Comparative ultrastructure of the epidermal ciliary rootlets and associated structures in species of the Nemertodermatida and Acoela (Plathelminthes)

Lundin, Kennet

doi:10.1007/s004350050033

Cited by 48 publications

(31 citation statements)

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“…Present morphological and ultrastructural evidence favours the view that the Nemertodermatida and Acoela are sister taxa, with the Nemertodermatida being the more plesiomorphic taxon of the Acoelomorpha (Tyler andRieger, 1975, 1977;Ehlers, 1985;Smith et al, 1986;Lundin and Hendelberg, 1996;Lundin, 1997Lundin, , 2000Lundin and Sterrer, 2001). Surprisingly, the two groups have been assigned widely separate positions in phylogenetic hypotheses of the Platyhelminthes based on molecular data (Carranza et al, 1997;Littlewood et al, 1999;Ruiz-Trillo et al, 1999).…”

Section: Introductionmentioning

confidence: 67%

“…The uniflagellar sperm structure, unusual for flatworms, further supported this view (Tyler andRieger, 1975, 1977;Rieger et al, 1991). Similarities between Nemertodermatida and Acoela in epidermal ciliation (Hendelberg and Hedlund, 1974;Tyler and Rieger, 1977;Lundin, 1997), intestine organisation (Tyler and Rieger, 1977), glandular and sensory structures (Ehlers, 1992) and the near absence of extracellular matrix were used by Tyler and Rieger (1977) to argue for a sister-group relationship of the two taxa. Later, Ehlers (1985) united the Acoela and the Nemertodermatida in the taxon Acoelomorpha Ehlers, 1984, within the Platyhelminthes.…”

Section: Introductionmentioning

confidence: 99%

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Basiepidermal nervous system in Nemertoderma westbladi (Nemertodermatida): GYIRFamide immunoreactivity

Raikova

Reuter

Gustafsson

et al. 2004

Zoology

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Section: Introductionmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Basiepidermal nervous system in Nemertoderma westbladi (Nemertodermatida): GYIRFamide immunoreactivity

Raikova

Reuter

Gustafsson

et al. 2004

Zoology

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“…However, using alternative methodologies and datasets, Philippe and collaborators proposed (Philippe et al, 2007;Philippe et al, 2011) that Acoela could instead be a deuterostomian group, with affinities to the Ambulacraria (Echinoderms and Hemichordates). Those authors suggested that Acoelomorpha sit within the Ambulacraria, grouped with another taxon, the Xenoturbellida, and thus erected a new monophyletic group, the Xenacoelomorpha, a classification also supported by some morphological data (Tyler and Rieger, 1975;Tyler and Rieger, 1977;Ehlers, 1985;Smith et al, 1986;Lundin and Hendelberg, 1996;Lundin, 1997;Lundin, 2000;Lundin and Sterrer, 2001). Now, these alternative views, one placing the Acoelomorpha as basal bilaterians and the other placing them within the Deuterostomia, continue to provoke debate.…”

Section: Introduction Phylogenetic Affinities Of the Members Of Xenacmentioning

confidence: 92%

The nervous system of Xenacoelomorpha: a genomic perspective

Perea-Atienza

Gavilán

Chiodin

et al. 2015

Journal of Experimental Biology

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Xenacoelomorpha is, most probably, a monophyletic group that includes three clades: Acoela, Nemertodermatida and Xenoturbellida. The group still has contentious phylogenetic affinities; though most authors place it as the sister group of the remaining bilaterians, some would include it as a fourth phylum within the Deuterostomia. Over the past few years, our group, along with others, has undertaken a systematic study of the microscopic anatomy of these worms; our main aim is to understand the structure and development of the nervous system. This research plan has been aided by the use of molecular/developmental tools, the most important of which has been the sequencing of the complete genomes and transcriptomes of different members of the three clades. The data obtained has been used to analyse the evolutionary history of gene families and to study their expression patterns during development, in both space and time. A major focus of our research is the origin of 'cephalized' (centralized) nervous systems. How complex brains are assembled from simpler neuronal arrays has been a matter of intense debate for at least 100 years. We are now tackling this issue using Xenacoelomorpha models. These represent an ideal system for this work because the members of the three clades have nervous systems with different degrees of cephalization; from the relatively simple sub-epithelial net of Xenoturbella to the compact brain of acoels. How this process of 'progressive' cephalization is reflected in the genomes or transcriptomes of these three groups of animals is the subject of this paper.

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“…Recent phylogenetic analysis maintains that together with xenoturbellids [8], which form another taxon of considerably larger marine worms, they constitute the phylogenetic group Xenacoelomorpha [9][10][11]. This relationship is also supported by morphological similarities [1,3,7,[12][13][14][15][16][17][18], for instance the ultrastructure of the ciliary tips and the system of epidermal ciliary rootlets [5,6,15,18].…”

Section: The Phylogenetic Placement Of Xenacoelomorphamentioning

confidence: 99%

Xenacoelomorpha: a case of independent nervous system centralization?

Gavilán

Perea-Atienza

Martı́nez

2016

Phil. Trans. R. Soc. B

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One contribution of 16 to a discussion meeting issue 'Homology and convergence in nervous system evolution'. Centralized nervous systems (NSs) and complex brains are among the most important innovations in the history of life on our planet. In this context, two related questions have been formulated: How did complex NSs arise in evolution, and how many times did this occur? As a step towards finding an answer, we describe the NS of several representatives of the Xenacoelomorpha, a clade whose members show different degrees of NS complexity. This enigmatic clade is composed of three major taxa: acoels, nemertodermatids and xenoturbellids. Interestingly, while the xenoturbellids seem to have a rather 'simple' NS (a nerve net), members of the most derived group of acoel worms clearly have ganglionic brains. This interesting diversity of NS architectures (with different degrees of compaction) provides a unique system with which to address outstanding questions regarding the evolution of brains and centralized NSs. The recent sequencing of xenacoelomorph genomes gives us a privileged vantage point from which to analyse neural evolution, especially through the study of key gene families involved in neurogenesis and NS function, such as G protein-coupled receptors, helixloop-helix transcription factors and Wnts. We finish our manuscript proposing an adaptive scenario for the origin of centralized NSs (brains).

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Comparative ultrastructure of the epidermal ciliary rootlets and associated structures in species of the Nemertodermatida and Acoela (Plathelminthes)

Cited by 48 publications

References 13 publications

Basiepidermal nervous system in Nemertoderma westbladi (Nemertodermatida): GYIRFamide immunoreactivity

Basiepidermal nervous system in Nemertoderma westbladi (Nemertodermatida): GYIRFamide immunoreactivity

The nervous system of Xenacoelomorpha: a genomic perspective

Xenacoelomorpha: a case of independent nervous system centralization?

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