Karyotype, ribosomal genes, and telomeric sequences in the crayfish Procambarus clarkii (Decapoda: Cambaridae)

Mitotic and meiotic chromosomes of the crayfish Procambarus clarkii (Girard, 1852) were characterized by means of heterochromatin staining techniques (C-, DAPI- and CMA(3)-bandings), and FISH of major ribosomal genes and telomeric pentameric repeat (TTAGG)(n). Nucleolar organizer regions have been located on four chromosome pairs. GC-rich heterochromatin was mostly associated with NORs, and brightly fluorescent centromeric/pericentromeric AT-rich bands were present in most chromosomes. Telomeric pentameric repeats (TTAGG)(n), occurred in all the P. clarkii telomeres and in the interstitial region of the largest chromosome pair, not co-located to ribosomal genes; as possible explanation of the origin of this chromosome, a fusion event was hypothesized.