The arthropod body plan is comprised of several repeating segments along the anteroposterior body axis. This high degree of conservation, however, obfuscates the wide degree of underlying developmental variation present across and within arthropod groups. In chelicerates, the arthropod clade containing mites, spiders, scorpions, and horseshoe crabs, development is the most similar at the stages following early germ band segmentation. Comparative studies of chelicerate segmentation prior to these events, however, remain scarce. In order to elucidate and identify possible shared and derived aspects of chelicerate segmentation, we followed the early prosomal (anterior) segmentation in the model mite Archegozetes longisetosus using the expression of the conserved segmental marker hedgehog (hh). Our data indicate that the ancestral chelicerate likely utilized the gene hedgehog in a group of cells surrounding the germ disc. We also provide evidence that chelicerate segmentation, albeit via the conserved “short/intermediate germ” mode, progresses differently in the prosoma between Archegozetes and spiders and thus early, anterior segmentation in chelicerates is heterochronic.

中文翻译：

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在螨长寿菌中的早期分割揭示了螯合物发育的保守和衍生方面。

节肢动物的身体计划包括沿前后身体轴的几个重复部分。但是，这种高度的保守性掩盖了节肢动物群内和节肢动物群内广泛的潜在发育变异。在螯虫中，节肢动物进化枝包含螨虫，蜘蛛，蝎子和horse，在早期细菌带分割后的阶段发育最为相似。然而，在这些事件发生之前进行螯合物细分的比较研究仍然很少。为了阐明和识别螯合物细分的可能的共享和派生方面，我们使用了保守的分段标记刺猬蛋白的表达，对模型螨螨Archegozetes longisetosus中的早期早体（前）细分进行了追踪。（hh）。我们的数据表明，祖先螯合物可能在围绕生殖盘的一组细胞中利用了基因刺猬。我们还提供证据表明，螯合物的分割，尽管是通过保守的“短/中间胚芽”模式进行的，但在弓形虫和蜘蛛之间的质瘤中进展不同，因此，螯合物的早期，前切是异时的。