Seawater(SW)-acclimated Nile tilapia,Oreochromis niloticus,reared under a salinity 30 environment had lower growth and survival than the freshwater(FW)-acclimated fish.It was hypothesized that cells of the SW-acclimat...Seawater(SW)-acclimated Nile tilapia,Oreochromis niloticus,reared under a salinity 30 environment had lower growth and survival than the freshwater(FW)-acclimated fish.It was hypothesized that cells of the SW-acclimated fish had not been able to synthesize an adequate level of a compatible osmolyte,myo-inositol(MI),in adjusting to the salinity 30 environment.In this study,MI supplements,at 250,500,and 750 mg/kg pellets,were provided to the fish through top-dressing.After the 30-day feeding trial,the following parameters were determined:final body weights;survival;biomass increase;feed conversion ratio(FCR);plasma osmolality and ions;and two transcripts in the gills mips250 and mipa1 encoding enzymes responsible for MI biosynthesis.The SW-acclimated O.niloticus receiving 500-mg MI supplement had significantly higher survival,biomass increase,and lower FCR than those of the SW-acclimated fish receiving no supplement.At 500-mg MI supplemental level,the increasing values of plasma osmolality and Na+observed in SW-acclimated fish were significantly attenuated.The transcript mipa1,but not mips250,was markedly up-regulated in the SW-acclimated O.niloticus,compared with that of the FW-acclimated fish.Again,MI at 500-mg supplement attenuated the up-regulation significantly.This study suggests that MI supplement at the optimum level enhanced the performance of SW-acclimated O.niloticus,and through yet unknown mechanisms,attenuated some of their physiological responses to the osmotic stress.展开更多
文摘Seawater(SW)-acclimated Nile tilapia,Oreochromis niloticus,reared under a salinity 30 environment had lower growth and survival than the freshwater(FW)-acclimated fish.It was hypothesized that cells of the SW-acclimated fish had not been able to synthesize an adequate level of a compatible osmolyte,myo-inositol(MI),in adjusting to the salinity 30 environment.In this study,MI supplements,at 250,500,and 750 mg/kg pellets,were provided to the fish through top-dressing.After the 30-day feeding trial,the following parameters were determined:final body weights;survival;biomass increase;feed conversion ratio(FCR);plasma osmolality and ions;and two transcripts in the gills mips250 and mipa1 encoding enzymes responsible for MI biosynthesis.The SW-acclimated O.niloticus receiving 500-mg MI supplement had significantly higher survival,biomass increase,and lower FCR than those of the SW-acclimated fish receiving no supplement.At 500-mg MI supplemental level,the increasing values of plasma osmolality and Na+observed in SW-acclimated fish were significantly attenuated.The transcript mipa1,but not mips250,was markedly up-regulated in the SW-acclimated O.niloticus,compared with that of the FW-acclimated fish.Again,MI at 500-mg supplement attenuated the up-regulation significantly.This study suggests that MI supplement at the optimum level enhanced the performance of SW-acclimated O.niloticus,and through yet unknown mechanisms,attenuated some of their physiological responses to the osmotic stress.
