| Effects of temperature and salinity on survival rate, asphyxiation point and theactivity of antioxidant enzymes of Trachinotus ovatus and structural changes of themitochondrion-rich cell in gills under different salinities were studies. The resultsshowed as follows:1．Effects of temperature and salinity on survival rate and asphyxiation point ofselective group of Trachinotus ovatusIn order to study the effects of salinity and temperature on survival andasphyxiation point on Trachinotus ovatus, by declining salinity gradually, changingsalinity and temperature suddenly, to determine the survival rate and asphyxiationpoint of selective group of Trachinotus ovatus at different salinities (0,3,5,10,15,20,25,30,35,40) and different temperatures (16℃,17℃,18℃,21℃,24℃,27℃,30℃,33℃,36℃) respectively. The results showed that in groups with declining salinitygradually, the survival rate of salinities0,3,40were significant lower than controlgroups at21d (P<0.05).The other groups had no significant difference with controlgroups (P>0.05). In groups with declining salinity suddenly, the survival rate ofsalinity0,3were significant lower than control groups at48h (P<0.05).The othergroups had no significant difference with control groups (P>0.05). In groups withchanging temperature suddenly, the survival rate of16℃,17℃,33℃,36℃weresignificant lower than control groups at48h (P<0.05). The survival rate of18~30℃had no significant difference with control groups (P>0.05). The asphyxiation point ofdeclining salinity gradually, changing salinity and temperature suddenly all appeareddecreasing first and then increasing with salinity or temperature changing. In salinities15~40, the effects of different salinities mutation amplitude on the asphyxiation pointwas same. But different temperatures mutation amplitude of the effects on theasphyxiation point had abvious difference. It was thus clear that，Trachinotus ovatushad a remarkable ability to the water salinity changes，but the adaptive capacity to the water temperature changes was weak.2．Structural changes of the mitochondrion-rich cell in gills of selective group ofTrachinotus ovatus under different salinitiesDistribution and structural changes of the mitochondrion-rich cell in gills ofselective group of Trachinotus ovatus under different salinities (5,20,30) wereexamined by light and transmission electron micrograph. The results showed thatmitochondrion-rich cells were mainly present on the base of gill filament and branchleaf; the volume and number of mitochondrion-rich cells increased with increasing ofthe salinity. Ultrastructure modifications included: the different salinities groups allhad the apical crypt which was constituted by the mitochondrion-rich cell, pavementcell and accessory cell. But the mitochondrion-rich cell of salinity5had large apicalmembrane with the developed microridge, the apical crypt was shallow; the apicalcrypt of salinity20and30, with small apical membrane and the undevelopedmicroridge, were improved obviously. In the cytoplasm of mitochondrion-rich cells ofsalinity5and30had developed tubular system and abundant cristae mitochondriale;the tubular system of salinity20was non-spacially constant and looseness of structure.Part of the tubular system contracted into a pearl bubble structure and shared togetherwith rough endoplasmic reticulum under salinity20. It was clear that after30days’acclimation, Trachinotus ovatus under salinity5and20shared both of seawater-typeMR cells and freshwater-type MR cells’ characteristics; Trachinotus ovatus undersalinity30had typical characteristics as seawater-type MR cells. Structural changes ofmitochondrion-rich cells were suited to different osmotic pressure.3．Effects of salinity and temperature on the activity of antioxidant enzymes in liversof selective group of Trachinotus ovatusBy changing water salinity gradually and temperature suddenly, the activities ofSuperoxide Dismutase(SOD), Catalase(CAT) and Glutathione Peroxidase (GPX) inlivers of selective group of Trachinotus ovatus at different salinities (10,20,30,40)and different temperatures (18.0℃,21.0℃,24.6℃,29.0℃,32.0℃) were studiedrespectively. At the end of the experiment, in groups with salinity of10, the activity ofenzymes had no significant differences with control groups (P>0.05); in groups withsalinity of20, the activity of SOD was significantly lower than control groups(P<0.01). In groups with salinity of40, the SOD and GPX activities weresignificantly lower than control groups at120h (P<0.05), the CAT activity had nosignificant differences with control groups(P<0.05). In groups with temperatures of 18.0℃and21.0℃, the activity of SOD was higher than control groups at1,3,6,12,24h, the activity of CAT was significant higher than control groups at24h (P<0.01).At the end of the experiment (24h)，in groups with temperature of29℃the activitiesof SOD and CAT were significant higher than those in control groups (P<0.05). Ingroups with temperature of32.0℃, the activities of SOD and CAT were significantlower than control groups at5sampling time (P<0.05). The results indicated that thechanging of water salinity and temperature could enhance the antioxidant enzymeactivities in Trachinotus ovatus liver. The activation of test could also be inhibitedwhen the salinity and temperature varied beyond the tolerance range of the body．... |
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