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Zoomorphology

, Volume 118, Issue 2, pp 69–77 | Cite as

A commissural brain! The pattern of 5-HT immunoreactivity in Acoela (Plathelminthes)

  • Olga I. Raikova
  • M. Reuter
  • Elena A. Kotikova
  • Margaretha K. S. Gustafsson
ORIGINAL ARTICLE

Abstract

 In order to solve the question whether Plathelminthes belonging to the taxon Acoela have a brain and an orthogon of the common flatworm type, an immunocytochemical study of the pattern of serotonin (5-HT) in four species was performed. In all species the 5-HT immunoreactivity revealed no ganglionic cell mass typical for other Plathelminthes, only a symmetrical brain-like structure composed of commissural fibres associated with a few cell bodies. 5-HT immunoreactivity was detected in three to five pairs of longitudinal nerve cords, connected by an irregular network of immunoreactive transverse fibres. No regular orthogon was visualised. All the surface sensilla were strongly immunoreactive. The unique commissural brain and cordal nervous system found in Acoela support the view of a deep gap lying between Acoela and other Plathelminthes.

Keywords

Nervous System Serotonin Cell Body Cell Mass Nerve Cord 
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 1998

Authors and Affiliations

  • Olga I. Raikova
    • 1
  • M. Reuter
    • 2
  • Elena A. Kotikova
    • 1
  • Margaretha K. S. Gustafsson
    • 2
  1. 1.Zoological Institute, 199034 St Petersburg, RussiaRU
  2. 2.Department of Biology, Åbo Akademi University, Artillerigatan 6, FIN-20520 Åbo, Finland e-mail: mreuterÉra.abo.fi, Fax: 358 2 265 4748FI

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