Establishment And Evaluation Of Crossbreeding System In Pacific Abalone (Haliotis Discus Hannai Ino) And Its Application

Pacific abalone (Haliotis discus hannai Ino) is the most valuable mollusk of economic important in China. Its wild population distributed in Shandong and Liaodong peninsula while the abalone aquaculture spread along most part of the coastline of China. In the past 15 years, great achievement has been made by hybriding between Pacific abalone from Chinese and Japanese wild populations. Today, the Chinese wild Pacific abalones are using up and little attention is paid on abalone genetic seeding. Following the successful breeding program of agriculture, crossbreeding should be introduced to the breeding of elite abalone seeds which will be the future of abalone breeding system. Stressful high temperature in summer could cause heavy mortality both in Northern and Southern Chinese abalone aquaculture regions. We established the crossbreeding system by reciprocal hybriding between"97","98"strains with high growth rate and S strain with high temperature acclamation ability.The hybriding F1 of the crossbreeding system grow faster than the traditional hybriding F1 of Chinese and Japanese wild populations. Hybriding progenies acquired 33.9% higher survival rate than pure"97"and"98"strain during the oversummer while they have higher survival rate than pure S strain during the overwinter. Abalones gained extended range of acclimation temperature through crossbreeding. Hybriding juveniles of 11 month old had highest growth rate at 24°C which is 2°C higher than that of pure"97"and"98"strains. Hybriding abalones performed almost the same growth rate under normal temperature, but they showed better growth rate under extreme high and low temperature. There was no significant difference (P>0.05) on growth and survival between hybriding and pure bred abalones under all the experimental temperature (8-30°C).We detected genetic differentiation between Northern stain ("97") and Southern strain ("S") after four generations of diverging selective breeding under different temperature environments. The heterozygosity is lower in S strain than that in"97"strain which probably caused by the extreme high culture temperature stress for S strain.Chronic acclimation to different temperature changed the expression patter of Hsp70 and Hsp90 in Pacific abalone drastically. Abalones acclimated to low temperature response slowly compared to the fast response of high temperature acclimated ones. Hsp70 and Hsp90 play different roles in acute and chronic thermal incubation. Abalones could vary their expression pattern according to the environment which enlighted us to find out how could Pacific abalone managed to survive in Southern China.