Function and development of male nuptial pads in frogs: from the better-grip-theory to the transfer of sex pheromones

青蛙雄性婚垫的功能和发育：从更好的握力理论到性信息素的传递

• 批准号: 531353982
• 负责人: Professorin Dr. Lisa Maria Schulte
• 金额: --
• 依托单位: Arbeitskreis Wild- und Zootierbiologie und Systematik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/531353982?language=en
• 关键词: Function; development; male; nuptial; pads

Male secondary sexual characters play an important role during reproduction in many animal species. In frogs, one of the most common characteristics that can only be found in males in breeding condition are so-called nuptial pads. These pads can be found on the first digits of the hand (therefore also called thumb pads) and are often covered in dark, cornified, spiny epidermal projections (EPs). Because of these EPs, it is frequently suggested that the nuptial pads develop to give the male a better grip when clutching the female during amplexus – especially when mating in water. However, many species do not develop such EPs, but have smooth, light nuptial pads. While the epidermal structures (i.e. EPs vs. smooth) vary substantially between species, the underlying dermal structures always contain glands, that resemble amphibian specialized breeding glands shown to be involved in protein pheromone or adhesive protein production. This suggests that the breeding glands may be involved in chemical communication or in adhesion of the male during amplexus. Glands and EPs of the nuptial pads may therefore have different functions during anuran reproduction. In the proposed study we aim to investigate both, the potential roles of the glands and their secreted content, as well as the association between the EPs and the breeding ecology of the frogs. For this we suggest three work packages: WP1 is a large-scale theoretical approach that compares the nuptial pads of a phylogenetically wide range of anuran species, and systematically reviews and analyses the relationship between their outer morphology and their ecological and life history traits related to mating and reproduction. With this WP we aim to learn more about the ecological and evolutionary causes regarding the development of large, dark, and spiny nuptial pads. In WP2 we focus more on the potential production of pheromones and adhesive proteins in the nuptial pads and aim to find potential patterns among species. For this, we will sample over 40 frog species (from different families, in temperate and tropical zones) and analyse and cluster the gene expression patterns of their nuptial pads. Finally, in WP3, we will use a developmental approach. Using a smaller set of species from temperate zones, we will compare how the nuptial pads change morphologically as well as how their gene expression and co-expression networks vary between breeding versus non-breeding season. With this, we intend to advance our understanding of which structures and genes are especially important for reproduction, e.g., being involved in the dark colouration, the maintenance of glandular tissue or the production of pheromones and adhesives. Altogether, we are confident that our study will drastically improve our understanding of the reproductive significance of both, the outer nuptial pad morphology as well as the breeding glands and the herein produced proteins and secretions.

在许多动物物种中，雄性第二性征在繁殖过程中起着重要作用。在青蛙中，最常见的特征之一是所谓的婚礼垫，这一特征只有在繁殖条件下的雄性青蛙身上才能找到。这些垫子可以在手的第一个手指上找到(因此也称为拇指垫子)，通常覆盖着黑色的角化的带刺的表皮突起(EP)。由于这些EPs，人们经常认为，婚礼垫的发展是为了让雄性在丛生时更好地抓住雌性--特别是在水中交配的时候。然而，许多物种并不发育这样的EPs，而是有光滑、轻盈的婚礼垫。虽然不同物种的表皮结构(即EPs和Smooth)有很大的不同，但底层的真皮结构总是含有腺体，类似于两栖动物的专门繁殖腺体，被证明参与了蛋白质信息素或粘附性蛋白质的产生。这表明，生殖腺可能参与了化学交流或雄性在丛丛中的粘连。因此，在无尾两栖动物繁殖过程中，结节垫上的腺体和EP可能具有不同的功能。在拟议的研究中，我们旨在研究腺体及其分泌内容的潜在作用，以及EPs与青蛙繁殖生态之间的联系。为此，我们提出了三个工作包：WP1是一种大规模的理论方法，它比较了广泛的无尾两栖动物物种的系统发育，并系统地回顾和分析了它们的外部形态与它们与交配和繁殖相关的生态和生活史特征之间的关系。通过这个可湿性粉剂，我们的目标是了解更多关于大的，黑暗的和带刺的婚礼垫发展的生态和进化原因。在WP2中，我们更多地关注婚礼垫中信息素和黏附蛋白的潜在产生，并旨在寻找物种之间的潜在模式。为此，我们将采样40多种青蛙(来自不同的科，在温带和热带地区)，并分析和聚类它们婚礼垫的基因表达模式。最后，在WP3中，我们将使用开发方法。使用来自温带的一小部分物种，我们将比较婚礼垫如何在形态上发生变化，以及它们的基因表达和共表达网络在繁殖和非繁殖季节之间的变化。通过这一点，我们打算推进我们对哪些结构和基因对生殖特别重要的理解，例如，参与深色、腺组织的维持或信息素和粘合剂的产生。总之，我们相信，我们的研究将极大地提高我们对外婚垫形态以及繁殖腺和这里产生的蛋白质和分泌物的生殖意义的理解。