POPULATION ENERGETICS OF BACTERIAL-FEEDING NEMATODES - STAGE-SPECIFICDEVELOPMENT AND FECUNDITY RATES

By grazing on bacteria, bacterial-feeding nematodes participate in dec omposition food webs and N mineralization to an extent determined by m etabolic and behavioral attributes and by life history. We determined the stage-specific development and fecundity rates for seven species o n a physiological time scale to allow time and temperature-varying pre dictions of population progressions. Development from egg to adult of four species in the Rhabditidae (Bursilla labiata, Caenorhabditis eleg ans, Cruznema tripartitum and Rhabditis cucumeris) was faster than tha t for three species in the Cephalobidae (Acrobeloides bodenheimeri, A. buetschlii and Cephalobus persegnis) on a Julian rime (calendar) basi s at 20 degrees C. Development in the Rhabditidae was generally faster on a physiological (degree-day) time scale as well, but those times a re not directly comparable as the basal threshold for degree-day (DD) accumulation differed among the species. The fecundity period for fema les of the seven species varied between 55 and 75% of the total durati on of the life course, during which they produced between 125 eggs (B. labiata) and 567 eggs (C. tripartitum). Simulated population growth u nder favorable temperature conditions, using parameter values determin ed in these studies, indicated rapid population growth in the large-bo died, highly-fecund rhabditid species (R. cucumeris and C. tripartitum ). Population growth was intermediate in the small-bodied, less-fecund rhabditids with short egg-production periods (B. labiata), slower in the cephalobids (A. bodenheimeri and A. buetschlii) and slowest in C. persegnis. R. cucumeris spent a greater proportion of its development time in the egg stage than did any of the other species.