LMU Munich, Biocenter, Großhaderner Str. 2, 82152, Planegg-Martinsried, Germany.
GeoBio-Center of the LMU Munich, Richard-Wagner-Str. 10, 80333, München, Germany.
Dev Genes Evol. 2021 Jul;231(3-4):47-56. doi: 10.1007/s00427-021-00675-y. Epub 2021 Apr 18.
Most morphological studies focus on adult specimens, or if developmental studies are pursued, especially in Euarthropoda, they focus on embryonic development. Araneae (spiders) is one of these groups, in consequence with understudied post-embryonic development. Here we present aspects of the post-embryonic stages of different species of Mesothelae, sister group to the remaining spiders (when fossil species are not taken into account). We used different imaging methods and measured different external morphological structures to detect possible ontogenetic changes. One structure exhibiting post-embryonic changes is the chelicera. Here the significant change occurs between the last immature stage and the adult, yet only in males. For the spinnerets, we could not detect ontogenetic changes, but instead a high variability in length and width, probably due to their lack of pivot joints between the elements. The strongest morphological change during ontogeny occurred on the sternum, which begins with a rather roundish shape in the first stage and changes to being fairly elongate in shape in the last immature stages and the adult. This specific sternum shape only occurs in adults of mesothelan spiders, while opisthothelan spiders have a broader sternum also in the adult. We discuss our results in an evolutionary context, also taking into account recent finds of fossil spiders.
大多数形态学研究都集中在成年标本上，或者如果进行发育研究，特别是在节肢动物门的研究中，它们主要集中在胚胎发育上。蜘蛛目（蜘蛛）就是其中之一，因此其胚胎后发育研究不足。在这里，我们介绍了Mesothelae 不同物种的胚胎后阶段的各个方面，Mesothelae 是剩余蜘蛛（当不考虑化石物种时）的姐妹群。我们使用了不同的成像方法和测量了不同的外部形态结构来检测可能的个体发生变化。一种表现出胚胎后变化的结构是螯肢。在这里，在最后一个未成熟阶段和成虫之间发生了显著的变化，但仅在雄性中发生。对于纺器，我们无法检测到个体发生的变化，但长度和宽度的变化很大，可能是由于它们在元素之间没有枢轴关节。在个体发生过程中发生的最强的形态变化发生在胸板上，胸板在第一阶段具有相当圆形的形状，并在最后一个未成熟阶段和成虫中变为相当长的形状。这种特定的胸板形状仅出现在 Mesothelae 蜘蛛的成虫中，而 Opisthothelan 蜘蛛的成虫中胸板也更宽。我们在进化背景下讨论我们的结果，同时考虑到最近发现的化石蜘蛛。
