Changes in Na+,K+-ATPase
activity and gill chloride cell morphology in the grouper Epinephelus
coioides larvae and juveniles in response to salinity and temperature
N.B.Caberoy,
G.F. Quinitio-2000
Fish Physiology and Biochemistry, 23 (1) : 83-94
(from Current Contents)
Abstract:
The activity of the enzyme Na+, K+-ATPase and
morphological changes of gill chloride cells in grouper, Epinephelus
coioides larvae and juveniles were determined 6-48 h after abrupt transfer
from ambient rearing conditions (30-32 ppt, 26.5-30 °C) to different
salinity (8, 18, 32, 40 ppt) and temperature (25, 30 °C) combinations. Na+,
K+-ATPase activity in day 20 larvae did not change at salinities 8-32 ppt.
Activity decreased significantly (P <0.01) after exposure to 40 ppt at
25-30 °C, which was accompanied by an increase (P <0.05) in density and
fractional area of chloride cells. Enzyme activity in 40 ppt did not reach a
stable level and larvae failed to recover from an osmotic imbalance that
produced a low survival at 25 °C and death of all larvae at 30 °C. Enzyme
activity and chloride cell morphology in day 40 groupers did not change in
8-40 ppt at 25 °C and 8-32 ppt at 30 °C. A significant decrease and a
subsequent increase in Na+, K+-ATPase activity in 40 ppt at 30 °C was
associated with the increase in chloride cell density resulting in an
increased fractional area but a decreased cell size. Enzyme activity and
chloride cells of day 60 grouper were unaffected by abrupt transfer to test
salinities and temperatures. These results demonstrate that grouper larvae
and juveniles are efficient osmoregulators over a wide range of salinities.
Salinity adaptation showed an ontogenetic shift as the larvae grew and
reached the juvenile stage. This development of tolerance limits may reflect
their response to actual conditions existing in the natural environment.
(SE Asian Fisheries Dev Ctr, Dept Aquaculture,
Iloilo, Philippines, e-mail: nbcaberoy@aqd.seafdec.org.ph)
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