The homeobox transcription factor Engrailed is involved in controlling segmentation during arthropod germ band formation but also in establishing individual neuronal identities during later embryogenesis. In Crustacea, most studies analysing the expression of Engrailed so far have focussed on its function as segment polarity gene. In continuation to these previous studies, we analysed the neuronal expression of the Engrailed protein by immunohistochemistry in the embryonic nerve cord of a parthenogenetic crustacean, the Marbled Crayfish (Marmorkrebs). We paid particular attention to the individual identification of Engrailed expressing putative neuroblasts in the crayfish embryos. Engrailed positive cells in the neuroectoderm were counted, measured and mapped from 38 to 65% of embryonic development. That way, several Engrailed positive putative neuroblasts and putative neurons were identified. Our findings are compared with earlier studies on Engrailed expression during germ band formation in Crustacea. Recent data on neurogenesis in an amphipod crustacean have provided compelling evidence for the homology of several identified neuroblasts between this amphipod and insects. The present report may serve as a basis to explore the question if during crustacean neurogenesis additional communalities with insects exist.

中文翻译：

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大理石纹小龙虾 (Marmorkrebs) 胚胎腹神经索中的雕刻样免疫反应性。

同源盒转录因子 Engrailed 参与控制节肢动物胚带形成过程中的分割，但也参与后期胚胎发生过程中建立个体神经元身份。在甲壳纲中，迄今为止，大多数分析 Engrailed 表达的研究都集中在其作为片段极性基因的功能上。继续这些先前的研究，我们通过免疫组织化学分析了孤雌生殖甲壳动物大理石纹小龙虾 (Marmorkrebs) 胚胎神经索中 Engrailed 蛋白的神经元表达。我们特别关注在小龙虾胚胎中表达 Engrailed 的推定神经母细胞的个体鉴定。从胚胎发育的 38% 到 65%，对神经外胚层中的咬伤阳性细胞进行计数、测量和绘制。那样，鉴定了几个 Engrailed 阳性推定神经母细胞和推定神经元。我们的研究结果与早期对甲壳类动物胚带形成过程中 Engrailed 表达的研究进行了比较。最近关于片脚类甲壳类动物神经发生的数据为这种片脚类动物和昆虫之间几种已鉴定的神经母细胞的同源性提供了令人信服的证据。本报告可作为探讨甲壳类动物神经发生过程中是否存在与昆虫其他群落的问题的基础。