Ionocyte

Microscopic image of two ionocytes in a gill

An ionocyte (formerly called a chloride cell) is a mitochondrion-rich cell within ionoregulatory organs of animals, such as the gills of teleost fish, insect Malpighian tubules, crustacean gills, antennal glands and maxillary glands, and copepod Crusalis organs. These cells contribute to the maintenance of optimal osmotic, ionic, and acid-base levels within metazoans. In aquatic invertebrates, ionocytes perform the functions of both ion uptake and ion excretion. In marine teleost fish, by expending energy to power the enzyme Na+/K+-ATPase and in coordination with other protein transporters, ionocytes pump excessive sodium and chloride ions against the concentration gradient into the ocean. Conversely, freshwater teleost ionocytes use this low intracellular environment to attain sodium and chloride ions into the organism, and also against the concentration gradient. In larval fishes with underdeveloped / developing gills, ionocytes can be found on the skin and fins.

Mechanism of action

Marine teleost fishes consume large quantities of seawater to reduce osmotic dehydration. The excess of ions absorbed from seawater is pumped out of the teleost fishes via the ionocytes. These cells use active transport on the basolateral (internal) surface to accumulate chloride, which then diffuses out of the apical (external) surface and into the surrounding environment. Such mitochondrion-rich cells are found in both the gill lamellae and filaments of teleost fish. Using a similar mechanism, freshwater teleost fish use these cells to take in salt from their dilute environment to prevent hyponatremia from water diffusing into the fish. In the context of freshwater fish, ionocytes are often referred to as "mitochondria-rich cells", to emphasis their high density of mitochondria.

See also

References

  1. ↑ Gerber, Lucie; Lee, Carol Eunmi; Grousset, Evelyse; Blondeau-Bidet, Eva; Boucheker, Nesrine Boudour; Lorin-Nebel, Catherine; Charmantier-Daures, Mireille; Charmantier, Guy (2016). "The Legs Have It: In Situ Expression of Ion Transporters V-Type H+-ATPase and Na+/K+-ATPase in the Osmoregulatory Leg Organs of the Invading Copepod Eurytemora affinis". Physiological and Biochemical Zoology. 89 (3): 233–250. doi:10.1086/686323. PMID 27153133.
  2. ↑ Charmantier G, Charmantier-Daures M, Towle D. "Osmotic and ionic regulation in aquatic arthropods". Osmotic and Ionic Regulation: 165–230.
  3. 1 2 Evans DH, Piermarini PM, Choe KP (January 2005). "The multifunctional fish gill: dominant site of gas exchange, osmoregulation, acid-base regulation, and excretion of nitrogenous waste". Physiological Reviews. 85 (1): 97–177. doi:10.1152/physrev.00050.2003. PMID 15618479.
  4. ↑ Marshall WS (August 2002). "Na(+), Cl(-), Ca(2+) and Zn(2+) transport by fish gills: retrospective review and prospective synthesis". The Journal of Experimental Zoology. 293 (3): 264–83. doi:10.1002/jez.10127. PMID 12115901.
  5. 1 2 Hirose S, Kaneko T, Naito N, Takei Y (December 2003). "Molecular biology of major components of chloride cells". Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology. 136 (4): 593–620. doi:10.1016/s1096-4959(03)00287-2. PMID 14662288.
  6. ↑ Glover CN, Bucking C, Wood CM (October 2013). "The skin of fish as a transport epithelium: a review". Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology. 183 (7): 877–91. doi:10.1007/s00360-013-0761-4. PMID 23660826. S2CID 17089043.
  7. ↑ Kwan GT, Wexler JB, Wegner NC, Tresguerres M (February 2019). "Ontogenetic changes in cutaneous and branchial ionocytes and morphology in yellowfin tuna (Thunnus albacares) larvae". Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology. 189 (1): 81–95. doi:10.1007/s00360-018-1187-9. PMID 30357584. S2CID 53025702.
  8. ↑ Varsamos S, Nebel C, Charmantier G (August 2005). "Ontogeny of osmoregulation in postembryonic fish: a review". Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology. 141 (4): 401–29. doi:10.1016/j.cbpb.2005.01.013. PMID 16140237.
  9. 1 2 Allaby M. "Chloride cells". A Dictionary of Zoology. Retrieved 4 July 2015.
  10. 1 2 Wilmer P, Stone G, Johnston I (2005). Environmental Physiology of Animals. Malden, MA: Blackwell. pp. 85. ISBN 978-1-4051-0724-2.
  11. ↑ Fernandes, M.N. (2019) "Respiration and Ionic-Osmoregulation". In: Formicki K and Kirschbaum F (Eds.) The Histology of Fishes pages 246–266, CRC Press. ISBN 9781498784481.

Further reading