Gonadal morphology of female diploid gynogenetic and triploid rainbow trout

Chromosome sets of fishes can be manipulated; this practice includes the pr oduction of triploid and gynogenetic salmonids. Such chromosomal modificati ons often result in abnormal ovarian development. In rainbow trout (RBT), t riploid females have string-like gonads lacking significant developing oocy tes and are suggested to be sterile due to the odd set of chromosomes disru pting oogenesis. Aberrant ovarian development is reported to occur in about 30% of gynogenetic females. It has been suggested that gynogenetic fish ar e more prone to expressing developmental abnormalities due to either increa sed homozygosity or to incomplete inactivation of the paternal chromatin. T his investigation was done to compare the ovarian morphology of female trip loid and induced gynogenetic diploid RBT. The objective was to determine wh ether the presence of supernumerary chromosomal fragments, potentially gene rated during the process of sperm genome inactivation, would result in abno rmal gonadal development in gynogens comparable to that observed in triploi d females. Gonadal morphology was observed and karyotypical analysis was co mpleted on 21 gynogenetic fish. In 90% of the fish examined, the presence o f chromosomal fragments was positively correlated with irregular ovarian de velopment. The atypical gonadal morphology observed in the gynogens resembl ed triploid RBT ovarian morphology. The results of this investigation suppo rt the hypothesis that disruption of the normal diploid chromosomal complem ent alters germ cell development in gynogenetic female RBT due to the unbal anced nature of the genome. (C) 2000 Wiley-Liss, Inc.