Low pH and calcium
effects on net Na+ and K+ fluxes in two catfish species from the Amazon River (Corydoras: Callichthyidae)
Volume 35, Issue 3,
Matsuo, A Y; Val, A L
Summary of points:
·
The study analyzes Na+ and K+ disturbances caused by low pH in two
catfish species from the Amazon
·
Corydoras adolfoi
inhabits ion-poor, black-stained, low pH (3.5-4.0) waters, while C. schwartzi is native to ion-rich waters at circumneutral pH.
·
Fish were exposed to pH 3.5 Ca2+-free, and Ca2+-enriched
(approximately 500 micromol/l) water to determine the
protective effects of calcium.
·
Net Na+ and K+ fluxes were measured in the water collected from
the fish experimental chambers.
·
C. adolfoi was unable to control the Na+
efflux at low pH
·
In C. schwartzi, at pH 3.5, the initial
high Na+ loss was gradually attenuated.
·
A K+ loss occurred in both species, but remained relatively
constant throughout exposure.
·
High [Ca2+] affected ion
losses in both species. C. adolfoi had 70% loss attenuation,
indicating incapacity to control Na+ efflux.
·
In C. schwartzi, elevated [Ca2+]
completely prevented the Na+ losses caused by exposure to low pH.
·
Rather different patterns were seen for K+ fluxes, with C. adolfoi showing no K+ disruption when exposed to low
pH/high [Ca2+]. Thus, C. adolfoi loses Na+ during
acid exposure, but has the ability to control K+ loss, while C. schwartzi controls diffusive Na+ loss but exhibits a
slightly higher K+ loss. Ion balance was influenced by [Ca2+] at low pH in C. schwartzi but not in C. adolfoi.
[Journal Article; In English;