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Evolutionary Loss of Parasitism by Nematodes? Discovery of a Free-Living Filaroid Nematode

2006; American Society of Parasitologists; Volume: 92; Issue: 3 Linguagem: Inglês

10.1645/ge-672r.1

1937-2345

Wim Bert, Marjolein Messiaen, Joeri Manhout, Wouter Houthoofd, Gaëtan Borgonie,

Parasitic Diseases Research and Treatment

A cattle-drinking pool in nature reserve "Zwin" on the Belgian coast contained free-living third-stage infective filaroid juveniles. These juveniles clearly differ morphologically from all known nematodes. Morphological and molecular analyses indicate a position within the Filaroidea. The aberrant biology of this nematode, namely, a free-living stage in an aquatic environment, is unknown within this superfamily, and the evolution of the parasitic phenotype to a free-living state is generally thought to be unlikely. However, the obtained placement in the small subunit molecular phylogenetic tree suggests that this free-living stage is most likely a secondary adaptation. It is reasonable to assert that nematodes with complex life cycles still have the genetic potential for a reversion from parasitism to a (partial) free-living stage.