The life cycle of the earthworm includes three stages: hatching,growing and mating. The N and cisotopic ratios of earthworm in the three stages of the life cycle, including earthworm cast and growth substrate, were measured and shown in Figs. 4 and 5. Adults had the biggest values of 15N, followed by hatchlings, cocoons, cast and
growth substrate, while 13C in the biological samples (adults, hatchlings and cocoons) were higher than that in the non-biological ones (cast and growth substrate) (one-way ANOVA, P < 0.001) (Fig. 4). The results indicated that there were consistent enrichments of 15N and 13C in cocoons, hatchlings and adults relative to the growth substrate, corresponding to those of the previous studies