Protein and lipid content of the rotifer Brachionus plicatilis during variable growth and feeding condition

Abstract

Rotifers (Brachionus plicatilis) grown at different growth rate (µ = 0.05−0.39 d⁻¹) were analyzed for protein, lipid, fatty acids, amino acids and free amino acids, and values are expressed in terms of individuals and dry weight. Increase in growth rate is equivalent with increased food ration of the individual rotifer, which responded by higher egg ratio. The protein content per individual rotifer increased by 60–80% when the growth rate increased, whereas the protein content per dry weight showed a slight, although insignificant, increase (p>0.05). The lipid content per individual was constant, whereas lipid per dry weight decreased when the growth rate increased. The ratio DHA/EPA decreased when the growth rates increased. The amino acids profile in percent of total amino acids showed low variation between cultures maintained at different growth rates, whereas the values expressed in terms of amino acid per individual showed higher variation. The range of variation for free amino acids was more pronounced than for total amino acids.

Short-term food enrichment of poorly fed rotifers (µ = 0.05 d⁻¹) with balanced protein rich diet resulted in increased protein and lipid content per rotifer. The protein content per dry weight showed only minor changes whereas lipid per dry weight increased. Contrary, short term enrichment with a lipid rich diet resulted in increased lipid content per individual rotifer and per dry weight, whereas the protein content per individual remained constant and the protein content per dry weight showed a slight decrease.

Our experiments show that the amount of protein, was quite variable in rotifers, and that feeding and growth condition were decisive factors affecting it. The range of variation was large enough to be an important factor during first feeding of marine larvae, and should therefore be considered in feeding larvae.