Cross-mating of euryhaline rotifer Brachionus plicatilis strains as a means to develop useful strains for larval fish food

In the field of live food science, newly inbred strains resulting from cross-mating are of interest, especially if these strains have valuable characteristics, such as high fecundity or suitable size for the mouth of larvae. We conducted cross-mating trials using Japanese and German strains of Brachionus plicatilis and reproductive parameters were characterized and compared among their progenies. Two hybrid strains A and B were obtained from the cross-mating between a Japanese female and German male, and between a German female and Japanese male, respectively. Percent mictic female production and fertilization in both hybrid strains were lower (0%), compared with the parental strains (16.7–78.4%). Strain A did not reproduce sexually, but was capable of asexual reproduction. Higher population growth was observed in the hybrid strains within crosses relative to parents. The population growth rates of parental strains were 0.31, while those of hybrid strains ranged from 0.35 to 0.37. Lorica length of hybrid strains was intermediate between the two parental strains. Using the cross-mating technique, it may be possible to produce new rotifer strains with phenotypes useful to aquaculturists.