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M Reuter, OI Raikova, and MKS Gustafsson (2001)

Patterns in the nervous and muscle systems in lower flatworms


In order to test the monophyly of the Plathelminthes and the phylogenetic relationships of Acoela and Nemertodermatida., studies on the neuroanatomy of these groups were performed using anti-serotonin (5-HT) and anti-FMRF related peptides (FaRPs) immunocytochemistry. The Catenulida + Rhabditophora seem to be monophyletic. Four synapomorphies are proposed for these taxa. The presence of: 1. a bilobed brain showing 5-HF- and FaRP immunoreactivity. 2. a distinct neuropile, showing 5-HT and FaRP immunoreactivity. 3. two main nerve cords (MC's) aligned by 5-HT-immunoreactive (IR) marker neurones, 4. FaRP-immunoreactivity in the stomatogastric nervous system (NS). No synapomorphies were detected between Acoela and other Plathelminthes. The IR patterns of Acoela are characterised by: 1. The presence of a 5-HT-IR commissural brain. 2. The presence of clusters of FaRP-IR cells not integrated into a brain of the flatworm type. 3. The absence of a regular orthogon. 4. The absence of serotoninergic marker neurones along the main nerve cords (MC's). 5. The absence of a stomatogastric FaRP positive nervous system (NS). No support was obtained for a taxon Acoelomorpha. Our data are compatible with the hypothesis that both the Acoela and the Nemertodermatida do not belong to the Plathelminthes.

neurons; muscles; phylogeny; Platyhelminthes
9th International Symposium on the Biology of the Turbellaria (ISBT), BARCELONA, SPAIN, JUN, 2000
  • ISSN: 0777-6276

ISSN 2295-0451 (online version)
ISSN 0777-6279 (printed version)
impact factor 2015: 0,87.

Prof. Dr. Isa Schön
Royal Belgian Institute of Natural Sciences
Vautierstraat 29
1000 Brussels, Belgium


Annales de la Société malacologique de Belgique
​Annales de la Société royale malacologique et zoologique de Belgique
Annales de la Société Royale Zoologique de Belgique
Belgian Journal of Zoology