Three ploidy levels indicated by genome quantification in Acipenseriformes of North America

The order Acipenseriformes comprises more than 20 species of sturgeons and two species of paddlefish worldwide. Extant Acipenseriformes are important in the study of evolutionary mechanisms and are potentially valuable in commercial aquaculture. The genome size in seven of the eight North American Acipenseriformes was de-termined by quantifying the DNA in erythrocytes using flow cytometry. Genome size ranged from 4.6 to 13.1 picograms. Three distinct groupings of genome size occur in an approximately 1:2:3 ratio, indicating ploidy differences between groups. Species with the smallest genomes are considered tetraploids of some ancestral fish and, therefore, 4C. Our study supports the conclusion that the intermediate genome size consists of octaploid (8C)-derived species and the largest genome is a dodecaploid (12C)-derived species. Spontaneous triploids (3N) of the lake sturgeon, Acipenser fulvescens, and the Gulf of Mexico sturgeon, A. oxyrhynchus desotoi, indicate that polyploidization mechanisms continue in the Acipenseriformes today. The mean genome size of white sturgeon, A. transmontanus, from Idaho was found to be significantly smaller (P <.05) than that of white sturgeon from California and Wash-ington. From the Department of Animal Sciences, Purdue Uni-versity, West Lafayette, IN 47907. Blood samples were collected and shipped to us from all over the United States by researchers interested in the biology and preservation of sturgeon and paddlefish species. The authors thank all those who contributed samples, in