| Fish are cold-blooded animals.Growth and development rate of fish relied on species,sex,water temperature,light,and air pressure,in which water temperature played an extremely important role.Rainbow trout(Oncorhynchus mykiss) is a cold water fish and categorized in Salmonidae family,salmoniformes order,and actinopterygii class.It has become one of the top valuable species in the world wide aquaculture[2].The fish likes living in a clean water body with sand sediment,high dissolved oxygen,and slight flow.Its suitable water temperature ranges within 12-18℃,in which 16-18℃is the optimum.Reduced feeding and growth rate were observed when water temperature was less than 7℃or higher than 20℃.Temperature beyond 24℃will result in feeding loss,physiological function attenuation,and die of this fish.The narrow suitable water temperature range of rainbow trout limited its culture region and scale.This is one of the reasons why wide range of its aquaculture was not completely successful in south China.A lot of studies have reported the morphology,taxonomy,ecology,and physiology of rainbow trout.However,there is no report documenting physiological responses of rainbow trout to increased water temperature.In the present research, responses of hematological index,hormone,enzyme,and organ functions of rainbow trout to increased water temperature were studied.The research can explain the physiological death mechanism of rainbow trout to increased water temperature, provide theoretical information for rainbow trout aquaculture,and may provide reference information for physiological research of other cold water fishes.The results showed:(1) In the water temperature range of 14—23℃,the number of RBC(red blood cells) of Rainbow Trout reduced rapidly with increased water temperature,while the activities of Alanine Aaminotransferase of serum of Rainbow Trout increased with water temperature.Activities of ASpartese Tranasaminasa increased within the range of 14—19℃then declined within 19—23℃;the content of Total Protein and Globulin in serum increased with water temperature,and the content of Albu2min, Blood Sugar,and Total Cholesterol increased within the range of 14—19℃,then reduced within 19—23℃,but the content of Triglyceride decreased in response to increased water temperature.Concentration of Cu in serum of Rainbow Trout decreased a little within the water temperature range of 14—19℃,but increased remarkably within 19—23℃.Compared with Bighead Carp,however,the concentrations of K,P,Ca,Mg,Na and Cl in serum had unremarkable change.This paper analyzed the change mechanism of the biochemical factor of Rainbow Trout in the condition of warm water,which could provide useful technical data for genetic engineering of Rainbow Trout and Rainbow Trout breeding in warm water in south region,and could provide breaching way for playing down the response of Rainbow Trout to warm water.(2) Activities of Glutamate dehydrogenase(GLDH) andα-hydroxybutyric acid deaminase(α-HBDH) decreased slightly within the water temperature range of 15℃-16.5℃,increased sharply within 16℃-18.5℃,and decreased sharply within 18.5℃-22℃;activity of lipase(LPS) increased slightly within 15℃-16.5℃, decreased slightly within 16.5℃-18.5℃,and increased slightly within 18.5℃-22℃;activity of amylase(AMS) decreased slightly within 15℃-16.5℃but increased slightly within 16.5℃-22℃.(3) Within the suitable water temperature range(i.e.,15℃-19℃),the increased temperature resulted in gradual decrease of thyroid stimulating hormone(TSH),but sharp increases of a free three-iodine gland of the original acid(FT3) and free thyroxine(FT4).In the range of 19℃-26℃,increased temperature resulted in gradual increase of TSH,but sharp decreases of FT3 and FT4.(4) When 22℃,During the experiment,many Sistani's bodies of rainbow trout were observed;spleen cells scattered as patches;gill spaced with concentrated mucus on gill-chips;ovarian eggs were fully interstitial,the 4:00 eggs were large which arranged with uniform size,yolk particles around,and about 10-15 ball oils were formed within nucleus;kidney ago after the narrow width,was tapered,kidney These lanes are small spherical ellipsoid,kidney capsule of small film was a two-tier structure,glomerulosclerosis was circled by capillary vessels,the proximal tubule and distal convoluted tubules were circular pipes,the small part was formed with single layer epithelial cells,and the collecting duct cells were cylindrical.
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