Allozymic variation in tubificid oligochaetes from the Laurentian Great Lakes

Aquatic oligochaetes are an important component of the benthos in many freshwater habitats. Yet, virtually nothing is known about the population genetics of this group. Electrophoretic surveys of allozymic variation of selected members of the Family Tubificidae were conducted at six locations in the Laurentian Great Lakes of North America. Branchiura sowerbyi was the dominant member of the oligochaete fauna at two sites, and was found to be monomorphic at all enzyme loci that were examined. In contrast, members of the genus Limnodrilus, which included L. cervix, L. claparedianus, L. hoffmeisteri, L. maumeensis, and L. udekemianus showed considerable allozymic variation at several enzyme loci. L. udekemianus exhibited tri- and tetra-allelic heterozygous electromorph banding patterns at the monomeric Pgm locus, along with unbalanced heterozygous patterns at both Pgm and the dimeric Pgi locus.Genetic distance analyses suggest that L. cervix, L. claparedianus, and L. maumeensis are closely-related (genetic identifies ranged from 0.92–0.85), and may represent subspecies rather than distinct species. Breeding studies need to confirm this assertion. This survey represents the first attempt to characterize allozymic variation of aquatic oligochaetes in North America. Additional work should focus on elucidating taxonomic ambiguities within this group via both morphological and biochemical genetic studies.