Gene expression response to irradiation and social environments in the reproductive tracts of male seed beetles, Callosobruchus maculatus

We studied the effect of social environment (presence of conspecific males and/or females) and gamma irradiation on gene expression in the male reproductive tract (aedeagus, ejaculatory bulb, 2 bilobed testes and 3 pairs of smaller accessory glands; the two pairs of larger accessory glands were removed) in a full factorial design. Overall design: The experiment was replicated in two lines (MA1 & MA3) and over two days, resulting in 4 replicate samples per irradiation/social environment combination. Both lines are experimental evolution lines evolved under intense sexual selection with natural selection removed (Baur and Berger, 2020, Nature Ecology and Evolution 4, 737-744, https://doi.org/10.1038/s41559-020-1140-7). Males were held in one of four social environments (virgin: alone, mated: with one conspecific female, male-male: in groups of 5 conspecific males, mixed: in groups of 5 conspecific males and 5 conspecific females) for 24 hours. Afterwards males were isolated and either irradiated (a dose of 25 Gray of gamma radiation from a caesium-137 source over 35 min) or kept as controls. After a 2 hour recovery period males were flash-frozen and stored at -80 °C until dissections. Per sample, we pooled the reproductive tracts from 9-10 males within each line/day/treatment combination resulting in a total of 32 samples.