Development of the nervous system in the "head" of Limulus polyphemus (Chelicerata: Xiphosura): morphological evidence for a correspondence between the segments of the chelicerae and of the (first) antennae of Mandibulata.

摘要: We investigated brain development in the horseshoe crab Limulus polyphemus and several other arthropods via immunocytochemical methods, i.e. antibody stainings against acetylated α-tubulin synapsin. According to traditional view, first appendage-bearing segment chelicerates (the chelicerae) is not homologous of mandibulates (first antenna, deutocerebrum) but second antenna (tritocerebrum) or intercalary hexapods myriapods. Accordingly, deutocerebrum would be completely reduced. The main arguments for this view are: (1) postoral origin cheliceral ganglion, (2) a poststomodaeal commissure, (3) connection ganglion stomatogastric system. Our data show that these are convincing. During crabs there no evidence former additional front chelicerae. Instead, comparison structure (neuropil ring) between chelicerates, crustaceans insects shows remarkable similarities. Furthermore, commissure runs mainly praestomodaeal, which unique tritocerebral commissure. An unbiased developing nervous system "head" leads homologisation (first) (= also congruous interpretation Hox gene expression patterns. Thus, our provide morphological existence chelicerate deutocerebrum.