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. Farnworth et al. 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. The authors used genome editing and established transgenic lines to mark homologous genetic neural lineages in both the fly Drosophila melanogaster and the beetle Tribolium castaneum. This approach allowed them to demonstrate the first example of sequence heterochrony in brain development, in which an immature developmental stage of the central complex gains functionality in Tribolium larvae. The image shows beetle and fly brains (left half and right half, respectively); blue is a DNA marker for cell nuclei, the red color represents antibody staining for the retinal homeobox protein.

Image Credit: Max Farnworth