Homology of prostomial and pharyngeal structures in eunicida (Annelida) based on innervation and morphological similarities

Zanol, Joana

doi:10.1002/jmor.10843

Cited by 13 publications

(31 citation statements)

References 41 publications

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“…the diameter of the palps, runs from their distal tips to the anterior of the prostomium (e.g., Figures 1B, 1C, 2A-2C, S1D, S1G, and S2A). An even darker, thinner carbon-rich structure traces the same pathway within this channel ( Figures 1C, 2A, 2C, and S1D-S1F), consistent with the neural architecture of many extant polychaetes, with neural pathways converging on a dense central neuropil region in the prostomium [9][10][11][12]. The larger, lightly shaded pathway within the palps is consistent with a coelomic cavity [8] (Figure 3).…”

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confidence: 63%

A New Burgess Shale Polychaete and the Origin of the Annelid Head Revisited

Nanglu

Caron

2018

Current Biology

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Annelida is one of the most speciose (∼17,000 species) and ecologically successful phyla. Key to this success is their flexible body plan with metameric trunk segments and bipartite heads consisting of a prostomium bearing sensory structures and a peristomium containing the mouth. The flexibility of this body plan has traditionally proven problematic for reconstructing the evolutionary relationships within the Annelida. Although recent phylogenies have focused on resolving the interrelationships of the crown group [1-3], many questions remain regarding the early evolution of the annelid body plan itself, including the origin of the head [4]. Here we describe an abundant and exceptionally well-preserved polychaete with traces of putative neural and vascular tissues for the first time in a fossilized annelid. Up to three centimeters in length, Kootenayscolex barbarensis gen. et sp. nov. is described based on more than 500 specimens from Marble Canyon [5] and several specimens from the original Burgess Shale site (both in British Columbia, Canada). K. barbarensis possesses biramous parapodia along the trunk, bearing similar elongate and thin notochaetae and neurochaetae. A pair of large palps and one median antenna project from the anteriormost dorsal margin of the prostomium. The mouth-bearing peristomium bears neuropodial chaetae, a condition that is also inferred in Canadia and Burgessochaeta from the Burgess Shale, suggesting a chaetigorous origin for the peristomial portion of the head and a secondary loss of peristomial parapodia and chaetae in modern polychaetes.

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Section: (Legend Continued On Next Page)supporting

confidence: 63%

A New Burgess Shale Polychaete and the Origin of the Annelid Head Revisited

Nanglu

Caron

2018

Current Biology

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“…Features of prostomium and pharynx (characters 6–16) were especially informative for basal relationships in the tree and in supporting the monophyly of Eunicidae. Eunicidan families in general have consistently different anterior ends, and robust hypotheses of primary homology were possible by the examination of similarities in the innervation (Pruvot & Racovitza ; Haffner ; Orrhage ; Zanol ). Two of these characters yielded the only unique synapomorphies of Eunicidae that are consistently present in all species of the family examined here (with exception of Lysidice unicornis (Schmarda, 1861) which lacks dorsal buccal lip), dorsal buccal lip fused to the dorsal side of the prostomium (Fig.…”

Section: Discussionmentioning

confidence: 99%

Reconciling taxonomy and phylogeny in the bristleworm family Eunicidae (polychaete, Annelida)

2013

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Zanol, J., Halanych, K.M., Fauchald, K. (2014). Reconciling taxonomy and phylogeny in the bristleworm family Eunicidae (polychaete, Annelida). -Zoologica Scripta, 43, 79-100. Eunicid annelids inhabit diverse marine habitats worldwide, have ecological and economic importance and have been pictured in the news as giant predator worms. They compose a traditional stable taxon recently supported as monophyletic but characterized by plesiomorphies. Most genera within the family have been recovered as paraphyletic in previous studies. We present a phylogenetic hypothesis for eunicid based on molecular (COI, 16S rDNA, 18S rDNA) and morphological data (213 characters), including an explicit attempt to account for serial homology. Eunicidae as well as monophyletic genera Marphysa sensu stricto and Lysidice is redefined based on synapomorphies. Nematonereis is synonymized to Lysidice. Leodice and Nicidion are resurrected to name monophyletic groups including species previously included in Eunice and Marphysa sensu lato. Traditional diagnostic characters such as the absence/presence of peristomial cirri, lateral antennae and branchiae are homoplasies and not informative at the generic level. Different coding of traditional characters (i.e. articulation of prostomial appendages) and novel characters of prostomial features and regionalization of the body support the monophyly of the family and genera level clades. Thus, the phylogenetic hypothesis presented here and the evolution of characters provided background information for taxonomic changes yielding evolutionary meaningful classification and diagnoses for the family and genera.

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“…The appendages are innervated from different tracts inside or outside the brain proper; these innervation patterns were used to homologize the different head appendages as palps or antennae albeit abandoning the term tentacles or using it as a neutral term without any homology implications. The number and position of these various tracts emanating from the ventral and dorsal roots of the circumesophageal connectives and their commissures in the brain have been compared across a broad range of annelid taxa [1, 26, 27], although their evolutionary history and phylogenetic significance within Annelida have never been properly tested. Despite this fact, Müller [28] proposed a generalized scheme of the anterior central nervous system of Annelida.…”

Section: Introductionmentioning

confidence: 99%

The central nervous system of Oweniidae (Annelida) and its implications for the structure of the ancestral annelid brain

et al. 2019

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BackgroundRecent phylogenomic analyses congruently reveal a basal clade which consists of Oweniidae and Mageloniidae as sister group to the remaining Annelida. These results indicate that the last common ancestor of Annelida was a tube-dwelling organism. They also challenge traditional evolutionary hypotheses of different organ systems, among them the nervous system. In textbooks the central nervous system is described as consisting of a ganglionic ventral nervous system and a dorsally located brain with different tracts that connect certain parts of the brain to each other. Only limited information on the fine structure, however, is available for Oweniidae, which constitute the sister group (possibly together with Magelonidae) to all remaining annelids.ResultsThe brain of Oweniidae is ring- shaped and basiepidermal. Ganglia, higher brain centers or complex sensory organs do not exist; instead the central nervous system is medullary. Posterior to the brain the ventral medullary cord arises directly from the ventral region of the brain in Myriowenia sp. while in Owenia fusiformis two medullary cords arise perpendicular to the brain ring, extend caudally and fuse posterior. The central nervous system is composed of a central neuropil and surrounding somata of the neurons. According to ultrastructural and histological data only one type of neuron is present in the central nervous system.ConclusionThe central nervous system of Oweniidae is the simplest in terms of enlargement of the dorsal part of the brain and neuron distribution found among Annelida. Our investigation suggests that neither ganglia nor commissures inside the brain neuropil or clusters of polymorphic neurons were present in the annelid stem species. These structures evolved later within Annelida, most likely in the stem lineage of Amphinomidae, Sipuncula and Pleistoannelida. Palps were supposedly present in the last common ancestor of annelids and innervated by two nerves originating in the dorsal part of the brain. A broader comparison with species of each major spiralian clade shows the medullary nervous system to be a common feature and thus possibly representing the ancestral state of the spiralian nervous system. Moreover, ganglia and clusters of polymorphic neurons seemingly evolved independently in the compared taxa of Spiralia and Annelida.Electronic supplementary materialThe online version of this article (10.1186/s12983-019-0305-1) contains supplementary material, which is available to authorized users.

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Homology of prostomial and pharyngeal structures in eunicida (Annelida) based on innervation and morphological similarities

Cited by 13 publications

References 41 publications

A New Burgess Shale Polychaete and the Origin of the Annelid Head Revisited

A New Burgess Shale Polychaete and the Origin of the Annelid Head Revisited

Reconciling taxonomy and phylogeny in the bristleworm family Eunicidae (polychaete, Annelida)

The central nervous system of Oweniidae (Annelida) and its implications for the structure of the ancestral annelid brain

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