Mating generally occurs after individuals reach adulthood. In many arthropods including spiders, the adult stage is marked by a final moult after which the genitalia are fully developed and functional. In several widow spider species (genus Latrodectus), however, immature females may mate a few days before they moult to adulthood, i.e. in their late-subadult stage. While the “adult” mating typically results in cannibalism, males survive the “immature” mating. During both “immature” and “adult” matings, males leave parts of their paired copulatory organs within female genitalia, which may act as mating plugs. To study potential costs and benefits of the two mating tactics, we investigated female genital morphology of the brown widow spider, L. geometricus. Light microscopy, histology and micro-computed tomography of early-subadult, late-subadult and adult females were conducted to determine the overall pattern of genital maturation. We compared genitalia of mated late-subadult and adult females to reveal potential differences in the genitalic details that might indicate differential success in sperm transfer and different environments for sperm storage and sperm competition. We found that the paired sperm storage organs (spermathecae) and copulatory ducts are developed already in late-subadult females and host sperm after immature mating. However, the thickness of the spermathecal cuticle and the staining of the secretions inside differ significantly between the late-subadult and adult females. In late-subadult females mating plugs were found with higher probability in both spermathecae compared to adult females. Sperm transfer in matings with late-subadult females follows the same route as in matings with adult females. The observed differences in the secretions inside the spermathecae of adult and late-subadult females likely reflect different storage conditions for the transferred sperm which may lead to a disadvantage under sperm competition if the subadult female later re-mates with another male. However, since males mating with late-subadult females typically transfer sperm to both spermathecae they might benefit from numerical sperm competition as well as from monopolizing access to the female sperm storage organs. The assessment of re-mating probability and relative paternity will clarify the costs and benefits of the two mating tactics in light of these findings.

中文翻译：

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寡妇蜘蛛未成熟交配的功能形态

交配通常在个体成年后发生。在包括蜘蛛在内的许多节肢动物中，成年阶段的特征是最终蜕皮，之后生殖器得以充分发育并发挥功能。但是，在一些寡妇蜘蛛属（Latrodectus属）中，未成年雌性可能会在交配成年之前几天交配，即处于成年后期。虽然“成人”交配通常会导致自相残杀，但雄性在“未成熟”交配中存活下来。在“未成熟的”和“成人的”交配过程中，雄性都会将成对的交配器官的一部分留在雌性生殖器中，而雌性生殖器可能会充当交配插头。为了研究两种交配策略的潜在成本和收益，我们调查了棕色寡妇蜘蛛L. geometricus的女性生殖器形态。早期亚成人的光学显微镜，组织学和计算机断层扫描 进行了晚亚成年和成年雌性以确定生殖器成熟的总体模式。我们比较了已交配的晚期亚成年女性和成年女性的生殖器，以揭示生殖器细节上的潜在差异，这可能表明精子转移成功以及精子储存和精子竞争的不同环境下的成功不同。我们发现成对的精子存储器官（spermathecae）和交配导管已经在未成年的雌性和未成熟交配后的宿主精子中发育。然而，晚成年雌性和成年雌性之间，精囊表皮的厚度和内部分泌物的染色明显不同。在亚成年后期雌性动物中，与成年雌性动物相比，两个精子囊中都有交配栓的可能性更高。与成年雌性交配的精子转移遵循与成年雌性交配的相同途径。观察到的成年雌性和晚成年雌性的精囊内分泌物的差异可能反映了所转移精子的不同储存条件，如果该成年雌性后来与另一雄性交配，则在精子竞争中可能会处于不利地位。但是，由于雄性与成年后成年雌性交配通常会将精子转移到两个精子囊中，因此他们可能会受益于精子竞争的竞争以及对雌性精子存储器官的垄断。根据这些发现，对重新交配概率和相对亲权的评估将阐明两种交配策略的成本和收益。观察到的成年雌性和晚成年雌性的精囊内分泌物的差异可能反映了转移的精子的不同贮藏条件，如果该成年雌性后来与另一雄性交配，则在精子竞争中可能会处于不利地位。但是，由于雄性与成年后成年雌性交配通常会将精子转移到两个精子囊中，因此他们可能会受益于精子竞争的竞争以及对雌性精子存储器官的垄断。根据这些发现，对重新交配概率和相对亲权的评估将阐明两种交配策略的成本和收益。观察到的成年雌性和晚成年雌性的精囊内分泌物的差异可能反映了转移的精子的不同贮藏条件，如果该成年雌性后来与另一雄性交配，则在精子竞争中可能会处于不利地位。但是，由于雄性与成年后成年雌性交配通常会将精子转移到两个精子囊中，因此他们可能会受益于精子竞争的竞争以及对雌性精子存储器官的垄断。根据这些发现，对重新交配概率和相对亲权的评估将阐明两种交配策略的成本和收益。