Population energetics of bacterial-feeding nematodes: Stage-specific development and fecundity rates

By grazing on bacteria, bacterial-feeding nematodes participate in decomposition food webs and N mineralization to an extent determined by metabolic and behavioral attributes and by life history. We determined the stage-specific development and fecundity rates for seven species on a physiological time scale to allow time and temperature-varying predictions of population progressions. Development from egg to adult of four species in the Rhabditidae (Bursilla labiata, Caenorhabditis elegans, Cruznema tripartitum and Rhabditis cucumeris) was faster than that for three species in the Cephalobidae (Acrobeloides bodenheimeri, A. buetschlii and Cephalobus persegnis) on a Julian time (calendar) basis at 20°C. Development in the Rhabditidae was generally faster on a physiological (degree-day) time scale as well, but those times are not directly comparable as the basal threshold for degree-day (DD) accumulation differed among the species. The fecundity period for females of the seven species varied between 55 and 75% of the total duration of the life course, during which they produced between 125 eggs (B. labiata) and 567 eggs (C. tripartitum). Simulated population growth under favorable temperature conditions, using parameter values determined in these studies, indicated rapid population growth in the large-bodied, 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.