3-D EM Reconstructions of Neurons in the Nudibranch, Berghia stephanieae Reveal Novel Ultrastructural Features

Presenter

Sarah Jane DeAmicis

Campus

UMass Amherst

Sponsor

Paul Katz, Department of Biology, UMass Amherst

Schedule

Session 5, 3:30 PM - 4:15 PM [Schedule by Time][Poster Grid for Time/Location]

Location

Poster Board A58, Campus Center Auditorium, Row 3 (A41-A60) [Poster Location Map]

Abstract

Volume electron microscopy (vEM) exposes features of nervous systems that are inaccessible through other techniques. Here we segmented and reconstructed neurons from a vEM dataset obtained from the rhinophore ganglion (rhg) of the nudibranch mollusc, Berghia stephanieae. The rhg contains 9000 somata whose functions and axonal projections are not known. Half of the rhg including the connective to the cerebral ganglion (ceg) was serially sectioned at 33 nm thickness and imaged using SEM, generating a dataset of 2,175 sections with 4x4 nm lateral resolution. There were distinct neuropil regions including one receiving axonal projections from a peptidergic  ceg neuron. We reconstructed several neurons, including one that had a soma in the rhg and an axon that projected into the connective. Its dendrites lacked vesicles but contacted many vesicle-filled presynaptic boutons. We also reconstructed an axon terminal arbor that branched profusely in the neuropil region occupied by the terminals of the peptidergic ceg neuron, which contained many vesicle-filled varicosities - likely sites of peptide release. We also found novel structures, namely independent vesicle-filled boutons that were free of axon attachments. Some, but not all of these independent boutons were surrounded by glial cells suggesting that they might be in the process of degradation. The features that we uncovered using vEM reconstruction could help generate hypotheses about the function of this enigmatic ganglion.

Keywords

gastropod mollusc, invertebrate neurobiology, 3D reconstruction, synapses, connectomics

Research Area

Neuroscience and Cognitive Science

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