Respiration activity of Dendrobaena octaedra (Lumbricidae) under constant and diurnally fluctuating temperature regimes in laboratory microcosms

Abstract

Adult Dendrobaena octaedra were kept individually in microcosms with leaf litter/sand substrate under constant (15 °C) or fluctuating (10–20 °C or 5–25 °C) diurnal temperature regimes and an optimum moisture content. After 10, 34, 61, 92, 109 or 126 days, the rate of worms CO 2 production was measured at the corresponding acclimation temperatures. A clear pattern of ‘day/night’ change in CO 2 production rate ( V) was obtained under T 10–20 and T 5–25 regimes. Under T 15, no evidence of diurnal respiration cycle was observed. The average V values of acclimated animals at 5, 10, 15, 20 and 25 °C were 32.3, 50.3, 73.5, 105.0 and 148.5 mm 3·g −1·h −1, respectively. The relationship between V and temperature ( T, °C) in the 5–25 °C interval is close to a straight line on the semi-logarithmic scale and it can be expressed as log 10 V = 1.3610.0337 T. Compared with the T 15 regime, the effect of temperature fluctuations on the average daily respiration rate [( V day V night)/2] was hardly pronounced at T 10–20 while being significantly stimulatory at T 5–25 Two trends in the metabolic reactions to the change in constant temperature regimes can be suggested for earthworms: i) a compensatory reaction within the optimal temperature range; and ii) a decrease or lack of compensation in less favourable conditions. The V/T relationships in fluctuating regimes can be markedly different from those observed in constant conditions. This should be regarded as ecological interpretations. The relationship between CO 2 production and body weight in D. octaedra depended on the temperature regime. The display of this effect coincided with the temperature zone optimal for reproduction in the population studied: it was significant at 15 and 20 °C and close to the surface principle reaction ( b = 0.71). A trade-off effect was observed in the distribution of individual resources between respiration, reproduction and survival of D. octaedra in relation to the type of temperature regime.