Data from: X-Ray micro-CT scanning reveals temporal separation of male harm and female kicking during traumatic mating in seed beetles

In the seed beetle Callosobruchus maculatus, the male intromittent organ is covered in sharp spines that pierce the female copulatory tract wall during mating. Though the fitness consequences of traumatic mating are well studied in this species, we know much less about how the male and female genitalia interact during mating. This is partly due to the fact that genital interactions occur primarily inside the female, and so are difficult to observe. In this study we use X-ray micro-CT scanning to examine the proximate mechanisms of traumatic mating in C. maculatus in unprecedented detail. We show that this technique can be used to identify female tissue damage before the melanisation of wound sites. We visualise the positioning of the male intromittent organ inside the female copulatory tract during mating, and show how this relates to tract wounding in three dimensions. By scanning pairs flash-frozen at different times during mating, we show that significant tract wounding occurs before the onset of female kicking. There is thus some degree of temporal separation between the onset of wounding and the onset of kicking, which supports recent suggestions that kicking is not an effective female counter-adaptation to reduce copulatory wounding in this species. We also present evidence that the sharp teeth protruding from the female tract wall are able to pierce the spermatophore as it is deposited, and may thus function to aid sperm release.

在种子甲虫（Callosobruchus maculatus）中，雄性插入器官（intromittent organ）表面覆盖有尖锐棘刺，交配过程中这些棘刺会刺穿雌性交配道（copulatory tract）壁。尽管该物种创伤性交配（traumatic mating）的适合度后果已得到充分研究，但我们对雌雄生殖器在交配过程中的互作机制仍知之甚少。这在一定程度上源于生殖器互作主要发生在雌性体内，难以直接观测。本研究采用X射线显微计算机断层扫描（X-ray micro-CT）技术，以前所未有的细节解析了该物种创伤性交配的近因机制。我们证实，该技术可用于识别伤口黑化（melanisation）发生前的雌性组织损伤。我们可视化了交配过程中雄性插入器官在雌性交配道内的定位，并从三维层面揭示了其与交配道损伤的关联。通过对交配不同阶段快速冷冻（flash-frozen）的虫对进行扫描，我们发现交配道的显著损伤发生在雌性踢腿行为起始之前。由此可见，损伤起始与踢腿行为起始存在一定程度的时间分离，这支持了近期提出的观点：雌性踢腿并非该物种减少交配创伤的有效反适应（counter-adaptation）策略。我们还提供证据表明，雌性交配道壁突出的尖锐齿状结构可在精包（spermatophore）沉积时刺穿其外壁，或可借此辅助精子释放。