Induced meiotic gynogenesis and sex differentiation in summer flounder ( Paralichthys dentatus)

Meiogynogenesis and temperature manipulation were used to produce XX male summer flounder broodstock for future production of monosex (all female) populations. Meiogynogens were produced by fertilizing eggs with UV-irradiated (70 mJ/cm 2) black sea bass sperm and applying 6-minute pressure shocks (58,600 kPa), two min post-fertilization. From 4 females, 132,000 eggs were produced, of which 95.6 ± 1.8% were viable, 51.0 ± 13.0% fertilized, and 15.9 ± 8.3% hatched. Following metamorphosis, meiogynogens and controls were raised under a low temperature regime (12 °C gradually increased to 20 °C), 21, and 26 °C for up to 376 days post hatch (DPH). Female sex differentiation was greater in meiogynogens (62.5%) and control fingerlings (22.6%) raised under a low temperature regime compared to those raised at the higher rearing temperatures: 0% at 21 °C, and 0 and 3.9% at 26 °C in meiogynogens and controls, respectively. These results suggest that temperature, during the critical phase preceding gonadal development, influences sex differentiation in summer flounder.