Effectiveness of Heat Shock (40°C) With Different Duration for Tetraploid Formed in Mutiara Catfish (Clarias sp.) Juvenile

Abstract

This study seeks to determine the best method for preventing separating one cell into two cells in early embryogenesis as a means to induce tetraploid in the Mutiara catfish strain (Clarias sp.). Heat shocks were applied to newly fertilized eggs. Heat shock that was administered at 40 °C, for 4 min at 30 min post-spawning, was the best method for tetraploid induction, as evidenced by the highest percentage of forming four pronuclei in syngamy (84.12%). Therefore, heat shock induction was employed to further explore the advantage of tetraploid over diploid catfish. After hatching of the heat-shocked eggs, the larvae were allowed to reach juvenile levels of development. At day 30 in culture, the number and amount of chromosomes were determined in juvenile stages, using Silver Nitrate Staining methods, by which the catfish were divided into diploid and tetraploid groups. The average specific growth rate of the tetraploid (22.55%/gr/day) was significantly higher (Pb 0.05) than that of their diploid counterparts (15.42%/gr/day). These results reveal the advantages of growing tetraploid over diploid Mutiara catfish strain and its feasibility for future commercial production.