Molecular phylogeny of Kalyptorhynchia (Rhabdocoela, Platyhelminthes) inferred from ribosomal sequence data

Abstract

Tessens, B., Janssen, T. & Artois, T. (2014). Molecular phylogeny of Kalyptorhynchia (Rhabdocoela, Platyhelminthes) inferred from ribosomal sequence data. -Zoologica Scripta, 43, 519-530. With 556 species described to date, Kalyptorhynchia includes about one-third of all species of rhabdocoel flatworms. In this study, we present the first molecular phylogenetic analysis of this taxon. The final analysis comprises 110 species. These represent 11 of the 17 known families. The largest family (241 known species), Polycystididae, is represented by nine of 10 subfamilies and 33 of the 58 genera. Sequence data from 18S rDNA and 28S rDNA were analysed using maximum likelihood and Bayesian approaches. Of the two taxa traditionally recognised within Kalyptorhynchia, Eukalyptorhynchia and Schizorhynchia, only Schizorhynchia is monophyletic. All eukalyptorhynch families, except Cicerinidae, are monophyletic. On the other hand, two of the three schizorhynch families included are not monophyletic. Within Polycystididae, the traditional taxonomy was not reflected in our phylogenetic analyses and most subfamilies are polyphyletic. These results suggest that current classification, mostly based on characters of the genital system, suffers from homoplasy. Where possible, a revised classification, taking into account these new findings, is given.

The first multi-gene phylogeny of the Macrostomorpha sheds light on the evolution of sexual and asexual reproduction in basal Platyhelminthes

“…Evolutionary transitions from penis stylets to cirri may indeed occur frequently in other free-living flatworms (e.g. at least three times in the Polycystididae, Tessens et al, 2014), supporting the idea of homology. Interestingly, Myozona aerumnosa Sopott-Ehlers and Schmidt 1974b, has a cirrus with two small sclerotized hooks, which might possibly represent an intermediate state.…”

“…The complete 18S ($1700 bp) and partial 28S ribosomal RNA genes ($1100 bp) have been useful in resolving the phylogeny of these and other Platyhelminthes (e.g. Baguña and Riutort, 2004;Tessens et al, 2014;Schärer et al, 2011). We further add the ''Folmer'' region of the mitochondrial cytochrome c oxidase subunit 1 gene, COI (709 bp) widely used in species barcoding (primer sequences modified from Folmer et al, 1994) and a second mitochondrial gene, partial 16S rRNA (463 bp) (primer sequences modified from Xiong and Kocher, 1991).…”

“…Like in most other free-living flatworms, the taxonomic classification of the Macrostomorpha is largely based on the morphology of their hermaphroditic reproductive system. However, recent studies show that these morphological traits are prone to convergent evolution (Schärer et al, 2011;Tessens et al, 2014), making a comparative molecular phylogenetic framework indispensable to understand the evolution of reproductive systems in this group. This convergent evolution of reproductive morphologies is further supported by our results, and, to better understand these, we therefore briefly introduce the main evolutionary forces driving the evolution of reproductive systems in simultaneous hermaphrodites.…”

Cicerina debrae n. sp. (Platyhelminthes: Kalyptorhynchia, Cicerinidae) from the Southern Atlantic Coast, USA

“…A blastn search returned the sequence from Linguabana tulai Rundell & Leander 2014 (JN205121) at e 0 and 96% identity. Blasting the sequence for C. debrae against the unpublished sequence for Cicerina tetradactyla (Tessens et al submitted) resulted in e 0 and 97% identity.…”

Microturbellarians (Platyhelminthes and Acoelomorpha) in Brazil: invisible organisms?

“…Some marine flatworms, such as acoels and polyclads, and freshwater rhabdocoels are planctonic (Hyman, 1951;Rocha et al, 1990;Dumont et al, 2014). Some microturbellarians may occur in humid terrestrial environments (Hyman, 1951;Tessens et al, 2014); land triclads may be a species-rich group in tropical and subtropical ecosystems (Carbayo et al, 2009). The temnocephalids, a group of the taxon Dalytyphloplanida, and some members of other taxonomic groups of microturbellarians live in association with other invertebrates or with turtles, usually as ectosymbionts (Hyman, 1951;Jennings, 1997).…”