Annelida and Arthropoda are Not Sister Taxa: A Phylogenetic Analysis of Spiralian Metazoan Morphology

Eernisse, Douglas J.; Albert, James S.; Anderson, Frank E.

doi:10.2307/2992569

Cited by 78 publications

(110 citation statements)

References 19 publications

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“…Whether brachiopods (together with ectoprocts, phoronids and pterobranchs) belong amongst protostomes or deuterostomes (or neither group) has long been a matter of debate, arising because they variously display mixtures of the supposedly diagnostic characters. Whereas many recent morphology-based reviews have favoured deuterostome a¤nities of these lophophorates (Brusca & Brusca 1990;Schram 1991;Eernisse et al 1992;Nielsen et al 1996), current molecular data unequivocally associate pterobranchs with other deuterostomes but place brachiopods, ectoprocts and phoronids with other protostomes (Field et al 1988;Patterson 1989;Lake 1990;Halanych et al 1995;Conway Morris et al 1996;Cohen et al 1998). …”

Section: Discussion (A) Terebratuloid Brachiopod Phylogenymentioning

confidence: 98%

Comparison of articulate brachiopod nuclear and mitochondrial gene trees leads to a clade–based redefinition of protostomes (Protostomozoa) and deuterostomes (Deuterostomozoa)

Cohen

Stark

Gawthrop

et al. 1998

Proc. R. Soc. Lond. B

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Nuclear and mtDNA sequences from selected short-looped terebratuloid (terebratulacean) articulate brachiopods yield congruent and genetically independent phylogenetic reconstructions by parsimony, neighbour-joining and maximum likelihood methods, suggesting that both sources of data are reliable guides to brachiopod species phylogeny. The present-day genealogical relationships and geographical distributions of the tested terebratuloid brachiopods are consistent with a tethyan dispersal and subsequent radiation. Concordance of nuclear and mitochondrial gene phylogenies reinforces previous indications that articulate brachiopods, inarticulate brachiopods, phoronids and ectoprocts cluster with other organisms generally regarded as protostomes. Since ontogeny and morphology in brachiopods, ectoprocts and phoronids depart in important respects from those features supposedly diagnostic of protostomes, this demonstrates that the operational de¢nition of protostomy by the usual ontological characters must be misleading or unreliable. New, molecular, operational de¢nitions are proposed to replace the traditional criteria for the recognition of protostomes and deuterostomes, and the clade-based terms Protostomozoa' and`Deuterostomozoa' are proposed to replace the existing terms`Protostomia' and Deuterostomia'.

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Section: Discussion (A) Terebratuloid Brachiopod Phylogenymentioning

confidence: 98%

Comparison of articulate brachiopod nuclear and mitochondrial gene trees leads to a clade–based redefinition of protostomes (Protostomozoa) and deuterostomes (Deuterostomozoa)

Cohen

Stark

Gawthrop

et al. 1998

Proc. R. Soc. Lond. B

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“…Couso, 2009;Chipman, 2010). Even within the protostomes, arthropods and annelids belong to distinct clades (Eernisse et al, 1992), each containing several unsegmented phyla RNAi phenotypes show high levels of apoptosis both in midline neuroectoderm tissue with pycnotic nuclei (arrowhead) and in midline neuroectoderm tissue that still appears superficially wild-type (asterisks). (D,DЈ) Even apparently mild phenotypes show high levels of midline apoptosis compared with controls (AЈ).…”

Section: Discussionmentioning

confidence: 99%

Notch/Delta signalling is not required for segment generation in the basally branching insectGryllus bimaculatus

et al. 2011

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SUMMARYArthropods and vertebrates display a segmental body organisation along all or part of the anterior-posterior axis. Whether this reflects a shared, ancestral developmental genetic mechanism for segmentation is uncertain. In vertebrates, segments are formed sequentially by a segmentation 'clock' of oscillating gene expression involving Notch pathway components. Recent studies in spiders and basal insects have suggested that segmentation in these arthropods also involves Notch-based signalling. These observations have been interpreted as evidence for a shared, ancestral gene network for insect, arthropod and bilaterian segmentation. However, because this pathway can play multiple roles in development, elucidating the specific requirements for Notch signalling is important for understanding the ancestry of segmentation. Here we show that Delta, a ligand of the Notch pathway, is not required for segment formation in the cricket Gryllus bimaculatus, which retains ancestral characteristics of arthropod embryogenesis. Segment patterning genes are expressed before Delta in abdominal segments, and Delta expression does not oscillate in the pre-segmental region or in formed segments. Instead, Delta is required for neuroectoderm and mesectoderm formation; embryos missing these tissues are developmentally delayed and show defects in segment morphology but normal segment number. Thus, what initially appear to be 'segmentation phenotypes' can in fact be due to developmental delays and cell specification errors. Our data do not support an essential or ancestral role of Notch signalling in segment generation across the arthropods, and show that the pleiotropy of the Notch pathway can confound speculation on possible segmentation mechanisms in the last common bilaterian ancestor.

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“…Other organisms placed in the Ecdysozoa include kinorhynchs, priapulids, nematomorphs, onychophorans and tardigrades (Aguinaldo et ai., 1997). Because chaetognaths appear to be allied to nematodes , they are also presumably Eernisse et al, 1992;Aguinaldo et al, 1997;Eernisse, 1997;; see text for additional references), this topology represents a consensus ilustrating the relationships between major metazoan taxa. Many lesser-known "phyla" (e.g., gastrotrichs, acanthocephalans, placozoans, nematomorphs, etc,) were not included for simplicity or because their phylogenetic affinities are not clear.…”

Section: Phylogenetic Hypotheses In Many Modernmentioning

confidence: 96%

Molecular phylogenetics of the Metazoan clade Lophotrochozoa

Passamaneck¹

2003

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Annelida and Arthropoda are Not Sister Taxa: A Phylogenetic Analysis of Spiralian Metazoan Morphology

Cited by 78 publications

References 19 publications

Comparison of articulate brachiopod nuclear and mitochondrial gene trees leads to a clade–based redefinition of protostomes (Protostomozoa) and deuterostomes (Deuterostomozoa)

Comparison of articulate brachiopod nuclear and mitochondrial gene trees leads to a clade–based redefinition of protostomes (Protostomozoa) and deuterostomes (Deuterostomozoa)

Notch/Delta signalling is not required for segment generation in the basally branching insectGryllus bimaculatus

Molecular phylogenetics of the Metazoan clade Lophotrochozoa

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