GENETIC EXPRESSION OF TEMPERATURE TOLERANCE IN THE COPEPOD EURYTEMORA-AFFINIS IN DIFFERENT SALINITY AND TEMPERATURE ENVIRONMENTS

The genetic expression of temperature tolerance in Eurytemora affinis Poppe in different environments was investigated by testing temperature tolerance of broods in pairs of salinity and temperature environments. Three methods were used to identify interaction between genotype and environment: (1) the correlation between mean tolerances of halves of broods grown in the two environments, (2) brood by environment interaction and (3) heritabilities in the two environments. All correlations between means of half broods were positive, only one of six brood by environment interactions was significant and the heritability estimates were not markedly different. Thus, the variability in temperature tolerance in different salinities and in different temperatures seems to be due to the same genes; and selection pressure on temperature tolerance is in the same direction with seasonal changes in temperature and salinity.