| As the longest river of china, Yangtze River is a treasure trove of fish resources fostering more than350fish species. The upper reaches of the Yangtze River is mainly located in the mountainous areas with steep slopes and swift streams.Due to the complicated flow pattern there are approximately124kinds of endemic fish. In recent years, as a result of the damming, thefish migration routes had been blocked, causing habitat fragmentation, spawning grounds and habitat destruction or loss. To be worse, a variety of fish stocks are close to be exhausted due to the lack of strict and scientific management. Consequently, species conservation of the endemic fish in Yangtze River are badly in need. Largemouth bronze gudgeon, Coreius guichenoti belongs to Cyprinidae in the Cypriniformes, and is one of the rare endemic fishes in the upper Yangtze River in China. The fish is a potamodromous migration species living in schools and producing pelagic eggs, and can usually be found in rivers with torrential flow. Due to its tender meat, delicious taste and high nutrition, C. guichenoti used to be an important economic fish in the upper Yangtze River. However, in recent years, the catch of this species has declined dramatically and the fish tends to become stunted owing to overcatching and construction of hydroelectrical projects. The construction of hydropower stations in the Yangtze River and in the middle and lower reaches of the Jinsha River has blocked most of the passage of C. guichenoti and submerged most of its spawning fields. This endemic and important economic fish is facing the threat of extinction if measures are not taken in the succeeding period.Fishery stock enhancement and releasing has been proved to be an effective measure to protect the rare and endangered fish species. Culturing adequate broodstocks is the precondition to start the artificial propagation, but intense stress response and high susceptibility to ichthyophthiriasis are critical challenges to the collection, domestication and culture of C. guichenoti during the aquaculture practice. To date, the culture of C. guichenoti can only be performed in cages of vessels near the shore in the upper reaches of the Yangtze River from Luzhou to Hejiang. To the best of our knowledge, no report has been published about the successful indoor culture of C. guichenoti, except for experimental culture. For the key parts of the transfering and domestication in C. guichenoti, we tested the changes of blood physiology and biochemistry, the morphology and strcture of the key tissues, as well as the stress protein HSP70/HSC70. We tried to explore the basic laws of stress response of Coreius, and find measures to mitigate the corresponding stress response. And the specific content and key findings are as follows:We tested the morphology of blood cell and physiological and biochemical parameters of C. guichenoti cultured for almost one year in the cage; and established the corresponding reference intervals. Compared with other fish, the blood cortisol levels of C.guichenoti remained at a relatively higher level (185.70ng/mL), which may be related to the preference and physiological traits of C.guichenoti, such as preference for torrent, high swimming speed, and long-distance migration, well-developed liver and pancreas combination, and high efficiency in ingestion, digestion, and transformation. In addition, C.guichenoti the low degree of domesticatiton and the long period adapt to farmed environment may cause the high cortisol level. Compared with the wild C.guichenoti, the levels of glucose, triglycerides, total protein and globulin are singnificantly higher. This can be attributed to the large amount of high-energy food (relatively high protein, lipid and carbohydrates) that the fish get and the reduction of activities in the culturing environment versus the wild.We expoursed the Cage-cultured C.guichenoti to a low intensity(out of water for30s) and high intensity(out of water for50s) acute handling stress; and the tissues including blood, liver, gill and kidney were sampled at0,1,4,12,24,72,120and168h after the handling stress. We tested the changes of the blood physiology and biochemistry as well as the morphology and strcture of the key tissues. The results suggest that the treated fish all displayed typical acute stress response including the abrupt increase in plasma cortisol, lysozyme, glucose and ALT. the abservation of tissues morphology suggest that the low and high intensity acute handling stress both caused the changes or damage of the gill and kidney. The treated fish in both groups were spontaneously infected with Ichthyophthirius multifiliis. By the end of the experiment168h), the of plasma glucose, lysozyme and lactate remainded at relitively high levels, although the levels of plasma cortisol, ALT and AST had retained to the resting levels. This suggested that the fish also remainded in the state of diseases and adapting the new environment of chronic stress.We get the appropriate anaesthesia concentration of MS-222(20-40mg/L) used in the long-distance transport of C.guichenoti by the preliminary experiment including behavior observation and the survival rate of the pratical transport. In order to investigate the basic characteristics of the physiological stress response of fish subjected to transport stress and evaluate the effects of MS-222anesthesia, temperature reduction and the combination of both practices as sedative during transportation, we set up the four groups including Ana (ambient temperature with no anesthetic) group, Aa (ambient temperature with MS-222anesthetic) group, Lna (low temperature with no anesthetic) group, and La (low temperature with MS-222anesthetic) group. And we sampled the blood at0,4,24,72and168h. The results suggested the concentrations of TAN, NH3-N, and TN among the four treatment groups were significantly higher than before transport. Most of the examined plasma biochemical parameters, such as plasma COR, GLU, LA, ALT, and AST, displayed an increase, followed by a gradual decrease, similar to the stress responses of other bony fish. MS-222anesthesia, temperature reduction or the combination of the both had the effect of decreasing the metabolism and activity of C. guichenoti to different degrees. The results suggest that for a successful long-term transportation of C. guichenoti employing the combination of temperature reduction and MS-222is most preferable, followed by the use of temperature reduction alone, or MS-222at a relatively high temperature, and the fasting period before transport will be ensured for48-72h. In additon, the fish also remained in the acute or chronic stress state in the first two week after the transport, so it is critical to nurse the fish.Full length cDNAs of HSC70and HSP70were cloned from the liver SMART cDNA library. The full length cDNA sequences of HSC70and HSP70are2,330bp and2,290bp respectively and encoding649amino acids and643amino acids respctively. Multiple amino acid sequence alignment suggests that the two gens HSC70and HSP70have high homology to other animals. Tissue distribution analysis revealed that the transcription levels of HSP70and HSC70were different in various tissues, with HSP70transcribed in a reduced trend in muscle, eye, kidney, gill, brain, spleen, heart and fin, together with HSC70transcribed most in liver followed by eye, gill, fin, heart, spleen, brain, muscle and kidney. Under acute handling stress, the transcription levels of HSP70and HSC70in different tissues changed not variously except in livers, and showed little consistency with the changes of the parameters of blood physiology and biochemistry. Therefore, it is not applicable to include the transcription levels of HSP70and HSC70as one of the evaluation parameters during the acute handling stress and long-term transportation stress in C. guichenoti, and further research is needed in this area. |
PDF Full Text Request