AN ANALYSIS OF THE PHOTOTACTIC BEHAVIOR OF DAPHNIA-MAGNA CLONES AND THEIR SEXUAL DESCENDANTS

Daphnia magna clones, isolated from different natural populations, were inbred and crossbred. Some aspects of the heredity of the phototactic behaviour, quantified by an index, were analysed. Heritability in the broad sense was determined for several assemblages of clones through calculation of the clonal repeatability. Heritability sensu strictu was determined by offspring-parent regressions. Frequency distributions of a phototactic index of several inbred and crossbred families are given. The results indicate a significant contribution of additive genetic variance to the total phenotypic variance. Comparison of heritability estimates suggests an important genetic interaction component. Some implications of these results on the variability of vertical migration patterns in natural populations are discussed.