Abstract
Eisenia andrei/fetida complex of lumbricid earthworms contains E. andrei (Ea) and two mitochondrial lineages of E. fetida (Ef), referred to as Ef1 and Ef2. These earthworms are hermaphrodites capable of self-fertilization and hybridization as evidenced in laboratory mated earthworms from Ea and Ef1 lineage of Ef. The aim of the present investigations was to compare reproductive performance of Ea and Ef2 lineage from French laboratory stocks reared for a decade in Polish laboratories. These were cultured either in isolation and/or in intra-specific or inter-specific pairs for up to 57 weeks from hatching. Parental specimens and offspring were identified by species/lineage-specific sequences of the haploid mitochondrial COI gene, either 'a' or 'f2', and species-specific sequences of the nuclear 28s rRNA gene, either 'AA' or 'FF', thus delimitated as aAA or f2FF for Ea or Ef2, respectively, or aAF for hybrids. Isolated virgin earthworms produced a few sterile cocoons only, more frequently in Ef2 than in Ea, but no hatchlings. Analysis of cocoon production and reproduction of laboratory-mated intra-specific Ea+Ea and Ef2+Ef2 pairs revealed higher fecundity of Ea than Ef2 measured by numbers of cocoons and hatchlings, while inter-specific Ea+Ef2 pairs gave plenty cocoons but low numbers of aAF hybrids developed from Ea ova fertilized by Ef2 spermatozoa.
Highlights
PODOLAK A., KOSTECKA J., HOFMAN S., OSIKOWSKI A., BIGAJ J., PLYTYCZ B. 2020
Spanish specimens of E. andrei (Ea) and E. fetida (Ef) were capable of uniparental reproduction due to self-fertilization, since isolated virgin earthworms produced cocoons and hatchlings (DOMINGUEZ et al 2003), while such phenomenon was absent in Eisenia sp. cultured in Polish laboratories
Parental specimens were vital throughout a whole year of investigations except two E. fetida 2 (Ef2) specimens from the Ef2+Ef2 group; their growth was inhibited versus their partners and they died before reaching maturity
Summary
PODOLAK A., KOSTECKA J., HOFMAN S., OSIKOWSKI A., BIGAJ J., PLYTYCZ B. 2020. Annual reproductive performance of Eisenia andrei and E. fetida 2 in intra- and inter-specific pairs and lack of reproduction of isolated virgin earthworms. Eisenia andrei/fetida complex of lumbricid earthworms contains E. andrei (Ea) and two mitochondrial lineages of E. fetida (Ef), referred to as Ef1 and Ef2 These earthworms are hermaphrodites capable of self-fertilization and hybridization as evidenced in laboratory mated earthworms from Ea and Ef1 lineage of Ef. The aim of the present investigations was to compare reproductive performance of Ea and Ef2 lineage from French laboratory stocks reared for a decade in Polish laboratories. Inter-specific hybrids were detected in natural populations of Ea and Ef from Scandinavia (MARTINSSON & ERSEUS 2018) and the fertile hybrids were found during controlled laboratory mating between Ea and the Ef1 mitochondrial lineage of Ef from French/Polish laboratory stocks The latter were genotyped by both mitochondrial COI genes (‘a’ or ‘f/f2’) and diploid nuclear genes (‘A’ or ‘F’) as aAA (Ea) or fFF/f2FF (Ef1/Ef2), or as interspecific hybrids derived from Ea cocoons (aAF) or Ef1 cocoons (fFA) (PLYTYCZ et al 2018a,b). Further studies on reproduction of these hermaphroditic species capable of self-fertilization were worthwhile
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