|Reuter M, Raikova OI, Gustafsson MKS (2001)
Patterns in the nervous and muscle systems in lower flatworms.
Belg J Zool 131 (Suppl 1): 47-53
Abstract / Notes"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-HT- 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 Plathhelminthes. 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 neurons 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 Plathhelminthes.
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