Ichthyological Research

, Volume 62, Issue 4, pp 487–494 | Cite as

Occurrence of larval and adult types of ion-secreting ionocytes in Japanese eel Anguilla japonica

  • Mi Young Seo
  • Mari Kuroki
  • Akihiro Okamura
  • Katsumi Tsukamoto
  • Soichi Watanabe
  • Toyoji Kaneko
Full Paper


The anguillid eels are catadromous fishes that migrate between marine and freshwater habitats. The long migration of eel larvae, called leptocephali, as long as thousands of kilometers in the ocean is important to determine their recruitment successes. The leptocephali in the ocean have a pelagic lifestyle totally different from the benthic one of glass eels and yellow eels in rivers. It is known that eel leptocephali have ionocytes on the body surface that may maintain ionic and osmotic status in the internal environment; however, detailed morphology and function of ionocytes in leptocephali are still unknown. In the present study, we aimed 1) to clarify the morphological features of the epidermis in Japanese eel Anguilla japonica leptocephali cultured in hyper-osmotic condition, and 2) to examine the ion-transporting functions of ionocytes of both leptocephali and yellow eels. Na+/K+-ATPase-immunoreactive ionocytes were distributed all over the body surface of leptocephali. Ionocytes were in contact with external environments through their apical membrane, which was located at the boundary of pavement cells. Na+/K+-ATPase-immunopositive cells were not observed in the skin of seawater-acclimated yellow eels. In ionocytes of the larval skin, the apical membrane appeared as a slightly projecting disk with a microvilli-like structure. Meanwhile, the apical membrane of gill ionocytes of yellow eels formed a concave surface. In ionocytes of leptocephali, mitochondria were enlarged and the tubular system was well developed, as compared with those of the gill of yellow eels. Ionocytes of leptocephali showed CFTR immunoreaction in their apical region and NKCC1 immunoreaction in their basolateral region, suggesting that the skin ionocytes are involved in salt secretion. These results support the notion that Japanese eel maintain their ion balance through skin ionocytes during early life stages, and that the skin ionocytes of leptocephali disappear in yellow eel stages after the formation of functional gills and gill ionocytes.


Anguillia Japanese eel Leptocephalus Ionocytes Osmoregulation 



We thank Y. Yamada, N. Horie, and N. Mikawa of the IRAGO Institute for their kind support during the experiment. This work was supported in part by KAKEN C (No. 25450270) from Japan Society for the Promotion of Science.


  1. Alderdice DF (1988) Osmotic and ionic regulation in teleost eggs and larvae. In: Hoar WS, Randall DJ (eds) Fish Physiology, Vol. XIA. Academic Press, San Diego, pp 163–251Google Scholar
  2. Bonhommeau S, Castonguay M, Rivot E, Sabatié R, Pape OL (2010) The duration of migration of Atlantic Anguilla larvae Migration duration of Atlantic eel larvae. Fish Fish 11:289–306Google Scholar
  3. Evans DH, Piermarini PM, Choe KP (2005) The multifunctional fish gill: dominant site of gas exchange, osmoregulation, acid-base regulation, and excretion of nitrogenous waste. Physiol Rev 85:97–177Google Scholar
  4. Hiroi J, Kaneko T, Uchida K, Hasegawa S, Tanaka M (1998) Immunolocalization of vacuolar-type H+-ATPase in the yolk-sac membrane of tilapia (Oreochromis mossambicus) larvae. Zool Sci 15:447–453Google Scholar
  5. Hiroi J, McCormick SD, Ohtani-Kaneko R, Kaneko T (2005) Functional classification of mitochondrion-rich cells in euryhaline Mozambique tilapia (Oreochromis mossambicus) embryos, by means of triple immunofluorescence staining for Na+/K+-ATPase, Na+/K+/2Cl cotransporter and CFTR anion channel. J Exp Biol 208:2023–2036Google Scholar
  6. Hulet WH (1978) Structure and functional development of the eel leptocephalus Ariosoma balearicum (De La Roche, 1809). Philos T Roy Soc B 282:107–138Google Scholar
  7. Ingrain GA (1980) Substances involved in the natural resistance of fish to infection—a review. J Fish Biol 16:23–60Google Scholar
  8. Kaneko T, Hasegawa S, Takagi Y, Tagawa M, Hirano T (1995) Hypoosmoregulatory ability of eyed-stage embryos of chum salmon. Mar Biol 122:165–170Google Scholar
  9. Kaneko T, Hasegawa S, Sasai S (2003) Chloride cells in Japanese eel (Anguilla japonica) during their early life stages and downstream migration. In: Aida K, Tsukamoto K, Yamauchi K (eds) Eel biology. Springer, Tokyo, pp 457–468Google Scholar
  10. Karnaky KJ Jr, Kinter LB, Kinter WB, Stirling CE (1976) Teleost chloride cell II. Autoradiographic localization of gill Na, K-ATPase in killifish Fundulus heteroclitus, adapted to low and high salinity environments. J Cell Biol 70:157–177Google Scholar
  11. Katoh F, Shimizu A, Uchida K, Kaneko T (2000) Shift of chloride cell distribution during early life stages in seawater-adapted killifish, Fundulus heteroclitus. Zool Sci 17:11–18Google Scholar
  12. Katoh F, Kaneko T (2003) Short-term transformation and long-term replacement of branchial chloride cells in killifish transferred from seawater to freshwater, revealed by morphofunctional observations and a newly established ‘time differential double fluorescent staining’ technique. J Exp Biol 206:4113–4123Google Scholar
  13. Kurokawa T, Okamoto T, Gen K, Uji S, Murashita K, Unuma T, Nomura K, Matsubara H, Kim SK, Ohta H, Tanaka H (2008) Influence of water temperature on morphological deformities in cultured larvae of Japanese eel, Anguilla japonica, at completion of yolk resorption. J World Aquacult Soc 39:726–735Google Scholar
  14. Kuroki M, Miller MJ, Tsukamoto K (2014) Diversity of early life history traits in freshwater eels and the evolution of their oceanic migrations. Can J Zool 92:749–770Google Scholar
  15. Lee KM, Yamada Y, Okamura A, Tsukamoto K, Kaneko T (2013) Hyposmoregulatory ability and ion- and water-regulatory mechanisms during the leptocephalus stages of Japanese eel Anguilla japonica. Fish Sci 79:77–86Google Scholar
  16. Leonard JB, Summers RG (1976) The ultrastructure of the integument of the American eel, Anguilla rostrata. Cell Tiss Res 171:1–30Google Scholar
  17. Marshall WS, Bryson SE, Midelfart A, Hamilton WF (1995) Low conductance anion channel activated by cAMP in teleost Cl secreting cells. Am J Physiol 268:R963–969Google Scholar
  18. Masuda Y, Jinbo T, Imaizumi H, Furuita H, Matsunari H, Murashita K, Fujimoto H, Nagao J, Kawakami Y (2013) A step forward in development of fish protein hydrolysate-based diets for larvae of Japanese eel Anguilla japonica. Fish Sci 79:681–688Google Scholar
  19. McCormick SD (1995) Hormonal control of gill Na+/K+-ATPase and chloride cell function. In: Wood CM, Shuttleworth TJ (eds) Cellular and molecular approaches to fish ionic regulation. Fish physiology, Vol. 14. Academic Press, New York, pp 285–315Google Scholar
  20. McCormick SD, Sundell K, Bjornsson BT, Brown CL, Hiroi J (2003) Influence of salinity on the localization of Na+/K+-ATPase, Na+/K+/2Cl- cotransporter (NKCC) and CFTR anion channel in chloride cells of the Hawaiian goby (Stenogobius hawaiiensis). J Exp Biol 206:4575–4583Google Scholar
  21. Nakamura O, Saeki M, Kamiya H, Muramoto K, Watanabe T (2002) Development of epidermal and mucosal galectin containing cells in metamorphosing leptocephali of Japanese conger. J Fish Biol 61:822–833Google Scholar
  22. Okamura A, Yamada Y, Horita T, Horie N, Mikawa N, Utoh T, Tanaka S, Tsukamoto K (2009a) Rearing eel leptocephali (Anguilla japonica Temminck & Schlegel) in a planktonkreisel. Aquacult Res 40:509–512Google Scholar
  23. Okamura A, Yamada Y, Mikawa N, Horie N, Utoh T, Kaneko T, Tanaka S, Tsukamoto K (2009b) Growth and survival of eel leptocephali (Anguilla japonica) in low-salinity water. Aquaculture 296:367372Google Scholar
  24. Okamura A, Horie N, Mikawa N, Yamada Y, Tsukamoto K (2014) Recent advances in artificial production of glass eels for conservation of anguillid eel populations. Ecol Freshw Fish 23:95–110Google Scholar
  25. Philpott CW (1980) Tubular system membranes of teleost chloride cells: osmotic response and transport sites. Am J Physiol 238:R171–184Google Scholar
  26. Roberts RJ, Bell M, Young H (1973) Studies on the skin of plaice (Pleuronectes platessa L.). II. The development of larval plaice skin. J Fish Biol 5:103–108Google Scholar
  27. Saglio Ph, Escaffre AM, Blanc JM (1988) Structural characteristics of the epidermal mucosa in yellow and silver European eel, Anguilla anguilla (L.) J Fish Biol 32:505–514Google Scholar
  28. Sasai S, Kaneko T, Hasegawa S, Tsukamoto K (1998) Morphological alteration in two types of gill chloride cells in Japanese eel (Anguilla japonica) during catadromous migration. Can J Zool 76:1480–1487Google Scholar
  29. Sasai S, Katoh F, Kaneko T, Tsukamoto K (2007) Ontogenic change of gill chloride cells in leptocephalus and glass eel stages of the Japanese eel, Anguilla japonica. Mar Biol 150:487496Google Scholar
  30. Schreiber AM, Specker JL (1999) Metamorphosis in the summer flounder Paralichthys dentatus: Changes in gill mitochondria-rich cells. J Exp Biol 202:24752484Google Scholar
  31. Seo MY, Lee KM, Kaneko T (2009) Morphological changes in gill mitochondria-rich cells in cultured Japanese eel Anguilla japonica acclimated to a wide range of environmental salinity. Fish Sci 75:1147–1156Google Scholar
  32. Seo MY, Mekuchi M, Teranishi K, Kaneko T (2013) Expression of ion transporters in gill mitochondrion-rich cells in Japanese eel acclimated to a wide range of environmental salinity. Comp Biochem Physiol A 166:323–332Google Scholar
  33. Seikai T, Matsumoto J (1994) Mechanism of pseudoalbinism in flatfish: an association between pigment cell and skin differentiation. J World Aquacult Soc 25:78–85Google Scholar
  34. Shinoda A, Aoyama J, Miller MJ, Otake T, Mochioka N, Watanabe S, Minegishi Y, Kuroki M, Yoshinaga T, Yokouchi K, Fukuda N, Sudo R, Hagihara S, Zenimoto K, Suzuki Y, Oya M, Inagaki T, Kimura S, Fukui A, Lee TW, Tsukamoto K (2011) Evaluation of the larval distribution and migration of the Japanese eel in the western North Pacific. Rev Fish Biol Fish 21:591–611Google Scholar
  35. Silva P, Solomon R, Spokes K, Epstein FH (1977) Ouabain inhibition of gill Na-K-ATPase: relationship to active chloride transport. J Exp Zool 199:419-426Google Scholar
  36. Shephard KL (1994) Functions for fish mucus. Rev Fish Biol Fish 4:401429Google Scholar
  37. Suzuki Y, Otake T (2000) Skin lectin and the lymphoid tissues in the leptocephalus larvae of the Japanese eel Anguilla japonica. Fish Sci 66:636–643Google Scholar
  38. Tanaka H (2014) Progression in artificial seedling production of Japanese eel Anguilla japonica. Fish Sci 81:1119Google Scholar
  39. Tse WK, Au DW, Wong CK (2006) Characterization of ion channel and transporter mRNA expressions in isolated gill chloride and pavement cells of seawater acclimating eels. Biochem Biophys Res Commun 346:11811190Google Scholar
  40. Tsukamoto K, Nakai I, Tesch WV (1998) Do all freshwater eels migrate? Nature 396:635–636Google Scholar
  41. Tsukamoto K, Chow S, Otake T, Kurogi H, Mochioka N, Miller MJ, Aoyama J, Kimura S, Watanabe S, Yoshinaga T, Shinoda A, Kuroki M, Oya M, Watanabe T, Hata K, Ijiri S, Kazeto Y, Nomura K, Tanaka H (2011) Oceanic spawning ecology of freshwater eels in the western North Pacific. Nat Commun 2:179Google Scholar
  42. Uchida K, Kaneko T, Miyazaki H, Hasegawa S, Hirano T (2000) Excellent salinity tolerance of Mozambique tilapia (Oreochromis mossambicus): elevated chloride cell activity in the branchial and opercular epithelia of the fish adapted to concentrated seawater. Zool Sci 17:149160Google Scholar
  43. Varsamos S, Diaz JP, Charmantier G, Blasco C, Connes R, Flik G (2002) Location and morphology of chloride cells during the post-embryonic development of European sea bass, Dicentrarchus labrax. Anat Embryol 205:203–213Google Scholar
  44. Wilson JM, Reis-Santos P, Fonseca AV, Antunes JC, Bouca PD, Coumbra J (2007) Seasonal changes in ionoregulatory variables of the glass eel Anguilla anguilla following estuarine entry: comparison with resident elvers. J Fish Biol 70:12391253Google Scholar
  45. Yanagie R, Lee KM, Watanabe S, Kaneko T (2009) Ontogenic change in tissue osmolality and developmental sequence of mitochondria-rich cells in Mozambique tilapia developing in freshwater. Comp Biochem Physiol A 154:263–269Google Scholar
  46. Zadunaisky JA (1984) The chloride cell: The active transport of chloride and the paracellular pathways. In: Hoar WS, Randall DJ (eds) Fish Physiology, Vol. XB. Academic Press, Orlando, pp 129176Google Scholar

Copyright information

© The Ichthyological Society of Japan 2015

Authors and Affiliations

  • Mi Young Seo
    • 1
  • Mari Kuroki
    • 1
  • Akihiro Okamura
    • 2
  • Katsumi Tsukamoto
    • 2
    • 3
  • Soichi Watanabe
    • 1
  • Toyoji Kaneko
    • 1
  1. 1.Department of Aquatic Bioscience, Graduate School of Agricultural and Life SciencesThe University of TokyoTokyoJapan
  2. 2.IRAGO InstituteTaharaJapan
  3. 3.College of Bioresource SciencesNihon UniversityFujisawaJapan

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