Effects of different light/dark regimes and algal food on growth, fecundity, ephippial induction and molting of freshwater cladoceran, Ceriodaphnia quadrangula

Abstract

Combined effects of different light regimes and algal foods on population growth, ephippia (resting eggs) production, fecundity, molting and body size of Ceriodaphnia quadrangula were investigated. Four light/dark regimes in combination with two algal diets of Scenedesmus quadricauda (S) and Chlorella vulgaris (C) namely: 4L: 4D+S, 6L: 6D+S, 8L: 8D+S, 12L: 12D+S, 4L: 4D+C, 6L: 6D+C, 8L: 8D+C, and 12L: 12D+C were assigned to present study. The highest population density and growth rate were obtained at 12L:12D+C (1860 ind/l and 0.29/day) and 6L:6D+C (1760ind./l and 0.28/day), which were significantly different from other treatments (p<0.05). Ephippium production was affected by light/dark period, decreasing with increasing light duration when fed on S. quadricauda and increasing when fed C. vulgaris. Although the ephippium was observed at all treatments, significantly higher ephippium (285 eggs/l) were recorded at 4L:4D+S (p<0.05). Fecundity ranged between 0.67 and 3.00/female/day, with the lowest value occurring at 4L:4D+S and the highest at 6L:6D+S. The molting rate was significantly (p<0.05) different among the various treatments. The range of molting was 1.59–8.43/female/week, lowest at 4L:4D+C and the highest with 12L:12D+S. Based on our results, 12L:12D+S is recommended for growth and molting, and 4L:4D+S for ephippium production in C. quadrangula.