Triploid induction by hyponotic shock in the Chinese pearl oyster (Pinctada martensii)

Triploid technology is widely used in aquatic animal breeding and has produced huge economic benefits. It is possible to increase the size of pearl by using the fast growth of triploid. In this study, the hypotonic shock was used to induce triploid of Pinctada martensii for the first time to explore the comprehensive effect of hatching rate, growth rate, survival rate and triploid rate. We used the controlled variable method to find the optimal conditions for inducing triploid P. martensii from 7 different salinity, 3 different initial induction times and 3 different induction time. Meanwhile, the cleavage rate, hatching rate, the changes in survival rate, shell length and triploid rate of P. martensii were explored. Results showed that the highest triploid rates of D-shaped larvae were 64.16%±6.92%, 65.87%±6.51%, and 65.14%±1.93%. The optimal conditions for highest triploid rates were at a salinity of 14, when 50% of first polar body (PB I) was released from fertilized eggs, and 15 min after induction, respectively. The results showed that triploid larvae did not show obvious advantages. The effect of hypotonicity shock on embryos caused a decrease in larval survival rate and triploid rate. Through principal component analysis of cleavage rate, hatching rate, 15-day-old survival rate, shell length and triploid rate, the first two principal components were retained in the three induction conditions. The cumulative variance contribution rate of the retained principal components exceeds 85%. The comprehensive evaluation scores of 50% PB I released from fertilized eggs, salinity of 14, and 15 minutes of induction were 6th, 1st, and 1st respectively in their respective experiments. The study showed that there was no obvious advantage in the growth of the triploid of P. martensii larvae, and the two conditions of 50% PB I released from fertilized eggs and 15 minutes of induction were suitable for the triploid induction of P. martensii. This study can provide a new idea for the P. martensii triploid breeding, which may improve production efficiency.