WIDESPREAD POLYPLOID FORMS OF LUMBRICILLUS-LINEATUS (MULLER) (ENCHYTRAEIDAE, OLIGOCHAETA) - COMMENTS ON POLYPLOIDISM IN THE ENCHYTRAEIDS

Studies of a small fresh collection of the marine intertidal enchytrae id oligochaete Lumbricillus lineatus (Muller) and taxonomic collection s from 27 additional locations in Europe, Canada, and Australia reveal the presence of morphotypes corresponding to parthenogenetic autopoly ploid forms, triploid, tetraploid, and pentaploid, of the species in a ll the regions represented by the collections. The extension of the ra nge of these cytotypes from Europe to a virtually global distribution raises questions about the significance of parthenogenesis and polyplo idism to their invasion of new habitats. Differences in reproduction r ates and the ecological breadth of the different ploidy levels are not known. The geographical distribution and abundance of polyploids of L . lineatus, in themselves, do not provide conclusive evidence for the repeated origins of polyploids within the species, but strongly sugges t that possibility. General theories link evolutionary polyploidy amon g animals with parthenogenesis, as seen in the polyploid forms of L. l ineatus. However, polyploidism combined with out-crossing underlies th e present taxonomic diversity of the family Enchytraeidae.