Effects Of Environmental Stress And Allometric Growth Of Lates Calcarifer

In this paper,Lates calcarifer(Bloch)was selected as the research object,and the allometric growth phenomenon and the effects of various environmental stress factors on its anti-oxidation and digestion were discussed.The early organ development of Barramundi was studied.The changes of antioxidant and digestive indexes in the body under regular and environmental stress,in order to provide reference for the early breeding of barramundi.Ten samples of the seabass(Lates calcarifer)were randomly selected since one day post of hatching.The morphological changes of the key organs were observed with a stered microscope.The Auto CAD software 2014 was used to measure the indicators of the head region,the tail region and the torsel region.The mathematical model y=aebxwas used to fit the relation between the total length and the day post hatch.Using the eqation of y=axbto simulate the model of allomatric growth.The 16 th day was choosen as the joint between the larvae and juveniles.The results presented that organs relating to feeling,swimming,breathingand feeding displayed the allometric patterns.Mouth width exhibited positive allometric growth of different rates in larval stage.Eye diameterexhibited the same rate with total length in the larval stage,but exhibited negative allometric growth in the juvenile stage.Head region height of larvae presented positive allometric growth,but exhibited negative allometric growth in the juvenile stage.Body height and anal length showed the same rate with total length.Pectoral fin showed the same rate with total length in the larval stage,showed positive allometric growth during the juvenile stage.Dorsal,pelvic anal fin produced in juvenile stage exhibited fast growing.Tail fin length showed negative allometric growth in the larval stage,but showed the same rate with total length in the juvenile stage.The main morphological characteristics of the larvae and juveniles(1-23 day post hatching)were studied by using the cartilage-bony double staining technique.The results exhibited that the spines of the 3-day-old larvae were bent,the chordate format and the pectoral fins and the caudal fins formed.The vertebral column warped and the dorsal fins developed on 5DPH.The neural arch,haemal arch,and dorsal fins wrinkles presented on 9DPH,and genital opening appeared while anal fin started development.On 13 DPH,the initial development of pectoral fins and caudal fins completed,and neural spines and haemal spines appeared.The development of dorsal fins and pectoral fins were completed on 16 DPH.On 19 DPH,ossification process of the spine started from the two ends to the middle,pectoral fins continually developed,and the appendages of skeletal development close to be completed.There was a difference in the bony ossification of the appendage on 21 DPH.The dorsal spine,pleural spine,neural arch,haemal arch,neural spine and haemal spine became hard ossification,and the tail fin fully developed.On 23 DPH,the vertebral column remained rigid ossification.The pectoral fins fully developed.The basic framework of the fish bones developed.The fin rays changed ossification and section,and completed metamorphosis.The experiment shows bone ontogeny characteristics.Skeletal malformation began to appear 10 days after hatching,with a high deformity of 20 to 22 days after hatching.The spine of the seabass and its attached bones were in the same developmental sequence as other fish,but the development time was different.Skeletal development deformity began to appear about 10 days after incubation,mainly in the 20-22 days after hatching.The 96h-semistatic water toxicity experimental method was used.The ammonia concentrations were set as 0 mg/L,5 mg/L,10 mg/L,15 mg/L,20 mg/L,each group has three replicates,there were 120 healthy seabass larvae(15 day post of hatch)in each experimental container with a capacity of 50 L,5 fishes were respectively sampled in 24,48,72 and 96 h.With the increase of concentration,SOD activity showed a trend of decline after rising firstly under 24 h stress,and with prolonged stress,SOD enzyme activity in high concentration bagan falling.CAT activity was similar to the change of SOD activity.GSH-Px activity showed a rising and falling trend.GSH-Px activity was similar to the change of SOD and CAT activity.In this experiment,ammonia had a inhibitory effect on POD activity.ACP presents the decreasing trend after rising firstly,and then ACP showed an increasing trend.With the increase of concentration,lipase,amylase and trypsin showed a trend of increase firstly and then decrease.The increase of digestive enzyme activities in short time improve the ability of digestion and absorption utilization,which is used to compensate for the energy consumption induced by environmental stress.the high concentration of ammonia can inhibit the activity of digestive enzymes,showing a significantly reducing trend.The 72h-semistatic toxicity experimental method was used to calculate the effect of acute nitrite stress on activities of antioxidant and digestive enzymes ofjuvenile Lates calcarifer.In this study,five kinds of antioxidant enzyme activities showed significant difference in the influence of time and dose of nitrite.SOD activity was higher than the control group and POD activity was significantly lower than the control group except the highest concentration of treatment group at the end of the experiment,the CAT activity is significantly higher than the control group.ACP activities were lower or slightly lower than the control group.The concentration and processing time has significant impact on the lipase activity.The lipase of individuals fluctuate under the early stress.and there was no difference between the lipase activities of low concentration group and the control group at the end of the experiment,with the increase of nitrite concentration,then appeared the trend of rising,falling and rising again,that was seemly associated with the selected test concentration and individual differences.Both stress dose and stress time had a significant effect on the activities of antioxidant enzymes and digestive enzymes.Semi-static bioassay methodwas used to calculate the acute temperature stress to juveniles(15 DPH)and understand the physical response of larvae to low temperature.In this study,20 oC,22oC,24 oC and 26 oC were tested and 28 oC was used as control.The SODactivities were elevated to scavenge excess ROS after exposure to lower temperature and increased dramatically with the increasing of the residue time.POD enzyme activities presented at a low level in the early stage of cold exposure and increased to a high level with the extension of time.Catalase activitieswere elevated.The activities of GSH-Px were elevated,what’s more,the GSH-Px activities gradually return with the extension of time.The ACPactivities were elevated after exposure to lower temperature.Lipase activities were decreased and modestly elevated with the extension of time.Amylase activities decreased.The trypsin and pepsin activities were elevated with the decrease of temperature.Barramundi exhibited a certain tolerance of low temperature in a short period of time.