Reproduction, Metabolic Rate and Survival in a Carabid Beetle

Abstract

This study of the carabid beetle Notiophilus biguttatus F. concerns whether in poikilotherms, a negative relationship between reproduction and survival may arise as a special case of the negative relationship between metabolic rate and longevity. We therefore carried out an experiment in which we varied food intake rate by means of prey supply (the springtail Orchesella cincta (Linne)) and temperature. The data allowed us to establish relationships between the rate of oxygen consumption and rate of egg production for the different temperature regimes. In a second experiment we chose three temperature/feeding regimes at which we established survival and egg production for a good two years. With one regime, rates of metabolism, egg production and consumption were high due to an ad lib. supply of prey plus a relatively high temperature; for the other two regimes the rates were low, food intake rate being reduced either by food supply or by temperature. Median and maximum survival time were shortest in the high expenditure group (51 weeks and 114 weeks respectively) and longest in the group with limited food supply (median survival time 117 weeks). Using the relations between rate of oxygen consumption and rate of egg production we estimated total oxygen consumed in the three groups. These estimates did not differ in the two groups kept with excess prey at different temperatures; it was however, much higher in the group with restricted prey supply. We conclude that in this species survival is negatively related to rates of egg production and metabolism, with the relationship seeming to depend on whether the rates are manipulated by temperature or by food supply.