A Snapshot seminar hosted by the School of Physiology, Pharmacology and Neuroscience

Stanley Heinze, Senior lecturer at Division of Sensory Biology

Abstract: The insect central complex (CX) is a brain region responsible for context dependent action selection, in particular in relation to visually guided spatial orientation. Recently, the CX connectome of the fruit fly Drosophila melanogaster has revealed extraordinarily tight structure-function links in this brain region, in which the implemented neural computations of many circuits are directly defined by the morphological projection patterns and connectivity of the involved neurons. This makes the CX a prime target for comparative analysis of neural circuit function. While the CX is fundamentally important, the demands on its circuits differ between species - depending on motor abilities, sensory environments, and behavioral strategies. To illuminate how evolution has modified these circuits to enable the enormous diversity of insect ecologies, but without disrupting the region’s core functions, we have started to generate CX connectomes across the insect phylogeny, supplemented by selected crustacean species. We aim at, firstly, defining the core elements of the CX circuits to determine their likely ancestral state, and secondly, at identifying evolutionary hotspots that allow novel functions to emerge from the CX circuits. We have so far obtained EM image volumes for six species of bees and ants, a cockroach, a praying mantis, a locust, two species of dung beetles, and a mantis shrimp. We combine projectomes of the entire CX with embedded local connectomes to extract key connectivity principles. While analysis is ongoing at different degrees of completion across our species, we found that all core components are conserved across all analyzed insects, but that even highly conserved circuits contain hotspots of high circuit diversity that could serve as access points for evolutionary change. Additionally, we have identified entire sets of neurons, in particular in the youngest parts of the CX lineages, that exist in some, but not other species, suggesting that species specific behavioral abilities could emerge from these unique elements.