The chelifores of sea spiders (Arthropoda, Pycnogonida) are the appendages of the deutocerebral segment
The chelifores of sea spiders (Arthropoda, Pycnogonida) are the appendages of the deutocerebral segment
复制标题
DOI：
10.1111/j.1525-142x.2008.00285.x
复制
发表时间：
2008-11-01
影响因子：
2.9
通讯作者：
Scholtz, Gerhard
中科院分区：
文献类型：
--
作者：
Brenneis, Georg;Ungerer, Petra;Scholtz, Gerhard
在过去的十年中，基因表达模式和神经解剖数据已经导致了一个新的共识，关于前肢和neuromeres在节肢动物头部之间的长期争论的关联。根据这一新的观点，在所有现存的真节肢动物的第一个附属物是由第二个神经节，中脑，而最前面的头部区域轴承的前脑缺乏一个附件。这与Onychophora的明确的proocerebralally靶向“触角”和一些真节肢动物化石中的proocerebrallimbs的证据形成鲜明对比。然而，后者的“前附属物”或“初级触角”很可能在谱系中减少或丢失，导致现存的分类群。令人惊讶的是，最近一项关于密蛛的神经解剖学研究挑战了这一进化场景，报告了第一附属物（螯肢）的原脑神经支配。然而，这种解释很快就受到Hox基因表达数据的质疑。为了重新评估尚未解决的争议，我们分析了神经解剖和神经发生在四个pycnogonid物种使用免疫组化技术。我们清楚地表明，postprotocerebral神经支配的chelifores，这是解决的plesiomorphic条件在pycnogonids时，对最近发表的综合性神经发育评估。通过提供直接的形态学支持的cheliforal神经节的中脑状态，我们调和形态和基因表达数据，并主张在所有现存的真节肢动物的前最附属物之间的相应位置。因此，必须仔细检查其他结构，以阐明最近真节肢动物中推定的原脑附属物的命运。一些甲壳类动物的唇和“额丝”可能是这种方法的候选者。
Within the last decade, gene expression patterns and neuro-anatomical data have led to a new consensus concerning the long-debated association between anterior limbs and neuromeres in the arthropod head. According to this new view, the first appendage in all extant euarthropods is innervated by the second neuromere, the deutocerebrum, whereas the anterior-most head region bearing the protocerebrum lacks an appendage. This stands in contrast to the clearly protocerebrally targeted "antennae" of Onychophora and to some evidence for protocerebral limbs in fossil euarthropod representatives. Yet, the latter "frontal appendages" or "primary antennae" have most likely been reduced or lost in the lineage, leading to extant taxa. Surprisingly, a recent neuro-anatomical study on a pycnogonid challenged this evolutionary scenario, reporting a protocerebral innervation of the first appendages, the chelifores. However, this interpretation was soon after questioned by Hox gene expression data. To re-evaluate the unresolved controversy, we analyzed neuro-anatomy and neurogenesis in four pycnogonid species using immunohistochemical techniques. We clearly show the postprotocerebral innervation of the chelifores, which is resolved as the plesiomorphic condition in pycnogonids when evaluated against a recently published comprehensive phylogeny. By providing direct morphological support for the deutocerebral status of the cheliforal ganglia, we reconcile morphological and gene expression data and argue for a corresponding position between the anterior-most appendages in all extant euarthropods. Consequently, other structures have to be scrutinized to illuminate the fate of a presumptive protocerebral appendage in recent euarthropods. The labrum and the "frontal filaments" of some crustaceans are possible candidates for this approach.