title: Physiological responses to salinity increase in blood parrotfish (Cichlasoma synspilum ♀ × Cichlasoma citrinellum ♂).
abstract: This study aims to evaluate the effects of adding salt to water on the physiological parameters of the blood parrot cichlid (Cichlasoma synspilum ♀ × Cichlasoma citrinellum ♂). The blood parrot cichlid is a popular species in the aquarium trade because of its behaviour and beauty. Salt is usually added to water during the culture or transportation of this fish. However, the manner by which the fish adjusts its physiological responses to salinity change is unclear. The effects of salinity on serum osmolality, immune-related enzyme activities, Na(+)-K(+)-ATPase activities in the gill, skin carotenoid content and oxygen consumption were analysed. Blood parrotfish individuals were transferred from freshwater to water with four salinity levels (0.16, 2.5, 5 and 7.5 ‰) for 168 h, and physiological responses were evaluated at 0, 6, 12, 24 and 168 h. Results showed no significant differences in serum acid phosphatase and alkaline phosphatase activities, skin carotenoid content and oxygen consumption rate among the different groups. However, the serum osmolality at 6 h was significantly elevated. Moreover, salinity increase stimulated superoxide dismutase (SOD) activity from 0 to 6 h. SOD activity increased from 6 to 24 h but significantly reduced at 168 h when the fish were exposed to salt water. The SOD activity in the salinity 2.5 ‰ group recovered the initial level, whereas those in the salinity 5 and 7.5 ‰ groups decreased to levels lower than the initial level. The gill Na(+)-K(+)-ATPase activity significantly declined with time and salinity increase. Thus, adding an appropriate amount of salt can save energy consumption during osmoregulation and temporarily enhance the antioxidant activity of blood parrotfish. However, this strategy is insufficient for long-term culture. Therefore, adding salt to water only provides short-term benefit to blood parrot cichlid during transportation.
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, 999 Huchenghuan Road, Shanghai, 201306 China.|Key Laboratory of East China Sea and Oceanic Fishery Resources Exploitation, Ministry of Agriculture of China, East China Sea Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Shanghai, 20090 China.
authors.forename: Yanming
authors.initials: Y
authors.lastname: Sui
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, 999 Huchenghuan Road, Shanghai, 201306 China.
authors.forename: Xizhi
authors.initials: X
authors.lastname: Huang
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, 999 Huchenghuan Road, Shanghai, 201306 China.
authors.forename: Hui
authors.initials: H
authors.lastname: Kong
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, 999 Huchenghuan Road, Shanghai, 201306 China.|Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai, 201306 China.
authors.forename: Weiqun
authors.initials: W
authors.lastname: Lu
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, 999 Huchenghuan Road, Shanghai, 201306 China.|Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai, 201306 China.
authors.forename: Youji
authors.initials: Y
authors.lastname: Wang
keywords: Blood parrotfish; Physiological parameter; Salinity