DNA evidence that Marshallagia marshalli Ransom, 1907 and M-occidentalis Ransom, 1907 (Nematoda : Ostertagiinae) from Svalbard reindeer are conspecific

The gastro-intestinal parasitic nematodes of ruminants Marshallagia marshal li and M. occidentalis are morphs of a single species according to indirect evidence. In this study, their taxonomic status and molecular identificati on were assessed more directly in isolates from the abomasal nematode commu nity of Svalbard reindeer using genetic data. DNA sequences of the first an d second internal transcribed spacers of nuclear ribosomal RNA genes were o btained from individual nematodes by the polymerase chain reaction (PCR). B oth taxa contained virtually identical sequences of each ITS and shared mos t of the polymorphisms detected. A PCR assay based on ITS-2 sequences previ ously developed to identify M. marshalli and Ostertagia gruehneri, the seco nd common species in this community, gave identical results for M. marshall i and M. occidentalis. Genetic data thus confirmed that M. marshalli and M. occidentalis are conspecific.