Ammonia and urea dynamics in the Lake Magadi tilapia, a ureotelic teleost fish adapted to an extremely alkaline environment

C. M. Wood, S. F. Perry, P. A. Wright, H. L. Bergman, D. J. Randall

Research output: Contribution to journalArticle

102 Citations (Scopus)

Abstract

The tilapia Oreochromis alcalicus grahami, which thrives under harshly alkaline conditions in Lake Magadi, Kenya, was studied in its natural environment (pH = 10, total CO2 = 180 mmol/L, osmolality = 525 mOsm/kg, 30-36.5 ° C). At rest, this species excretes all nitrogenous waste as urea. This is the first known instance of complete ureotelism in an entirely aquatic teleost fish. Very small 'apparent' ammonia excretion (<5% of overall N excretion) was attributable to faecal/bacterial production. Ammonia excretion could not be induced by feeding, reduced temperature, or exposure to pH 7. Exhaustive exercise induced only a small efflux of ammonia. Urea output was inhibited completely by pH 7 water and partly by exhaustive exercise, and greatly stimulated by exposure to 500 μmol/L NH3 (at pH 10). A related species, nominally Oreochromis nilotica, which lives in freshwater at circumneutral pH in the same geographic region, excretes 85% ammonia-N and 15% urea-N at pH 7 in the standard teleost fashion. Urea-N efflux increased to 33% upon transfer of O. nilotica to pH 10 in freshwater. Urea output in this species was only marginally stimulated by exposure to 500 μmol/L NH3 (at pH 7). Plasma and white muscle urea levels were 4- to 5-fold higher in O. a. grahami than in O. nilotica, and plasma levels increased between caudal and cardiac sampling sites, indicating hepatic ureagenesis. Blood pH and PNH3 levels, when corrected for sampling artifact, were unusually high in O. a. grahami. We hypothesize that complete ureotelism in O. a. grahami in evolutionary response to the problems of excreting ammonia into highly buffered water at pH 10 and/or acid-base balance in this extreme environment.

Original languageEnglish
Pages (from-to)1-20
Number of pages20
JournalRespiration Physiology
Volume77
Issue number1
DOIs
StatePublished - Jan 1 1989

Fingerprint

Tilapia
Lakes
Ammonia
Urea
Fishes
Cichlids
Fresh Water
Acid-Base Equilibrium
Water
Kenya
Osmolar Concentration
Artifacts

Keywords

  • Acid-base balance
  • Ammonia
  • High pH
  • Ornithine-urea cycle
  • Tilapia
  • Urea

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine

Cite this

Ammonia and urea dynamics in the Lake Magadi tilapia, a ureotelic teleost fish adapted to an extremely alkaline environment. / Wood, C. M.; Perry, S. F.; Wright, P. A.; Bergman, H. L.; Randall, D. J.

In: Respiration Physiology, Vol. 77, No. 1, 01.01.1989, p. 1-20.

Research output: Contribution to journalArticle

Wood, C. M. ; Perry, S. F. ; Wright, P. A. ; Bergman, H. L. ; Randall, D. J. / Ammonia and urea dynamics in the Lake Magadi tilapia, a ureotelic teleost fish adapted to an extremely alkaline environment. In: Respiration Physiology. 1989 ; Vol. 77, No. 1. pp. 1-20.
@article{a9beed2ddc0a402c9726d333b36e4ac6,
title = "Ammonia and urea dynamics in the Lake Magadi tilapia, a ureotelic teleost fish adapted to an extremely alkaline environment",
abstract = "The tilapia Oreochromis alcalicus grahami, which thrives under harshly alkaline conditions in Lake Magadi, Kenya, was studied in its natural environment (pH = 10, total CO2 = 180 mmol/L, osmolality = 525 mOsm/kg, 30-36.5 ° C). At rest, this species excretes all nitrogenous waste as urea. This is the first known instance of complete ureotelism in an entirely aquatic teleost fish. Very small 'apparent' ammonia excretion (<5{\%} of overall N excretion) was attributable to faecal/bacterial production. Ammonia excretion could not be induced by feeding, reduced temperature, or exposure to pH 7. Exhaustive exercise induced only a small efflux of ammonia. Urea output was inhibited completely by pH 7 water and partly by exhaustive exercise, and greatly stimulated by exposure to 500 μmol/L NH3 (at pH 10). A related species, nominally Oreochromis nilotica, which lives in freshwater at circumneutral pH in the same geographic region, excretes 85{\%} ammonia-N and 15{\%} urea-N at pH 7 in the standard teleost fashion. Urea-N efflux increased to 33{\%} upon transfer of O. nilotica to pH 10 in freshwater. Urea output in this species was only marginally stimulated by exposure to 500 μmol/L NH3 (at pH 7). Plasma and white muscle urea levels were 4- to 5-fold higher in O. a. grahami than in O. nilotica, and plasma levels increased between caudal and cardiac sampling sites, indicating hepatic ureagenesis. Blood pH and PNH3 levels, when corrected for sampling artifact, were unusually high in O. a. grahami. We hypothesize that complete ureotelism in O. a. grahami in evolutionary response to the problems of excreting ammonia into highly buffered water at pH 10 and/or acid-base balance in this extreme environment.",
keywords = "Acid-base balance, Ammonia, High pH, Ornithine-urea cycle, Tilapia, Urea",
author = "Wood, {C. M.} and Perry, {S. F.} and Wright, {P. A.} and Bergman, {H. L.} and Randall, {D. J.}",
year = "1989",
month = "1",
day = "1",
doi = "10.1016/0034-5687(89)90025-X",
language = "English",
volume = "77",
pages = "1--20",
journal = "Respiratory Physiology and Neurobiology",
issn = "1569-9048",
publisher = "Elsevier",
number = "1",

}

TY - JOUR

T1 - Ammonia and urea dynamics in the Lake Magadi tilapia, a ureotelic teleost fish adapted to an extremely alkaline environment

AU - Wood, C. M.

AU - Perry, S. F.

AU - Wright, P. A.

AU - Bergman, H. L.

AU - Randall, D. J.

PY - 1989/1/1

Y1 - 1989/1/1

N2 - The tilapia Oreochromis alcalicus grahami, which thrives under harshly alkaline conditions in Lake Magadi, Kenya, was studied in its natural environment (pH = 10, total CO2 = 180 mmol/L, osmolality = 525 mOsm/kg, 30-36.5 ° C). At rest, this species excretes all nitrogenous waste as urea. This is the first known instance of complete ureotelism in an entirely aquatic teleost fish. Very small 'apparent' ammonia excretion (<5% of overall N excretion) was attributable to faecal/bacterial production. Ammonia excretion could not be induced by feeding, reduced temperature, or exposure to pH 7. Exhaustive exercise induced only a small efflux of ammonia. Urea output was inhibited completely by pH 7 water and partly by exhaustive exercise, and greatly stimulated by exposure to 500 μmol/L NH3 (at pH 10). A related species, nominally Oreochromis nilotica, which lives in freshwater at circumneutral pH in the same geographic region, excretes 85% ammonia-N and 15% urea-N at pH 7 in the standard teleost fashion. Urea-N efflux increased to 33% upon transfer of O. nilotica to pH 10 in freshwater. Urea output in this species was only marginally stimulated by exposure to 500 μmol/L NH3 (at pH 7). Plasma and white muscle urea levels were 4- to 5-fold higher in O. a. grahami than in O. nilotica, and plasma levels increased between caudal and cardiac sampling sites, indicating hepatic ureagenesis. Blood pH and PNH3 levels, when corrected for sampling artifact, were unusually high in O. a. grahami. We hypothesize that complete ureotelism in O. a. grahami in evolutionary response to the problems of excreting ammonia into highly buffered water at pH 10 and/or acid-base balance in this extreme environment.

AB - The tilapia Oreochromis alcalicus grahami, which thrives under harshly alkaline conditions in Lake Magadi, Kenya, was studied in its natural environment (pH = 10, total CO2 = 180 mmol/L, osmolality = 525 mOsm/kg, 30-36.5 ° C). At rest, this species excretes all nitrogenous waste as urea. This is the first known instance of complete ureotelism in an entirely aquatic teleost fish. Very small 'apparent' ammonia excretion (<5% of overall N excretion) was attributable to faecal/bacterial production. Ammonia excretion could not be induced by feeding, reduced temperature, or exposure to pH 7. Exhaustive exercise induced only a small efflux of ammonia. Urea output was inhibited completely by pH 7 water and partly by exhaustive exercise, and greatly stimulated by exposure to 500 μmol/L NH3 (at pH 10). A related species, nominally Oreochromis nilotica, which lives in freshwater at circumneutral pH in the same geographic region, excretes 85% ammonia-N and 15% urea-N at pH 7 in the standard teleost fashion. Urea-N efflux increased to 33% upon transfer of O. nilotica to pH 10 in freshwater. Urea output in this species was only marginally stimulated by exposure to 500 μmol/L NH3 (at pH 7). Plasma and white muscle urea levels were 4- to 5-fold higher in O. a. grahami than in O. nilotica, and plasma levels increased between caudal and cardiac sampling sites, indicating hepatic ureagenesis. Blood pH and PNH3 levels, when corrected for sampling artifact, were unusually high in O. a. grahami. We hypothesize that complete ureotelism in O. a. grahami in evolutionary response to the problems of excreting ammonia into highly buffered water at pH 10 and/or acid-base balance in this extreme environment.

KW - Acid-base balance

KW - Ammonia

KW - High pH

KW - Ornithine-urea cycle

KW - Tilapia

KW - Urea

UR - http://www.scopus.com/inward/record.url?scp=0024333386&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0024333386&partnerID=8YFLogxK

U2 - 10.1016/0034-5687(89)90025-X

DO - 10.1016/0034-5687(89)90025-X

M3 - Article

C2 - 2799103

AN - SCOPUS:0024333386

VL - 77

SP - 1

EP - 20

JO - Respiratory Physiology and Neurobiology

JF - Respiratory Physiology and Neurobiology

SN - 1569-9048

IS - 1

ER -