Weight gain and weight loss of the earthworm Lumbricus terrestris L at different temperatures and body weights

The effect of temperature, body weight and resource availability on weight gain, maturation time, mortality and weight loss of juvenile L. terrestris was determined in the laboratory. With L. terrestris fed ad libitum, the optimum temperature for weight gain was 15-17.5 degrees C and weight gain scaled with body weight (W) by W-0.41. The age at which incipent male pores appeared ranged from 9.4 weeks (20 degrees C) to 25.7 weeks (7.5 degrees C). The mean weight with incipient male pores and clitellum was 2.3 and 3.2 g (fresh weight), respectively. The mortality increased with increasing temperature. Earthworms deprived of food resources lost more weight at higher temperatures. Calculations based on oxygen requirements, depending on temperature and body weight, closely agreed with the measured rates of weight loss. It is concluded that earthworms deprived of their food resources reduced the costs of living to the maintenance costs, to minimise weight loss and to maximise survival time. Differences in maturation time between field and laboratory studies (more than 1 y vs less than 1/2 y at 10 degrees C, respectively) might be due to different food resource availability. Since the ratio of the potential weight gain to weight loss was significantly greater than 1, it was hypothesized, that slow rates of weight loss during prolonged periods of food resource deprivation and rapid compensation during brief favourable periods are important for the survival of L. terrestris. Copyright (C) 1996 Elsevier Science Ltd