title: Novelty in phylogeny of gastrotricha: evidence from 18S rRNA gene.
abstract: Gastrotricha form a phylum which is crucial for defining the origin of pseudocoelomates, in that they share a number of characters with Rotifera and Nematoda but also with acoelomates, and even the evolutionary relationships within the phylum are anything but defined. For this reason the first extensive molecular data on Gastrotricha from the 18S rRNA sequences of both orders have been obtained and analyzed. Sequence analyses show that the phylum Gastrotricha is strictly monophyletic along an evolutionary line quite distinct from that of both Rotifera and Nematoda. A new view of the evolutionary history of the phylum Gastrotricha is put forward, in which Chaetonotida, and not Macrodasyida, are the most primitive forms of the group, contrary to the commonly held view. A polyphyletic origin of aschelminthes is supported, and the misleading term pseudocoelomates should be discarded.
authors.affiliation: Dipartimento di Biologia Animale, Università di Modena, via Università, 4, Modena, I-41100, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Wirz
authors.forename: S
authors.initials: S
authors.lastname: Pucciarelli
authors.forename: C
authors.initials: C
authors.lastname: Miceli
authors.forename: P
authors.initials: P
authors.lastname: Tongiorgi
authors.forename: M
authors.initials: M
authors.lastname: Balsamo
mesh_terms: D000818:Animals; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D020459:Genes, rRNA / Q000235:genetics; D006376:Helminths / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S