Ovarian development and sex ratios of gynogenetic Atlantic cod (Gadus morhua)
University of New Brunswick
Pre-harvest sexual maturation is common in farmed Atlantic cod ( Gadus morhua). This redirection of resources from muscle tissue to gonadal development results in reduced flesh quality prior to harvest. A potential solution is to culture triploid females, as their ovarian development is greatly reduced. However, an understanding of the sex determining mechanism is necessary to produce all-female populations. The genetic basis of sex for Atlantic cod was investigated using gynogenesis. This process results in uniparental maternal inheritance following irradiation of spermatozoa and subsequent duplication of the maternal genome. The optimum treatment for production of gynogenetic diploids was determined to be egg activation with UV -treated spermatozoa (milt pre-diluted to 15% spermatocrit followed by further 1: 10 dilution and exposure to 113 mJ/cm2 UV light) followed by the application of hydrostatic pressure to retain the second polar body (5 min at 58,600 kPa, beginning 180°C-min post-activation). All gynogens were determined to be female, demonstrating female homogamety for sex determination. However, most gynogens exhibited delays in early stages of oogenesis at 8 months of age.