Olfaction is essential for how animals locate food, avoid predators, and navigate their environment. In many species, early olfactory processing occurs in structures called glomeruli, where olfactory sensory neurons converge and synapse with downstream neurons. While glomeruli are well described in vertebrates and insects, their presence in molluscs, particularly nudibranchs, remains unclear, with previous studies reporting mixed results.

The nudibranch Berghia stephanieae relies heavily on chemosensation for prey detection, making it a useful system for examining olfactory circuit organization. Volume electron microscopy data from the rhinophore ganglion reveal a localized region of sensory convergence that may represent an early olfactory processing site. Neurons within this candidate neuropil region were reconstructed using Neuroglancer and the Volume Annotation and Segmentation Tool (VAST).

Reconstructed cells were analyzed to determine their morphology, cell type, and spatial organization. The composition of the region, specifically the presence and relative amount of sensory neurons, interneurons, and projection neurons, was used to assess whether it is consistent with known olfactory glomeruli in other taxa. Where possible, synaptic connections between neurons were also examined to evaluate patterns of connectivity consistent with glomerular organization.

These analyses clarify whether olfactory processing in Berghia stephanieae follows a glomerular organizational model or a distinct neural strategy. The findings refine understanding of olfactory circuit diversity and how sensory processing varies across taxa, particularly in aquatic environments.