A complete adult Drosophila melanogaster brain tracheolar network
The tracheal system of the fruit fly, Drosophila melanogaster, is a complex network of epithelial tubules that supplies oxygen and removes carbon dioxide throughout the organism, with gases entering and exiting through spiracles along the body. While tracheal development and patterning in the embryonic and larval stages have been extensively studied, particularly in the body, much less is known about tracheal and tracheolar organization within the adult brain. To address this gap, we manually traced every tracheole in the brain of a female adult Drosophila using the Full Adult Fly Brain (FAFB) open-access electron microscopy dataset. We reconstructed 117 tracheoles that branch within the parenchyma, terminating in 1,376 endings without forming an interconnected network. Joint analysis of these skeleton reconstructions with volumetric mesh segmentations from the FlyWire connectome revealed that tracheole volume fraction is heterogeneous across neuropils and largely symmetric in overall tracheation between left and right hemispheres. We observe that synapses are not preferentially positioned near tracheoles, and are instead slightly depleted from a region approximately 15 um around tracheoles, relative to other points along the same neurons. We also quantify the relative proximity of neurotransmitter-specific synapses and cables to tracheoles across neuropils. This detailed anatomical description of the tracheolar network establishes a reference for future studies examining how neuronal patterning, activity, and metabolic demand couple with tracheole development and function.