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Olson CS, Schulz NG, Ragsdale CW. Neuronal segmentation in cephalopod arms. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.29.596333. [PMID: 38853825 PMCID: PMC11160704 DOI: 10.1101/2024.05.29.596333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
The prehensile arms of the cephalopod are among these animals most remarkable features, but the neural circuitry governing arm and sucker movements remains largely unknown. We studied the neuronal organization of the adult axial nerve cord (ANC) of Octopus bimaculoides with molecular and cellular methods. The ANCs, which lie in the center of every arm, are the largest neuronal structures in the octopus, containing four times as many neurons as found in the central brain. In transverse cross section, the cell body layer (CBL) of the ANC wraps around its neuropil (NP) with little apparent segregation of sensory and motor neurons or nerve exits. Strikingly, when studied in longitudinal sections, the ANC is segmented. ANC neuronal cell bodies form columns separated by septa, with 15 segments overlying each pair of suckers. The segments underlie a modular organization to the ANC neuropil: neuronal cell bodies within each segment send the bulk of their processes directly into the adjoining neuropil, with some reaching the contralateral side. In addition, some nerve processes branch upon entering the NP, forming short-range projections to neighboring segments and mid-range projections to the ANC segments of adjoining suckers. The septa between the segments are employed as ANC nerve exits and as channels for ANC vasculature. Cellular analysis establishes that adjoining septa issue nerves with distinct fiber trajectories, which across two segments (or three septa) fully innervate the arm musculature. Sucker nerves also use the septa, setting up a nerve fiber "suckerotopy" in the sucker-side of the ANC. Comparative anatomy suggests a strong link between segmentation and flexible sucker-laden arms. In the squid Doryteuthis pealeii, the arms and the sucker-rich club of the tentacles have segments, but the sucker-poor stalk of the tentacles does not. The neural modules described here provide a new template for understanding the motor control of octopus soft tissues. In addition, this finding represents the first demonstration of nervous system segmentation in a mollusc.
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Affiliation(s)
- Cassady S. Olson
- Committee on Computational Neuroscience, The University of Chicago, Chicago, IL 60637
| | - Natalie Grace Schulz
- Committee on Development, Regeneration and Stem Cell Biology, The University of Chicago, Chicago, IL 60637
| | - Clifton W. Ragsdale
- Committee on Development, Regeneration and Stem Cell Biology, The University of Chicago, Chicago, IL 60637
- Department of Neurobiology, The University of Chicago, Chicago, IL 60637
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Wang ZY, Ragsdale CW. Signaling Ligand Heterogeneities in the Peduncle Complex of the Cephalopod Mollusc Octopus bimaculoides. BRAIN, BEHAVIOR AND EVOLUTION 2024:1-13. [PMID: 38688255 DOI: 10.1159/000539128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 04/16/2024] [Indexed: 05/02/2024]
Abstract
INTRODUCTION The octopus peduncle complex is an agglomeration of neural structures with remarkably diverse functional roles. The complex rests on the optic tract, between the optic lobe and the central brain, and comprises the peduncle lobe proper, the olfactory lobe, and the optic gland. The peduncle lobe regulates visuomotor behaviors, the optic glands control sexual maturation and maternal death, and the olfactory lobe is thought to receive input from the olfactory organ. Recent transcriptomic and metabolomic studies have identified candidate peptide and steroid ligands in the Octopus bimaculoides optic gland. METHODS With gene expression for these ligands and their biosynthetic enzymes, we show that optic gland neurochemistry extends beyond the traditional optic gland secretory tissue and into lobular territories. RESULTS A key finding is that the classically defined olfactory lobe is itself a heterogeneous territory and includes steroidogenic territories that overlap with cells expressing molluscan neuropeptides and the synthetic enzyme dopamine beta-hydroxylase. CONCLUSION Our study reveals the neurochemical landscape of the octopus peduncle complex, highlighting the unexpected overlap between traditionally defined regions.
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Affiliation(s)
- Z Yan Wang
- Department of Psychology, University of Washington, Seattle, Washington, USA
- Department of Biology, University of Washington, Seattle, Washington, USA
- Department of Neurobiology, University of Chicago, Chicago, Illinois, USA
| | - Clifton W Ragsdale
- Department of Neurobiology, University of Chicago, Chicago, Illinois, USA
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Derby CD, Caprio J. What are olfaction and gustation, and do all animals have them? Chem Senses 2024; 49:bjae009. [PMID: 38422390 DOI: 10.1093/chemse/bjae009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Indexed: 03/02/2024] Open
Abstract
Different animals have distinctive anatomical and physiological properties to their chemical senses that enhance detection and discrimination of relevant chemical cues. Humans and other vertebrates are recognized as having 2 main chemical senses, olfaction and gustation, distinguished from each other by their evolutionarily conserved neuroanatomical organization. This distinction between olfaction and gustation in vertebrates is not based on the medium in which they live because the most ancestral and numerous vertebrates, the fishes, live in an aquatic habitat and thus both olfaction and gustation occur in water and both can be of high sensitivity. The terms olfaction and gustation have also often been applied to the invertebrates, though not based on homology. Consequently, any similarities between olfaction and gustation in the vertebrates and invertebrates have resulted from convergent adaptations or shared constraints during evolution. The untidiness of assigning olfaction and gustation to invertebrates has led some to recommend abandoning the use of these terms and instead unifying them and others into a single category-chemical sense. In our essay, we compare the nature of the chemical senses of diverse animal types and consider their designation as olfaction, oral gustation, extra-oral gustation, or simply chemoreception. Properties that we have found useful in categorizing chemical senses of vertebrates and invertebrates include the nature of peripheral sensory cells, organization of the neuropil in the processing centers, molecular receptor specificity, and function.
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Affiliation(s)
- Charles D Derby
- Neuroscience Institute, Georgia State University, Atlanta, GA, United States
| | - John Caprio
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, United States
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Voss G, Rosenthal JJC. High-level RNA editing diversifies the coleoid cephalopod brain proteome. Brief Funct Genomics 2023; 22:525-532. [PMID: 37981860 DOI: 10.1093/bfgp/elad034] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Revised: 07/20/2023] [Accepted: 07/25/2023] [Indexed: 11/21/2023] Open
Abstract
Coleoid cephalopods (octopus, squid and cuttlefish) have unusually complex nervous systems. The coleoid nervous system is also the only one currently known to recode the majority of expressed proteins through A-to-I RNA editing. The deamination of adenosine by adenosine deaminase acting on RNA (ADAR) enzymes produces inosine, which is interpreted as guanosine during translation. If this occurs in an open reading frame, which is the case for tens of thousands of editing sites in coleoids, it can recode the encoded protein. Here, we describe recent findings aimed at deciphering the mechanisms underlying high-level recoding and its adaptive potential. We describe the complement of ADAR enzymes in cephalopods, including a recently discovered novel domain in sqADAR1. We further summarize current evidence supporting an adaptive role of high-level RNA recoding in coleoids, and review recent studies showing that a large proportion of recoding sites is temperature-sensitive. Despite these new findings, the mechanisms governing the high level of RNA recoding in coleoid cephalopods remain poorly understood. Recent advances using genome editing in squid may provide useful tools to further study A-to-I RNA editing in these animals.
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Affiliation(s)
- Gjendine Voss
- The Eugene Bell Center, The Marine Biological Laboratory, 7 MBL Street, Woods Hole MA 02543, United States
| | - Joshua J C Rosenthal
- The Eugene Bell Center, The Marine Biological Laboratory, 7 MBL Street, Woods Hole MA 02543, United States
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Allard CA, Valencia-Montoya WA, Bellono NW. Cephalopod chemotactile sensation. Curr Biol 2023; 33:R1081-R1082. [PMID: 37875087 PMCID: PMC11055638 DOI: 10.1016/j.cub.2023.08.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
Allard et al. describe the remarkable 'taste by touch' abilities of cephalopods, in particular octopuses.
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Affiliation(s)
- Corey A Allard
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Wendy A Valencia-Montoya
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA
| | - Nicholas W Bellono
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
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Marx V. Welcome to the nursery. Nat Methods 2023:10.1038/s41592-023-01902-2. [PMID: 37202538 DOI: 10.1038/s41592-023-01902-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
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Reardon S. How octopuses taste with their arms. Nature 2023:10.1038/d41586-023-01010-3. [PMID: 37045964 DOI: 10.1038/d41586-023-01010-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
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Allard CAH, Kang G, Kim JJ, Valencia-Montoya WA, Hibbs RE, Bellono NW. Structural basis of sensory receptor evolution in octopus. Nature 2023; 616:373-377. [PMID: 37045920 PMCID: PMC10228259 DOI: 10.1038/s41586-023-05822-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 02/10/2023] [Indexed: 04/14/2023]
Abstract
Chemotactile receptors (CRs) are a cephalopod-specific innovation that allow octopuses to explore the seafloor via 'taste by touch'1. CRs diverged from nicotinic acetylcholine receptors to mediate contact-dependent chemosensation of insoluble molecules that do not readily diffuse in marine environments. Here we exploit octopus CRs to probe the structural basis of sensory receptor evolution. We present the cryo-electron microscopy structure of an octopus CR and compare it with nicotinic receptors to determine features that enable environmental sensation versus neurotransmission. Evolutionary, structural and biophysical analyses show that the channel architecture involved in cation permeation and signal transduction is conserved. By contrast, the orthosteric ligand-binding site is subject to diversifying selection, thereby mediating the detection of new molecules. Serendipitous findings in the cryo-electron microscopy structure reveal that the octopus CR ligand-binding pocket is exceptionally hydrophobic, enabling sensation of greasy compounds versus the small polar molecules detected by canonical neurotransmitter receptors. These discoveries provide a structural framework for understanding connections between evolutionary adaptations at the atomic level and the emergence of new organismal behaviour.
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Affiliation(s)
- Corey A H Allard
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Guipeun Kang
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jeong Joo Kim
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Wendy A Valencia-Montoya
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
- Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA
| | - Ryan E Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Department of Neurobiology, University of California, San Diego, La Jolla, CA, USA.
| | - Nicholas W Bellono
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA.
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