RESUMO
The nucleotide variation in a mitochondrial DNA (mtDNA) fragment within and among species of Capillaria sensu lato from Australian marsupials and rodents was analyzed using a mutation scanning/sequencing approach. The fragment of the cytochrome c oxidase subunit I (COI) was amplified by PCR from parasite DNA, and analysed by single-strand conformation polymorphism (SSCP) and sequencing. There was no significant variation in SSCP profiles within a morphospecies from a particular host species, but significant variation existed among morphospecies originating from different host species. The same morphospecies was found to occur in 1-3 tissue habitats within one host individual or within different individuals of a particular species of host from the same or different geographical areas, and morphospecies appeared to be relatively host specific at the generic level. The results indicated that the species of Capillaria sensu lato examined, although highly variable in their host and tissue specificity, may exhibit the greatest degree of specificity at the level of host genus.