| Summary: | 碩士 === 東海大學 === 生物學系 === 90 === Scylla serrata is a euryhaline marine crab, which can tolerate a wide range of salinities between 1 ppt and 42 ppt. And the salinity fluctuation may cause serious changes in hemolymph osmolality and influence the physiological functions. The osmoregulatory organs of crab primarily include gills, antennal glands and guts. Most studies on crustacean osmoregulation had their focus on the gills only, but very rarely were these organs investigated simultaneously. Since Na+, K+-ATPase has been known as the driving force of ions transportations, it can be taken as a valid indicator of osmoregulatory ability. From previous literatures, posterior gills, antennal gland and gut respectively showed a higher Na+, K+-ATPase activity when the crabs were kept in diluted seawater. This implies that the relative importance in osmoregulation among these organs is not identical. And whether this increase resulted from the modulation of pre-existing Na+, K+-ATPase or new protein synthesis is still unclear. In this study, after transferring S. serrata from 25 ppt to 5, 25 and 45 ppt respectively, hemolymph osmolality, Na+, K+-ATPase activity and the level of Na+, K+-ATPase α-subunit in western blotting were examined at different time intervals. The results indicated that S. serrata maintained their hemolymph osmolality significantly higher than their respective environments of 5 and 25 ppt, therefore, it should be categorized as a hyper-osmoregulator. The posterior gill (gill 6) and antennal gland were significantly higher than the anterior gill (gill 2) and gut in both the Na+, K+-ATPase activities and their α-subunit levels. Upon 14 days after transfer, the activity of the posterior gill was significantly higher in 5 ppt than in the other two salinity treatments. Such differences among salinity levels were not observed in other organs. In the results of western blotting, salinity did not cause a significant change in the protein levels of Na+, K+-ATPase α-subunit among these osmoregulatory organs, except the gut in the first day after transferring. The protein level of Na+, K+-ATPase α-subunit did not change significantly in the posterior gill while the enzyme activity fluctuated with environmental salinity. In conclusion, the posterior gills played the most important role in osmoregulation when the crabs were in diluted SW and the activity of the enzyme might be modulated by the pre-existing Na+, K+-ATPase.
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