The response of three chydorid species to temperature, pH and food

The responses of three chydorid species, Chydorus sphaericus (O.F. Muller), Alona affinis (Leydig) and Alonopsis elongata (Sars) to temperature, pH and food type were examined. Egg development time of all species decreased with increasing temperature. although the degree of change was different for each species. C. sphaericus had the fastest development time at all temperatures, and A. elongata the slowest. pH also affected the egg development time of each species differently. A. elongata failed to reproduce at low and medium pH. the egg development time of C. sphaericus was fastest at high pH while that of A. affinis was fastest at low pH. Food type was found to have significant effects on the population growth of individual species. C. sphaericus populations grew equally well in all three food types provided, and grew more than the other two species when fed on an algae culture. and filtered pond water. A. affinis and A. elongata populations grew best when fed on a detritus food source. The responses of each species to the different variables tested are discussed in relation to field observations of their distribution and abundance.