Structure of the glial cells in the nervous system of parasitic and free-living flatworms

Biserova, N. M.; Гордеев, И. И.; Korneva, Janetta V.; Сальникова, М. М.

doi:10.1134/s106235901003009x

Cited by 12 publications

(14 citation statements)

References 20 publications

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“…The pattern of the ''haves'' and ''have nots'' of glia supports the idea that evolving glia is a necessity for a complex nervous system, even one as simple as that of a parasitic cestode (Biserova et al, 2010). This complicates the picture because it means that the pressure for parallel evolution of glia is strong, and it should be expected that lines lacking glia will independently evolve offshoots capitalizing on its advantages, to build a more capable nervous system.…”

Section: Discussion: When Where and Why Glia?mentioning

confidence: 73%

The evolutionary origins of glia

Hartline

2011

Glia

108

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The evolutionary origins of glia are lost in time, as soft tissues rarely leave behind fossil footprints, and any molecular footprints they might have been left we have yet to decipher. Nevertheless, because of the growing realization of the importance glia plays in the development and functioning of the nervous system, lessons we can draw about commonalities among different taxa (including vertebrates) brought about either from a common origin, or from common adaptational pressures, shed light on the roles glia play in all nervous systems. The Acoelomorpha, primitive interstitial flatworms with very simple cellular organization and currently at the base of the bilaterian phylogeny, possess glia-like cells. If they indeed represent the ancestors of all other Bilateria, then it is possible that all glias derive from a common ancestor. However, basal taxa lacking convincing glia are found in most major phyletic lines: urochordates, hemichordates, bryozoans, rotifers, and basal platyhelminths. With deep phylogenies currently in flux, it is equally possible that glia in several lines had different origins. If developmental patterns are any indication, glia evolved from ectodermal cells, possibly from a mobile lineage, and even possibly independently in different regions of the body. As to what functions might have brought about the evolution of glia, by-product removal, structural support, phagocytic needs, developmental programming, and circuit modulation may be the more likely. Explaining possible cases of glial loss is more difficult, as once evolved, glia appears to keep inventing new functions, giving it continued value even after the original generative need becomes obsolete. Among all the uncertainties regarding the origin of glia, one thing is certain: that our ideas about those origins will change with every rearrangement in deep phylogeny and with continued advances in invertebrate molecular and developmental areas.

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Section: Discussion: When Where and Why Glia?mentioning

confidence: 73%

The evolutionary origins of glia

Hartline

2011

Glia

108

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“…erinaceus and described as a part of proboscis and bulbar nerves (Biserova, 2002, 2004, 2008a, 2008b). Four bulbar nerves are innervating the musculature of hydroprotractors and found in all trypanorhynch species studied (Rees, 1950, 1988; Biserova, 2002, 2004, 2008a, 2008b; Biserova, Gordeev, Korneva, & Salnikova, 2010; Biserova & Korneva, 2012). The morphological position of the bulbar nerves containing the GAs differs among species.…”

Section: Discussionmentioning

confidence: 99%

The brain structure of selected trypanorhynch tapeworms

Biserova

Korneva

Polyakova

2020

Journal of Morphology

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The brain architecture in four species of tapeworms from the order Trypanorhyncha has been studied. In all species, the brain consists of paired anterior and lateral lobes, and an unpaired central lobe. The anterior lobes connect by dorsal and ventral semicircular commissures; the central and lateral lobes connect by a median and an Xshaped crisscross commissure. In the center of the brain, five well-developed compact neuropils are present. The brain occupies a medial position in the scolex pars bothrialis. The ventral excretory vessels are situated outside the lateral lobes of the brain; the dorsal excretory vessels are located inside the brain and dorsal to the median commissure. The brain gives rize four anterior proboscis nerves and four posterior bulbar nerves with myelinated giant axons (GAs). The cell bodies of the GAs are located within the X-commissure and in the bulbar nerves. Highly developed serotonergic neuropils are present in the anterior and lateral lobes; numerous 5-HT neurons are found in the brain lobes including the central unpaired lobe. The X-cross commissure consists of the α-tub-immunoreactive and 5-HT-IR neurites. Eight ultrastructural types of neurons were found in the brain of the three species investigated. In addition, different types of synapses were present in the neuropils. Glial cells ensheath the brain lobes, the neuropils, the GAs, and the bulbar nerves. Glia cell processes form complex branching patterns of thin cytoplasmic sheets sandwiched between adjacent neural processes and filling the space between neurons. Multilayer myelin-like envelopes and a mesaxon-like structure have been found in Trypanorhyncha nervous system. We compared the brain architecture of Trypanorhyncha with that of an early basal cestode taxon, that is, Diphyllobothriidea, and present a hypothesis about the homology of the anterior brain lobes in order Trypanorhyncha; and the lateral lobes and median commissure are homologous brain structures within Eucestoda.

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“…It is difficult for us to tell from the micrographs whether they are a type of spinule or some unique structure. In addition, representatives of all of the major groups of flatworms including planarians, flukes, and tapeworms have thin glial processes that extend into invaginations in some neuron cell bodies and nerve processes (Sukhdeo and Sukhdeo 1994; Mäntylä et al 1998; Biserova 2008; Biserova et al 2010). Similar glial invaginating projections may be present also in the brain of an acanthocephalan worm, although the glial origins of these are not clearly described (Budziakowski and Mettrick 1985).…”

Section: Synapse/neuronal Invaginating Projections In the Simplest Anmentioning

confidence: 99%

Structure, Distribution, and Function of Neuronal/Synaptic Spinules and Related Invaginating Projections

et al. 2015

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Neurons and especially their synapses often project long thin processes that can invaginate neighboring neuronal or glial cells. These “invaginating projections” can occur in almost any combination of postsynaptic, presynaptic, and glial processes. Invaginating projections provide a precise mechanism for one neuron to communicate or exchange material exclusively at a highly localized site on another neuron, e.g., to regulate synaptic plasticity. The best-known types are postsynaptic projections called “spinules” that invaginate into presynaptic terminals. Spinules seem to be most prevalent at large very active synapses. Here, we present a comprehensive review of all kinds of invaginating projections associated with both neurons in general and more specifically with synapses; we describe them in all animals including simple, basal metazoans. These structures may have evolved into more elaborate structures in some higher animal groups exhibiting greater synaptic plasticity. In addition to classic spinules and filopodial invaginations, we describe a variety of lesser-known structures such as amphid microvilli, spinules in giant mossy terminals and en marron/brush synapses, the highly specialized fish retinal spinules, the trophospongium, capitate projections, and fly gnarls, as well as examples in which the entire presynaptic or postsynaptic process is invaginated. These various invaginating projections have evolved to modify the function of a particular synapse, or to channel an effect to one specific synapse or neuron, without affecting those nearby. We discuss how they function in membrane recycling, nourishment, and cell signaling and explore how they might change in aging and disease.

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Structure of the glial cells in the nervous system of parasitic and free-living flatworms

Cited by 12 publications

References 20 publications

The evolutionary origins of glia

The evolutionary origins of glia

The brain structure of selected trypanorhynch tapeworms

Structure, Distribution, and Function of Neuronal/Synaptic Spinules and Related Invaginating Projections

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