Effect Of Acute Temperature Stress On Hematological Physiology And Reproductive Endocrine Functions Of Gestational Ovoviviparous Black Rockfish, Sebastes Schlegelii

This paper mainly studies on gestational ovoviviparous black rockfish, Sebastes schlegelii. Hematological physiological parameters, serum sexual steroids hormones as well as gene expressions related to reproduction in ovary and brain are detected through endocrinological and molecular biological methods after acute temperature stress. The results we got are as follows:1. Effect of acute temperature stress on hematological physiological parameters ofgestational black rockfish This study focused on levels of serum cortisol and hematological physiological parameters in gestational black rockfish exposed to acute heat shock (16℃ to 25℃) or acute chilling shock (16℃ to 7℃). Results showed that serum cortisol (COR) and glucose (GLU) concentrations rapidly increased, after which concentrations of serum proteins and lipids changed significantly in order to meet energy needs. Transaminases in liver cells, which were damaged by acute stress, moved to blood. Besides, the levels of blood cells and Hemoglobin (HGB) were modulated remarkably. The study demonstrated that obvious differences were found in fish exposed to acute thermal or cold stress compared to fish in control group. The physiological conditions of black rockfish were found hard to restore to normal levels during post-stress recovery period and interestingly, the response of fish exposed to thermal stress exhibited more severe contrasted with that in chilling stress. All in all, metabolic and immune conditions of black rockfish would change after acute heat or cold shock, more seriously, which might do harm to health and physiological status even reproductive proceed offish.2. Effect of acute temperature stress on levels of serum sexual steroids hormones and gene expressions related to reproduction in ovary of gestational black rockfish 125I radioimmunoassay and molecular biological methods were used in order to determine the changes of serum 17β-Estradiol (E2), Progesterone (P4) concentrations and expression levels of gonadal P450 aromatase gene (CYP19ala), estrogen receptors (ERs) and Foxl2 in ovary after acute temperature shock. The temperature sensitivity of aromatase were demonstrated in gestational black rockfish.The results indicated that serum E2 concentration and expression level of ERa exhibited similar trends, whereas the mechanism of temperature on them needed more detailed research. On the other hand, expression levels of ERPs varied with different factors. Considered as a precursor of 17a-hydroxy-20(3-dihydroprogesterone (DHP), serum P4 was thought to have some unknown functions during gestation of black rockfish. No notable changes were found in expression level of transcription factor Foxl2 under acute heat or cold shock, which might indicate the participation of some other regulators.In a word, levels of sexual steroids and gene expressions related to reproduction in ovary of gestational black rockfish changed remarkably after acute temperature stress. Furthermore, thermal duress were found to induce sharper responses and need longer recovery time. In this regard, temperature shock probably disturbed the ovarian physiological functions of gestational black rockfish and, thus, had a detrimental effect on reproductive status.3. Effect of acute temperature stress on gene expression levels related to reproduction in brain of gestational black rockfishThis research detected the expression levels of brain P450 aromatase gene (CYP19alb), ERs and Foxl2 in brain after acute temperature shock. The results suggested that the expression level of CYP19alb in brain elevated significantly under acute thermal stress in contrast with CYP19ala in ovary, perhaps indicating distinct physiological functions of CYP19s among tissues. It was tempting to suggest that there was an auto-feedback loop involved in regulating expression levels of CYP19alb, E2 and ERa in order to promote trscription of CYP19alb. In addition, the results indicated that aromatase expression can be up-regulated by Foxl2 both in brain and ovary. To sum up. acute thermal stress had significant influence on gene expressions related to reproduction in brain while those did not change remarkably after acute chilling stress, of which the detailed mechanism needed more researches.4. ConclusionIn summary, this study investigated the effect of acute heat or cold stress on hematological physiology and reproductive endocrine functions of gestational black rockfish, Sebastes schlegelii. This was the first report to describe the effect of acute temperature challenge on reproductive endocrine functions of gestational black rockfish, suggesting to have remarkable theoretical significance on cultivation of the ovoviviparous fish. The results indicated the heat-sensitivity of gestational black rockfish and fish might need longer recovery time after thermal challenge. It was of high importance to monitor water temperature fluctuation closely especially heat challenge, as for female fish entering the reproductive phase, in order to decrease injury induced by temperature stress during pregnancy. It was suggested that maintaining the water temperature could be beneficial for embryonic development and delivery process of gestataional black rockfish.