Heat shock treatments for polyploid induction in Clarias gariepinus: Different time after fertilization and treatment duration

Manipulation chromosome through heat shock treatment is safe method and can be applied to mass production in order to fulfil demand in animal food industry. The aim of the study was to evaluate how heat shock affected fertilized eggs after 4 minutes (triploid) and 40 minutes (tetraploid) of fertilization. After heat treatment of Clarias gariepinus fish eggs, the rate of abnormality of fertilized eggs were also determined. Heat shock treatments were 39°C, 40°C, and 41°C for 4 minutes, with times of 4 minutes after fertilization and 40 minutes after fertilization, with three repetitions of each treatment. The results showed that heat shock after 4 minutes of fertilization significantly affected the rate of slow embryonic development starting from the cleavage stage of 8 cell up to hatching compared to treatment 40 minutes after fertilization. The treatment with a shocking temperature of 41°C after 4 minutes of fertilization resulted in the highest percentage rate of abnormalities, 45.67%. Thus, this study revealed that tetraploid development was superior to triploid development due to higher egg abnormalities in triploid. Tetraploids are preferable as broodstocks to produce sterile triploids and can enlarge rapidly.