, Volume 126, Issue 2, pp 73–87 | Cite as

The nervous system of Convolutriloba (Acoela) and its patterning during regeneration after asexual reproduction

  • Christian W. Gaerber
  • Willi SalvenmoserEmail author
  • Reinhard M. Rieger
  • Robert Gschwentner
Original Paper


We describe the serotonergic and cholinergic nervous system of the asexually reproducing acoel Convolutriloba longifissura Bartolomaeus & Balzer, 1997 by means of immunohistochemistry, conventional histochemistry and transmission electron microscopy. Immunocytochemical staining for serotonin revealed neurons in the brain, in a pair of ventral main longitudinal cords, in two pairs of smaller dorsal longitudinal nerve cords, and in a submuscular nerve net. The brain comprises a ventral-anterior commissure and a less intensely stained dorsal commissure joined together by connectives into a three-ringed scaffold from which the longitudinal nerves extend. We followed the regeneration of the serotonergic part of the nervous system up to the second day after fission. Within this time period, the offspring reestablished bilateral symmetry in the nervous system and developed full motor control. The presence of aminergic cell bodies associated with the main lateral nerve cords of C. longifissura shows that the acoelan nervous system is more similar to that of other platyhelminths (triclads, rhabditophorans) than previously assumed. The presence of serotonergic cell bodies along the main nerve cord correlates with the capacity for asexual reproduction via fissioning. We also describe the single fission mode of C. hastifera Winsor 1990, which brings the modes of asexual reproduction employed by members of the Convolutrilobinae to three.


Serotonin Acetylcholin Platyhelminthes 5-HT Architomy 



We would like to thank Peter Ladurner, Bernhard Egger, Johannes Achatz for valuable discussions and Gunde Rieger for TEM interpretations. This work was supported by FWF grant P16618.


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Christian W. Gaerber
    • 1
  • Willi Salvenmoser
    • 1
    Email author
  • Reinhard M. Rieger
    • 1
  • Robert Gschwentner
    • 1
  1. 1.Institute of ZoologyUniversity of InnsbruckInnsbruckAustria

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