Studies On Hyperthermal Endurance And Cultivation Traits Of The Thermotolerance Sea Cucumber Apostichopus Japonicas Cultured In Southeast Coast Of China

This study examines hyperthermal endurance of the thermotolerance sea cucumber Apostichopus japonicas which is vastly cultivated in southeast coast of China.The Critical Temperature Maximum(CTM),168-h Upper Incipient Lethal Temperature(168-h UILT50)and the optimum growth temperature have been determined.In addition,some parameters of the sea cucumber's cultivation traits had been measured,e.g.the optimum growth temperature,growth rate,the yield,and the somatic index of the natural growth environment in the southern China water.Moreover,a comparison of those parameters has been made between south and north origination area.The main results are presented as follows:The south aquacultured sea cucumber was excellently hyperthermal tolerant and the CTM was measured as high as 35.85±1.37?.The 168-h UILT50 was 32.81?under a drastically changed environment temperaturebut it could only be 33.98?when the environment temperature changed gentlely.The hyperthermal endurance of southern aquaculture sea cucumber was much better than that of northern species.Heat stress induction under the sublethal temperature in advance could enhance the hyperthermal endurance of the southern population.The environment temperature ranged from 14 to 26?fell in the fitness survival temperature of the the southern rearing population,and the temperature for the suitable growth ranged between 14 and 23?.The optima temperature was 17.34?for the large sea cucumbers(5.54±0.74 g)and was 18.97?for the small one(2.21±0.33 g).The metobolism of southern aquaculture population was intense when the environment temperature was higher 26 ?.However,the growth rate was extremely low because most of the energy was used to antagonize the high temperature.Under the condition of environment temperature of 14?,the major energy supplier for the small individual southern population was protein.While it was originated from protein and fat if the temperature ranged 17-26 ?.After the 172 d aquaculture at the natural environment where temperature was 12.5-19.2 ?,the accumulative survival rate for the southern sea cucumber with the initial weight 9.05±0.74 g were 86.80±5.72%,the accumulative growth rate was 987.07%,the specific growth rate is1.39±0.66,the yield is 92.00±2.67%and the somatic index is 58.69±3.05%,respectively.Compared to that of the northern population,the southern one were 13.0%,11.2%(S.G.R),35.29%,and 7.27%higher,respectively.Under the natural environment condition,the 2-year old southern aquaculture sea cucumber?ividuals with the initial weight of(57.68±6.96 g)could normally and integrally pass the summer at the southeast China coast,i.e.,suriving the period with high water temperature of24.5??29.3?.In addition,the water temperature for the begining of aestivation was 25.5?and was 23.1?for the end of aestivation.Since the water temperature for the north aquaculture sea cucumbers were 24.5?for begining of aestivation and 23.1?for the end of aestivation,the dormancy time of the southern aquaculture animals was shortened by 18-20d,the survival rate was raised up to 19.75%,and the loss rate of the?ividual body weight decreased by11.09%.After the 42-d stress under high temperature(28.0±0.5?),the south aquaculture groups with the initial weight(57.68±6.96 g)went into aestivation.The activity decreased,the metabolism reduced and the body shrank and became hard.Furthermore,the averaged individual weight decreased by 43.8%,alimentary tract degenerated,and the relative weight was decreasing with time.While the averaged weight-loss ratio was 53.1%for north aquaculture groups,the ividual weight-loss ratio reduced by 9.3%and the reduction reaching up to 17.51%.Under the consistent stress of high temperature of 28 ?,the south aquaculture groups with the averaged individual weight of(30.26±2.16 g)will go into aestivation,and obtain compensated growth after the environment temperature became more suitable.However,it was related to the duration of the high temperature stress.In conclusion,south aquaculture sea cucumber was much suitable for being aquacultured in south China coast,since the hyperthermal endurance and the cultivation traits were more superior compared to the northern species.