This study was aimed at optimizing the induction of tetraploid in African catfish Clarias gariepinus eggs using cold shock protocol. Three temperatures (0, 5, and 10 °C) were applied at three durations (2, 5, 10 min) to suppress the first mitotic cell division at about 1.4 τ₀ after fertilization. Thereafter, the treatment and control groups were incubated at room temperature till the eggs were hatched and the performance characteristics of the progenies evaluated. The result obtained showed that the 0 and 10 °C respectively resulted in poor hatchability and low tetraploid percentage of the induced eggs. However, 5 °C cold shock for 2 or 5 min gave the highest hatchability (70%) and tetraploid percentage (35%); beyond this time, performance significantly reduces. The cytogenetically confirmed tetraploid progenies (4n = 112) in this study had higher erythrocyte axis length compared to their diploid counterparts (2n = 56). The exclusive tetraploid range of 12.5–17.4 μm and 10.2–14.1 μm was identified for the cell major and minor axis respectively, hence can be used to discriminate the progenies of the two ploidy groups. However, the progenies were similar in terms of morphological characterization and growth performance. It was concluded that 5 °C cold shock for 2–5 min at about 1.4 τ₀ after fertilization is sufficient to induce reasonable percentages of tetraploids in C. gariepinus.

本研究旨在使用冷激方案优化非洲鲶鱼Clarias gariepinus卵中四倍体的诱导。在三个持续时间（2、5、10 分钟）施加三个温度（0、5 和 10 °C），以在约 1.4 τ ₀抑制第一次有丝分裂细胞分裂受精后。此后，处理组和对照组在室温下孵化，直到卵孵化并评估后代的性能特征。所得结果表明，0°C 和 10°C 分别导致孵化率差和诱导卵的四倍体百分比低。然而，5 °C 冷激 2 或 5 分钟的孵化率 (70%) 和四倍体百分比 (35%) 最高；超过这个时间，性能会显着降低。本研究中经细胞遗传学证实的四倍体后代 ( 4n  = 112) 与其二倍体后代( 2n = 112) 相比具有更高的红细胞轴长度 = 56）。分别为细胞长轴和短轴确定了 12.5-17.4 μm 和 10.2-14.1 μm 的专属四倍体范围，因此可用于区分两个倍性群的后代。然而，后代在形态特征和生长性能方面相似。得出的结论是，受精后约 1.4 τ _{0 下}5 °C 冷激 2-5 分钟足以在C. gariepinus 中诱导合理百分比的四倍体。