| In this study, the cultivation methods and feasibility of selective breeding andcross-breeding of Strongylocentrotus intermedius strains in heat-resistant were studied,and the feasibility of using the expression of HSP70under high temperature in theearly age of sea urchin larva to the breeding of strains in heat-resistant was explored.The main results were showed as follows:This study investigated effects of family, temperature and family by temperatureinteraction (G×E) on the growth, survival of the sea urchin S. intermedius during itswhole growth period. At the age of eight months,40sea urchins were randomlychosen from11families and exposed to two simulated water temperatureenvironments, high temperature (HE) and cold temperature (CE). In addition,20seaurchins were chosen from another9families and exposed to HE. HE were set tosimulate the high water temperature of northern East China’s Sea, while CE was thesimulated cool water temperature environment of northern Yellow Sea near Dalian. Inboth of HE and CE, the experiment was divided into5periods (i.e., P1,lowtemperature period, P2, optimal temperature period, P3, high temperature period, P4,death period and P5, recovery period) as the water temperature changed. Testdiameter (TD) and body weight (BW) of the trial sea urchin and survival rate (SR) inboth HE and CE were measured monthly. The specific growth rate (SGR) of bodyweight was computed monthly in each environment. The results revealed that, in CE,family had significant effects on the BW in P2, P3, P4and P5, as well as on the TD(P<0.05). In HE, family significantly affected the BW in P3, P4and P5, and TD in P4and P5(P<0.05). Temperature had significant effects on TD and BW in P4and P5,and SR (P<0.05). G×E effects were significant in neither TD nor BW (P>0.05). Incontrary, family ranking changes revealed the existence of G×E in SR. The G×Eresults suggested that, it is necessary to apply family selection in both CE and HE forSR, but not for TD or BW. Based on above results, a optimal breeding program wasdeveloped The selected families provided the basis for the breeding of S. intermediusstrains in heat-resistant.In this study, complete inter-specific, diallel cross as well as correspondingreciprocal cross were built with S. intermedius (Si) and S. nudus (Sn)(Si♂×Si♀、Sn♂×Sn♀、Sn♂×Si♀、Si♂×Sn♀). Success rates of fertilization, hatching and deformity for each period were recorded under18℃,22℃,26℃,30℃, respectively.In addition, the growth traits of offsprings in every period with temperatures as factorswere measured. The results showed that, the fertilization rate of inter-specific hybridswas significantly lower than intra-specific offsprings (P<0.05). The difference onhatching rate of Si♂×Si♀was not significant between intra-specific offsprings andinter-specific offsprings at18℃(P>0.05). According to the present study,temperature had significant effect on fertilization rate and hatching rate (P<0.05).Both the maximum fertilization rate and hatching rate of S. intermedius wereobserved at22℃. The corresponding optimal temperature for S. nudus was18℃.Interestingly, the maximal fertilization rate and hatching rate of Si♂×Sn♀washeterogeneous, founded at22℃and18℃respectively. During the larvaldevelopment period, temperature brought significantly effect on the deformity rateand growth traits (P<0.05). The optimal temperature for all sea urchin larvae was18℃. The four-arm larva in Si♂×Sn♀presented the lowest deformity rate as well as theworst growth. For six-arm larva and eight-arm larva periods, the performance of Si♂×Sn♀was generally between inter-specific cross groups but the deformity rate ofeight-arm larva was the highest. Due to the maternal effects, the Si♂×Sn♀offspringswere able to tolerant high temperature in the early embryonic development stages, butalso presented the worst performance in growth traits. Along with development period,the maternal effects were weakened. The heterosis of hybridization in growth wasgradually reflected. By the method of interspecific hybridization, the ability ofheat-resistant in the early stage of embryonic development and the development ofpost-larval in S. intermedius can be improved. However, for the the ability ofheat-resistant and growth in adult sea urchin, further studies are needed.In the present study, the effect of temperature on the development of larvae at thestage of gastrula, prism and four-arm in S. intermedius was investigated. Theexpression of HSP70after heat shock in each larva period of S. intermedius wasstudied. The results showed that the four-arm larva has a strong resistance to heatcomparing to the gastrula larva and prism larva, while the prism larva had a poorperformance in heat-resistance. The expression of HSP70of sea urchin larva afterthermal stimulation was significantly different among times. In the periods beforehatching, the expression of HSP70of sea urchin larva was increasing along with thetime of thermal stimulation and the peak occurred at4fours. However, after hatching,the expression of HSP70of sea urchin larva presented first increased and thendecreased, and the peak appeared at2hours. The highest expression of HSP70was found in the period of prism larva before hatching, while the expression of HSP70inthe period of six-arm larva was higher than any other periods. In addition, both thedeformity rate and the expression of HSP70of prism larva after thermal stimulationwas the highest in the stage of gastrula larva, prism larva and four-arm larva. Thisindicated that, after thermal stimulation, the expression of HSP70has a correlation tothe deformity rate of larval development. This correlation can be used in the selectivebreeding of S. intermedius strains in heat-resistant to save breeding time and improvebreeding efficiency. |
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