Tandem BspMII DNA repeats confirm the monophyletic origin of freshwater cottoid fishes

DNAs of the Baikalian cottoid fishes (Cottoidei, sculpins) include a family of Bsp tandem repeats composed mostly of 154- and 238-bp sequences. Quite similar repeats were found in DNAs of seven Cottoidei species from East Sib eria, North America, and Japan by PCR with primers complementary to various regions of the repeat unit. Restriction analysis suggested a scheme of org anization of tandem BspMII repeats in DNAs of freshwater cottids which may be represented by the formula [238bp + k(154bp)](N) where k varies from 0 t o 3 and N is species-specific depending on the k value. Such repeats were n ot found in marine cottids. The presence of BspMII repeats in DNAs of all t he freshwater cottids and the universal organization of tandem repeats argu e in favor of their monophyletic origin.