A new model for fish ion regulation: Identification of ionocytes in freshwater- and seawater-acclimated medaka (Oryzias latipes)

Hao Hsuan Hsu, Li Yih Lin, Yung Che Tseng, Jiun Lin Horng, Pung Pung Hwang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

100 Citations (Scopus)


The ion regulation mechanisms of fishes have been recently studied in zebrafish (Danio rerio), a stenohaline species. However, recent advances using this organism are not necessarily applicable to euryhaline fishes. The euryhaline species medaka (Oryzias latipes), which, like zebrafish, is genetically well categorized and amenable to molecular manipulation, was proposed as an alternative model for studying osmoregulation during acclimation to different salinities. To establish its suitability as an alternative, the present study was conducted to (1) identify different types of ionocytes in the embryonic skin and (2) analyze gene expressions of the transporters during seawater acclimation. Double/triple in situ hybridization and/or immunocytochemistry revealed that freshwater (FW) medaka contain three types of ionocyte: (1) Na+/H+ exchanger 3 (NHE3) cells with apical NHE3 and basolateral Na+-K+-2Cl- cotransporter (NKCC), Na+-K+-ATPase (NKA) and anion exchanger (AE); (2) Na+-Cl- cotransporter (NCC) cells with apical NCC and basolateral H+-ATPase; and (3) epithelial Ca2+ channel (ECaC) cells [presumed accessory (AC) cells] with apical ECaC. On the other hand, seawater (SW) medaka has a single predominant ionocyte type, which possesses apical cystic fibrosis transmembrane conductance regulator (CFTR) and NHE3 and basolateral NKCC and NKA and is accompanied by smaller AC cells that express lower levels of basolateral NKA. Reciprocal gene expressions of decreased NHE3, AE, NCC and ECaC and increased CFTR and NKCC in medaka gills during SW were revealed by quantative PCR analysis.

Original languageEnglish
Pages (from-to)225-243
Number of pages19
JournalCell and Tissue Research
Issue number1
Publication statusPublished - 2014 Jul


  • CFTR
  • ECaC
  • Ion regulation
  • Ionocytes
  • Medaka
  • NHE3
  • NKCC

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Histology
  • Cell Biology


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