Abstract
As a catadromous species, salinity is a key parameter that affects gonadal development of Chinese mitten crab Eriocheir sinensis during reproductive migration. It is however unclear the effects of salinity on the gonadal development of male E. sinensis as well as their physiological responses to salinity during reproductive migration. This study investigated the effects of four salinities (0 ‰, 6 ‰, 12 ‰ and 18 ‰) on gonadal development, osmoregulation and metabolism of adult male E. sinensis over a 40-day period. The results showed that elevating salinity promote gonadal development, increase hemolymph osmolality and K+ and Mg2+ concentrations (P < 0.05). The 12 ‰ salinity resulted in the highest contents of taurine and arginine in the hemolymph while the highest contents of threonine, phenylalanine, lysine, ß-alanine, tryptophan, ornithine and total free amino acids were found for 0 ‰ treatment (P < 0.05). A decreasing trend was detected for the Na+/K+-ATPase activity and its mRNA expression level in the posterior gills with salinity (P < 0.05). Total saturated fatty acids in the anterior gills decreased with increasing salinity (P < 0.05); the 0 ‰ treatment had the highest total polyunsaturated fatty acids in the posterior gills while total n-6 polyunsaturated fatty acids increased with salinity (P < 0.05). The hemolymph glucose and uric acid showed a decreasing trend as salinity while an increasing trend was found for the hemolymph triglyceride and high-density lipoprotein cholesterol (P < 0.05). The 12 ‰ treatment had the highest levels of hemolymph malonaldehyde and hepatopancreatic γ-glutamyltranspeptidase (P < 0.05). In conclusion, these results suggested that the brackish water promote gonadal development of male E. sinensis, and increase osmolality and ionic concentrations in hemolymph while reduced the activity of Na+ /K+- ATPase and its mRNA expression in the posterior gills as well as metabolism.
Highlights
The Chinese mitten crab, Eriocheir sinensis, is a catadromous crustacean species, which distribute widely across East Asia from China to the Korean Peninsula and has a very complex life history: the juvenile E. sinensis spend most of their lives in freshwater, but after puberty molt, adult crabs must migrate downstream to estuaries for reproduction [1,2,3]
An increasing trend was detected for the gonadosomatic index (GSI) of adult male E. sinensis with increasing salinity (Fig 1A)
The present study showed that the GSI of adult male E. sinensis increased significantly at salinity of 12 ‰ and 18 ‰ as compared to lower salinities of 0 ‰ and 6 ‰, suggesting that brackish water promotes gonadal development of the adult E. sinensis
Summary
The Chinese mitten crab, Eriocheir sinensis, is a catadromous crustacean species, which distribute widely across East Asia from China to the Korean Peninsula and has a very complex life history: the juvenile E. sinensis spend most of their lives in freshwater, but after puberty molt, adult crabs must migrate downstream to estuaries for reproduction [1,2,3]. E. sinensis is known as a euryhaline species and a strong osmoregulator as they can function well in freshwater or brackish environments [8,9]. This can be attributed to its welldeveloped osmoregulatory capacity [10,11]. A previous study has investigated the effects of long term salinity acclimation on osmoregulation and physiological metabolism of adult male E. sinensi [15], it is unclear the effects of different salinities on gonadal development as well as physiological responses to salinity during gonadal development
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