Abstract:
The effects of a diurnal sine-wave temperature cycle
(250 +- 5° C) on the wa terI-e etc r o1 yt est a t us 0 f gol df1' Sh ,
Carassius auratus, was assessed through determination of Na+,
K+, Mg2+, Ca2+, Cl- and water content in plasma, Red blood
cells and muscle tissue. Animals were also acclimated to
o 0 0
static temperatures (20 C, 25 c, 30 C) corresponding to the
high, low and mid-ooint temperatures of the cycle. All groups
were sampled at 03:00, 09:00, 15:00 and 21:00 hr. Hemoglobin
content and packed cell volume, as well as electrolyte and
'water levels were determined for each animal and red cell ion
concentrations and ion : hemoglobin ratios estimated.
Cycled animals were distinct from those at constant
temperatures in several respects. Hematological parameters
were elevated above those of animals at constant temperature
and were, on a diurnal basis, more stable. Red blood cell
electrolyte levels varied in an adaptively appropriate
fashion to cycle temperatures. This was not the case in the
constant temperature groups_ Under the cycling regime, plasma
ion levels were more diurnally stable than those of constant
temperature fish. Although muscle parameters in cycled fish
exhibited more fluctuation than was observed in plasma, these
also tended to be relatively more stable than was the caseErythrocytic data are discussed in terms of their
effects on hemoglobin-oxygen affinity while plasma and
muscle observations were considered from the standpoint of
overall water-electrolyte balance.
In general, cycled fish appeared to be capable of
stabilizing overall body fluid composition, while
simultaneously effecting adaptively-appropriate modifications
in the erythrocytic ionic microenvironment of hemoglobin.
The sometimes marked diurnal variability of water-electrolyte
status in animals held at constant temperature as opposed
to the conservation of cycled fish suggests that this
species is, in some fashion, programmed for regulation in a
thermally-fluctuating environment. If this interpretation
is valid and a phenomenon of general occurrence, some
earlier studies involving constant acclimation of eurythermal
species normally occupying habitats which vary in temperature
on a daily basis may require reconsideration.
at constant temperature.
