Diurnal rhythm and effect of temperature on oxygen consumption in earthworms, Amynthas gracilis and Pontoscolex corethrurus

Different species of earthworms show distinct patterns of oxygen consumption pattern. Amynthas gracilis has a diurnal rhythm of oxygen consumption, consuming more oxygen at night, whether being incubated at 20, 25, or 30degreesC. The higher oxygen consumption of A. gracilis is directly related to its behavior, as it shows higher activity at night. In contrast, Pontoscolex corethrurus showed no obvious diurnal rhythms of oxygen consumption or behavior. In addition, its oxygen demand is not related to temperature. A. gracilis has higher oxygen consumption than P. corethrurus at 20 and 30degreesC. The difference in temperature adaptation of oxygen consumption between these two species may be a strategy by which earthworms adapt to different temperatures. This might explain why A. gracilis disperses on the soil surface at night after a rain, in contrast to P. corethrurus for which such behavior was not been observed. (C) 2004 Wiley Liss, Inc.