Increased phototaxis in the field leads to enhanced diel vertical migration

Abstract

Downward and upward displacement velocity of diel vertical migration in Lake Maarsseveen by the hybrid Daphnia galeata × hyalina, was correlated with the relative change in light intensity at dawn and dusk, indicating a phototactic basis for these migrations. The significance of the regression function increased over a period of 4 yr. Changes in environmental factors such as water transparency and food concentration are not responsible.