Effect of freshwater pH on osmolarity and gill and kidney Na+/K+-ATPase activity in juvenile rainbow trout during seawater adaptation
DOI:
https://doi.org/10.33910/2687-1270-2026-7-2-254-266Keywords:
osmolarity, water pH, Na+/K+-ATPase, gill, kidney, hyperosmotiс environment, adaptation, rainbow troutAbstract
The article discusses adaptation of juvenile rainbow trout Parasalmo (Oncorhynchus) mykiss to a hyperosmotic environment after initial exposure to freshwater with varying pH levels. The study determined the following parameters in fish in freshwater and at various time intervals after their transfer to artificial seawater with a salinity of 15.3‰: serum osmolarity by cryoscopy, serum Na+ concentration by flame photometry, and Na+/K+-ATPase activity in gill and kidney tissue by spectrophotometry. The study showed that in freshwater, an acidic environment (pH = 5.0) disrupts osmo- and ion regulation mechanisms, which are restored when juvenile trout are transferred to a hyperosmotic environment. At the same time, the preserved functional activity of transport enzymes, particularly Na+/K+-ATPase, in these individuals enables the fish to transition to a hypoosmotic type of regulation in a marine environment. Maintenance of juvenile trout in an alkaline environment (pH = 9.0) does not affect their osmo- and ion regulation in freshwater but does reduce the activity of transport enzymes, which subsequently prevents the fish from fully adapting to the marine environment. The study concludes that acidification and alkalinization of the freshwater habitat of juvenile rainbow trout Parasalmo (Oncorhynchus) mykiss have a pathological effect on osmotic and ion regulatory capacities in freshwater and seawater, but the mechanisms underlying this effect are different and are based on different morphological and functional changes in the effector organs.
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