Energy metabolism and its relation to survival and infectivity of infective juveniles of Steinernema carpocapsae under aerobic conditions

Energy metabolism of the infective juveniles (IJ) of Steinernema carpocapsa e under aerobic conditions and its relation to survival and infectivity of the IJ was studied by monitoring the changes in mean dry weight, levels of key energy reserve compounds, oxygen consumption rate, respiratory quotient , survival and infectivity of freshly harvested IJ incubated in tap water o n a shaker at 28 degreesC over time. The survival rate of the IJ exceeded 9 0% for the first 6 weeks and then dropped sharply to about 50% at week 8. T he infectivity of the IJ did not change markedly within the first 3 weeks, dropped slightly during weeks 4 and 5 and then decreased sharply to week 6. The mean dry weight of the IJ dropped at a roughly constant rate from an i nitial level of 74 ng/IJ to 41 ng/IJ at week 6. Thus, during the period of 6 weeks at 28 degreesC, each IJ consumed nearly half of its initial dry wei ght. Consumption of the lipids, proteins, glycogen and trehalose accounted for 91, 41, 56 and 78% of the initial levels of these compounds and 47, 41, 9 and 3% Of the total dry weight of materials consumed, respectively. Most lipids were consumed in the first 3 weeks while most proteins, glycogen an d trehalose were consumed in the last 2 or 3 weeks. Oxygen consumption rate decreased from 3.0 to 0.5 ml/million IJ/day from day 1 to week 6 while the respiratory quotient remained constant at about 0.7 for the first 4 weeks then dropped sharply to 0.3 at week 6. Both survival time and the rate of r eduction in mean dry weight of IJ were severely affected by temperature and buffering. The functions of the individual energy reserve materials, chara cteristics of the energy metabolism and the relationship between energy met abolism and the survival and infectivity of the IJ are discussed.