Optimization of cold shock conditions for triploid induction in Siniperca scherzeri

Objective The purpose of this experiment is to explore the optimal induction conditions for triploidy in Siniperca scherzeri using cold shock method.

Methods The experiment set three time points of induction (TP) (2.5, 4.0, 5.5 min after insemination), three temperatures of induction (T) (2, 4, 6 ℃), and three durations of induction (D) (10, 12, 14 min) , respectively. Nine experimental groups were obtained using the orthogonal experimental table L₉(3⁴), and denoted as P1−P9, respectively, with P0 (S. scherzeri normally developed at 22 ℃) serving as the control (untreated) group.

Results 1) Cold shock had a significant effect on the hatching rate of fertilized eggs in S. scherzeri, with the hatching rate of group P0 significantly higher than those of the other groups (P<0.01). 2) Group P4 (TP 4.0 min, T 2 ℃, D 12 min) exhibited the highest triploid induction rate in S. scherzeri at (83.33±5.77)%, followed by group P5 (TP 4.0 min, T 4 ℃, D 14 min) at (73.33±5.77)% and group P7 (TP 5.5 min, T 2 ℃, D 14 min) at (70.00±0.00)%. The induction rate of group P7 was not significantly different from that of group P4 (P>0.05), but the rates of P5 and P7 groups were significantly higher than those of the other experimental groups besides group P4 (P<0.05). While group P9 (TP 5.5 min, T 6 ℃, D 12 min) had the lowest induction rate at only (3.33±5.77)%. 3) The interaction among TP, T and D was not significant (P>0.05), but significant interactions existed between each pair of the three factors (P<0.05), and no primary-secondary order existed among the three factors. 4) One-way ANOVA showed that the mean triploid induction rate in S. scherzeri at 4.0 min after insemination (TP) was significantly higher than that at 2.5 and 5.5 min after insemination (P<0.05). The mean triploid induction rate in S. scherzeri at 2, 4 ℃ (T) was significantly higher than that at 6 ℃ (P<0.05). The mean triploid induction rate in S. scherzeri at 12, 14 min (D) was significantly higher than that at 10 min (P<0.05). 5) The total length and body mass of 6-month-old triploid S. scherzeri show no significant differences compared with those of diploids (P>0.05).

Conclusion Triploidy can be successfully induced in S. scherzeri by the cold shock method. Using the induction rate as the evaluation index, the suitable conditions for inducing triploidy in S. scherzeri by the cold shock method are as follows: TP at 4.0 min after insemination, T at 2 or 4 ℃, and D of 12 or 14 min. The optimal conditions are TP at 4.0 min after insemination, T at 2 ℃, and D of 14 min.