Expression of G Proteins in the Eyes and Parietovisceral Ganglion of the Bay Scallop Argopecten irradians

Abstract

A multitude of image-forming eyes are spread across the bodies of certain invertebrates. Recent efforts have characterized how these eyes function, but less progress has been made toward describing the neural structures associated with them. Scallops, for example, have a distributed visual system that includes dozens of eyes whose optic nerves project to the lateral lobes of the parietovisceral ganglion (PVG). To identify sensory receptors and chemical synapses associated with the scallop visual system, we studied the expression of four G protein α subunits (Gα, Gα, Gα, and Gα) in the eyes and PVG of the bay scallop Argopecten irradians (Lamarck, 1819). In the eyes of A. irradians, we noted expression of Gα by the ciliary photoreceptors of the distal retina, expression of Gα by the rhabdomeric photoreceptors of the proximal retina, and the expression of Gα and Gα by the cells of the cornea; we did not, however, detect expression of Gα or Gα in the eyes. In the PVG of A. irradians, we noted widespread expression of Gα, Gα, and Gα. The expression of Gα 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 Gα or Gα, that the corneal cells of scallops may contain sensory receptors and/or receive neural input, and that G protein labeling is useful for visualizing substructures and identifying specific populations of cells within the nervous systems of invertebrates.

Light organ photosensitivity in deep-sea shrimp may suggest a novel role in counterillumination

“…The immunohistochemistry followed, with modification, the protocol previously reported for thick invertebrate tissue sections 61,62 using commercially available G-alpha q protein antibodies (henceforth, Gq) recently reported in scallop eyes and non-ocular photosensitive tissues 63 . The anti-Gq was designed against amino acids QLNLKEYNLV (MilliporeSigma, Catalog number: 371751), which have 100% identity with the J. spinacauda Gq transcript identified from RNAseq.…”

Core–shell nanospheres behind the blue eyes of the bay scallopArgopecten irradians

“…It is unlikely that they are mineralized: an elemental analysis using EDS indicates that they do not contain detectable amounts of calcium or silicon (figure 4 a ). It is also unlikely that they are formed from pigment: images of sectioned scallop eyes obtained by light and confocal microscopy reveal that the distal halves of epithelial cells from the eyes of A. irradians (the location of the nanospheres) are transparent, whereas the proximal halves of these cells (the location of the pigment granules) are opaque [23,24]. Steps towards more fully evaluating the structural basis of eye colour in scallops will include characterizing the material composition of the nanospheres, measuring the RI (or RIs) of the nanospheres and identifying the pigment(s) housed in the pigment granules lying underneath the nanospheres.…”

Molluscan phylogenomics requires strategically selected genomes

“…Available genomes either represent interesting adaptive features that capture the public imagination (for example the scaly-foot snail and octopus, [10,30]), or species with importance for fisheries (for example oysters and scallops, [20,31]), and potentially other economic impacts such as biomineralization and bio-materials. There is a comparatively high number of genomes in Pectinoidea (Pectinida + Ostreida), due to the economic importance of these bivalves as well as the independent origin of a dispersed visual system [32]. These selections reflect a research landscape where sequencing and assembling one molluscan genome is challenging and resource intensive, and one strategically selected high-quality genome can produce a high impact publication.…”