Physiological and respiratory responses of the Mozambique tilapia (Oreochromis mossambicus) to salinity acclimation

John D. Morgan, Tatsuya Sakamoto, E. Gordon Grau, George K. Iwama

Research output: Contribution to journalArticlepeer-review

149 Citations (Scopus)


We have examined several physiological variables related to salinity acclimation in the euryhaline tilapia, Oreochromis mossambicus. Tilapia reared in fresh water (FW) were transferred to FW, isosmotic salinity (ISO, 12‰%) and 75% seawater (SW, 25‰). Oxygen consumption, plasma levels of cortisol, growth hormone (GH), prolactins (tPRL177 and tPRL188), glucose, ions (Na+, K+, Cl-), and gill Na+,K+-ATPase activities were measured for up to 4 days in each salinity treatment. Plasma Na+ and Cl- concentrations were elevated 1 day after transfer to SW, but returned to FW values on day 4. Plasma cortisol and glucose levels were higher in FW and ISO than in SW 1 day after transfer. Plasma GH levels of tilapia in SW increased above FW and ISO values after 4 days, whereas plasma PRL levels decreased in ISO and SW compared to FW at 4 days. These results are consistent with the possible osmoregulation roles of GH and PRL in SW and FW, respectively. Gill Na+,K+-ATPase activity of tilapia in SW increased more than 2-fold over the FW value after 4 days, but activity of this enzyme did not change in ISO. Oxygen consumption rates of tilapia in SW were significantly elevated 4 days after transfer compared to FW and ISO. The results of this study indicate that the physiological changes associated with SW acclimation in tilapia represents a significant short-term energetic cost, and may account for as much as 20% of total body metabolism after 4 days in SW.

Original languageEnglish
Pages (from-to)391-398
Number of pages8
JournalComparative Biochemistry and Physiology - A Physiology
Issue number3
Publication statusPublished - Jul 1997
Externally publishedYes


  • K-ATPase
  • cortisol
  • gill Na
  • growth hormone
  • osmoregulation
  • oxygen consumption
  • prolactin
  • salinity
  • tilapia

ASJC Scopus subject areas

  • Physiology


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