Ammonia tolerance in the slender lungfish (Protopterus dolloi): The importance of environmental acidification

Chris M. Wood, Patrick J. Walsh, Shit F. Chew, Yuen K. Ip

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Protopterus dolloi Boulenger, 1900 is an obligate air-breather and exhibits ammoniotely (88% ammonia-N excretion, 12% urea-N excretion) under normal aquatic conditions, but tolerates 7 days of exposure to 30 mmol·L -1 NH4Cl, a treatment fatal to most other fish. Internal N accumulation is minimal and the subsequent washout of ammonia-N and urea-N after return to control conditions is negligible, indicating that N excretion continues and (or) that N metabolism is markedly depressed. Exposure to 30 mmol·L-1 NH4Cl in a closed system without aeration results in depressed urea-N excretion. The lungfish greatly acidifies the external water, a volume 25-fold greater than its own volume. The extent of this acidification increases with time. After several days, the external pH falls from about 7.0 to below 5.0 over a 24-h period, thereby markedly reducing the concentration of NH3 (the form that diffuses across biological membranes). CO2 excretion is partially responsible for this acidification, because vigorous water aeration reduces but does not eliminate the acidification, and urea-N excretion increases moderately. However, a substantial excretion of titratable acid (non-CO2 acidity) also occurs. One exceptional lungfish was able to maintain its aerated environment at a stable pH of 3.7. Environmental acidification may be a less costly strategy for avoiding toxicity than detoxifying ammonia by increasing urea production.

Original languageEnglish
Pages (from-to)507-517
Number of pages11
JournalCanadian Journal of Zoology
Volume83
Issue number4
DOIs
StatePublished - Apr 1 2005

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excretion
acidification
ammonia
tolerance
urea
aeration
closed loop systems
Protopterus
acidity
water
metabolism
carbon dioxide
membrane
toxicity
fold
air
acids
acid
fish

ASJC Scopus subject areas

  • Animal Science and Zoology

Cite this

Ammonia tolerance in the slender lungfish (Protopterus dolloi) : The importance of environmental acidification. / Wood, Chris M.; Walsh, Patrick J.; Chew, Shit F.; Ip, Yuen K.

In: Canadian Journal of Zoology, Vol. 83, No. 4, 01.04.2005, p. 507-517.

Research output: Contribution to journalArticle

Wood, Chris M. ; Walsh, Patrick J. ; Chew, Shit F. ; Ip, Yuen K. / Ammonia tolerance in the slender lungfish (Protopterus dolloi) : The importance of environmental acidification. In: Canadian Journal of Zoology. 2005 ; Vol. 83, No. 4. pp. 507-517.
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