Ontogenetic development and functioning of the anterior end of Cossura pygodactylata Jones, 1956 (Annelida: Cossuridae)

Zhadan, Anna; Vortsepneva, Elena; Tzetlin, Alexander B.

doi:10.1007/s00435-015-0282-7

Cited by 10 publications

(7 citation statements)

References 11 publications

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“…Intraepidermal nervous system is also known in species of Opheliidae, Spionidae, Syllidae, Maldaniidae, Cossuridae, Polygordiidae, Protodrillidae etc as well as basal radiation Chaetopteridae, Magelonidae and Oweniidae [47,60–62]. Also, meiobenthic forms like Polygordiidae, Protodrilidae, Dinophiilidae have intraepidermal nervous system.…”

Section: Discussionmentioning

confidence: 99%

Annelid brain and nerve cord in siboglinidRiftia pachyptila

Rimskaya-Korsakova

Galkin

Малахов

2018

Preprint

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Vestimentifera is a peculiar group of marine gutless siboglinids which has uncertain position in annelid tree. The detailed study of the fragmentary explored central nervous system of vestimentiferans and other siboglinids is requested to trace the evolution of the siboglinid group. Among all siboglinids the vestimentiferans preserve the gut rudiment what makes them a key group to homologize main cerebral structures with the ones of typical annelids, such as supra- and subesophageal commissures, cirsumesophageal connectives etc. Histologically we revealed main annelid brain structures in the compact large brain of Riftia pachyptila: circumesophageal connectives (longitudinal nerve tracts) and commissures (dorsal, supra- and subenteral commissures). Innervation of tentacles makes them homologous to peristomial palps of the rest annelids. The single nerve cord is represented by paired intraepidermal longitudinal strands associated with the ventral ciliary field in vestimentum and bearing giant axons originating from at least four pairs of perikarya. The absence of regularly positioned ganglia and lateral nerves in the nerve cord in vestimentum and trunk and presence of them in the opisthosome segments. Among siboglinids, the vestimentiferans distinguished by a large and significatly differentiated brain which is reflection of the high development of the palp apparatus. Osedax, frenulates and Sclerolinum have less developped brain. Frenulates and Sclerolinum have good ganglionization in the opisthosome, which probably indicates its high mobility. Comparative neuroanatomical analysis of the siboglinids and annelid sister clades allows us to hypothesize that the last common ancestor of siboglinids might had brain with a dorsal commissure giving rise neurite bundles to palps and paired ventral nerve cord.

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Section: Discussionmentioning

confidence: 99%

Annelid brain and nerve cord in siboglinidRiftia pachyptila

Rimskaya-Korsakova

Galkin

Малахов

2018

Preprint

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“…13C). Although the information is scarce, fabriciids could be deposit and/ or suspension feeders (61,83,85).…”

Section: Evolution Of the Tentacle Apparatusesmentioning

confidence: 99%

The non-brain anterior nerve center and tentacle crown structure of Owenia borealis (Annelida, Oweniidae): the evolution of the nervous system and tentacles in Bilateria

Rimskaya-Korsakova¹,

Dyachuk²,

Temereva³

2021

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The Oweniidae are marine annelids with many unusual features of organ system, development, morphology, and ultrastructure. Together with magelionds, oweniids have been placed within the Palaeoannelida, a sister group to all remaining annelids. The study of this group may increase our understanding of the early evolution of annelids (including their radiation and diversification) and of the morphology of the last common bilaterian ancestor. In the current research, scanning electron microscopy revealed that the tentacle apparatus consists of 10 branched arms. The tentacles are covered by monociliary cells that form a ciliar groove that extends along the oral side of the arm base. Light, confocal, and transmission electron microscopy revealed that head region contains two circular intraepidermal nerves (outer and inner) that give rise to the neurites of each tentacle, i.e., intertentacular neurites are absent. Each tentacle contains a coelomic cavity with a network of blood capillaries. Monociliar myoepithelial cells of the tentacle coelomic cavity form both the longitudinal and the circular muscles. The structure of this myoepithelium is intermediate between simple and pseudo-stratified myepithelium. Overall, tentacles lack prominent zonality, i.e., co-localization of ciliary zones, neurite bundles, and muscles. This organization, which indicates a non-specialized tentacle crown in O. borealis and other oweniids with tentacles, is probably ancestral for annelids and for all Bilateria. The outer circular nerve of O. borealis is a dorsal medullary commissure that apparently functions as an anterior nerve center and is organized at the ultrastructural level as a stratified neuroepithelium. Given the hypothesis that the anterior nerve center of the last bilateral ancestor might be a diffuse neural plexus network, these results suggest that the ultra anatomy of that plexus brain might be a stratified neuroepithelium. Alternatively, the results could reflect the simplification of structure of the anterior nerve center in some bilaterian lineages.

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“…The siboglinids have an intraepidermal paired medullary ventral nerve cord (VNC) containing giant axons (except Sclerolinum and Osedax) and associated with the ventral ciliary field. The intraepidermal position of the VNC is also known in species of Opheliidae, Spionidae, Syllidae, Maldaniidae, Cossuridae, Polygordiidae and Protodrillidae as well as in the basally branching Chaetopteridae, Magelonidae and Oweniidae [45][46][47][48]. Siboglinids are one more annelid group with the intraepidermal VNC, additionally underlining that such a condition might be part of the annelid ground pattern.…”

Section: Ventral Nerve Cord In Siboglinids and Annelidsmentioning

confidence: 99%

The neuroanatomy of the siboglinid Riftia pachyptila highlights sedentarian annelid nervous system evolution

2018

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Tracing the evolution of the siboglinid group, peculiar group of marine gutless annelids, requires the detailed study of the fragmentarily explored central nervous system of vestimentiferans and other siboglinids. 3D reconstructions of the neuroanatomy of Riftia revealed that the “brain” of adult vestimentiferans is a fusion product of the supraesophageal and subesophageal ganglia. The supraesophageal ganglion-like area contains the following neural structures that are homologous to the annelid elements: the peripheral perikarya of the brain lobes, two main transverse commissures, mushroom-like structures, commissural cell cluster, and the circumesophageal connectives with two roots which give rise to the palp neurites. Three pairs of giant perikarya are located in the supraesophageal ganglion, giving rise to the paired giant axons. The circumesophageal connectives run to the VNC. The subesophageal ganglion-like area contains a tripartite ventral aggregation of perikarya (= the postoral ganglion of the VNC) interconnected by the subenteral commissure. The paired VNC is intraepidermal, not ganglionated over most of its length, associated with the ciliary field, and comprises the giant axons. The pairs of VNC and the giant axons fuse posteriorly. Within siboglinids, the vestimentiferans are distinguished by a large and considerably differentiated brain. This reflects the derived development of the tentacle crown. The tentacles of vestimentiferans are homologous to the annelid palps based on their innervation from the dorsal and ventral roots of the circumesophageal connectives. Neuroanatomy of the vestimentiferan brains is close to the brains of Cirratuliiformia and Spionida/Sabellida, which have several transverse commissures, specific position of the giant somata (if any), and palp nerve roots (if any). The palps and palp neurite roots originally developed in all main annelid clades (basally branching, errantian and sedentarian annelids), show the greatest diversity in their number in sedentarian species. Over the course of evolution of Sedentaria, the number of palps and their nerve roots either dramatically increased (as in vestimentiferan siboglinids) or were lost.

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Ontogenetic development and functioning of the anterior end of Cossura pygodactylata Jones, 1956 (Annelida: Cossuridae)

Cited by 10 publications

References 11 publications

Annelid brain and nerve cord in siboglinidRiftia pachyptila

Annelid brain and nerve cord in siboglinidRiftia pachyptila

The non-brain anterior nerve center and tentacle crown structure of Owenia borealis (Annelida, Oweniidae): the evolution of the nervous system and tentacles in Bilateria

The neuroanatomy of the siboglinid Riftia pachyptila highlights sedentarian annelid nervous system evolution

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