In this study we elaborate the phylogeny of Dalytyphloplanida based on complete 18S rDNA (156 sequences) and partial 28S rDNA (125 sequences), using a Maximum Likelihood and a Bayesian Inference approach, in order to investigate the origin of a limnic or limnoterrestrial and of a symbiotic lifestyle in this large group of rhabditophoran flatworms. The results of our phylogenetic analyses and ancestral state reconstructions indicate that dalytyphloplanids have their origin in the marine environment and that there was one highly successful invasion of the freshwater environment, leading to a large radiation of limnic and limnoterrestrial dalytyphloplanids. This monophyletic freshwater clade, Limnotyphloplanida, comprises the taxa Dalyelliidae, Temnocephalida, and most Typhloplanidae. Temnocephalida can be considered ectosymbiotic Dalyelliidae as they are embedded within this group. Secondary returns to brackish water and marine environments occurred relatively frequently in several dalyeliid and typhloplanid taxa. Our phylogenies also show that, apart from the Limnotyphloplanida, there have been only few independent invasions of the limnic environment, and apparently these were not followed by spectacular speciation events. The distinct phylogenetic positions of the symbiotic taxa also suggest multiple origins of commensal and parasitic life strategies within Dalytyphloplanida. The previously established higher-level dalytyphloplanid clades are confirmed in our topologies, but many of the traditional families are not monophyletic. Alternative hypothesis testing constraining the monophyly of these families in the topologies and using the approximately unbiased test, also statistically rejects their monophyly.
Some taxonomic groups are less amenable to mitochondrial DNA barcoding than others. Due to the paucity of molecular information of understudied groups and the huge molecular diversity within flatworms, primer design has been hampered. Indeed, all attempts to develop universal flatworm-specific COI markers have failed so far. We demonstrate how high molecular variability and contamination problems limit the possibilities for barcoding using standard COI-based protocols in flatworms. As a consequence, molecular identification methods often rely on other widely applicable markers. In the case of Monogenea, a very diverse group of platyhelminth parasites, and Rhabdocoela, representing one-fourth of all free-living flatworm taxa, this has led to a relatively high availability of nuclear ITS and 18S/28S rDNA sequences on GenBank. In a comparison of the effectiveness in species assignment we conclude that mitochondrial and nuclear ribosomal markers perform equally well. In case intraspecific information is needed, rDNA sequences can guide the selection of the appropriate (i.e. taxon-specific) COI primers if available.
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.
Fifteen species of kalyptorhynch flatworms, twelve of them eukalyptorhynchs and three schizorhynchs, are reported from the KwaZulu-Natal coast in South Africa. Six species are new to science, five of which belong to Eukalyptorhynchia, the remaining one to Schizorhynchia. One of the new eukalyptorhynch species, Uncinorhynchus linusi n. sp., belongs to the taxon Gnathorhynchidae Meixner, 1929 and can be distinguished from other species of Uncinorhynchus Karling, 1947 based on the detailed structure of the proboscis hooks and the hard part in the male genital system. Two other species are members of the Koinocystididae Meixner, 1924. Itaipusa sbui n. sp. is characterised by an armed cirrus with two transversal bands of lamellar spines and by the detailed structure of the female genital system. The other new koinocystidid cannot be placed in any existing taxon and therefore a new genus is erected: Bhambathorhynchus abursalis n. gen. n. sp. It is characterised by the presence of two bent hooks in the male system, each one connected to a muscular bulb, and by the absence of a copulatory bursa. The remaining two new species of Eukalyptorhynchia, Lagenopolycystis mandelai n. sp. and Phonorhynchoides gondwanae n. sp., are members of the taxon Polycystididae Graff, 1905 and can be distinguished from their respective congeners by the detailed structure of their hard parts in the male genital system. The latter species also occurs on the Indian subcontinent. The discussion on the phylogenetic position of the new species of Phonorhynchoides leads to the formal split of this non-monophyletic genus into two taxa: Phonorhynchoides Beklemischev, 1927 and Phonorhynchopsis n. gen. The sixth and last new species, Baltoplana cupressus n. sp., is a member of the taxon Cheliplanidae Schilke, 1970 (Schizorhynchia) and combines an armed cirrus with a single accessory cirrus in the copulatory organ. For two more species, Prognathorhynchus spec. and Carcharodorhynchus spec., the available material is inadequate for a formal description, but they are mentioned and illustrated to allow future recognition. Six known species, Pocillorhynchus spiroductus Schockaert, 1982, Duplacrorhynchus heyleni Artois & Schockaert, 1999, Gyratrix hermaphroditus Ehrenberg, 1831, Paulodora contortoides Artois & Tessens, 2008, P. drepanophora Artois & Tessens, 2008 and Cheliplana pileola Jouk & De Vocht, 1989 are reported from South Africa for the first time and additional remarks on their morphology are given. An additional species, Brachyrhynchoides oosterlyncki (Willems, Reygel & Artois, 2013) Willems, Reygel & Artois, 2013 was recently described from South Africa and India (see Artois et al., 2013b, 2013c), and is mentioned here for the sake of completeness.
Nineteen taxa of Dalytyphloplanida Willems et al., 2006 collected from southwestern Andalusia are discussed. Although most taxa were found in freshwater, three are marine, one occurred in brackish water and Protoplanella simplex Reisinger, 1924 was even collected in a dry, limnoterrestrial habitat. Four taxa are new to science. Castrada purgatorialis n. sp., Castrada paradisea n. sp. and Strongylostoma devleeschouweri n. sp., all belong to the Typhloplanidae Graff, 1905. The first two species differ from other species of Castrada Schmidt, 1861 by the presence of a large accessory bursa and the morphology of the copulatory atrium. C. purgatorialis n. sp. has zoochlorellae while these are lacking in C. paradisea n. sp. Strongylostoma devleeschouweri n. sp. is unique because of its coalescing testes and because of the presence of a sphincter around the stalk of the seminal receptacle. Gieysztoria iberica n. sp. belongs to the Dalyelliidae Graff, 1905 and is characterized by the extreme length of the girdle of the stylet. Except for five taxa, all specimens were collected within the boundaries of the Doñana National Park. Most of the taxa could easily be identified to species level except for one taxon of Kytorhynchidae Rieger, 1974 and one species of Phaenocora Ehrenberg, 1836. Four species are new for the Iberian Peninsula. Three of these, Trigonostomum penicillatum (Schmidt, 1857) Micoletzky, 1910, Promesostoma maculosum Ax, 1956 and Gieysztoria macrovariata (Weise, 1942) Ruebush & Hayes, 1939, were already known from other European localities, whereas Parapharyngiella involucrum Willems et al., 2005, a marine species, has previously only been found in Zanzibar, Tanzania.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.