Figure 1. EM reconstruction of the pharyngeal nerves of Drosophila larva.

(A) Left: schematic diagram shows a lateral view of an adult mouse brain and the broad organization of different cranial nerves targeting the medulla of the brainstem. Right: topographical chart of the medulla and part of the spinal cord. Primary sensory and primary motor nuclei are shown on the left and on the right, respectively. (B) Schematic overview of external, pharyngeal and internal sensory systems targeting the subesophageal zone (SEZ), median neurosecretory cells (mNSCs) and the antennal lobe (AL) in Drosophila (left panel). Schematic overview of central output neurons targeting feeding related muscles and the enteric nervous system (right panel). Median neurosecretory cells (mNSCs) target neuroendocrine organ and the periphery, by releasing neuropeptides such as Dilps, DMS and DH44. The mushroom body (MB), a learning and memory center, serves as a landmark. (C) EM reconstruction of pharyngeal sensory input (left panel). Sensory neurons enter the brain via the antennal nerve (AN), maxillary nerve (MxN) and prothoracic accessory nerve (PaN), and cover large parts of the SEZ (left panel). Arrowheads mark respective nerve entry site. Two of the AN sensory projections (per side) extend into the protocerebrum. EM reconstruction of pharyngeal motor output (right panel). Pharyngeal motor neurons (PMNs) and serotonergic output neurons (Se0) leave the CNS via the antennal nerve (AN) and innervate the cibarial dilator musculature (for pharyngeal pumping) and part of the esophagus and the enteric nervous system. MxN motor neurons leave the CNS via the maxillary nerve (MxN) and innervate mouth hook elevator and depressor, labial retractor and salivary gland ductus opener. PaN motor neurons leave the CNS via the prothoracic accessory nerve (PaN) and innervate the dorsal protractor (for head tilt movements). All neurons are colored based on their morphological class. See Figure 1—figure supplements 1–4 and Figure 2—figure supplement 6 for detailed anatomy and description of morphological clustering.

Figure 1—figure supplement 1. Anatomy of the pharyngeal nerves.

(A) The cephalic, pharyngeal and enteric sensory system of the larval head (lateral view). Sensory neurons of the dorsal organ ganglion (DOG), dorsal pharyngeal sensilla (DPS), dorsal pharyngeal organ (DPO) and posterior pharyngeal sensilla (PPS) project to the subesophageal zone (SEZ) via the antennal nerve (AN). Sensory neurons of the enteric nervous system, including the frontal nerve (FN) and recurrent nerve (RN), esophageal ganglion (EG), hypocerebral ganglion (HCG) and proventricular ganglion (PG), fuse together with the AN shortly after the frontal nerve junction (FNJ). The terminal organ ganglion (TOG), ventral organ (VO), labial organ (LBO) and ventral pharyngeal sensilla (VPS) project to the SEZ via the maxillary nerve (MxN). The prothoracic accessory nerve (PaN) contains sensory pathways from dorsal head region and enters the brain between the tritocerebrum and ventral ganglion. (B) Feeding related muscle system. The motor neurons of the antennal nerve (PMNs) innervate the cibarial dilator muscles (CDM) through the frontal nerve. The mouth hook elevator (MHE), mouth hook depressor (MHD), salivary gland ductus opener (SGDO) and labial retractor (LR) are innervated by side branches of the maxillary nerve. The dorsal protractor (Pro_doA) is innervated by the prothoracic accessory nerve. (C) EM reconstruction of all motor neurons innervating the feeding related muscles in the larval head. Arrowheads mark respective nerve entry site.

Figure 1—figure supplement 2. Sensory neurons of the antennal nerve.

(A) Hierarchical morphology similarity score was calculated for all non-olfactory sensory neurons of the antennal nerve (AN). Clustering revealed three distinct axon bundles within the nerve. Asterisk marks two sensory neurons with projections to the protocerebrum. Dendrogram shows exemplary neurons of the left side. (B) EM reconstruction of AN sensory projections colored based on their morphological class. (C) Hierarchical morphology clustering was calculated separately for each AN axon bundle. Dendrograms are colored based on synapse similarity score (Figure 2, Figure 2—figure supplements 1–5). (D) EM reconstruction of each AN axon bundle. Neurons colored based synapse similarity score. (Figure 2, Figure 2—figure supplements 1–5).

Figure 1—figure supplement 3. Sensory neurons of the maxillary nerve.

(A) Hierarchical morphology similarity score was calculated for all sensory neurons of the maxillary nerve (MxN). Clustering revealed three distinct axon bundles within the nerve. Dendrogram shows exemplary neurons of the left side. (B) EM reconstruction of MxN sensory projections colored based their morphological class. (C) Hierarchical morphology clustering was calculated separately for each MxN axon bundle. Dendrograms are colored based on synapse similarity score (Figure 2, Figure 2—figure supplements 1–5). (D) EM reconstruction of each MxN axon bundle. Neurons colored based synapse similarity score. (Figure 2, Figure 2—figure supplements 1–5).

Figure 1—figure supplement 4. Sensory neurons of the prothoracic accessory nerve.

(A) Hierarchical morphology similarity score was calculated for all sensory neurons of the prothoracic accessory nerve (PaN). Dendrogram is colored based on synapse similarity score (Figure 2, Figure 2—figure supplements 1–5). (B) EM reconstruction of PaN sensory neurons. Neurons are colored based on synapse similarity score. (Figure 2, Figure 2—figure supplements 1–5). (C) Neuron name definition. Neurons were named based on their nerve, nerve entry side to the brain, type (Sens = sensory), distinct axon bundle, synaptic area based on synapse similarity score. (Figure 2, Figure 2—figure supplements 1–5).