Medaka (Oryzias latipes) as a model for hypoosmoregulation of euryhaline fishes

Tatsuya Sakamoto, Tomohiro Kozaka, Akiyoshi Takahashi, Hiroshi Kawauchi, Masaaki Ando

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


We examined the hypoosmoregulatory ability of a model fish, medaka (Oryzias latipes), in relation to the gill-chloride cells or mitochondrion-rich (MR) cells, and to cortisol. When the medaka were transferred from freshwater (FW) to 30% seawater (SW), muscle water content decreased by 8% after 2 h and normalized within 1 week. Size and density of MR cells in the gill filament increased after 1-2 weeks in SW. Immersion of medaka in FW containing cortisol (10 μg/ml) for 1-2 weeks also doubled the number of MR cells, and abolished the decrease in muscle water content after SW transfer. In SW-adapted medaka, prolactin (PRL; 10 μg/g body weight) injection reduced muscle water content. However, when cortisol (50 μg/g) was injected simultaneously with PRL, cortisol abolished the decrease in muscle water. We concluded that cortisol plays an important role in the SW adaptation of the medaka, whereas PRL may be involved in ion uptake. Medaka seems to be a good model fish useful for the study of osmoregulatory mechanisms in general.

Original languageEnglish
Pages (from-to)347-354
Number of pages8
Issue number3-4
Publication statusPublished - Feb 15 2001
Externally publishedYes


  • Chloride cell
  • Cortisol
  • Medaka
  • Oryzias latipes
  • Osmoregulation
  • Prolactin

ASJC Scopus subject areas

  • Aquatic Science


Dive into the research topics of 'Medaka (Oryzias latipes) as a model for hypoosmoregulation of euryhaline fishes'. Together they form a unique fingerprint.

Cite this