Responses of the major mitochondrial respiratory enzyme succinate dehydrogenase (SDH) activity in gill and muscle tissue of tilapia (Oreochromis mossambicus) were investigated upon their transfer to a new pond habitat. Sixty healthy adult fish were procured from each of the three ponds used and were distributed in three cages in equal numbers; the cages were placed in each of the other two ponds as well as into original rearing pond. Four fish were removed from each cage every week and were sacrificed for the assay of SDH activity in gills and muscles. Transfer of fish from a stress condition to a benign environment and vice versa resulted in an increase and decrease in SDH activity of fish, respectively. The intensity of increase upon transfer was again dependent upon the amount of stress in the new habitat. In general, the SDH activity of the test fish strongly correlated with the ammonia concentration (P?<?0.05) of water regardless of habitats. Time required for the introduced fish to acclimatize with new environmental conditions was dependent upon the environmental milieu of both its initial and final place of rearing and hence their physiological states. Differences in water quality, especially ammonia concentration, between its original place of rearing and the place of transfer were found to be responsible for the differences in acclimation period of two or three weeks. Relatively less difference in ammonia (2.68 for gills and 3.20 for muscles) between the initial place of rearing and new habitat resulted in acclimation of the fish one week earlier (second week) than the relatively wide difference (4.46 for gills and 5.62 for muscles) for third week. It may be reasonable to conclude that the varied responses of the mitochondrial respiratory enzyme of exogenously introduced fishes with the differences in the water quality—especially the ammonia concentration of ambient water between the original fish holding pond and growout pond—can be used to predict the time that will be required for the exogenously introduced fish to fully acclimatize with the new habitat. 相似文献
We investigated changes in concentrations of abscisic (ABA) and salicylic acid (SA), phenolic compounds and phenylalanine ammonia-lyase (PAL) activity in relation to cold-induced tolerance of four androgenic genotypes of Festulolium ( Festuca × Lolium hybrids ) to frost and to the snow mould fungus Microdochium nivale . Cold acclimation increased frost tolerance and resistance to snow mould. Resistant genotypes were characterized by higher ABA concentrations during the first 54 h of cold acclimation and lower concentrations of SA than susceptible genotypes. After cold acclimation, the content of phenolics was significantly lower in genotypes tolerant to frost and M. nivale infection than in susceptible genotypes, while PAL activity was significantly higher. Signalling networks controlling cold acclimation to frost (abiotic) and mould infection (biotic) appears to involve increases in foliar concentrations of ABA and decreases in the SA level during successful cold acclimation. Higher PAL activity and lower concentrations of phenolic compounds also appear to be associated with enhanced tolerance to frost and fungal attack. 相似文献