Ploidy Level Determination in Genetically Manipulated Bream, Abramis brama, Based on the Number of Active Nucleoli Per Cell

Abstract

ABSTRACT Ploidy level on genetically manipulated bream, Abramis brama, was determined using the mean number of silver staining nucleoli per cell. Haploid bream resulted from activation of eggs with UV-irradiated sperm, and triploid specimens were obtained by applying cold-temperature shock. Cell preparations were made for 20 fish of each ploidy level: IN, 2N, and 3N. The frequency of one, two, and three nucleoli per cell were calculated based on observation of 200 cells per studied individual. Cells of haploid individuals had one or, sporadically, two nucleoli, and depending on the specimen, mean number of nucleoli per nucleus ranged from 1.0 to 1.02; cells of diploid fish had one, two, or, sporadically, three nucleoli with the mean ranging from 1.70 to 1.76; in triploids there were one, two, or three nucleoli per cell, with the mean ranging from 2.15 to 2.41. Positive identification of ploidy level in bream requires examination of no more than 40 cells per individual, as has been determined by regression analysis. The method requires very small amounts of any kind of tissue, enabling determination of ploidy level in juvenile fish without sacrificing the fish.