Fisheries Science

, Volume 79, Issue 1, pp 77–86 | Cite as

Hyposmoregulatory ability and ion- and water-regulatory mechanisms during the leptocephalus stages of Japanese eel Anguilla japonica

  • Kyung Mi Lee
  • Yoshiaki Yamada
  • Akihiro Okamura
  • Katsumi Tsukamoto
  • Toyoji Kaneko
Original Article Biology


We explored osmoregulatory ability and mechanisms of ion and water regulation in Japanese eel leptocephali. Tissue osmolality of leptocephali ranged from 360 to 540 mOsm/kg·H2O. Immunocytochemical observations revealed that Na+/K+-ATPase-immunoreactive mitochondrion-rich (MR) cells were distributed over the entire body surface of leptocephali. Using a fluorescent sodium indicator and the chloride test, we localized Na+ and Cl secreting sites at the apical region of cutaneous MR cells. To further examine drinking behavior and water absorption in the intestine, leptocephali were exposed to seawater containing dextran labeled with Alexa Fluor. To calculate relative water absorption, fluorescent intensity was measured along the digestive tract. Whereas water was hardly absorbed in the stomach and intestine, water absorption predominantly took place in the rectum. Our findings indicate that Japanese eel exert hyposmoregulatory ability as early as during leptocephalus stages, secreting Na+ and Cl through cutaneous MR cells and primarily absorbing water from ingested seawater in the rectum.


Drinking Japanese eel Leptocephalus Mitochondrion-rich cell Osmoregulation Rectum Water absorption 


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Copyright information

© The Japanese Society of Fisheries Science 2012

Authors and Affiliations

  • Kyung Mi Lee
    • 1
  • Yoshiaki Yamada
    • 2
  • Akihiro Okamura
    • 2
  • Katsumi Tsukamoto
    • 2
    • 3
  • Toyoji Kaneko
    • 1
  1. 1.Department of Aquatic Bioscience, Graduate School of Agricultural and Life SciencesThe University of TokyoBunkyo, TokyoJapan
  2. 2.IRAGO InstituteTaharaJapan
  3. 3.Atmosphere and Ocean Research InstituteThe University of TokyoKashiwaJapan

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