Practical PCR tools for the delineation of Contracaecum rudolphii A and Contracaecum rudolphii B (Ascaridoidea: Anisakidae) using genetic markers in nuclear ribosomal DNA.

Abstract Using genetic markers defined previously in the internal transcribed spacers (ITS-1 and ITS-2) of nuclear ribosomal DNA (rDNA), PCR-coupled restriction fragment length polymorphism (PCR-RFLP) and specific PCR assays were established for the specific detection of each of two morphologically indistinguishable operational taxonomic units ( Contracaecum rudolphii A and Contracaecum rudolphii B) within Contracaecum rudolphii ( s.l. ) and their differentiation from Contracaecum septentrionale , a closely related congener. Application of these tools to C. rudolphii ( s.l. ) adults from Phalacrocorax carbo sinensis (the Eurasian subspecies of the great cormorant) from Qinghai Lake in China, revealed C. rudolphii B to infect this host. This is the first report of C. rudolphii B in P. carbo sinensis outside of Europe (where it was originally detected), supporting the proposal that this species has a broad geographical distribution. Together with other methods, each of these molecular tools will be useful for investigating the ecology of C. rudolphii A and C. rudolphii B as well as C. septentrionale .