Journal of Molecular Evolution

, Volume 49, Issue 2, pp 250–259

Origin and Evolution of Paralogous rRNA Gene Clusters Within the Flatworm Family Dugesiidae (Platyhelminthes, Tricladida)

  • Salvador  Carranza
  • Jaume  Baguñà
  • Marta  Riutort

DOI: 10.1007/PL00006547

Cite this article as:
Carranza, S., Baguñà, J. & Riutort, M. J Mol Evol (1999) 49: 250. doi:10.1007/PL00006547

Abstract.

Analysis of the 18S rDNA sequences of five species of the family Dugesiidae (phylum Platyhelminthes, suborder Tricladida, infraorder Paludicola) and eight species belonging to families Dendrocoelidae and Planaridae and to the infraorder Maricola showed that members of the family Dugesiidae have two types of 18S rDNA genes, while the rest of the species have only one. The duplication event also affected the ITS-1, 5.8S, ITS-2 region and probably the 28S gene. The mean divergence value between the type I and the type II sequences is 9% and type II 18S rDNA genes are evolving 2.3 times more rapidly than type I. The evolutionary rates of type I and type II genes were calibrated from biogeographical data, and an approximate date for the duplication event of 80–120 million years ago was calculated. The type II gene was shown, by RT-PCR, to be transcribed in adult individuals of Schmidtea polychroa, though at very low levels. This result, together with the fact that most of the functionally important positions for small-subunit rRNA in prokaryotes have been conserved, indicates that the type II gene is probably functional.

Key words: 18S rDNA — Polymorphism — Dugesiidae — Platyhelminthes — Variability — Multigene family — Metazoan — Phylogeny 

Copyright information

© Springer-Verlag New York Inc. 1999

Authors and Affiliations

  • Salvador  Carranza
    • 1
  • Jaume  Baguñà
    • 1
  • Marta  Riutort
    • 1
  1. 1.Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal 645, 08071 Barcelona, SpainES

Personalised recommendations