Molecular analysis of spinneret diversification in spiders

蜘蛛有51,000多种现存物种，是节肢动物中最似是而非的类群之一。蜘蛛属于海蛛纲，是由多足类、六足类和甲壳类组成的曼陀罗的姐妹类群。蜘蛛有两个标签(前前肢和后后肢)和八条腿，很容易在其他节肢动物中辨认出来。蜘蛛在后椎体的节段上带有几个特殊的附肢。在胚胎发育过程中，后裂体节2到5发育出小的肢芽。在第二节和第三节上发育的肢芽将发育成专门的呼吸器官，而在第四节和第五节上更靠后的两个肢芽发育成喷丝器，这是一种改良的附属物，用来沉积丝线。对于许多蜘蛛来说，产丝是生活不可缺少的。蜘蛛用蚕丝捕捉祈祷、筑巢、交流或利用气流进行传播。大多数雌性蜘蛛还会投入大量的能量来构建丝绸茧，以保护卵免受干燥和机械损伤。此外，一些蜘蛛物种使用特殊的蚕丝来伪装蚕茧，另一些蜘蛛物种利用蚕茧的致密性携带它四处走动，保护后代免受捕食者的侵害。不同的蜘蛛科通常表现出不同的吐丝数量和形态。有趣的是，以前的研究揭示了某些胚胎吐丝花蕾的基本性质。然而，形状多样性或喷丝板数量的形成所涉及的分子机制在很大程度上是未知的。在这项拟议的研究中，我们计划使用不同蜘蛛物种的吐丝器的全转录组测序(RNA-Seq)来识别与吐丝器多样化有关的基因。随后，我们将分析用这种方法鉴定的基因的表达部位和功能。总体而言，这项研究旨在确定被招募来改变蜘蛛吐丝器的数量、身份和形态的分子因素和途径，这些结构是这些迷人动物进化和适应过程的基础。

With more than 51,000 extant species, spiders are one of the most specious groups of arthropods. Spiders belong to the Chelicerata, the sister group of the Mandibulata that comprise myriapods, hexapods and crustaceans. With their two tagmata (anterior prosoma and posterior opisthosoma) and their eight legs, spiders are easily recognizable among other arthropods. Spiders carry several specialized appendages on the segments of the opisthosoma. During embryogenesis, the opisthosomal segments two to five develop small limb buds. While the limb buds that develop on the second and third opisthosomal segment will develop into specialized breathing organs, the two more posteriorly located limb buds on the fourth and fifth opisthosomal segment develop into the spinnerets, modified appendages that are used to deposit silk threads. For many spiders, silk production is indispensable to life. Spiders use silk to capture pray, to build a nest, to communicate or to get distributed using air currents. Most spider females also invest large amounts of energy to build a silken cocoon to protect the eggs from desiccation and mechanical damage. Furthermore, some spider species use specialized silk to camouflage the cocoon, others use the compactness of the cocoon to carry it around and protect the offspring from predators. Different spider families often show a different number and morphology of the spinnerets. Interestingly, previous studies revealed the rudimentary nature of certain embryonic spinneret buds. However, the molecular mechanisms involved in the formation of the diversity of shapes or the number of spinnerets are largely unknown. In the here proposed study, we plan to use whole-transcriptome-sequencing (RNA-Seq) of spinnerets of different spider species, to identify relevant genes responsible for spinneret diversification. Subsequently, we will analyse the genes identified by this method for their site of expression and function. Overall, this study aims to identify the molecular factors and pathways that were recruited to change the number, identity and the morphology of the spider spinnerets, the structures that were fundamental to the evolution and adaptation processes of these fascinating animals.