Immune Challenge and Pre- and Post-copulatory Female Choice in the Cricket Teleogryllus commodus
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Life history theory predicts a trade off between the expression of male sexual traits and the immune system. To test for this trade off, male crickets Teleogryllus commodus were injected with bacterial lipopolysaccharides (LPS) to induce an immune response and their subsequent pre- and post-copulatory sexual attractiveness to virgin and non-virgin females was assessed. Pre-copulatory attractiveness was quantified based on the time taken for males to court and mate with a female. Post-copulatory attractiveness was measured as the time that elapsed between mating and a female interrupting sperm transfer by removing the externally attached spermatophore. We found no difference in pre- or post-copulatory attractiveness between LPS and control males. In contrast, virgin females retained spermatophores for almost twice as long as non-virgins, presumably to enhance fertilization and begin egg-laying. Finally, we note that although LPS is a widely used immune elicitor in insects, its effect might be transitory. After 24 h there was no detectable elevation in haemolymph antibacterial activity of LPS injected crickets compared to that of controls.
KeywordsImmunocompetence LPS male attractiveness trade off pre-copulatory choice cryptic female choice
We are grateful to J. Davies for excellent assistance during the mating trials and maintenance of the crickets, and to D. Gordon for much appreciated advice and the use of equipment during the lysozyme assays. This research was supported by a grant from the Australian Research Council to MDJ.
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