Influence of the addition of cerophyl® on the Selenastrum capricornutum diet of the cladoceran Ceriodaphnia dubia

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Abstract
A study of the green alga Selenastrum capricornutum and Cerophyl® was conducted to characterize the mixture as food for Ceriodaphnia dubia. The addition of an aqueous extract of Cerophyl to Selenastrum capricornutum resulted in consistently greater survival, growth, and productivity of Ceriodaphnia dubia cultured and tested in reconstituted hard water. Several supplemental foods, including yeast‐Cerophyl‐Trout Chow® (YCT), were tested with, or in addition to, Selenastrum capricornutum. Analysis of the protein, carbohydrate, and lipid content of the algae‐plus‐Cerophyl feeding suspension indicated that the addition of the aqueous extract of Cerophyl increased the protein concentration of the feeding suspension 30% and the carbohydrate concentration 50%. The amount of lipid contained in the Cerophyl extract was less than the detection limit of the method used for analysis. Treatment of the aqueous extract of Cerophyl for the removal of the protein and lipid components of the Cerophyl had no effect on the growth and productivity of Ceriodaphnia dubia when compared to those of the organisms fed an unaltered mixture of algae plus Cerophyl. The bacteria associated with the Selenastrum capricornutum cultures, the algae‐plus‐Cerophyl feeding suspension, the Ceriodaphnia dubia mass cultures, and the individual beakers in which isolated Ceriodaphnia dubia was tested were enumerated. The bacteria associated with the algae‐Cerophyl feeding suspension were shown to play a role in the diet of Ceriodaphnia dubia during the first 4 to 5 d of 7‐day tests. However, substituting bacteria for Cerophyl in the algal feeding suspension fed to Ceriodaphnia dubia did not result in the same level of survival, growth, and productivity.