Studies of the life-history and energetics of marine and brackish-water nematodes : II. Production, respiration and food uptake by Monhystera disjuncta.

An energy budget was constructed for the marine nematode Monhystera disjuncta. Respiration was measured with a modified Cartesian diver technique, in which the nematodes were kept in agar inside the diver 'head'. The relationship between respiration and body weight was: R =1.53 W0.75. Body growth was exponential during the juvenile phase, with a growth rate equal to 0.61 d-1. After maturation the growth rate fell to 0.17 d-1. Food uptake was measured in experiments with radiolabeled bacteria. In one series of experiments the accumulation of radiolabel in the nematodes was followed. In a second series the decrease in labeling was followed when pre-labeled nematodes fed on unlabeled bacteria. A model for label uptake permitted the calculation of assimilation efficiency and consumption rates. Consumption rates thus measured, correspond well to those calculated from the growth, reproduction and respiration rates. Assimilation efficiency was low, around 25%. Production efficiency (P/(P+R)) was high: 60% for the population at stable age distribution, and up to 75% for reproducing females. This seems to be a general feature in nematodes.