Induction of population growth, mictic female production and body size by treatment of a synthetic GnRH analogue in the freshwater rotifer, Brachionus calyciflorus Pallas
Sugumar, V.M.nuswamy, N.
Aquaculture 31 258(1-4): 529-534
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 microliter ml- 1 were added to Chlorella vulgaris suspension (2 x 10(6) cells ml- 1). Population growth significantly increased in treatments exposed to 0.05 and 0.5 microliter ml- 1 while higher mortality was observed at the concentrations of 50 and 5 microliter 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 micrometer in rotifers treated with 0.5 and 0.05 microliter ml- 1 hormone concentrations and decrease in lorica length was observed at 50 and 5 microliter ml- 1 concentrations (13.44 and 15.17 micrometer). Increase in the lorica width (13.41 micrometer) was observed on treatment with 0.5 microliter ml- 1 concentration of Ovaprim when compared to the control. The results of the experiment suggest that Ovaprim treatment at 0.5 microliter ml- 1 concentration have significant modulatory effects on the population growth, mictic female production and body size of B. calyciflorus.