Uniparental reproduction of Eisenia fetida and E. andrei (Oligochaeta: Lumbricidae): evidence of self- insemination

This study investigated the copulatory behaviour of the lumbricid earthworm Eisenia fetida (Savigny, 1826) in a natural population, and the uniparental reproduction of E. fetida and E. andrei Bouché 1972, two closely-related species. Sperm transfer occurred in 61 % of the matings observed, of which 88.2 % showed bi-directional sperm transfer, 9.8 % unidirectional sperm transfer and one earthworm was self-inseminating. Although uniparental reproduction in earthworms has been reported by many authors, self-insemination has never been recorded before this study. Moreover, specimens of the two species were reared in isolation from hatching to see if they were able to produce cocoons when clitellate. The percentage of earthworms that produced cocoons was significantly higher in E. andrei (33 %) than in E. fetida (3.5 %). Numbers of cocoon produced and the number of hatchlings per cocoon were also significantly higher in E. andrei than in E. fetida; the cocoon viability was similar in the two species. One of these isolated individuals of E. fetida that produced cocoons was dissected and sperm was found into the spermathecae, indicating that self-insemination could be responsible, to some extent, of uniparental reproduction. Since parthenogenesis has not been demonstrated in these species, further studies are needed to show if uniparental reproduction is due only to self-fertilization.