The ecology of marine microbenthos III. The reproductive potential of ciliates

Growth rates of populations of 9 benthic marine ciliate species were measured in pure cultures at different temperatures. All species had a maximal growth rate above 20°C which is above the average temperature in their natural environment. Several species multiplied at 4°C and one species also at 0°C, and it is suggested that all species are able to multiply at temperatures between 0 and 4°C at very slow rates after long periods of adaptation. At 20°C generation times varied between 2.4 hours (Uronema marina) and 46 hours (Condylostoma patulum) corresponding to intrinsic rates of natural increase (r, per day): 6.65–0.36 and finite rates of increase (λ per day): ca. 1000-1.4. The maximal reproductive rate of ciliates was found to be correlated with cell size. It was found that T = k × v0.44, where T is generation time and v is the average body volume. The reproductive rates of ciliates are compared with values of r for small metazoans (based on the literature or estimated from published data on fecundity and generation times). It is recommended that r is evaluated for a greater number of species as a measure of reproductive potential since this renders comparisons between different animals possible.