A chromosome study of the tapeworm Bathybothrium rectangulum (Bloch, 1782) (Cestoda: Pseudophyllidea).

The diploid number 2n = 18 was revealed in Bathybothrium rectangulum, a specific parasite of barbels (Barbus spp.). All chromosome pairs were biarmed (pairs 1, 4, 7, 8, and 9 were metacentric; pairs 2, 3, and 6 were meta-submetacentric; and pair 5 was submetacentric) and small (from 1.49 to 2.95 microm). The C-banding method revealed pericentromeric heterochromatin in pairs 1, 3, 5, and 7; distinct C-bands in pairs 2, 4, 8, and 9; and a slight band in short arms of pairs 1 and 6. The karyotype of B. rectangulum is discussed with respect to the irresolute taxonomic position of B. rectangulum within the Pseudophyllidea.