Classical and molecular cytogenetics of Khawia sinensis (Cestoda: Caryophyllidea), invasive parasite of carp, Cyprinus carpio.

Chromosomes of the invasive tapeworm Khawia sinensis (Caryophyllidea), the specific parasite of common carp, were analyzed by means of conventional Giemsa staining and using fluorescent DAPI and YOYO-1 dyes, silver staining, and fluorescent in situ hybridization (FISH) with 18S rDNA probe. The karyotype is composed of eight pairs of metacentric and telocentric chromosomes (2n = 16, n = 3m + 5t, TCL = 42.54 μm). Constitutive heterochromatin was located at pericentromeric regions of all pairs, except for the largest metacentric pair (no. 1), which possessed no DAPI-positive band. FISH with rDNA probe revealed that both homologues of chromosome pair no. 6 carry a cluster of ribosomal arrays, which were located interstitially close to the centromere. Present results are compared with previous cytogenetic data on Khawia spp., and comments are made on the karyotypes with respect to their phylogenetic links.