Life Strategies in Two Bacterivorous Marine Nematodes: Preliminary Results

Abstract. Temperature dependence of sex ratio and maximal densities of the estuarine, deposit-feeding nematodes Pellioditis marina (Rhabditidae ) and Diplolaimelloides meyli (Monhysreridae ) were investigated in vitro . Both species are characteristic for organically enriched habitats. Data from competition culture experiments with both species are integrated with information from respiration measurements at different temperatures, and from observations on the influence of temperature and bacterial density on uptake rates.
Sex ratio was significantly influenced by temperature in both species, with the highest relative numbers of males at the highest temperatures. Total numbers attained fluctuated only moderately in the 10 to 20 °C interval, but increased and decreased highly significantly at 25 °C for D. meyli and P. marina , respectively.
Respiration at temperatures from 5 °C to 30 °C was measured with nematodes from monospecific cultures using a modified Clark electrode procedure. Respiration was dependent upon temperature in the entire range for P. marina , but not for D. meyli , where only at 25 °C a clear respiratory acceleration was observed.
Feeding experiments with P. marina showed a dominant influence of bacterial density on uptake rates, with a lower but still significant temperature effect.
These data are discussed in relation to the overall life strategies of both species.