Growth of hatchling earthworms in the presence of adults: interactions in laboratory culture

Hatchling Lumbricus terrestris, Aporrectodea longa, Allolobophora chlorotica and L. rubellus were cultured in 1-1 pots at 15degreesC in darkness. Each species was grown in isolation and also in the presence of selected adult species representing a range of earthworm ecological groupings. The experiments were continued for 24-36 weeks (until animals matured). The effects of adult presence were determined by measuring survival, growth rate, maturation and cocoon production of original hatchlings. In all treatments greater than 90% of animals survived. Both inter- and intra-specific interactions negatively influenced growth, maturation and fecundity of experimental earthworms. The intensity of interactions was directly related to the degree of niche overlap between pairings. Growth of both anecie and endogeic species was significantly (P <0.05) reduced by the presence of adult L. rubellus. The behaviour of anecic hatchlings was seen to change from a sub-surface to a deep burrowing mode after 12 weeks (at approx. 1 g). Growth and cocoon production of A. chlorotica was enhanced by the presence of A. longa. Early growth of L. terrestris was significantly (P <0.05) greater in the presence of conspecific adults but such an advantage (possibly mediated by midden formation/use) decreased with age. Results indicated that the outcome of all inter-specific interactions could not be pre-determined by simple reference to ecological grouping. Furthermore the stage of individual earthworm development was seen to influence the intensity of inter- and intra-specific interactions. The results may help to inform field-based studies on earthworm interactions.