Published online by Cambridge University Press: 06 April 2009
During its life-cycle, the cestode Schistocephalus solidus is parasitic in both an ectotherm (Gasterosteus aculeatus) and an endotherm (Gallus domesticus) host, and so provides an excellent model with which to study temperature adaptation in parasites. A mitochondrial fraction was prepared from the adults and plerocercoids of S. solidus and from their respective hosts; the activities of the mitochondrial adenosine triphosphatase (ATPase) were then measured over the temperature range 1–45 °C. The plerocercoids of S. solidus show evidence of immediate temperature compensation; this would provide a mechanism for withstanding the abrupt temperature change experienced during infection of the final host. Analysis of the Michaelis constant data suggests that variation of Km, a with temperature may be a major factor in this immediate temperature compensation. In response to acclimation at 5 and 19°C, plerocercoid ATPase showed inverse or paradoxical rate compensation, as did the enzyme from the fish host. Acclimation at the two temperatures had no effect on the Q10 or on the linearity of the Arrhenius plots for the plerocercoid mitochondrial ATPase and only a small effect on the Km a. Acclimation of the fish host again had only a small effect on the Km, a of the fish mitochondrial ATPase but, in contrast to the plerocercoid, there was also a significant effect on the Q10 and the Arrhenius plots. Adult S. solidus ATPase showed partial rate compensation and had a biphasic Arrhenius plot, suggesting that after infection there had been a change in the enzyme or its micro-environment. In terms of the effect of temperature on the Q10 amd Km, a and in the biphasic nature of the Arrhenius plot, the mitochondrial ATPase of adult S. solidus showed similarities with the enzyme from its bird host.