Journal of Molecular Evolution

, Volume 42, Issue 5, pp 552-559

First online:

18S rRNA suggests that Entoprocta are protostomes, unrelated to Ectoprocta

  • L. Y. MackeyAffiliated withDepartment of Biological Sciences, Duquesne University
  • , B. WinnepenninckxAffiliated withDepartement Biochemie, Universiteit Antwerpen (UIA)
  • , R. De WachterAffiliated withKoninklijk Belgisch Instituut voor Natuurwetenschappen
  • , T. BackeljauAffiliated withKoninklijk Belgisch Instituut voor Natuurwetenschappen
  • , P. EmschermannAffiliated withInstitut für Biologie III, Albert-Ludwig-Universität-Freiburg
  • , J. R. GareyAffiliated withDepartment of Biological Sciences, Duquesne University

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The Ento- and Ectoprocta are sometimes placed together in the Bryozoa, which have variously been regarded as proto- or deuterostomes. However, Entoprocta have also been allied to the pseudocoelomates, while Ectoprocta are often united with the Brachiopoda and Phoronida in the (super)phylum Lophophorata. Hence, the phylogenetic relationships of these taxa are still much debated. We determined complete 18S rRNA sequences of two entoprocts, an ectoproct, an inarticulate brachiopod, a phoronid, two annelids, and a platyhelminth. Phylogenetic analyses of these data show that (1) entoprocts and lophophorates have spiralian, protostomous affinities, (2) Ento- and Ectoprocta are not sister taxa, (3) phoronids and brachiopods form a monophyletic clade, and (4) neither Ectoprocta or Annelida appear to be monophyletic. Both deuterostomous and pseudocoelomate features may have arisen at least two times in evolutionary history. These results advocate a Spiralia-Radialia-based classification rather than one based on the Protostomia-Deuterostomia concept.

Key words

Ectoprocta Entoprocta Phoronida Brachiopoda Lophophorata 18S rRNA Molecular phylogeny Oligochaeta Hirudinida Polychaeta