REPRODUCTION RATES IN RELATION TO FOOD CO NCENTRATION AND TEMPERATUREIN 3 SPECIES OF THE GENUS BRACHIONUS (ROTIFERA)

The influence of various algal (Chlorella) concentrations (from 5.10(3 ) to 1.10(7) cells mL(-1)) on the population dynamic is stu died at tw o temperatures (16 & 24 degrees C) in three species, Brachionus angula ris, B. calyciflorus (with two clones) and B. plicatilis. By observing about fifteen isolated females, the net reproduction rate, R(0), the intrinsic population growth rate, r(m), the threshold, food level (for which r(m)=0), S-0, and the algal concentration, Ks, supporting the m aximum population growth rate (or one-half) are determined. The values of these variables are compared with each others and with the literat ure data. The low values observed in the B. plicatilis strain are cons picuous. This peculiarity is related to the metabolism of the species adapted to various salinity and food conditions.