背景:近年来,随着经典研究和遗传学的整合,Chelicerata的比较胚胎学有了很大的进步,以蜘蛛的发育遗传工程为龙头。尽管如此,目前对Chelicerata中胚胎学特征的发育和极化的演变的理解是有限的,因为很少有非蜘蛛物种得到了很好的研究。螯合evo-devo的一个有希望的焦点物种是爸爸长腿(收割者)Phalangiumopilio,Opiliones命令的成员。Phal-opilio,品种丰富,在世界上许多地方都很容易获得,以及在实验室环境中易于处理。该物种的资源包括发育转录组,基因组草图,和RNA干扰的方案,但是对于这个新兴的模型系统来说,现代的分期系统是非常缺失的。
结果:我们提出了一种P.opilio胚胎发生的分期系统,该系统跨越了关于节段形成的最重要的形态发生事件,附件伸长和头部发育。使用延时成像,共聚焦显微镜,比色原位杂交,和免疫组织化学,我们追踪了从产卵到成年的同步离合器的发展。我们描述了分割中的关键事件,肌生成,神经发生,和生殖细胞的形成。
结论:考虑到Opiliones的系统发育位置及其基因组的不重复条件(与蜘蛛和蝎子等群体相反),该物种有望成为节肢动物发育和基因组进化比较研究的关键。本文提出的分期系统为P.opilio提供了有价值的参考,我们预计对节肢动物evo-devo群落有用,目的是振兴非蜘蛛蜘蛛的比较发展研究。
BACKGROUND: The comparative embryology of Chelicerata has greatly advanced in recent years with the integration of classical studies and genetics, prominently spearheaded by developmental genetic works in spiders. Nonetheless, the understanding of the evolution of development and polarization of embryological characters in Chelicerata is presently limited, as few non-spider species have been well studied. A promising focal species for chelicerate evo-devo is the daddy-long-legs (harvestman) Phalangium opilio, a member of the order Opiliones. Phalangium opilio, breeds prolifically and is easily accessible in many parts of the world, as well as tractable in a laboratory setting. Resources for this species include developmental transcriptomes, a draft genome, and protocols for RNA interference, but a modern staging system is critically missing for this emerging model system.
RESULTS: We present a staging system of P. opilio embryogenesis that spans the most important morphogenetic events with respect to segment formation, appendage elongation and head development. Using time-lapse imaging, confocal microscopy, colorimetric in situ hybridization, and immunohistochemistry, we tracked the development of synchronous clutches from egg laying to adulthood. We describe key events in segmentation, myogenesis, neurogenesis, and germ cell formation.
CONCLUSIONS: Considering the phylogenetic position of Opiliones and the unduplicated condition of its genome (in contrast to groups like spiders and scorpions), this species is poised to serve as a linchpin for comparative studies in arthropod development and genome evolution. The staging system presented herein provides a valuable reference for P. opilio that we anticipate being useful to the arthropod evo-devo community, with the goal of revitalizing research in the comparative development of non-spider arachnids.