Enzymatic variability in sympatric species of Tubifex (Clitellata : Tubificidae)

The globally distributed species Tubifex tubifex Muller, 1774 (Clitellata; Tubificidae) is sometimes considered to include several different morphological forms, each recognizable by their chaetal structure. The 'blanchardi' form is a distinct species: sympatric populations of Tubifex tubifex and Tubifex blanchardi Vejdovsky, 1871 show complete reproductive isolation. In an attempt to assess the genotypic differences between these closely related species, a comparative allozymic survey was carried out. More than 400 individuals of T. tubifex (235 specimens) and T. blanchardi (203 specimens), from a mixed community of tubificid species in a highly polluted river were examined, using as markers two enzymatic loci: phosphoglucose isomerase (PGI) and phosphoglucose mutase (PGM). Both species are polymorphic at the two loci, with at least one unshared allele for each locus, and show different electromorph patterns. Moreover, the occurrence of multiple banded patterns suggests a polyploid condition in both T. tubifex and T. blanchardi.