Ultrastructural evidence for a sensory-motor neuron in Ctenophora

Hernandez‐Nicaise, Mari‐Luz

doi:10.1016/0040-8166(74)90021-4

Cited by 52 publications

(37 citation statements)

References 9 publications

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“…Most likely, the revealed polygonal lattice results from a growth pattern where each polygon encircles a group of epithelial cells, even in very young larvae (Hernandez-Nicaise, 1991). In addition, there are intramesogleal nerve fibers and neurons (Hernandez-Nicaise, 1991;HernandezNicaise, 1973a;Hernandez-Nicaise, 1973b;Hernandez-Nicaise, 1973c;Hernandez-Nicaise, 1974), also visualized using antibodies against tubulins ( Fig. 3C) Moroz et al, 2014).…”

Section: Enigmatic Ctenophore Neuronsmentioning

confidence: 99%

“…The ctenophore asymmetrical synapse is structurally quite organized, forming a so-called 'presynaptic triad' (HernandezNicaise, 1991;Hernandez-Nicaise, 1973c;Hernandez-Nicaise, 1974). Each presynaptic element contains a tripartite complex of organelles: a single layer of synaptic vesicles lining the presynaptic membrane, a cistern of agranular endoplasmic reticulum just above the row of vesicles, followed by one or several mitochondria ( Fig.…”

Section: Tripartite Synapses In Ctenophoresmentioning

confidence: 99%

“…Different comb rows can beat synchronously or asynchronously, controlling various behaviors during prey capture or escape responses. Ciliated cells are under neuronal (primarily inhibitory) controls, with multiple different types of synapses described by electron microscopy (Hernandez-Nicaise, 1968;Hernandez-Nicaise, 1973a;HernandezNicaise, 1973b;Hernandez-Nicaise, 1973c;Hernandez-Nicaise, 1974;Hernandez-Nicaise and Amsellem, 1980;Hernandez-Nicaise et al, 1982;Horridge, 1965c;Horridge et al, 1962;Horridge and Mackay, 1964). The frequency of beating can be accelerated, decreased, arrested or even completely reversed, presumably by neuronal-mediated stimuli; high Mg 2+ , which suppresses synaptic transmission, eliminates these regulatory inputs (Horridge, 1974;Tamm, 1982).…”

Section: Neural Systems In Ctenophoresmentioning

confidence: 99%

“…They are quite diverse, with multiple recognized synapses between neurons and their potential effectors (Hernandez-Nicaise, 1991;Hernandez-Nicaise, 1973a;Hernandez-Nicaise, 1973b;HernandezNicaise, 1973c;Hernandez-Nicaise, 1974) such as ciliated and gland cells, muscles, colloblasts, sensory structures and photocytes (a type of light-emitting cell located in the meridional canals and responsible for bioluminescence, with a few exceptions such as Pleurobrachia). A unique feature of ctenophore neurons is the absence of morphologically recognized polarity in these cells: any part of the neuronal membrane can form a synapse into other cells, including symmetrical (two-way) synapses (Horridge et al, 1962) where opposing presynaptic triads face each other (Fig.…”

Section: Electron Microscopy Of Ctenophore Neurons and Synapsesmentioning

confidence: 99%

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Convergent evolution of neural systems in ctenophores

Moroz

2015

Journal of Experimental Biology

117

139

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Neurons are defined as polarized secretory cells specializing in directional propagation of electrical signals leading to the release of extracellular messengers -features that enable them to transmit information, primarily chemical in nature, beyond their immediate neighbors without affecting all intervening cells en route. Multiple origins of neurons and synapses from different classes of ancestral secretory cells might have occurred more than once during ~600 million years of animal evolution with independent events of nervous system centralization from a common bilaterian/cnidarian ancestor without the bona fide central nervous system. Ctenophores, or comb jellies, represent an example of extensive parallel evolution in neural systems. First, recent genome analyses place ctenophores as a sister group to other animals. Second, ctenophores have a smaller complement of pan-animal genes controlling canonical neurogenic, synaptic, muscle and immune systems, and developmental pathways than most other metazoans. However, comb jellies are carnivorous marine animals with a complex neuromuscular organization and sophisticated patterns of behavior. To sustain these functions, they have evolved a number of unique molecular innovations supporting the hypothesis of massive homoplasies in the organization of integrative and locomotory systems. Third, many bilaterian/cnidarian neuron-specific genes and 'classical' neurotransmitter pathways are either absent or, if present, not expressed in ctenophore neurons (e.g. the bilaterian/cnidarian neurotransmitter, γ-amino butyric acid or GABA, is localized in muscles and presumed bilaterian neuronspecific RNA-binding protein Elav is found in non-neuronal cells). Finally, metabolomic and pharmacological data failed to detect either the presence or any physiological action of serotonin, dopamine, noradrenaline, adrenaline, octopamine, acetylcholine or histamineconsistent with the hypothesis that ctenophore neural systems evolved independently from those in other animals. Glutamate and a diverse range of secretory peptides are first candidates for ctenophore neurotransmitters. Nevertheless, it is expected that other classes of signal and neurogenic molecules would be discovered in ctenophores as the next step to decipher one of the most distinct types of neural organization in the animal kingdom.

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Section: Enigmatic Ctenophore Neuronsmentioning

confidence: 99%

Section: Tripartite Synapses In Ctenophoresmentioning

confidence: 99%

Section: Neural Systems In Ctenophoresmentioning

confidence: 99%

Section: Electron Microscopy Of Ctenophore Neurons and Synapsesmentioning

confidence: 99%

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Convergent evolution of neural systems in ctenophores

Moroz

2015

Journal of Experimental Biology

117

139

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“…Two other kinds of shorter projections from epithelial cells are widely distributed over the epidermis of a variety of ctenophores: non-motile cilia with a remarkable, onion-like root structure, and thick pegs containing a large bundle of actin filaments (5, 6, 9 -15). Both types of projections may occur on the same epithelial cell (11,13). Ultrastructural evidence for synaptic contacts of these cells onto adjacent neurites and gland cells indicates that the cells are sensory receptors (11,12).…”

Section: It Is Rare Nowadays To Find Something That Nobody Has Seen Bmentioning

confidence: 99%

Novel Structures Associated with Presumed Photoreceptors in the Aboral Sense Organ of Ctenophores

Tamm

2016

The Biological Bulletin

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Dynamic control of reversible cell adhesion and actin cytoskeleton in the mouth ofBero�

Tamm

1999

Microsc. Res. Tech.

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Cell‐cell adhesion in the various types of intercellular junctions of differentiated tissues is relatively stable and permanent. In migrating cells of embryos, or in wound closure, inflammatory responses and tumors of adult tissues, however, bonds between cells are made and broken and made again, i.e., cell‐cell adhesions are transient and reversible. These nonjunctional contacts lack the organized structure of intercellular junctions, but may initiate their tissue‐specific formation during development. Investigation of dynamic, nonjunctional cell‐cell adhesions has been hampered by the asynchronous and heterogeneous distribution of these transient contacts among groups of moving cells. We recently discovered a novel system of reversible cell adhesion in a differentiated tissue that overcomes this difficulty. Here I review our current knowledge of this system, particularly its unique experimental advantages for investigating the mechanisms and control of dynamic cell adhesion. Microsc Res Tech 44:293–303, 1999. © 1999 Wiley‐Liss, Inc.

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Ultrastructural evidence for a sensory-motor neuron in Ctenophora

Cited by 52 publications

References 9 publications

Convergent evolution of neural systems in ctenophores

Convergent evolution of neural systems in ctenophores

Novel Structures Associated with Presumed Photoreceptors in the Aboral Sense Organ of Ctenophores

Dynamic control of reversible cell adhesion and actin cytoskeleton in the mouth ofBero�

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