Reproduction in Laboratory Stocks of Pleuroxus (Chydoridae,Cladocera) Under the Influence of Photoperiod and Light Intensity

The effects of photoperiod and light intensity on the reproduction of laboratory populations of three species in Pleuroxus from different geographic origins were determined statistically. There were highly significant differences in the numbers of gamogenetic individuals produced between the populations at different photoperiods but not at different light intensities. More males than ephippial females appeared at long-day photoperiods. Pleuroxus denticulatus stocks showed greater variation of gamogenetic response to photoperiod and geographic origin suggesting that local populations have evolved different reproductive patterns to meet the major environmental stresses of the region.