Anatomical Organization of the Cerebrum of the Desert Locust Schistocerca Gregaria

The desert locust Schistocerca gregaria is a major agricultural pest in North Africa and the Middle East. As such, it has been intensely studied, in particular with respect to population dynamics, sensory processing, feeding behavior flight and locomotor control, migratory behavior, and its neuroendocrine system. Being a long-range migratory species, neural mechanisms underlying sky compass orientation have been studied in detail. To further understand neuronal interactions in the brain of the locust, a deeper understanding of brain organization in this insect has become essential. As a follow-up of a previous study illustrating the layout of the locust brain (Kurylas et al. in J Comp Neurol 484:206-223, 2008), we analyze the cerebrum, the central brain minus gnathal ganglia, of the desert locust in more detail and provide a digital three-dimensional atlas of 48 distinguishable brain compartments and 7 major fiber tracts and commissures as a basis for future functional studies. Neuropils were three-dimensionally reconstructed from synapsin-immunostained whole mount brains. Neuropil composition and their internal organization were analyzed and compared to the neuropils of the fruit fly Drosophila melanogaster. Most brain areas have counterparts in Drosophila. Some neuropils recognized in the locust, however, have not been identified in the fly while certain areas in the fly could not be distinguished in the locust. This study paves the way for more detailed anatomical descriptions of neuronal connections and neuronal cell types in the locust brain, facilitates interspecies comparisons among insect brains and points out possible evolutionary differences in brain organization between hemi- and holometabolous insects.