Abstract:
Interactions of photoperiod and temperature upon waterelectrolyte
balance were examined in rainbow trout acclimated
to six combinations of two photoperiods {18h light: 6h dark,
o
6h light: l8h dark) and three temperatures (2, 10 and 18 C).
The influence of temperature and photoperiod upon plasma,
skeletal muscle, cardiac muscle and liver levels of sodium,
potassium, magnesi.um, calcium, chloride, water content,
water distribution and cellular ion concentrations was
determined by a one way analysis of variance. Significant
(p < 0.05 or better) temperature effects at common photoperiods
were observed in 70% of the analyses performed, showing
no bias toward either photoperiod. Significant photoperiod
effects occured in 57% of the analyses performed at common
temperatures. The influence of photoperiod was most prevalent
at reduced temperatures. Potassium and magnesium appeared to be
particularly thermosensitive, while sodium and calcium were the
most photosensitive of the electrolytes. The ionic composition
of all tissues studied were relatively thermosensitive, with
liver apparently being the most sensitive. On the other hand;
the ionic composition of skeletal and cardiac muscle appear to
be the mos.t photosensitive of the tissues examined. Water
content and distribution in skeletal muscle and liver were
significantly influenced by temperature in 50% of the analyses
performed showing a very strong bias toward UwinterU animals.
Photoperiod effects were significant in 56% of the water parameters
measured with a strong bias toward the two lower temperatures.
Body weight was of significant influence in 16% of the 174
analyses performed. These data are discussed in terms of the
effect of temperature upon ionregulatory mechanisms and the
possible impact of photoperiod variations on endocrine
systems influencing water-electrolyte metabolism.
