A bioenergetic study of a benthic nematode, Plectus palustris de man 1880, throughout its life cycle : I. The respiratory metabolism at different densities of bacterial food.

Respiration rates of the bacterivorous freshwater nematode Plectus palustris were measured during the whole life cycle of the species and for animals grown at two food densities. Covariance analysis showed that small, but significant differences exist in the elevation of the respiration rate-body weight regressions (R=aW b, in nl O2/ind·h and μg wet weight) for different food densities. At a food density of 6-9·108 bacterial cells/ml the level of respiration is 14% lower compared to rates of animals cultured at a ten times higher food density. However, the allometric function, R-aW b, adequately describes the relationship of respiration and body weight only during the larval growth phase and for young females, while respiration rates of newly hatched larvae and mature females at maximal egg production have lower metabolic rates. Cumulated metabolic costs to attain a certain age, size and stage of development have been determined and are used in a subsequent paper (Schiemer et al., 1979) to calculate the energy budgets of the species.