Induction of population growth, mictic fernale production and resting eggs formation by treatment of GnRh analogue in the freshwater rotifer Brachinous Calyciflorus Pallas

Enriched commercial and artificial diets are unsuitable for the post larval stages of various commercially important crustacea and fish, which require live foods (such as rotifers, brine shrimp or fairy shrimp). The larger size of the brine shrimp and fairy shrimp make them unsuitable for larval fish and shrimp requiring small zooplanktons such as rotifers, as their initial diet. This study was designed to develop a reliable technique for inducing population growth, mictic female production and body size in the freshwater rotifer, Brachionus calyciflorus by treatment with the synthetic hormone Ovaprim. Ovaprim is a synthetic GnRH analogue with domperidone. Concentrations of Ovaprim from 0.05, 0.5, 5 and 50 μl ml−1 were added to Chlorella vulgaris suspension (2×106 cells ml−1). Population growth significantly increased in treatments exposed to 0.05 and 0.5 μl ml−1 while higher mortality was observed at the concentrations of 50 and 5 μl ml−1. Ovaprim had no effect on mictic female production and hence also on the resting egg production. Lorica length increased to 19.47 and 19.16 μm in rotifers treated with 0.5 and 0.05 μl ml−1 hormone concentrations and decrease in lorica length was observed at 50 and 5 μl ml−1 concentrations (13.44 and 15.17 μm). Increase in the lorica width (13.41 μm) was observed on treatment with 0.5 μl ml−1 concentration of Ovaprim when compared to the control. The results of the experiment suggest that Ovaprim treatment at 0.5 μl ml−1 concentration have significant modulatory effects on the population growth, mictic female production and body size of B. calyciflorus.