| Three sections are included in the dissertation. The first part is related tostudy on cloning and expression of Na+-K+-ATPase of Scatophagus argus.The second part is the observation in organizational structure of the gill ofScatophagus argus.The third part is the basic study of survival andgrowing environment on Scatophagus argus, including the lowtemperature resistance and nutritional needs of Scatophagus argus underthe same salinity.1．The gill microstructure of Scatophagus argus juveniles was observed,using the technology of paraffin section and photomicrography. The resultsshowed that the gill of Scatophagus argus juveniles at salinity of20‰wasconstituted by gill bow，gill raker and gill filament. And the gill filament iscomposed of many gill lamella. Chloride cells, plenty in gill filament andgill epithelia, are mainly centralize to the base of gill lamellae and there aregreat many mucous cells. The gill structure could facillitate Scatophagusargus juveniles to adapt to the change of aqueous salinity. And the structureand number of chloride cells acclimatize to the environmental changes.2．Na+-K+-ATPase is ubiquitous in all mammalian cell membranes. As akey enzyme for ion transport in mammals, Na+-K+-ATPase transports K+into and Na+out of the cell, against a concentration gradient. The ATPwhich is needed to maintain the intracellular concentration of Na+and K+ accounts for1/4of mammalian metabolic capacity. In recent years,Na+-K+-ATPase becomes an important research content of fish physiologybecause of its crucial role in osmoregulation in teleosts. This paper is aimto illustrate the structure, function and role of Na+-K+-ATPase, and theaquatic environment factors which impact its activity in aquatic organisms.Firstly, the full length DNA and cDNA encoding the Na+-K+-ATPase werecloned from Scatophagus argus by homologous cloning, RACE-PCR,DNA Walking and other molecular technologies. Then we analyzed thesequence, structure and homology of the gene, and construct aphylogenetic tree. Secondly, we examined the expression ofNa+-K+-ATPase mRNA in different salinity, time and tissue, using realtimefluores-cence quantitative PCR(Realtime-PCR). Taken together, we couldwell understand the molecular mechanism of osmoregulation ofScatophagus argus at transcriptional and translational levels, and lay atheoretical foundation for the research of the molecular mechanism, alsoprovide further scientific theory for the freshwater aquaculture extensionand breeding of Scatophagus argus.3. The fish Scatophagus argus, which is a new resource of mariculture,has been paid much attention in South China now. However, few studiesmention about its biological background so far. In the process ofcultivating marine fish, temperature tolerance and feed nutritional needs are the main consideration. Fish in South China are more sensitive tochanges of temperature. In the current study, we performed the experimentof low temperature resistance in Scatophagus argus juveniles and provedthat LT50is about12.2℃and the lethal low temperature is11.0℃forthis species. In addition, experiments about nutritional needs ofScatophagus argus juveniles were also carried out in this study. Throughfeeding Scatophagus argus juveniles with three different kinds of feed, theresults showed that the group fed with plant protein was significantlyfaster than the other two groups fed with animal protein (p<0.01). We alsoobserved that Scatophagus argus preferred the synthetic feed made withplant protein. It proved that Scatophagus argus demands less animalprotein in feed. Therefore, it showed that we don’t have to spend muchmoney on the feed in the cultivation of Scatophagus argus. Scatophagusargus, as a new resource of mariculture, deserves the promotion andaquaculture. |
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