Meeting Abstract
A surprising diversity of invertebrates have many image-forming eyes scattered across their bodies. Recent efforts have characterized the structure and function of individual eyes from these distributed visual systems, but less progress has been made towards characterizing the neural structures associated with them. Scallops, for example, have a distributed visual system that includes dozens of image-forming eyes with mirror-based optics. The optic nerves that exit these eyes travel to the lateral lobes of the parietovisceral ganglion (PVG), but we have yet to learn how scallops may process spatial information within this brain-like organ. To learn more about the scallop visual system by identifying sensory receptors and chemical synapses, we studied the expression of four G protein α subunits (Gαi, Gαo, Gαq, and Gαs) in the eyes and PVG of the bay scallop Argopecten irradians. In the eyes, we noted expression of Gαo by the ciliary photoreceptors of the distal retina, expression of Gαq by the rhabdomeric photoreceptors of the proximal retina, and the expression of Gαo and Gαq by the cells of the cornea; we did not, however, detect expression of Gαi or Gαs. In the PVG, we noted widespread expression of Gαi, Gαo, and Gαq. The expression of Gαs was limited to fine neurites in the lateral and ventral central lobes, as well as large, unipolar neurons in the dorsal central lobes. Our findings suggest that light detection by the eyes of A. irradians is conferred primarily by photoreceptors that express Gαo or Gαq, that the corneal cells of scallops may contain sensory receptors and/or receive neural input, and that G protein labeling is useful for visualizing sub-structures and identifying specific populations of cells within the nervous systems of invertebrates.
