Thermal acclimation in the fresh water planarians, Dugesia tigrina and D. dorotocephala

Abstract

The planarians Dugesia tigrina and D. dorotocephala show well developed resistance adaptation responses following transfer from 5 to 25 °C or the reverse. Their rates of thermal acclimation are typical of most organisms, but the magnitudes of their responses are impressively large. Thermal acclimation in these two species is generally similar, although somewhat more rapid and perhaps more extensive in D. tigrina. Forward and reverse acclimation rates are similar and there is evidence of overshoot and undershoot time course patterns respectively. Our heat resistance data, although based on a different methodology (the CTM method, using loss of equilibrium as the end point criterion) agree well with published values for these triclads. The temperature tolerance and thermal acclimation responses of D. tigrina and D. dorotocephala correlate well with their apparent eurythermy and their widespread distributions.