Temperature, the abiotic master
environmental factor, has a profound effect on the abundance and distribution
of animals on the earth, in particular ectotherms. Ectothermic animals cannot
physiologically regulate their body temperature, and are therefore especially
vulnerable to temperature changes to which they are not adapted but to which
they might be exposed on the warming earth. Predicted increases in ambient
temperature will acts as a leading factor which control the boundary of
habitats, locomotion, reproduction, development, immune defense and general
performance level of fishes and other ectotherms, and thereby will impact the
distribution and abundance of animal species and possibly distort the precise balance
of the ecosystems to which they belong. Fishes represent the most variable and
largest group among vertebrates. In northern latitudes, All fishes have to accommodate
large range of temperature changes between winter and summer. Heart muscle is
electrically excitable, i.e. a small voltage change of plasma membrane (cardiac
action potential, AP) sets the rate and rhythm of the heart, initiates
contraction and regulates force production of cardiac myocytes. Cardiac AP is
generated by a harmonious co-operation between several ion channels in the cell
membrane. Hence, a small disturbance in ion channel function could cause cardiac
arrhythmias, conduction failure and compromise force of cardiac contraction. Electrical
excitability of fish heart should be sensitive and stable to temperature
changes to produce temperature-dependent acceleration and deceleration of heart
rate (fH) and parallel changes in the rate of impulse conduction
over the heart. Strongly response of fishes to the warming makes them as
indicator for reporting climate-induced modifications on aquatic ecosystems. To
this end, effects of seasonal acclimatzation on the electrical excitbility of
roach (Rutilus rutilus) heart, one of the most abundant fish species in
Finnish lakes and coastal waters, is examined.