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Gastrotricha and metazoan phylogeny
Author(s) -
Zrzavý Jan
Publication year - 2003
Publication title -
zoologica scripta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.204
H-Index - 64
eISSN - 1463-6409
pISSN - 0300-3256
DOI - 10.1046/j.1463-6409.2003.00104.x
Subject(s) - biology , monophyly , clade , paraphyly , phylogenetic tree , phylogenetics , zoology , sister group , synapomorphy , evolutionary biology , bilateria , genetics , gene
The phylogenetic position of the Gastrotricha within Bilateria and relationships among gastrotrich subgroups are reanalysed using morphological, developmental, nonsequence molecular, and ecological characters, together with the conserved regions of small‐subunit ribosomal RNA genes (SSU rDNA). The analysis shows that traditional ‘Macrodasyida’ is a paraphyletic stemline of Chaetonotida, with Dactylopodolida, Redudasys , and Turbanellida as the basalmost gastrotrich groups. The ‘Cycloneuralia hypothesis’, which assumes sister group relationships between Gastrotricha and Ecdysozoa is supported. The sensitivity analysis of the combined dataset yields the following scheme of relationships of the main bilaterian clades: (1) Acoelomorpha is a basalmost bilaterian clade; (2) both Deuterostomia and Protostomia (less Acoelomorpha) are monophyletic; (3) the phylogenetic position of Ectoprocta, Brachiopoda + Phoronida, and Cycloneuralia within Protostomia is unstable; (4) Trochozoa (incl. Entoprocta, Nemertea, Lobatocerebrum , and possibly Jennaria ), Platyhelminthes s.s ., and Gnathifera‐Myzostomida form a clade (‘Spiralia’); (5) Cycliophora and possibly also Chaetognatha may be close to the gnathiferans. Evolution of metazoan ciliation and cycloneuralian cuticle is discussed. It is concluded that cycloneuralian and gastrotrich ancestors were multiciliate and had epidermal cilia covered by cuticular sheaths.