Comparative neuroanatomy of ctenophores: Neural and muscular systems in Euplokamis dunlapae and related species

Moroz

2019

Preprint

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Cnidaria is the sister taxon to bilaterian animals, and therefore, represents a key reference lineage to understand early origins and evolution of the neural systems. The hydromedusa Aglantha digitale is arguably the best electrophysiologically studied jellyfish because of its system of giant axons and unique fast swimming/escape behaviors. Here, using a combination of scanning electron microscopy and immunohistochemistry together with phalloidin labeling, we systematically characterize both neural and muscular systems in Aglantha, summarizing and expanding further the previous knowledge on the microscopic neuroanatomy of this crucial reference species. We found that the majority, if not all (~2500) neurons, that are labeled by FMRFamide antibody are different from those revealed by anti-α-tubulin immunostaining, making these two neuronal markers complementary to each other and, therefore, expanding the diversity of neural elements in Aglantha with two distinct neural subsystems. Our data uncovered the complex organization of neural networks forming a functional 'annulus-type' central nervous system with three subsets of giant axons, dozen subtypes of neurons, muscles and a variety of receptors fully integrated with epithelial conductive pathways supporting swimming, escape and feeding behaviors. The observed unique adaptations within the Aglantha lineage (including giant axons innervating striated muscles) strongly support an extensive and wide-spread parallel evolution of integrative and effector systems across Metazoa.

Section: Discussioncontrasting

confidence: 99%

Section: Antibody Specificitymentioning

confidence: 99%

Atlas of the Neuromuscular System in the TrachymedusaAglantha digitale: Insights from the advanced hydrozoan

Moroz

2019

Preprint

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“…In contrast to ctenophores (Norekian & Moroz, , , ), we did not detect neuronal elements in the mesoglea of Aglantha using α‐tubulin AB). In fact, there were no neurons (labeled by α‐tubulin AB or with RFa IR) other than digestive canal neurons, lateral neurons and motor giant axons in the subumbrella region between digestive canals, unlike in scyphomedusae (Satterlie & Eichinger, ), where neuronal elements were described in large subumbrella areas between the digestive canals.…”

Section: Discussioncontrasting

confidence: 96%

“…As reported by Wehland et al ()—this rat monoclonal antibody “reacts specifically with the tyrosylated form of brain alpha‐tubulin from different species”(Wehland et al, ). We have successfully used this specific anti‐α‐tubulin antibody before on several species of ctenophores to label their nervous system (Norekian & Moroz, , , , ). In addition, we tested the specificity of immunostaining by omitting either the primary or the secondary antibody from the procedure.…”

Section: Methodsmentioning

confidence: 99%

Atlas of the neuromuscular system in the Trachymedusa Aglantha digitale: Insights from the advanced hydrozoan

J of Comparative Neurology

Moroz

2019

Self Cite

Cnidaria is the sister taxon to bilaterian animals, and therefore, represents a key reference lineage to understand early origins and evolution of the neural systems. The hydromedusa Aglantha digitale is arguably the best electrophysiologically studied jellyfish because of its system of giant axons and unique fast swimming/escape behaviors. Here, using a combination of scanning electron microscopy and immunohistochemistry together with phalloidin labeling, we systematically characterize both neural and muscular systems in Aglantha, summarizing and expanding further the previous knowledge on the microscopic neuroanatomy of this crucial reference species. We found that the majority, if not all (~2,500) neurons, that are labeled by FMRFamide antibody are different from those revealed by anti‐α‐tubulin immunostaining, making these two neuronal markers complementary to each other and, therefore, expanding the diversity of neural elements in Aglantha with two distinct neural subsystems. Our data uncovered the complex organization of neural networks forming a functional “annulus‐type” central nervous system with three subsets of giant axons, dozen subtypes of neurons, muscles, and a variety of receptors fully integrated with epithelial conductive pathways supporting swimming, escape and feeding behaviors. The observed unique adaptations within the Aglantha lineage (including giant axons innervating striated muscles) strongly support an extensive and wide‐spread parallel evolution of integrative and effector systems across Metazoa.

“…In either case no labeling was detected. This anti-tubulin antibody has been used to label the neural systems in the hydrozoan Aglantha digitale (Norekian and Moroz, 2020b) and several ctenophore species (Norekian and Moroz, 2016, 2019a, 2019b, 2020a.…”

Section: Immunocytochemistrymentioning

confidence: 99%

Structure and function of the nervous system in nectophores of the siphonophore Nanomia bijuga

Journal of Experimental Biology

Meech

2020

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i) Although Nanomia’s bell-shaped nectophores are specialized for locomotion, their cellular elements and complex nerve structures suggest they have multiple subsidiary functions.ii) The main nerve complex is a nerve ring at the base of the bell, an adjacent columnar-shaped matrix plus two associated nerve projections. An upper nerve tract may provide a sensory input while a lower nerve tract connects with the rest of the colony apparently via a cluster of nerve cells at the stem.iii) The structure of the extensively innervated “flask cells” located around the bell margin suggests a secretory function.iv) The numerous nematocytes present on exposed ridges of the nectophore appear to have an entangling rather than a penetrating role.v) Movements of the velum, produced by contraction of the Claus’ muscle system during backwards swimming, can be elicited by electrical stimulation of the surface epithelium even when the major nerve tracts serving the nerve ring have been destroyed (confirming Mackie, 1964).vi) Epithelial impulses generated by electrical stimulation elicit slow potentials and action potentials in the velum musculature. The slow potentials arise at different sites around the velum and give rise to action potentials in contracting Claus’ muscle fibres.vii) A synaptic rather than an electrotonic model can more readily account for the time course of the slow potentials.viii) During backward swimming radial muscle fibres in the endoderm contract isometrically providing the Claus’ fibres with a firm foundation.