Assessing sequence variation in the internal transcribed spacers of ribosomal DNA within and among members of the Contracaecum osculatum complex (Nematoda : Ascaridoidea : Anisakidae)

The anisakid nematodes of seals from different geographical origins, previo usly identified as Contracaecum osculatum A, C. osculatum B, C. osculatum C , C. osculatum D, C. osculatum E and C. osculatum baicalensis by multilocus enzyme electrophoresis, were characterised using a DNA approach. The first and second internal transcribed spacers (ITS-1, ITS-2) of ribosomal DNA (r DNA) were individually amplified by polymerase chain reaction (PCR) and ana lysed by single-strand conformation polymorphism (SSCP) and sequencing. SSC P analyses allowed the unequivocal differentiation of all taxa except C. os culatum D from C. osculatum I E. While C. osculatum D and C. osculatum E ha d identical ITS sequences, each of the other four taxa had distinct sequenc es, with interspecific differences ranging from 0.3% to 2.3%. C. osculatum C was genetically the most distinct taxon with respect to all other members of the species complex.