Effects Of Temperature Acclimation On Growth And Thermotolerance Of Sea Cucumber,Apostichopus Japonicus Selenka

1. Thermal resistance in sea cucumber (Apostichopus japonicus Selenka) with different thermal history:Upper thermal limit and hsp70gene expressionThermal history can affect organisms’thermal resistance, however, effects of thermal history on thermal resistance and roles of heat shock protein70(Hsp70) in sea cucumber Apostichopus japonicus are not well understood. In the present study, the lethal thermal limits and expressions of Hsp70of sea cucumbers that were acclimated at different temperatures (22℃or12℃) for30days were studied. The upper lethal temperatures (ULT50) for sea cucumbers acclimated at22and12℃were31.8℃(31.5～32.1℃) and30.9℃(30.6～31.3℃), respectively. In heat shock experiments, sea cucumbers acclimated at different temperatures (22℃or12℃) were exposed to several high temperatures (25,27,29,31and32℃) for2h, followed by2h recovery at17℃, and the levels of hsp70were measured using semi-quantitative RT-PCR. The maximum induction temperatures for sea cucumbers in22℃and12℃acclimation treatments were31℃and29℃, respectively. These results showed that the temperature acclimation could affect sea cucumbers’upper thermal limit, which was related to the changed expression pattern of Hsp70in the sea cucumber. In practice, sea cucumbers that overwinter in southern China could acquire higher thermal resistance than those reared in the north.2. Effects of rearing temperature on growth, metabolism and thermal tolerance of juvenile sea cucumber, Apostichopus japonicus Selenka:Critical thermal maximum and hsps gene expression Effects of different rearing temperatures (16,21and26℃) on growth, metabolic performance and thermal tolerance of juvenile sea cucumber Apostichopus japonicus (initial body weight7.72±0.96g, mean±SD) were investigated in the present study. During the40-day experiment, growth, metabolic performance, food intake and energy budget at different reared temperatures were determined. Sea cucumbers rearing at16℃obtained better growth (final body weight11.96±0.35g) than those reared at21(10.33±0.41g) and26℃(8.31±0.19g)(P<0.05), and more energy was allocated for growth at16℃(162.73±11.85J g-1d-1) than those at21(79.61±6.76J g-1d-1) and26℃(27.07±4.30J g-1d-1)(P<0.05). Critical thermal maxima (CTmax) values of juvenile sea cucumbers reared at16,21and26℃were33.1,34.1and36.6℃, respectively. The upregulation of hsps in sea cucumbers reared at26℃was higher than those acclimated at lower temperatures (16and21℃), indicating that temperature acclimation could change the thermal tolerance of the sea cucumber, and CTmax and hsps were sensitive indicators of the sea cucumber’s thermal tolerance.3. Effects of temperature and salinity acclimation on growth and hsps gene expression of juvenile sea cucumber, Apostichopus japonicus SelenkaEffects of temperature and salinity acclimation on growth and hsps gene expression of juvenile sea cucumber were investigated in this study. There were12treatments (temperature:16,20,24,28℃; salinity:22,27,32psu), each treatment had3replicates. After40-d culture, the body weight and specific growth rate was different from each other. At high temperature, salinity tolerance of sea cucumber was lower than those rearing at ralatively low temperature. Also, hsps gene expression was different among treatments. Levels of hsps increased with temperature increasing. After acclimation at high temperature, the adaptation to salinity stress of sea cucumber was strengthen, and the ability to cope with high temperature and low salinity was improved.4. Effects of heat-shock in pelagic stages on growth, survival and Hsp70expression of juvenile sea cucumber, Apostichopusjaponicus Selenka The effects of heat-shock in pelagic stages on growth, survival and Hsp70s expression of juvenile sea cucumber, Apostichopus japonicus Selenka were investigated. Larvae at the stage of blastula, gastrula and auricularia were heat-shocked at selected temperatures (21.5, control;26,28and30℃) for45min and returned to21.5℃for continuous rearing. After the heat-shock, there were significant differences in survival among larvae in the four heat-shocked treatments. The survival rate of larvae decreased with the increasing of heat-shock temperature, and was higher in the stage of gastrula than those in blastula and auricularia. The Hsp70s expression of larvae in the stage of gastrula was higher than those in the stages of blastula and auricularia, suggesting that the survival of larvae partly correlates with the expression of Hsp70s.5. Effects of heat-shock selection during pelagic stages on growth and thermal sensitivity of juvenile sea cucumber, Apostichopus japonicus SelenkaThe effects of heat-shock selection during pelagic stages on growth and survival of juvenile sea cucumber Apostichopus japonicus were investigated to test the possibility to acquire high thermal tolerance individuals after the heat-shock. Larvae at the stages of blastula (BLA), gastrula (GAS) and auricularia (AUR) were heat-shocked at selected temperatures (21.5, control;26,28and30℃) for45min and returned to21.5℃for continuous rearing. There was significant difference in thermal sensitivity among different developmental stages. Juveniles after the heat-shock selection at pelagic stages showed higher induced thermotolerance than those without heat-shock. Therefore, heat-shock application at early pelagic development stages is potentially an effective way to select sea cucumbers with a high thermotolerance.6. Preliminary study in seeding and summer spending of sea cucumber (Apostichopus japonicus Selenka) in Southern ChinaSeeding and summer spending of sea cucumber(Apostichopus japonicus Selenka) in Southern China was investigated in this study. There were some ways to help sea cucumbers to spend summer, such as pumping water at night, raising water level, feeding multiple vitamin. If we carry out seeding in the spring of Fujian province, we can harvest adult sea cucumbers next spring, so the growth cycle could be shorten obviously.