was the reference algal species, and Asteromonas gracilis, (Chlorophyta) (≈2150 µm³), Tetraselmis suesica (≈268 µm³), Dunaliella salina (≈52 µm³) and Chaetoceros sp. (≈150 µm³) the experimental species. Each was mixed with Chlorella and fed in three experiments. In the first experiment, filtration and ingestion rates of rotifers each fed with algae revealed that the highest values were measured with the mixture of Chlorella + Asteromonas, and the lowest for Chlorella + Chaetoceros. In the second and the third experiments, by using several combinations of algal densities with the mixture of Chlorella + Asteromonas, a selectivity ability of the rotifers for Asteromonas was found. A hypothesis is presented that accounts for the preference of rotifers for Asteromonas, which is suggested as a new candidate species for use in live food production of fish hatcheries.