Efficient transfer of chemical signals is important for successful mating in many animal species. Multiple evolutionary lineages of animals evolved direct sex pheromone transmission during traumatic mating—the wounding of the partner with specialized devices—which helps to avoid signal loss to the environment. Although such direct transmission modes of so-called allohormone pheromones are well-documented in invertebrates, they are considered rare in vertebrates. Males of several species of the frog genus Plectrohyla (Hylidae, Anura) have elongated teeth and develop swollen lips during the breeding season. Here we investigated the possibility that these structures are used to scratch the females’ skin and apply allohormone pheromones during traumatic mating in several Plectrohyla species. Our behavioural observations revealed that males press their upper jaw onto the females’ dorsum during amplexus, leaving small skin scratches with their teeth. Histological examinations of the males’ lips identified specialized mucus glands, resembling known amphibian pheromone glands. Whole-transcriptome sequencing of these breeding glands showed high expression of sodefrin precursor-like factor (SPF) proteins, which are known to have a pheromone function in multiple amphibian species. Our study suggests SPF delivery via traumatic mating in several anuran species: the males have specialized breeding glands in the lips for production and secretion and use their elongated teeth as wounding devices for application. We hypothesize that these SPF proteins end up in the females’ circulatory system, where understanding their exact function will require further molecular, physiological and behavioural testing.

中文翻译：

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爱情叮咬：雄性青蛙（Plectrohyla，Hylidae）在腋窝期间使用牙齿抓挠将sodefrin前体样因子传递给雌性

化学信号的有效传递对于许多动物物种的成功交配很重要。动物的多个进化谱系在创伤性交配过程中进化出直接的性信息素传输 - 用专门的设备伤害伴侣 - 这有助于避免信号丢失到环境中。尽管所谓的异激素信息素的这种直接传输模式在无脊椎动物中得到了充分证明，但它们在脊椎动物中被认为是罕见的。在繁殖季节，青蛙属（Hylidae，Anura）的几种雄性有拉长的牙齿和肿胀的嘴唇。在这里，我们研究了这些结构用于在几种 Plectrohyla 物种的创伤性交配期间刮伤雌性皮肤并应用异激素信息素的可能性。我们的行为观察表明，雄性在腋窝时将上颌压在雌性的背部，牙齿会留下小的皮肤划痕。雄性嘴唇的组织学检查确定了特殊的粘液腺，类似于已知的两栖动物信息素腺。这些繁殖腺体的全转录组测序显示出大豆蛋白前体样因子 (SPF) 蛋白的高表达，已知这些蛋白在多种两栖动物物种中具有信息素功能。我们的研究表明，SPF 通过创伤性交配在几种无尾猿物种中传递：雄性在嘴唇中有专门的繁殖腺用于生产和分泌，并使用它们细长的牙齿作为应用的伤口装置。我们假设这些 SPF 蛋白最终会进入雌性的循环系统，