LIFE STRATEGIES IN 2 BACTERIVOROUS MARINE NEMATODES - PRELIMINARY-RESULTS

Temperature dependence of sex ratio and maximal densities of the estua rine, deposit-feeding nematodes Pellioditis marina (Rhabditidae) and D iplolaimelloides meyli (Monhysteridae) were investigated in vitro. Bot h species are characteristic for organically enriched habitats. Data f rom competition culture experiments with both species are integrated w ith information from respiration measurements at different temperature s, and from observations on the influence of temperature and bacterial density on uptake rates. Sex ratio was significantly influenced by te mperature in both species, with the highest relative numbers of males at the highest temperatures. Total numbers attained fluctuated only mo derately in the 10 to 20 degrees C interval, but increased and decreas ed highly significantly at 25 degrees C for D. meyli and P. marina, re spectively. Respiration at temperatures from 5 degrees C to 30 degrees C was measured with nematodes from monospecific cultures using a modi fied Clark electrode procedure. Respiration was dependent upon tempera ture in the entire range for P. marina, but not for D. meyli, where on ly at 25 degrees C a clear respiratory acceleration was observed. Feed ing experiments with P. marina showed a dominant influence of bacteria l density on uptake rates, with a lower but still significant temperat ure effect. These data are discussed in relation to the overall life s trategies of both species.