Terminal investment in the gustatory appeal of nuptial food gifts in crickets

Investment in current versus future reproduction represents a prominent trade-off in life-history theory, and is likely dependent on an individual's life expectancy. The terminal investment hypothesis posits that a reduction in residual reproductive value (i.e., potential for future offspring) will result in increased investment in current reproduction. We tested the hypothesis that male decorated crickets (Gryllodes sigillatus), when cued to their impending mortality, should increase their reproductive effort by altering the composition of their nuptial food gifts (i.e., spermatophylaxes) to increase their gustatory appeal to females. Using a repeated-measures design, we analysed the amino acid composition of spermatophylaxes derived from males both before and after injection of either a saline control or a solution of heat-killed bacteria. The latter, although non-pathogenic, represents an immune challenge that may signal an impending survival threat. One principal component explainin...