A comparative ultrastructural study of tintinnid loricae (Alveolata, Ciliophora, Spirotricha) and a hypothesis on their evolution

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Tintinnid ciliates build loricae, whose structure, shape, and size still largely represent the basis for taxonomy and classification, although genetic analyses demonstrated their limited utility for inferring evolutionary relationships. The textures of the lorica walls, however, result from the chemical and physical properties of the forming material, which is supposed to be rather conserved in closely related taxa, viz., congeners and confamilial genera. Within a particular texture, small deviations in the chemical composition might affect the wall's stickiness and accordingly its capability to adhere foreign particles, explaining the intertwining of tintinnids with hyaline and agglutinated loricae in phylogenetic inferences. In a comprehensive comparative study, the lorica textures were electron microscopically and morphometrically analyzed in 21 species from 17 genera and more than nine families together with literature data. Most species were investigated for the first time, and the taxa cover a substantial portion of the molecular genealogy. The phylogeny-aware analysis of the lorica-related features provides a preliminary hypothesis on lorica evolution. Eventually, this conspectus suggests the dominance of hard lorica walls with an alveolar texture and proposes different modes of lorica formation.

Original languageEnglish
Article numbere12877
Pages (from-to)1-36
JournalJournal of Eukaryotic Microbiology
Issue number2
Early online date2021
Publication statusPublished - 2 Mar 2022

Bibliographical note

Publisher Copyright:
© 2021 The Authors. Journal of Eukaryotic Microbiology published by Wiley Periodicals LLC on behalf of International Society of Protistologists


  • character evolution
  • lorica formation
  • scanning electron microscopy
  • transmission electron microscopy
  • wall texture

Fields of Science and Technology Classification 2012

  • 106 Biology

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