Animal behavior is guided by the brain. Therefore, adaptations of brain structure and function are essential for animal survival, and each species differs in such adaptations. The brain of one individual may even differ between life stages, for instance, as adaptation to the divergent needs of larval and adult life of holometabolous insects. All such differences emerge during development, but the cellular mechanisms behind the diversification of brains between taxa and life stages remain enigmatic. In this study, we investigated holometabolous insects in which larvae differ dramatically from the adult in both behavior and morphology. As a consequence, the central complex, mainly responsible for spatial orientation, is conserved between species at the adult stage but differs between larvae and adults of one species as well as between larvae of different taxa. We used genome editing and established transgenic lines to visualize cells expressing the conserved transcription factor retinal homeobox, thereby marking homologous genetic neural lineages in both the fly Drosophila melanogaster and the beetle Tribolium castaneum. This approach allowed us for the first time to compare the development of homologous neural cells between taxa from embryo to the adult. We found complex heterochronic changes including shifts of developmental events between embryonic and pupal stages. Further, we provide, to our knowledge, the first example of sequence heterochrony in brain development, where certain developmental steps changed their position within the ontogenetic progression. We show that through this sequence heterochrony, an immature developmental stage of the central complex gains functionality in Tribolium larvae.

动物的行为由大脑引导。因此，大脑结构和功能的适应对于动物的生存至关重要，并且每种物种的适应性都不同。一个人的大脑甚至在生命的各个阶段之间可能会有所不同，例如，由于适应了全代谢昆虫的幼虫和成年生活的不同需求。所有这些差异在发育过程中都会出现，但是在分类和生命阶段之间大脑多样化背后的细胞机制仍然是个谜。在这项研究中，我们调查了全代谢昆虫，其中幼虫在行为和形态上与成虫有显着差异。因此，主要负责空间定位的中央建筑群 在成年阶段物种之间是保守的，但是在幼虫和一种物种的成年之间以及在不同分类单元的幼虫之间是不同的。我们使用基因组编辑和建立的转基因品系来可视化表达保守转录因子的细胞视网膜同源盒，从而在蝇果蝇和甲虫Tribolium castaneum中标记同源遗传神经谱系。这种方法使我们首次比较了从胚胎到成年的类群之间同源神经细胞的发育。我们发现复杂的异时变化包括胚胎期和p期之间发育事件的转变。此外，就我们所知，我们提供了大脑发育中序列异时性的第一个例子，其中某些发育步骤改变了它们在个体发育过程中的位置。我们证明了通过这个序列的异时性，中央复合体的不成熟发育阶段获得了Tribolium幼虫的功能。