The adaptations of fish to extremely alkaline environments

Michael P. Wilkie, Chris M. Wood

Research output: Contribution to journalArticle

67 Citations (Scopus)

Abstract

The Lake Magadi Tilapia (MT; Oreochromis alcalicus grahami, the Lahontan cutthroat trout (LCT; Oncorhynchus clarki henshawi) and the tarek (Ct; Chalcalburnus tarichi) have evolved unique strategies that allow them to overcome problems associated with ammonia excretion (J(Amm)) and acid-base regulation in their alkaline environments. In Lake Magadi, Kenya (pH 10), the MT circumvents problems associated with J(Amm) by excreting virtually all (> 90%) of its waste-nitrogen as urea. Base excretion appears to be facilitated by modified seawater-type gill chloride cells, through apical Cl-/HCO3- exchangers and an outwardly directed OH-/HCO3-/CO3 = excretion system. The LCT avoids potentially toxic increases in internal ammonia by permanently lowering ammonia production rates following transfer into alkaline (pH 9.4) Pyramid Lake, Nevada, from its juvenile freshwater (pH 8.4) environment. Greater apical exposure of LCT gill chloride cells, presumably the freshwater variety, probably facilitates base excretion by elevating Cl-/HCO3- exchange capacity. In Lake Van, Turkey (pH 9.8) high ammonia tolerance enables C. tarichi to withstand the high internal ammonia concentrations that it apparently requires for the facilitation of J(Amm). It also excretes unusually high amounts of urea. We conclude that adjustments to nitrogenous waste metabolism and excretion patterns, as well as modifications to gill functional morphology, are necessary adaptations that permit these animals to thrive in environments considered unsuitable for most fishes.

Original languageEnglish
Pages (from-to)665-673
Number of pages9
JournalComparative Biochemistry and Physiology - B Biochemistry and Molecular Biology
Volume113
Issue number4
DOIs
StatePublished - Jun 21 1996

Fingerprint

Ammonia
Fish
Lakes
Fishes
Fresh Water
Urea
Chlorides
Oncorhynchus
Chloride-Bicarbonate Antiporters
Tilapia
Trout
Poisons
Kenya
Seawater
Turkey
Metabolism
Animals
Nitrogen
Acids

Keywords

  • acid-base balance
  • ammonia
  • chloride cell
  • cut-throat trout
  • high pH
  • ion balance
  • Lake Magadi Tilapia
  • rainbow trout
  • urea

ASJC Scopus subject areas

  • Biochemistry
  • Physiology

Cite this

The adaptations of fish to extremely alkaline environments. / Wilkie, Michael P.; Wood, Chris M.

In: Comparative Biochemistry and Physiology - B Biochemistry and Molecular Biology, Vol. 113, No. 4, 21.06.1996, p. 665-673.

Research output: Contribution to journalArticle

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