The effect of temperature on asexual population growth of three species of Naididae (Oligochaeta)

The population growth rates of monospecific cultures of asexually reproducingNais variabilis, N. elinguis andPristina aequiseta were determined under laboratory conditions at 8 °C, 12 °C and 20 °C. Two different agar-based culture media were used to promote bacterial populations as a food for the worms. The exponential growth rate (r) of the worm populations was dependent upon species, temperature and culture medium. Highest r-values recorded were forN. variabilis andP. aequiseta at 20 °C (mean population doubling time about 3 days) and the lowest r-value recorded was forP. aequiseta at 8 °C (mean population doubling time about 22 days). The r-values forN. elinguis were generally lower than expected, possibly because conditions in the experimental cultures were less suitable for this species. Temperature, culture medium and species identity also affected the carrying capacity of the cultures. Carrying capacity increased with increase in temperature over the experimental range.P. aequiseta cultures supported significantly higher carrying capacities than theNais cultures at all temperatures.