Humboldt-Universität zu Berlin Institut für Biologie/Vergleichende Zoologie Philippstraße 13, 10115 Berlin, Germany.
Universität zu Köln Institut für Genetik, Zülpicher Straße 47a, 50674 Köln, Germany.
Front Zool. 2011 Jun 14;8(1):15. doi: 10.1186/1742-9994-8-15.
The spider Cupiennius salei (Keyserling 1877) has become an important study organism in evolutionary and developmental biology. However, the available staging system for its embryonic development is difficult to apply to modern studies, with strong bias towards the earliest developmental stages. Furthermore, important embryonic events are poorly understood. We address these problems, providing a new description of the embryonic development of C. salei. The paper also discusses various observations that will improve our understanding of spider development.
Conspicuous developmental events were used to define numbered stages 1 to 21. Stages 1 to 9 follow the existing staging system for the spider Achaearanea tepidariorum, and stages 10 to 21 provide a high-resolution description of later development. Live-embryo imaging shows cell movements during the earliest formation of embryonic tissue in C. salei. The imaging procedure also elucidates the encircling border between the cell-dense embryo hemisphere and the hemisphere with much lower cell density (a structure termed 'equator' in earlier studies). This border results from subsurface migration of primordial mesendodermal cells from their invagination site at the blastopore. Furthermore, our detailed successive sequence shows: 1) early differentiation of the precheliceral neuroectoderm; 2) the morphogenetic process of inversion and 3) initial invaginations of the opisthosomal epithelium for the respiratory system.
Our improved staging system of development in C. salei development should be of considerable value to future comparative studies of animal development. A dense germ disc is not evident during development in C. salei, but we show that the gastrulation process is similar to that in spider species that do have a dense germ disc. In the opisthosoma, the order of appearance of precursor epithelial invaginations provides evidence for the non-homology of the tracheal and book lung respiratory systems.
蜘蛛 Cupiennius salei（Keyserling 1877）已成为进化和发育生物学的重要研究生物。然而，现有的胚胎发育分期系统难以应用于现代研究，对早期发育阶段存在强烈的偏见。此外，重要的胚胎事件理解得还不够充分。我们解决了这些问题，提供了对 C. salei 胚胎发育的新描述。本文还讨论了各种观察结果，这些结果将有助于我们更好地理解蜘蛛的发育。
显著的发育事件被用来定义编号为 1 到 21 的阶段。阶段 1 到 9 遵循现有的蜘蛛 Achaearanea tepidariorum 的分期系统，阶段 10 到 21 提供了后期发育的高分辨率描述。活胚胎成像显示了 C. salei 中胚胎组织最早形成过程中的细胞运动。该成像程序还阐明了细胞密集的胚胎半球和细胞密度较低的半球之间的环绕边界（在早期研究中称为“赤道”）。该边界是由原始中胚层细胞从胚孔处的内陷位置向下方迁移形成的。此外，我们详细的连续序列显示：1）前螯神经外胚层的早期分化；2）反转的形态发生过程；3）呼吸系统的后体上皮的初始内陷。
我们对 C. salei 发育的改进的发育分期系统应该对未来的动物发育比较研究具有相当大的价值。在 C. salei 的发育过程中，没有明显的密集生殖盘，但我们表明，原肠胚形成过程与具有密集生殖盘的蜘蛛物种相似。在后体部，前体上皮内陷出现的顺序为气管和书肺呼吸系统的非同源性提供了证据。
