Ribbon worm relationships: a phylogeny of the phylum Nemertea

Abstract

We present the most extensive phylogenetic analysis to date, to our knowledge, of higher-level nemertean relationships, based on sequence data from four different genes (the nuclear genes for nuclear large subunit rRNA (28S rRNA) and histone H3 (H3), and the mitochondrial genes for mitochondrial large subunit rRNA (16S rRNA) and cytochrome c oxidase subunit I (COI)). Well-supported clades are, in general, compatible with earlier, more limited, analyses, and current classification is largely in agreement with our results, although there are some notable exceptions. Bdellonemertea (represented by Malacobdella) is found to be a part of Monostilifera, and Polystilifera is the monophyletic sister group to Monostilifera. Cratenemertidae is the sister group to the remaining monostiliferans (including Malacobdella), a group to which we apply the new name Distromatonemertea. Heteronemertea is monophyletic and forms a clade with Hubrechtella; for this clade we introduce the name Pilidiophora. Finally, Pilidiophora and Hoplonemertea (with Malacobdella) form a monophyletic group, and we introduce the name Neonemertea to refer to this group. Palaeonemertea is found to be non-monophyletic and basal among nemerteans.

A histology-free description of the branched-proboscis ribbonworm Gorgonorhynchus albocinctus sp. nov. (Nemertea: Heteronemertea)

“…Bootstrap support values were calculated using 1000 pseudoreplicates. Thollesson and Norenburg (2003); j Sundberg and Strand (2007).…”

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

“…The argument of a coelomate position for nemerteans was supported by ultrastructural similarity between the blood vessels of nemerteans and the coelom of spiralian coelomates (Turbeville and Ruppert, 1985;Turbeville, 1986;Jespersen and Liitzen, 1988). There is an increasing number of studies using molecular information to provide increasingly refined estimates of within-phylum phylogenetic relationships of nemerteans (e.g., Envall and Sundberg, 1998;Sundberg and Saur, 1998;Thollesson and Norenburg, 2003;Sundberg et al, 2003;Strand and Sundberg, 2005;Sundberg and Strand, 2007). Few studies have addressed the position of phylum Nemertea among metazoans.…”

A Taxonomic Catalogue of Japanese Nemerteans (Phylum Nemertea)

“…Although adopted by some researchers (e.g., Gibson, 1994), hypothesis was later questioned by Sundberg and Hylbom (1994), who found no morphological support for the Archinemertea. This group has lost acceptance among other nemertean researchers, since it is now regarded to be a group within the palaeonemerteans (Thollesson and Norenburg, 2003). However, embryological observations themselves are highly valued and frequently cited by modern researchers (e.g., Maslakova et al, 2004a, b;Nielsen, 2005).…”

“…Japanese Nemertean Species The higher classification system adopted here is based on Gibson (1982aGibson ( , b, 1994, Chernyshev (1995Chernyshev ( , 2003, and Thollesson and Norenburg (2003).…”