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Zoomorphology

, Volume 120, Issue 1, pp 15–28 | Cite as

The origin of the coelom in Brachiopoda and its phylogenetic significance

  • Carsten Lüter
Original Article

Abstract 

The origin of the mesoderm and the subsequent formation of the coelom in the larvae of the brachiopod species Notosaria nigricans and Calloria inconspicua is documented in detail at the ultrastructural level. During gastrulation, the blastocoel is completely displaced by the invaginating archenteron. Initial mesoderm formation was observed in late wedge-shaped to early three-lobed stages in both species. Proliferation of mesodermal cells from the archenteral epithelium mainly occurs in the dorsolateral (C. inconspicua) and caudolateral (N. nigricans) parts of the archenteral wall. Thus, a compact mesodermal cell mass pushes its way towards the subepidermal basal lamina. During further development of the larva, the mesoderm is separated from the archenteral epithelium by an extracellular matrix secreted frontad from behind. As a result, a single coelomic anlage is formed. The initial mesoderm in both species is of archenteral/endodermal origin. Considering endodermal origin as the crucial character for enterocoely, coelom formation through proliferation of a compact, endodermally derived mesodermal cell mass in Brachiopoda is clearly identified as enterocoely. Endodermal origin of mesoderm and, therefore, of the coelomic epithelium is hypothesised as a synapomorphy of Brachiopoda and Deuterostomia. As a consequence: (1) Brachiopoda and Deuterostomia are considered sister groups, (2) Brachiopoda group within Radialia and (3) lophophorates (”Tentaculata”) remain as a paraphyletic grouping.

Keywords

Extracellular Matrix Cell Mass Basal Lamina Sister Group Phylogenetic Significance 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Carsten Lüter
    • 1
  1. 1.Fakultät für Biologie der Universität Bielefeld, Zoomorphologie und Systematik, Postfach 100131, 33501 Bielefeld, Germany e-mail: carsten.lueter@biologie.uni-bielefeld.de Fax: +49-521-1066426DE

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