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Hot and cold waves decrease sperm production and bias sex ratio in the parasitoid wasp Cotesia typhae (Hymenoptera,
Christophe Bressac1, Ahmed El Sabrout2, Fatma Kifouche1
1IRBI, UMR 7261 CNRS, Institut de Recherche sur la Biologie de l'Insecte, Faculté des Sciences et Techniques, Université de Tours, Tours, France.
Journal of Insect Physiology
|August 11, 2023
Summary
Temperature stress during development significantly reduces sperm count in parasitoid wasps (Cotesia typhae), leading to fewer offspring and a male-biased sex ratio. This impacts biological control applications and overwintering survival.
Area of Science:
- Entomology
- Insect reproductive biology
- Pest management
Background:
- Parasitoid wasps are haplodiploid, with offspring sex ratio dependent on sperm availability.
- Male parasitoid wasps are sensitive to temperature stress during the pupal stage, impacting fertility.
- Cotesia typhae is a natural enemy of the invasive pest Sesamia nonagrioides.
Purpose of the Study:
- To investigate the effect of temperature stress on sperm production and offspring sex ratio in Cotesia typhae.
- To determine the impact of heat and cold stress on male parasitoid fertility.
- To assess the implications of temperature stress for the biological control potential of C. typhae.
Main Methods:
- Controlled experiments exposing C. typhae males to varying temperatures (heat: 34-36°C, cold: 0-10°C) during the pupal stage.
- Measurement of sperm production in adult males over seven days.
- Assessment of female sperm storage and offspring sex ratio after mating with temperature-stressed males.
Main Results:
- Sperm production plateaued by day three in control conditions (25-27°C), reaching ~25,000 sperm per male.
- Heat (34-36°C) and cold (0-10°C) stress significantly reduced sperm production after short exposure.
- Females mated with temperature-stressed males stored fewer sperm, produced fewer daughters, and resulted in a male-biased offspring sex ratio.
Conclusions:
- Temperature stress during the pupal stage negatively impacts C. typhae male fertility and offspring sex ratio.
- These findings suggest reduced overwintering survival and potential challenges for the establishment of C. typhae as a biological control agent in Europe.
- Optimal temperature management is crucial for the transport, storage, and application of C. typhae in biological control programs.
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