Restriction fragment length polymorphisms (RFLPs) of ribosomal DNA (rDNA) were compared between Diphyllobothrium latum and D. nihonkaiense using seven kinds of restriction endonucleases. No intra-specific variation in restriction fragment profiles was shown within both species of Diphyllobothrium. Digestion of the genomic DNA with three endonucleases, Smal, Hinfl and Hhal, provided one or two different bands between two species, although the hybridization patterns generated with the others, Hindlll, Xbal, Styl and Haelll, were the same in both. RFLPs in the digested profiles with Smal, Hinfl and Hhal could be used as species-specific markers even if only fragments of strobilae with morphological similarity were available. Other cestodes, Spirometra erinacei and Taenia saginata, used as controls showed quite different restriction fragment patterns with all the enzymes used.
