Artificial sex induction of Cobia using electrical technique

Abstract

The present study proposes a novel technique of monosex-male reversal for the commercially important marine fish of cobia (Rachycentron canadum) using transient square pulse-electric and androgen hormone dose. The eggs of R. canadum had a simple spherical shape (≈1.29 ± 0.02 mm. in diameter) which is smaller than that of the freshwater. The critical age of 6-19 hpf (hour post fertilization) were induced in the external field with square wave pulses of μs-duration and amplitude of 100-350 VDC (equivalent to 26.25-87.5 kV.m-1). The suspending medium of electroporation (EPM) contained a poor conductive medium with the minimized concentration of the androgen hormone 17 α-Methyltestosterone (MT). Using the amplitude of 350 VDC of 3 square-wave pulses of 50 μs duration with the concentration of 1,500-50,000 μg.l-1 MT could be made all-male sex reversal of hatching at 35.71±1.81 to 89.28±1.17% (n=700) with the maximum survival rate of 45.20±1.71%. Experimentations were achievable at a commercial density ranging from 700-1,000 eggs/10ml for each induction. Nevertheless, we have not yet accurately determined the sex reversal rate since their sex will be stable only after they are 2-3 years old. This novel technique could reduce the MT dose down to a minimized value with a rapid throughput of only quarter-hour per batch of eggs and using only 10 ml lots of hormone containing medium.