Monosex-Male Sex Reversal of Nile Tilapia Eggs Using Pulse-Electric Field Inductions

Abstract

This work proposes an alternative technique of monosex-male reversal for Nile tilapia (O.niloticus) using transient pulse-electric fields to minimize time consumption of the sex reversal treatment and androgen hormone dose instead of 28-days conventional feed-fry treated and immersion techniques which uses very large amounts of 17-methyltestosterone (MT) hormone. Electrical model of nonspherical fish’s egg was developed to evaluate the induced transmembrane potential using an RCmodel to correct the ambiguities about the shell thickness and the estimated dielectric properties of the egg membrane for inductions. The parallel-plate electrode equipped with a sequential signal pulse-generator (SPG) (to be patented) has been developed. The eggs of O.niloticus (2‐3 days postfertilization) were carefully induced in square-wave electric fields of 0.25‐87.50 kV ·m −1 .W e experimentally optimized induction of O.niloticus’s egg by adjusting the number of 1‐5 square wave pulses and 5‐10 s pulse durations. The suspending medium of electroporation (EPM) was prepared by mixing HEPES buffer with the minimized concentration of MT. Verifications of sex reversal of the induced eggs have been carried out with autopsies of 2 months old of sex-reversed fry by using the aceto-carmine stain technique. The optimized conditions were 3 square wave pulses of 87.50 kV ·m −1 electric fields but a 89.25% sex reversal of eggs was achieved with less than 25% egg death. The prototype of the electrode equipped with the controlled SPG for on-site inductions could operate with 50 eggs of O.niloticus for each induction with the rapid time consumption.