Morphometric characterization of a small-sized strain of Brachionus plicatilis in culture

The evolution of size frequency distribution in populations of three strains (Bs, S-1 and UK) of Brachionus plicatilis growing in cultures fed with Nannochloris oculata has been studied. Also the size frequency distribution of Bs has been determined in a natural population sample and in the exponential growth phase of two cultures of this strain fed with Tetraselmis suecica and Nannochloris maculata, respectively. For morphometric characterization of these three rotifer strains the anterior medial spine length to body length relationship was examined.The results shows a clear difference between the Bs strain and the two other strains in frequency distribution and range of size. At the end of the exponential phase S-1 and UK strains when cultured with Nannochloris oculata, could supply only 1 or 2% of individuals smaller than 150 μm while Bs strain could supply 80%.The Bs strain covers a range below 150 μm and may be appropriate as early food in the large-scale rearing of some marine species.