Gynogenesis in the African catfish, Clarias gariepinus (Burchell, 1822). Optimizing the induction of polar-body gynogenesis with combined pressure and temperature shocks

Abstract

The effect of a simultaneous temperature and hydrostatic pressure shock applied a few minutes after activation of the egg was evaluated by monitoring the short-term survival rate of polar-body gynogenetic embryos of African catfish, Clarias gariepinus (Burchell, 1822). The aim was to evaluate the interdependence of temperature and pressure in retaining the second polar body. The temperature shock varied between 4°C and 44°C in increments of 4°C, while the pressure shock varied between 0.1 and 68.8 MPa in increments of 13.8 MPa. Highest survival rates were attained at a pressure between 40 and 55 MPa, regardless of the temperature at which the shocks were applied. Optimal survival rates of shocks applied at lower temperatures required longer durations. If reliability to induce retention of the polar body is of prime concern, hydrostatic pressure shocks of 55 MPa at room temperature are recommended.