MITOTIC ANALYSIS OF THE NORTH-AMERICAN WHITE STURGEON, ACIPENSER-TRANSMONTANUS RICHARDSON (PISCES, ACIPENSERIDAE), A FISH WITH A VERY HIGH CHROMOSOME-NUMBER

The average chromosome number of the North American white sturgeon, Ac ipenser transmontanus Richardson, was found to be 271 +/- 2.5 (ranging from 265 to 276). This number is significantly higher than previous e stimates for this species. A representative karyotype was found to con sist of 132 meta- and submeta-centric chromosomes, 44 acrocentric chro mosomes, and 98 microchromosomes. An improved C-banding technique reve aled variation (2-7) between animals in the number of entirely heteroc hromatic metacentric chromosomes. These heterochromatic chromosomes ma y represent supernumerary chromosomes. There was no cytogenetic eviden ce of a heteromorphic sex chromosome pair or any sex-related chromosom al polymorphism in either sex of this species.