Overview: Methods for Estimating Ploidy Levels

Jenkins, J. A.. U.S. Geological Survey, National Wetlands Research Center, Lafayette, LA.

Numerous studies have demonstrated the link between triploidization and sterility in aquatic animals. Sterility may preclude gonadal development or functional germ cell production, and energies may be diverted toward growth and other performance characteristics rather than reproduction. Induced triploids have an extra chromosome set through treating fertilized eggs with either temperature shock, hydrostatic pressure, or chemical treatments shortly after fertilization. While there are no gross morphological differences between diploid and triploid animals, several methods have been devised to assess ploidy status. Diagnosis of triploidy by red blood cell size is possible due to increases in cell size and in nuclear volume measured by microscopy or Coulter counter. Direct chromosome numbers and morphologies can be determined through karyology. Silver-stained nucleoli can be counted in cells from any tissue. Quantification of DNA by flow cytometry is effective because triploid cells contain 1.5 times the quantity of DNA than diploid cells. These methods, and a new prediction method being developed in our laboratory, will be considered with regard to expense, availability, accuracy, and labor requirements.

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Texas Chapter of the American Fisheries Society
Last modified: 03/03/04 04:15:38 PM