Application of Spermatozoa from Neo-males (XX) to Induce Androgenetic Development in Rainbow Trout (Oncorhynchus mykiss)

In species like rainbow trout (Oncorhynchus mykiss) that show male heterogamety (XY), induced androgenesis results in production of females (XX) and males (YY). Morphological and genetic differences between rainbow trout X and Y chromosomes suggest that androgenetic males (YY) may show lower survival than androgenetic females (XX). To test this hypothesis, we produced lines of androgenetic rainbow trout composed of males (YY) and females (XX) and of only females (XX) using spermatozoa from normal males (XY) and neo-males (XX), respectively. Survival rates of the androgenotes were monitored until gonadal differentiation and no significant differences in survival between XX/YY and XX androgenetic rainbow trout lines were observed. Sex-genotypes of the paternal males and androgenetic offspring were confirmed using a rainbow trout Y chromosome-related DNA marker. Histological analysis performed to detect potential disturbances in the gonadal development of the androgenetic XX and YY rainbow trout showed proper development of testes and ovaries in most of the studied individuals. Our results indicated that differences between rainbow trout X and Y chromosomes did not affect survival of the androgenetic offspring. Application of spermatozoa from neo-males to induce androgenetic development may have some potential in rainbow trout aquaculture to produce homozygous females that may be used in breeding programmes and to establish clonal lines.