Abstract
Aquaculture in Europe aims to diversify and optimize fish farming. The meagre (Argyrosomus regius) arose as a promising species due to its fast growth rates and flesh quality. Thus, it is currently being produced in several Mediterranean countries, mainly in sea-cages and salt-marshes. However, although meagre naturally spend the first years of life in brackish waters, to date it is cultured in seawater. Here, we show that juveniles may not successfully face either freshwater or hyper-osmotic environments as high as 55 ppt salinity. We found that 55 ppt induced catabolism and mobilization of energy metabolites stored in the liver, probably to maintain its osmotic balance. Furthermore, we found that osmoregulatory tissues such as gills managed to maintain plasma osmolality levels without differences in meagre acclimated at 5, 12 and 39 ppt salinity. Our results demonstrate the euryhaline capacity of this species, highlighting that juveniles may be cultured in a wider range of salinities rather than just at seawater. Future studies should focus on optimal environmental salinities for the growth of A. regius juveniles, including long-term experiments limited to the range of 5 ppt to full-strength seawater. Minimizing fish energy consumption in osmoregulation could be economically beneficial for the aquaculture industry in Europe.
Highlights
Most fish and other aquatic animals inhabit waters with markedly different concentrations of solutes compared to the body fluids [1]
A. regius juveniles did not tolerate freshwater (100% mortality), but at salinities as low as 5 ppt, they managed to survive for at least 21 days
As the water osmolality increased with environmental salinity
Summary
Most fish and other aquatic animals inhabit waters with markedly different concentrations of solutes compared to the body fluids [1]. Marine species face continuous dehydration processes due to the high concentration of ions in the seawater, while maintaining their internal environment within a narrow range of ion concentrations [2] This imbalance with the external medium is achieved through the action of the osmoregulatory tissues, such as the gills, intestine, kidney and skin in teleost fish [3,4,5,6]. Absorb water and ions through their intestinal tract, and the excess of monovalent ions (mostly Na+ and Cl− ) are secreted actively through the branchial epithelium [7,8] This process occurs in the chloride cells Fishes 2018, 3, 48 cells) placed in the gills, and the efflux of ions is pumped by the Na+ /K+ -ATPase (NKA) enzyme [9].
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