Effect of nutritional stress and sex on melanotic encapsulation rate in the sexually size dimorphic Cook Strait giant weta

Nutritional condition and sex are known to influence efficacy and investment in immune function. A poor diet is costly to immune function because it limits the resources (e.g. protein) available to effector systems (e.g. melanotic encapsulation) whereas males and females are expected to differ in how they allocate resources to fitness-related traits. Males are expected to invest less in immunity, and more in mating, than females but this pattern could be reversed if fitness is more condition-dependent in males than females. I tested the effects of nutritional condition and sex on melanotic encapsulation rate in the Cook Strait giant weta (Deinacrida rugosa Buller 1871), an orthopteran insect exhibiting strong female-biased sexual size dimorphism that is, at least in part, the result of strong sexual selection for small male size. I found that male D. rugosa have a stronger encapsulation response than females whilst nutritional condition has only a small positive effect on this particular effector system in both sexes. Whether the observed sex difference in encapsulation ability is due to a physiological constraint in females or whether males allocate more resources to this effector system because their fitness is more condition-dependent than femaleâ s remains to be determined.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author