ABSTRACT

The mud crab Scylla olivacea is a well-known commercially and ecologically important species that inhabits intertidal mangroves. These mud crabs spend juvenile and adult stages in mangroves where they can experience daily fluctuations in salinity. They are almost certainly adapted to deal with salinity challenges. Although S. olivacea has a wide salinity tolerance, there is a lack of studies on its osmoregulatory responses. Antioxidant enzymes play crucial roles to counteract oxidative stress in various tissues of aquatic animals. However, salinity changes affecting antioxidant responses are not well studied in tropical decapod crustaceans. Therefore, this study aims to characterize the osmoregulatory and antioxidant responses of the male S. olivacea when exposed to salinity changes. Haemolymph osmolality, Na⁺/K⁺ ATPase and antioxidant enzyme activities in gills were analysed after they were exposed to various salinities. The results showed that S. olivacea is a hyper-hypoosmoregulator. The salinity had greater effects on Na⁺/K⁺ ATPase and antioxidant enzyme activities in the posterior gills than the anterior gills. Notably, the modifications of gill SOD activity were detected only in the posterior gills, which function highly in active ion uptake. These findings may imply some associations between osmoregulatory and antioxidant responses during salinity challenges. The increase in gill SOD activities be a response for coping with elevated ROS levels due to high metabolic demands for osmoregulation under salinity stress. Moreover, the crabs exhibited some modified activities of gill CAT in several salinity levels. Overall, the results demonstrated that S. olivacea were well-adapted to the salinity changes based on their osmoregulatory and antioxidant responses. These physiological adaptations may allow these crabs to disperse in some areas of mangroves. The salinity range of 15–25 psu would likely be the recommended optimal range for adult S. olivacea, which may enhance growth and minimize oxidative stress in gills of crabs, especially in aquaculture conditions.

摘要

泥蟹Sylla olivacea是一种著名的商业和生态上重要的物种，栖息在潮间带的红树林中。这些泥蟹在红树林中度过幼年和成年期，在那里它们每天都会经历盐度的波动。他们几乎可以肯定地适应了盐度挑战。尽管S.olivacea具有广泛的盐度耐受性，但对其渗透调节反应的研究仍缺乏研究。抗氧化酶在抵抗水生动物各种组织中的氧化应激方面起着至关重要的作用。然而，在热带十足动物甲壳类动物中，影响抗氧化反应的盐度变化尚未得到很好的研究。因此，本研究旨在表征男性寡脂链球菌的渗透调节和抗氧化反应。当暴露于盐度变化时。g暴露于各种盐度后，分析了它们的血淋巴渗透压，Na ⁺ / K ⁺ ATPase和抗氧化酶活性。结果表明，橄榄葡萄球菌是超低调节剂。盐度对Na ⁺ / K ^+的影响更大后g中的ATP酶和抗氧化酶活性高于前g。值得注意的是，仅在后g中检测到ill超氧化物歧化酶活性的改变，而后terior在活跃的离子吸收中起着很高的作用。这些发现可能暗示盐度挑战期间渗透调节和抗氧化反应之间存在某些关联。sal超氧化物歧化酶活性的增加是由于盐分胁迫下对渗透调节的高代谢需求而应对的ROS水平升高的响应。此外，这些螃蟹在几种盐度水平下都表现出modifiedCAT的某些修饰活性。总体而言，结果表明橄榄葡萄球菌基于它们的渗透压调节剂和抗氧化剂反应，它们非常适合盐度变化。这些生理适应性可能使这些螃蟹散布在红树林的某些区域。盐度范围为15–25 psu可能是成人成年链霉菌的推荐最佳范围，这可能会促进蟹g的生长并最大程度地降低氧化应激，特别是在水产养殖条件下。