Jeudi 26
Paléontologie et Anatomie Comparée

› 9:40 - 10:20 (40min)
New anatomical traits in Gastrotricha and potential impact on their phylogeny
Nicolas Bekkouche  1, *@  , Katrine Worsaae  1@  
1 : University of Copenhagen  (KU)  -  Site web
Marine Biological Section Universitetsparken 4 2100 København -  Danemark
* : Auteur correspondant

Gastrotricha is a cosmopolitan group of minute animals, which diversity, evolution, and morphology are still only partially known. Their long debated relationships with other Metazoa seem to be finally resolved by phylogenomic studies placing them as sister group to Platyhelminthes. Still, many aspects of their phylogeny and inner anatomy are far from well understood, leading sometimes to confusing relationships between gastrotrichs. Here we present results on the morphology of the nervous system and ciliation studied with confocal laser scanning microscopy of a variety of gastrotrichs showing a higher diversity of structures than previously described. For instance different arrangements of ciliation are found in the pharynx and on the ventral surface. Moreover additional longitudinal nerves extending along subparts of the animal or the entire body length have been found in several species, contrary to the single pair described so far in the majority of gastrotrichs. More precise structures such as specific nerves of the brain or nervous cells are also found, showing different states of characters. These different new characters may be of importance for resolving the phylogeny of Gastrotricha and will moreover help to reconstruct the evolution of their anatomy and nervous system. In a context where meiofauna seem to occupy a crucial place in the metazoan phylogeny these results may in the future aid to the understanding of their relation with Platyhelminthes.


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