Investigations into the phylogenetic position of Micrognathozoa using four molecular loci

Abstract

Micrognathozoa is the most recently discovered higher metazoan lineage. The sole known species of the group, Limnognathia maerski, was originally reported from running freshwater in Disko Island (Greenland), and has recently been recorded from the subantarctic region. Because of the presence of a particular type of jaws formed of special cuticularized rods, similar to those of gnathostomulids and rotifers, the three metazoan lineages were considered closely related, and assigned to the clade Gnathifera. A phylogenetic comparison of four molecular loci for Limnognathia maerski and other newly generated sequences of mainly acoelomate animals showed that Micrognathozoa may constitute an independent lineage from those of Gnathostomulida and Rotifera. However, the exact position of Micrognathozoa could not be determined due to the lack of support for any given relationships and due to the lack of stability in the position of Limnognathia maerski under analysis of different loci and of different parameter sets for sequence comparison. Nuclear loci tend to place Micrognathozoa with the syndermatan ⁄ cycliophoran taxa, but the addition of the mitochondrial gene cytochrome c oxidase subunit I favors a relationship of Micrognathozoa to Entoprocta.

Resurrection of Pomphorhynchus tereticollis (Rudolphi, 1809) (Acanthocephala: Pomphorhynchidae) based on new morphological and molecular data

“…Pomphorhynchus tereticollis individual samples from the type host (P. flessus) and the type region (Stralsund locality) were compared with previously published sequences of freshwater P. laevis (Králová-Hromadová et al, 2003;Giribet et al, 2004;Perrot-Minnot, 2004;Moret et al, 2007) (Table 1). DNA extraction, amplification and sequencing of the ITS1 + 5.8S + ITS2 rDNA region and the COI gene were done following Perrot-Minnot (2004).…”

Biological Systematics in the Evo-Devo era

“…Think of cirripeds like Balanus da Costa, 1778 and Lepas linnaeus, 1758, which begin the post-embryonic phase of development as typical crustacean larvae, but later change into very unusual adults whose real affinities were discovered only when their metamorphosis was first observed by Thompson (1830Thompson ( , 1835. This contrasts with organisms represented along their entire life cycle by oddly shaped stages such as the minuscule cycliophorans that live on the appendages of the norwegian lobster: to describe their developmental stages, zoologists were forced to introduce new terms such as the Pandora larva and the Prometheus larva, because the terminology available for other animals did not offer adequate labels for these unique forms (Obst & Funch 2003), whose phylogenetic affinities still remain problematic (Sørensen et al 2000;Giribet et al 2004;Neves et al 2012).…”

The complete mitochondrial genome of Cephalothrix simula (Iwata) (Nemertea: Palaeonemertea)

“…Nemertea was placed as the sister group of Brachiopoda in a few other studies using other datasets, e.g., myosin heavy chain type II (Ruiz-Trillo et al, 2002), three combined nuclear genes (18S rRNA, 28S rRNA, and EFla) (Struck et al, 2007); concatenated nuclear, ribosomal and mitochondrial genes (Bourlat et al, 2008), and expressed sequence tags for two nemerteans (or Brachiopoda + Phoronida; Dunn et al, 2008). However, Zrzavy et al (1998Zrzavy et al ( , 2001) inferred a sister relationship between Nemertea and Sipuncula, and Giribet et al (2004) did so with Entoprocta. Whereas there is increasing consensus among molecular analyses to support nemerteans as coelomate lophotrochozoans, placement of Nemertea within Lophotrochozoa remains in doubt, with analyses apparently influenced by the molecular markers and methods employed, as well as by taxon sampling.…”

“…Whereas none have supported a platyhelminth + nemertea clade; recent molecular analyses consistently place Nemertea within the coelomate Lophotro- chozoa, but at various positions-as sister to mollusks, brachiopods, entoprocts, etc. (e.g., Giribet et al, 2004;Turbeville and Smith, 2007;Struck et al, 2007;Bourlat et al, 2008;Dunn et al, 2008;Struck and Fisse, 2008). These findings have not been tested with nucleotide data and gene-order information from whole mitochondrial genome sequences.…”