Chromosome rearrangements and survival of androgenetic rainbow trout (Oncorhynchus mykiss).

The purpose of this work was to quantify the impact of spontaneous and X-radiation-induced chromosome rearrangements on survival rate of androgenetic rainbow trout (Oncorhynchus mykiss). Various doses of X irradiation (50, 150, 250, 350 Gy) were used for inactivation of nuclear DNA in oocytes. After the irradiation, eggs were inseminated with normal sperm from 4 males derived from a strain characterized by Robertsonian rearrangements and length polymorphism of the Y chromosome. The haploid zygotes were exposed to a high hydrostatic pressure (7000 psi) to duplicate the paternal DNA. Neither Robertsonian chromosome polymorphism nor the Y chromosome morphology impaired the viability of the androgenetic embryos and alevins. Moreover, survival of eyed embryos of the androgenetic rainbow trout increased significantly with increasing doses of oocyte X irradiation. After 6 months of rearing, only specimens from the 250 and 350 Gy variants survived. The number of fingerlings with remnants of the maternal genome in the forms of chromosome fragments was higher in the 250 Gy group. Intraindividual variation of chromosome fragment number was observed, and some individuals exhibited haploid/diploid mosaicism and body malformations. Individuals irradiated with less than 250 Gy died, presumably because of the conflict between intact paternally derived chromosomes and the residues of maternal genome in the form of chromosome fragments.