Ability to switch reproductive mode in Artemia is related to maternal heterozygosity

Brine shnmp Artemia spp.produce young as larvae or as encysted embryos resistant to unfavourable conditions.The factors controlling the switch between the 2 types of reproduction are unknown.Studies on A. franciscana from the Great Salt Lake of Utah, USA, show the percentage of zygotes produced as cysts is correlated with the level of heterozygosity (determined electrophoretically) in the mother.More heterozygous females also produce more zygotes, and tend to produce more broods and start to reproduce at a younger age than less heterozygous females.Coefficients of variation of reproductive characters are lower for more heterozygous and higher for less heterozygous mothers.These results show that heterozygosity in this species is highly correlated with important components of fitness and suggest that the ability to switch reproductive mode, a feature of considerable adaptive value in varying environments, and of importance in aquaculture, has a high degree of genetic determination.