Effect Of Temperature, Salinity, Dissolved Oxygen, And Light Cycle Stress On The Growth Index Of Paralichthys Olivaceus Juveniles

An experiment was conducted to investigate the growth index of juvenile brownflounder, Paralichthys olivaceus following temperature （high temperature and lowtemperature）, salinity （high salinity and low salinity）, low dissolved oxygen, andlight cycle （long light cycle and short light cycle） stress and the change of growth rateafter remove the stress, the secretion and physiology biochemistry reaction （the ratioof RNA/DNA, the change of moisture, protein, fat, sugar and energy density） changeof the hormone （Growth Hormone, Insulin-like Growth Factor I, Stanniocalcin andMelatonin）, and to discuss the reaction, mechanism and countermeasure toenvironment stress of juvenile brown flounder. The main results and conclusions asfollows:1) Effect of temperature stress on the growth index of Paralichthys olivaceusjuvenilesa) Except during stress processing stages plasma IGF-I content significantlylower than the disposal T_22.0, the plasma GH and IGF-I concentration of otherdifferent treatments don’t exist significant differences;b) After breeding10days during different temperature, different processing offish weight appear significant difference with each other, and22.0℃is the bestgrowth temperature level, and then adjust all the temperature to22.0℃lasting30days. And the result showed that all treatment weight were significant differencesbetween each other no longer, and the processing of experiencing high or lowtemperatures stress won completely compensation growth in the end; After all thetemperature recover to22.0oC, the specific growth rate appeared significantly higherthan control processing, which showed that compensation growth mainly occur at this stage; Comprehensive analysis: from the experiment results we couldn’t get theobvious relationship between GH and the growth of Paralichthys olivaceus juveniles,and the relationship between this may be due that GH internal secretion was too much,and IGF-I （playing the role of mediated of the GH） and its receptor system synthesisand vigor played vital part in fish growth.c) The liver RNA/DNA ratio of T_8.5and T_13.5processing appeared significantlybelow T_17.5, T_22.0and T_26.5processing during the20-30d stage, and T_26.5treatment isthe largest group of RNA/DNA ratio. The liver RNA/DNA ratio of T_8.5processing inthe recovery phase of30d-40d stage appeared significantly lower than othertreatment group, and liver RNA/DNA ratio during other stages different treatment didnot exist significant differences. Muscle RNA/DNA ratio of different treatments in alldifferent period did not exist significant differences. Comprehensive analysis: muscleRNA/DNA ratio had not appeared remarkable difference, and which did not show theconsistency with the growth of this period, so using RNA/DNA ratio as growth indexmay be exist some disadvantages.d) When the temperature stress over, the liver glycogen content of T_8.5, T_13.0,T_26.5processing appeared significantly lower than T_17.5processing, but glycogen indifferent treatment in the recovery phase have no significant difference, and glycogencontent were higher than those in the control group in the end. At the end of the stress,T_26.5processing muscle glycogen content was significantly higher than otherprocessing, and T_13.0processing muscle glycogen levels higher than other processingin the recovery of the first10d, and the rest of the processing slightly higher thancontrol processing. Then muscle glycogen content of different treatment did not existsignificant differences. Comprehensive analysis: in the experiment, the best growthtemperature of Paralichthys olivaceus juveniles might be17.5℃-22℃, and belowor above the temperature could cause the stress response of Paralichthys olivaceusjuveniles, so as to mobilize liver glycogen as the main metabolic substrate and lead tothe liver and muscles glycogen levels drop. And the main organization organs of glycogen synthesis and storage in fish is liver, and because that muscle content is low,and the change is relatively small,so the temperature changes have no obviousresponse in the law.2) Effect of salinity stress on the growth index of Paralichthys olivaceus juvenilesa) After10days stress of different salinity processing, the growth of salinitystress processing was significant restrained, while the secretion of plasma GH, IGF-Iand CT also is restrained, so the reduced weight of Paralichthys olivaceus juvenileswas involved to plasma hormone secretion restrained （all less than the control group）;And during the11th to40th day when the salinity had been recovered, although theSGF of IS5group appeared significantly more than the control group （IS47group SGFdidn’t catch the control group level）, but the weight of IS5treatment finally didn’t getcompensation growth （weigh less than the control group）, IS47never; At the sametime plasma GH of all the treatments did not show significant differences, but IGF-Iand STC content showed significant difference, so IGF-I and STC might be involvedin or at least partly involved in the compensation growth of Paralichthys olivaceusjuveniles, and GH probably not involved in this process.b) After days stress of different salinity processing, the liver RNA/DNA ratio ofParalichthys olivaceus juveniles between different treatment showed significantdifference, but muscle RNA/DNA ratio did not show significant difference, whichmeans that during low salinity stress, the reduce of liver and muscles RNA/DNA wasprobably involved to the secretion of GH, IGF-I and STC restrained; And during the11th to40th day when the salinity had been recovered, the liver and musclesRNA/DNA ratio of all treatments did not show significant differences, and at thesame time the GH content did not show significant differences, but IGF-I and STCsecretion appear significant difference, which means that GH might be of theimportant hormones to adjust the liver and muscles RNA/DNA ratio, and the effect ofIGF-I and STC on the liver and muscles RNA/DNA ratio was not much enough.c) After10days stress of different salinity processing, the liver glycogen content of all treatments showed significant difference, and muscle glycogen did not showsignificant difference, while plasma GH, IGF-I and STC content of stress group isrestrained, Which means that the change of content of hepatic glycogen is likely to beinvolved with the reduce secretion of GH, IGF-I and STC; And during the11th to40th day when the salinity had been recovered, the liver and muscle glycogen contentdid not show significant difference, at the same time, GH content also did not showsignificant difference, but IGF-I and STC secretion appeared significant difference, sothe change of liver and muscle glycogen content was likely to be involved with thechange of GH content;d) After days stress of different salinity processing, the serum osmotic pressurebetween different treatment showed significant difference, and the filamentsNa⁺-K⁺-ATP enzyme of IS5treatment significant higher than IS47treatment. Andduring the11th to20th day when the salinity had been recovered, serum osmoticpressure were recovered to control processing level, and the Na^＋-K^＋-ATP enzymeactivity of different treatment did not exist significant differences, which suggests thatserum osmotic pressure and had obviously positive correlation with salinity stress,and at the same time, the content of plasma GH, IGF-I and STC was also undercontrol, which means there might be some relation between these indexes.3) Effect of dissolved oxygen stress on the growth index of Paralichthys olivaceusjuvenilesDuring low dissolved oxygen stress, there was no significant difference of GHand IGF-I between different treatment, but the weight, muscle RNA/DNA ratio andliver glycogen content decreased significantly, while he liver RNA/DNA ratio andmuscle glycogen content showed no different significance, which suggests that lowdissolved oxygen stress led to weight loss, affected normal metabolism of muscle（muscle RNA/DNA ratio can be report the repair and update of muscle tissue oncertain level） and makes liver glycogen excessive use, but plasma GH and IGF-I didnot show obvious correlation; In the dissolved oxygen concentration recovery phase （30d）, plasma GH appeared significant difference in the end of first10d, while theweight, the day growth rate and muscle RNA/DNA ratio of different treatment alsoappearred significant differences, and liver glycogen content t restored to control level,the liver RNA/DNA ratio, muscle glycogen content and IGF-I content still didn’tshow significant differences, which indicated that GH is likely to play a veryimportant role in the change process of weight, muscle metabolism and liver glycogen.（4）Effect of light cycle stress on the growth index of Paralichthys olivaceusjuvenilesThis experiment set up five processing, the ratios of light and dark time （h） everyday respectively as1L:23D、9L:15D、12L:12D、15L:9D、24L:0D；Each dealtwith the three repeat, and each aquatic animal’s box with12tail fish; then weigh onceevery10days, the whole experiment last60days. And then experimental ecologicaland bioenergetics methods was used to investigate the effects of the plasma GH, IGF-Iand MT change on the growth, the rate of liver and muscle RNA/DNA of juvenilebrown flounder, Paralichthys olivaceus juveniles in light cycle stress condition.The results showed that plasma GH, IGF-I, MT content in different treatmentwith different light cycle during the whole experiment all did not appear remarkabledifference, while the weight and the day growth rate also did not show significantdifferences. It suggested that the influence on the final weight, GH, IGF-I and MT oflight cycle was very small; But the day growth rate showed significant differencesduring21st-30st stage, and the law also had been reflect, which shows that thegrowth rate of Paralichthys olivaceus juveniles would be affected when there was toolong or too short cycle of light, and melatonin was likely to play a very important rolein this process. Moreover, the trend of muscle RNA/DNA ratio is presented infirstly increased and secondly reduced（1L﹤9L﹤12L﹤15L﹥24L）, and liverRNA/DNA performance as15L﹤24L﹤9L﹤1L﹤12L, and at the same time, MTcontent performance as12L﹤15L﹤24L﹤9L﹤1L, and the specific reason needsto be further discussed.