CHARACTERIZATION OF MITOTIC CHROMOSOMES IN THE GOBIID FISH ZOSTERISESSOR-OPHIOCEPHALUS (PALLAS, 1811) (PERCIFORMES, GOBIIDAE)

A karyological study of ten specimens of the gobiid Zosterisessor ophi ocephalus (PALLAS, 1811) (Pisces: Perciformes) was conducted by standa rd, fluorochrome and silver nitrate staining, and C-, Alu-I, and BrdU banding methods. Irrespective of sex, the diploid complement was 2n = 46 and the karyotype included 22 pairs of uni-armed chromosomes (ST+A) (pairs No. 1 to 22) and one pair of biarmed chromosomes (M) (pair No. 23). The latter consisted of two small-sized NOR-bearing elements and was structurally heteromorphic. Application of in vivo BrdU technique indicated that replication of chromosomes was temporally clustered in to early and late replicating chromosomal regions. Presumptive mechani sms of evolution of the karyotype of Z. ophiocephalus are discussed.