Urea excretion as a strategy for survival in a fish living in a very alkaline environment

D. J. Randall, C. M. Wood, S. F. Perry, H. Bergman, G. M O Maloiy, T. P. Mommsen, P. A. Wright

Research output: Contribution to journalArticle

193 Citations (Scopus)

Abstract

Ammonia is toxic to all vertebrates. It can be converted to the less toxic urea, but this is a metabolically expensive process found only in terrestrial vertebrates that cannot readily excrete ammonia and marine fish that use urea as an osmotic filler. Freshwater fish mostly excrete ammonia with only a small quantity of urea. It seems the ornithine cycle for urea production has been suppressed in all freshwater teleosts except for some airbreathers which, when exposed to air, increase urea synthesis via the cycle. Here we show that the tilapia fish Oreochromis alcalicus grahami, the only fish living in Lake Magadi, an alkaline soda lake (pH = 9.6-10) in the Kenyan Rift Valley, excretes exclusively urea and has ornithine-urea enzymes in its liver. A closely related species that lives in water at pH 7.1 lacks these enzymes and excretes mainly ammonia with small amounts of urea produced via uricolysis. It dies within 60 min when placed in water from Lake Magadi. We suggest that urea production via the ornithine-urea cycle permits O. a. grahami to survive the very alkaline conditions in Lake Magadi.

Original languageEnglish
Pages (from-to)165-166
Number of pages2
JournalNature
Volume337
Issue number6203
StatePublished - Jan 1 1989

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Urea
Fishes
Lakes
Ammonia
Ornithine
Poisons
Fresh Water
Vertebrates
Tilapia
Water
Enzymes
Air
Liver

ASJC Scopus subject areas

  • General

Cite this

Randall, D. J., Wood, C. M., Perry, S. F., Bergman, H., Maloiy, G. M. O., Mommsen, T. P., & Wright, P. A. (1989). Urea excretion as a strategy for survival in a fish living in a very alkaline environment. Nature, 337(6203), 165-166.

Urea excretion as a strategy for survival in a fish living in a very alkaline environment. / Randall, D. J.; Wood, C. M.; Perry, S. F.; Bergman, H.; Maloiy, G. M O; Mommsen, T. P.; Wright, P. A.

In: Nature, Vol. 337, No. 6203, 01.01.1989, p. 165-166.

Research output: Contribution to journalArticle

Randall, DJ, Wood, CM, Perry, SF, Bergman, H, Maloiy, GMO, Mommsen, TP & Wright, PA 1989, 'Urea excretion as a strategy for survival in a fish living in a very alkaline environment', Nature, vol. 337, no. 6203, pp. 165-166.
Randall DJ, Wood CM, Perry SF, Bergman H, Maloiy GMO, Mommsen TP et al. Urea excretion as a strategy for survival in a fish living in a very alkaline environment. Nature. 1989 Jan 1;337(6203):165-166.
Randall, D. J. ; Wood, C. M. ; Perry, S. F. ; Bergman, H. ; Maloiy, G. M O ; Mommsen, T. P. ; Wright, P. A. / Urea excretion as a strategy for survival in a fish living in a very alkaline environment. In: Nature. 1989 ; Vol. 337, No. 6203. pp. 165-166.
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