Transepithelial potential in the Magadi tilapia, a fish living in extreme alkalinity
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Date
2011Author
Wood, Chris M.
Bergman, Harold L.
Bianchini, Adalto
Laurent, Pierre
Maina, John
Johannsson, Ora E.
Bianchini, Lucas F.
Chevalier, Claudine
Type
ArticleLanguage
enMetadata
Show full item recordAbstract
We investigated the transepithelial potential
(TEP) and its responses to changes in the external medium in
Alcolapia grahami, a small cichlid fish living in Lake
Magadi, Kenya. Magadi water is extremely alkaline
(pH = 9.92) and otherwise unusual: titratable alkalinity
(290 mequiv L-1, i.e. HCO3
- and CO3 2-) rather than Cl-
(112 mmol L-1) represents the major anion matching
Na? = 356 mmol L-1, with very low concentrations of
Ca2? and Mg2? (\1 mmol L-1). Immediately after fish
capture, TEP was ?4 mV (inside positive), but stabilized at
?7 mV at 10–30 h post-capture when experiments were
performed in Magadi water. Transfer to 250% Magadi water
increased the TEP to ?9.5 mV, and transfer to fresh water
and deionized water decreased the TEP to-13 and-28 mV,
respectively, effects which were not due to changes in pH or
osmolality.