Effects of Chicken Manure Extract on the Population Growth, Mixis Induction and Body Size of the Freshwater Rotifer Brachionus angularis Gosse 1851

This study investigated the effects of chicken manure extract (CME) on the population growth,mixis induction and body size of the freshwater rotifer Brachionus angularis Gosse 1851. Four concentrations of CME (i.e.0.5, 1.0, 2.0 and 3.0 ml.L^-1), each in triplicate, were used in glass jars containing 20 mL of sterilised pond water. Thirty clones (24 h old) of B. angularis were placed in each jar and the specified concentrations of CME were added except in the control jars. Chlorella vulgaris Beijerinck 1890 (2.5x10^6 cells.mL^-1) was supplied daily in all jars. The treatments were incubated at 25 °C in darkness for 7 days without exchanging water. CME significantly (P 0.05) increased the rotifer population density and amictic females from day 4-7 at 2.0 mL.L^-1 but reduced the mixis induction rate. However, the CME did not significantly (P 0.05) affect the unfertilised mictic females. The specific population growth rate was significantly (P 0.05) highest at 2.0 mL.L^-1 of CME. The resting egg production decreased with increasing concentrations of CME. The lorica length increased at 3.0 mL.L^-1 of CME but the lorica width was unaffected by CME. These results suggest that addition of 2.0 mL.L^-1 of CME enhances the population growth and regulates lorica size; hence can be applied in the freshwater larviculture initiatives.