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bioRxiv · 10.64898/2026.04.27.721165

Photoperiod induces sex-specific immune priming in Pyrrhocoris apterus

Bajgar, A.·Krejcova, G.·Smykal, V.·Dolezel, D.
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Abstract

Seasonal variation in day length provides a reliable cue that allows insects to anticipate upcoming environmental challenges. Here, we demonstrate that photoperiod induces pronounced, sex-specific immune priming in the linden bug Pyrrhocoris apterus. Females exposed to short-day, diapause-inducing conditions exhibited broadly enhanced immune activity compared with long-day females, whereas immune parameters in males were largely unaffected by photoperiod. Short-day females showed increased immune cell abundance, elevated expression of immune-related genes, enhanced humoral immune activity, and increased resistance to bacterial infection. Importantly, photoperiod-induced immune priming depended on a functional m-cryptochrome gene, linking seasonal immune regulation to the photoperiodic timer. Consistent with laboratory results, females collected under natural short-day conditions also displayed enhanced immune parameters despite increased environmental variability. Together, our findings identify photoperiod as a key regulator of immune preparedness in female insects and reveal a sex-specific anticipatory immune strategy associated with seasonal timing.

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Bajgar, A., Krejcova, G., Smykal, V., Dolezel, D.. 2026-04-30. Photoperiod induces sex-specific immune priming in Pyrrhocoris apterus. https://doi.org/10.64898/2026.04.27.721165

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