An Anatomical Description of a Miniaturized Acorn Worm (Hemichordata, Enteropneusta) with Asexual Reproduction by Paratomy

Worsaae, Katrine; Sterrer, Wolfgang; Kaul-Strehlow, Sabrina; Hay‐Schmidt, Anders; Giribet, Gonzalo

doi:10.1371/journal.pone.0048529

Cited by 53 publications

(66 citation statements)

References 68 publications

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“…The zooids of one colony live in tubular coenecia and stay interconnected by the stalk throughout lifetime (Lankester 1884 ; Hyman 1959 ). (Osborn et al 2012 ;Worsaae et al 2012 ). The position of Xenacoelomorpha is debated and not shown here (Hejnol et al 2009 ;Philippe et al 2011 ) …”

Section: Systematics and Phylogenetic Relationshipsmentioning

confidence: 88%

“…Enteropneusta comprises less than 110 described species of worm-shaped animals (Cameron 2005 ) ranging from 0.5 mm to more than 2 m in size (Hyman 1959 ;Worsaae et al 2012 ). Acorn worms are usually ground dwellers that live in muddy or sandy sediments; only few are known to be associated with the undersides of rocks (Spengel 1893 ;Hyman 1959 ;Cameron 2005 ).…”

Section: Enteropneustamentioning

confidence: 99%

“…Harrimaniidae includes the smallest representative of an acorn worm described so far, Meioglossus psammophilus (Worsaae et al 2012 ), with less than 1 mm in length. This taxon possesses the simplest anatomy, as their members lack liver sacs as well as genital wings within the dorsal trunk region (Fig.…”

Section: Systematics and Phylogenetic Relationshipsmentioning

confidence: 99%

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Hemichordata

Kaul-Strehlow¹,

Röttinger²

2015

Evolutionary Developmental Biology of Invertebrates 6

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Section: Systematics and Phylogenetic Relationshipsmentioning

confidence: 88%

Section: Enteropneustamentioning

confidence: 99%

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Hemichordata

Kaul-Strehlow¹,

Röttinger²

2015

Evolutionary Developmental Biology of Invertebrates 6

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“…Dramatic differences in organismal size, and especially the development of a secreted housing construction, the tubarium (rhabdosome) generally differentiate the Pterobranchia from the worm-like Enteropneusta; however, extremely small members of the Enteropneusta have been discovered recently (Worsaae et al 2012). All Graptolithina are also colonial, but the Cephalodiscida have a pseudo-colonial life style with unconnected mature zooids asexually budding new zooids from the short stalk (Fig.…”

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confidence: 99%

The classification of the Pterobranchia (Cephalodiscida and Graptolithina)

Maletz¹

2014

Bull. Geosci.

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This paper presents a proposal for a taxonomic approach to the classification of the Pterobranchia (Cephalodiscida and Graptolithina) to be adopted for the revision of the Treatise on Invertebrate Paleontology, Part V (Hemichordata), currently in preparation. A combination of traditional Linnaean taxonomy, supported by cladistic analyses in some groups is proposed herein as a practical solution for the classification of the Graptolithina as for many groups a cladistic analysis has never been attempted and is unlikely to be undertaken in the near future. The number of ranked taxa has been kept as low as possible, with all genus level taxa referred to a family. All families and higher taxonomic units are discussed, but new taxa have not been introduced. Paraphyletic (but not polyphyletic) taxa are accepted as useful units in this classification. A number of recently introduced taxonomic units, based on cladistic analyses (e.g. Eugraptoloida, Pan-Reclinata, Pan-Bireclinata), are discussed in the context of this classification and the usefulness of these taxa is critically evaluated. The solution proposed here opts not to name a number of nodes from the published cladistic analyses that potentially could be named and in some cases have been named -not to inflate the hierarchy of the used taxonomic system. Taxa are kept as close as possible to their original definition and not unnecessarily expanded or restricted. The taxonomy proposed here for the Graptolithina indicates that the extensive use of higher level taxa, e.g. orders for small groups of genera as has been done for many benthic graptolite groups in the past is unnecessary and should be avoided.•

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“…No such traces have been reported so far for acoelomorphs and deuterostomes, which is striking given the strong morphological signal in the set of characters defining deuterostomes. A recently reported enteropneust miniaturised to a size similar of many acoelomorphs (around 500 μm), claimed to be the product of progenetic processes, still displays iconic deuterostome traits such as gill slits or coelom (Worsaae et al 2012). Complete genomes of acoelomorphs, which are presently lacking, could shed new light, maybe by finding informative rare genomic changes (Rokas and Holland 2000) and other molecular signatures.…”

Section: Are Acoelomorphs Simple or Simplified?mentioning

confidence: 99%

Acoelomorpha: earliest branching bilaterians or deuterostomes?

Ruiz‐Trillo

Paps

2015

Org Divers Evol

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The Acoelomorpha is an animal group comprised by nearly 400 species of misleadingly inconspicuous flatworms. Despite this, acoelomorphs have been at the centre of a heated debate about the origin of bilaterian animals for 150 years. The animal tree of life has undergone major changes during the last decades, thanks largely to the advent of molecular data together with the development of more rigorous phylogenetic methods. There is now a relatively robust backbone of the animal tree of life. However, some crucial nodes remain contentious, especially the node defining the root of Bilateria. Some studies situate Acoelomorpha (and Xenoturbellida) as the sister group of all other bilaterians, while other analyses group them within the deuterostomes which instead suggests that the last common bilaterian ancestor directly gave rise to deuterostomes and protostomes. The resolution of this node will have a profound impact on our understanding of animal/bilaterian evolution. In particular, if acoelomorphs are the sister group to Bilateria, it will point to a simple nature for the first bilaterian. Alternatively, if acoelomorphs are deuterostomes, this will imply that they are the result of secondary simplification. Here, we review the state of this question and provide potential ways to solve this longstanding issue. Specifically, we argue for the benefits of (1) obtaining additional genomic data from acoelomorphs, in particular from taxa with slower evolutionary rates; (2) the development of new tools to analyse the data; and (3) the use of metagenomics or metatranscriptomics data. We believe the combination of these three approaches will provide a definitive answer as to the position of the acoelomorphs in the animal tree of life.

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An Anatomical Description of a Miniaturized Acorn Worm (Hemichordata, Enteropneusta) with Asexual Reproduction by Paratomy

Cited by 53 publications

References 68 publications

Hemichordata

Hemichordata

The classification of the Pterobranchia (Cephalodiscida and Graptolithina)

Acoelomorpha: earliest branching bilaterians or deuterostomes?

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