REVISED KARYOTYPES AND CHROMOSOME-BANDING OF COREGONID FISHES FROM THE LAURENTIAN GREAT-LAKES

Karyotypes of lake whitefish, Coregonus clupeaformis, and various Grea t Lakes cisco species, lake herring or cisco, C. artedi, bloater, C. h oyi, blackfin cisco, C. nigripinnis, and shortjaw cisco, C. zenithicus , were analyzed using Giemsa staining, C-banding, silver staining, and Chromomycin A(3) fluorescence. Coregonus clupeaformis had a karyotype (2n = 80, NF = 98) indistinguishable from that described for C. laver etus from Europe, with one pair of nuclear organizer regions (NORs) on the short arms of a small acrocentric chromosome pair and a second NO R on the short arms of another acrocentric chromosome pair. This speci es displayed a size polymorphism involving the heterochromatic short a rm of the largest metacentric-submetacentric pair. All four cisco spec ies had similar karyotypes (2n = 80, NF = 98), with the exception of s ome C. artedi from Lake Superior, which were heterozygous for a chromo some fusion involving the NOR chromosomes (2n = 79). One NOR was locat ed pericentromerically on the long arm of the second largest acrocentr ic chromosome and a second NOR on the short arms of another acrocentri c chromosome pair in several individuals. C-banding revealed that the difference in chromosome morphology between lake whitefish and the cis coes probably resulted from amplification of heterochromatin on the sh ort arms of one pair of large submetacentric-metacentric chromosomes.