Electrophoretic detection of population variation within Contracaecum ogmorhini (Nematoda : Ascaridoidea : Anisakidae)

This study examined genetic variation among specimens of Contracaecum ogmor hini from different otariid hosts and geographical origins using a polymera se chain reaction (PCR)-based mutation detection approach. The first (ITS-1 ) and second (ITS-2) internal transcribed spacers (ITS) of ribosomal DNA (r DNA) were amplified individually by PCR, scanned for sequence variation by single-strand conformation polymorphism (SSCP), and samples displaying vari able SSCP profiles were subjected to cycle sequencing. While C. ogmorhini i ndividuals from Arctocephalus pusillus pusillus (CoAPP) from South Africa a nd those from Arctocephalus pusillus doriferus (CoAPD) from Australia had v ery similar SSCP profiles for both ITS-1 and ITS-2, individuals of C. ogmor hini from Zalophus californianus (CoZC) from Pacific Canada could be unequi vocally distinguished based on their profiles. In accordance with SSCP resu lts, both CoAPP and CoAPD had identical ITS consensus sequences, whereas Co ZC differed in sequence from both CoAPP and CoAPD populations by 0.2% tone base in the ITS-1) and 0.7% (two bases in the ITS-2). Based on the nucleoti de difference in the ITS-2 sequence, a PCR-linked restriction fragment leng th polymorphism (RFLP) could be employed to distinguish individuals represe nting CoZC from those of both CoAPP and CoAPD. The findings suggest that C. ogmorhini may represent a complex of at least two species.