GEOGRAPHIC VARIABILITY IN THE GRAY MULLET MUGIL-CEPHALUS - PRELIMINARY-RESULTS OF MTDNA AND CHROMOSOME ANALYSES

The grey mullet, Mugil cephalus, plays an important role in the fisher ies and aquaculture of tropical and subtropical regions of the world. This species is considered cosmopolitan, but its distribution appears peculiar with regard to the coastal ecology of the species. A multidis ciplinary study of the geographic variability of this species, through a cytogenetic, molecular and morphometric characterization, was under taken to detect whether genetically distinct populations occur. The pr eliminary results from analyses of mitochondrial DNA and of chromosome s of seven different populations around the world are reported. The di fferent populations analysed are well discriminated by mtDNA analyses: samples are clustered in four groups, Mediterranean, East Atlantic, C entral Pacific and East Pacific, with a maximum sequence divergence of 3.3%. The karyotype of all the populations studied is uniformly compo sed of 48 acrocentric chromosomes, and neither heterochromatin distrib ution nor nucleolus organizer regions allow the identification of chro mosomal markers useful in distinguishing these genetically differentia ted groups of populations.