Feeding studies with natural food particles on tropical species of planktonic rotifers

Abstract

In order to assess the role of the planktonic rotifers in relation to the dynamics of the ecosystem of Parakrama Samudra, the filtering and feeding rates of Brachionus caudatus from Parakrama Samudra and B. calyciflorusfrom the Milk Factory Tank were measured on natural food particles of less than 33 µm, using a radio-tracer technique. The concentration of food was determined as carbon per millilitre. At 28 °C, the hourly filtering rates for B.caudatusranged from 1.63 to 6.10 µlind-1h-1in food concentrations from 6.27 to 2.21 µC ml-1. Assuming continuous feeding and uniformly labelled food, the daily feeding rates were 0.158–0.334µC ind-1d-1. Brachionus calyciflorus had higher filtering rates, 16.9–39.7 µl ind-1h-1, and higher feeding rates, 3.38–7.94 µC ind-1d-1at a food concentration of 8.34 µC ml-1, but this species was about 30 times larger by volume than the smallB. caudatusfrom Parakrama Samudra. These results are discussed in the light of experimental information of rotifer feeding on monospecific food available in the literature.