Characterization of mitotic chromosomes of four species of the genus Diplodus: karyotypes and chromosomal nucleolar organizer region phenotypes

Karyotypes have been described in four Mediterranean species of the genus Diplodus (Teleostei, Sparidae), D. vulgaris, D. puntazzo, D. sargus and D. annularis . Chromosomes were mainly acrocentric in all but D. vulgaris , where certain chromosome pairs were subtelocentric. A remarkable intraspecific heteromorphism in the number of NOR-bearing chromosomes along with a substantial interspecific variability in position of chromosomal Ag signals have been encountered. The presumed origin of multiple NOR-bearing chromosomes in Diplodus species and variation of the NOR location is discussed.