The Physiological And Biochemical Adaptation Of Long-Snout Catfish(Leiocassis Longirostris) To Overwintering

The relative changes of condition indicators and the effects of overwintering on health were studied in overwintering Leiocassis longirostris, which were reared under outdoor pond condition. The possible adaptive mechanism in relation to physiological and biochemical function was evaluated.This study focused on the changes of the biochemical component, the blood physiological and biochemical indices in some tissues and organs of Leiocassis longirostris. While the related morphological characteristics and ecological parameters also were examined, the change tendency concerning growth and adaptation of hormones secreted by endocrine was also identified.1. The loss of body weight was found in the winter. The liver weight did not show the significant difference in the first half of winter, whilst the liver weight reduced remarkably with the overwintering lasting. The somatic and hepatic index (K, VSI and HSI, respectively) and RNA: DNA ratio were determined. K declined steadily during overwintering, and the HSI and VSI dropped markedly after 50 days although the change of HSI and VSI in the first half of winter overwintering was not so significant. The RNA/DNA ratio decreased before the 50th day, but rose later on. Liver KNA/DNA ratio presenting the dynamic change different from muscle, which was not also consistent withthe RNA/DNA ratio under starved condition, was remarkably higher than that of the muscle, and this kind of difference reflected the interaction between temperature and starvation. Based on the data of HSI and K, it was revealed that HSI reflected the liver weight change, and condition factor then depended on the body weight change. The increase in RNA/DNA ratio in the later winter, which was the opposite to HSI and K, showed that it could be more sensitive to the environmental factor.2. The muscle moisture content increased with the overwintering time continuing, but it dropped on the 20th day and rose on the 50th day. During this period, the moisture content appeared to be reduced whilst the protein content increased. This possibly indicates that fish started to adapt to the new environmental condition. During overwintering, the protein content did not seem to indicate a significant difference, but the proportion in the terms of protein dry weight had a remarkable elevating in the last part of winter. The fat content remarkably reduced. The fatty acid in muscle and liver consisted mainly of the unsaturated fatty acid. The saturated fatty acid comparative content did not surpass 30%, and the monounsaturated fatty acid (MUFA) content was relatively high compared with polyunsaturated fatty acid (PUFA) although it reduced remarkably during overwintering. The fatty acid composition was also different in the muscle and liver, and the proportion of 18:3 and 20:5 in the liver was very low. The saturated fatty acid (SFA) and PUFA content in the muscle less changed, however those in the liver increased. It is possible that the reduction of MUFA content could secure the stability of PUFA proportion.3. Overwintering changed the hematological parameters of Leiocassis longirostris. The blood red blood cell (RBC) number dropped, while the white blood cell (WBC) number increased in the earlier period of winter and reduced later. The platelet (THC) number reduced suddenly in the beginning of overwintering but maintained at a low level after that. In the blood, the K+ concentration showed a reduction for the most time period, but an increase in the last part of overwintering. The Cl- and Na+ concentrations reduced first and then increased while the Ca+ concentration reduced remarkably all the time. The activeness of lactate dehydrogenase (LDH) and creatine kinase (CK) dropped in the earlier period of winter and climbed gradually afterwards. On the contrary, the alkaline phosphatase (ALP) level rose in the earlier period of winter, and then started to drop. The concentrations of alanine aminotransferase (ALT) and aspartateaminotransferase (AST) soared suddenly in the last part of winter. At the same time, the contents of total protein, triglycerides (TG), and glucose dropped gradually during overwintering. The Cortisol content had a higher level in the beginning of overwintering, and the Cortisol content dropped with the time lengthening. The FT3 and FT4 levels were lower than those of T3 and T4. T3 and T4 contents decreased gradually, but FT3 and FT4 levels increased in the first period of 50 days, then dropped remarkably.