<i>Discoplana malagasensis</i> sp. nov., a new turbellarian (Platyhelminthes: Polycladida: Leptoplanidae) symbiotic in an ophiuroid (Echinodermata), with a cladistic analysis of the <i>Discoplana/ Euplana</i> species

A new species of polyclad flatworm from Papua New Guinea is described. It is found symbiotic in the ophiuroid Ophiothrix purpurea von Martens, 1867 (Echinodermata: Ophiuroidea). Apparently it belongs to the taxon Discoplana Bock, 1913 and can be distinguished from the six previously described Discoplana species by its very short ejaculatory duct and a penial papilla covered with a penial sheath, but without any true sclerotised structures such as a stylet or spines. The cladistic analysis of the Discoplana/Euplana species, based on morphological features and including two outgroups, reveals that all species of Discoplana, except D. pacificola, form a monophyletic taxon, that is not a synonym of Euplana Girard, 1893. Therefore the name Discoplana is conserved and the new species will be described as Discoplana malagasensis sp. nov. A key for the Discoplana/Euplana group is provided. In this key the biogeographical distribution and possible synonyms are given

How unknown is the world's biodiversity? Free-living flatworms as an example

Even at the start of the 21st century, the actual biodiversity of the world's marine ecosystems is still largely unknown. Not surprisingly, especially the smallest creatures are much understudied. Among the least known taxonomical groups are the microturbellarians, small free-living flatworms that inhabit sandy beaches or live epiphytically on algae. With a rough conservative estimation of about 15.000 species still to be described, an enormous task still lays ahead for classical morphology-based taxonomy. And not only is the relative number of species already described limited, but on top of that most of them are described from a few marine ecoregions only, mostly from the Western and Northern Europe, and the Mediterranean. The major part of the world's coasts and deep sea habitats never were investigated. This lack of knowledge greatly hampers further research regarding biogeography, ecology or even phylogeny. In recent years we have tried to shed light on several questions regarding the evolution and ecology of these animals, including the origin of a symbiotic life style, the history of major habitat shifts and the "Everything small is everywhere"-hypothesis, research that is still ongoing. These studies were only possible because of a big taxonomical effort and trustable databases, and the results will briefly be presented

First record of Nemertodermatida from Belgian marine waters

Acoelomorpha; Nemertodermatida; new records; Belgium</td

Problematic barcoding in flatworms: A case-study on monogeneans and rhabdocoels (Platyhelminthes)

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.This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published pdf.NHM Repositor

A comprehensive molecular phylogeny of Dalytyphloplanida (Platyhelminthes: Rhabdocoela) reveals multiple escapes from the marine environment and origins of symbiotic relationships

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

Morphological studies on Nemertodermatida sampled in the Belgian part of the North Sea

Nemertodermatida is a taxon of small, acoelomate, marine, interstitial worms without a true gut but with a statocyst containing multiple statoliths. Their phylogenetic position is still the subject of debate. This has raised growing interest in the study of this group, on both the molecular and the morphological level. Nemertodermatida have not yet been reported in the Belgian part of the North Sea, and they are known to be sparse. After sampling on different locations in the Belgian part of the North Sea with a Van Veen grab, we were able to collect three different species of Nemertodermatida: Flagellophora apelti, Nemertinoides elongatus and Sterreria psammicola. These were fixed and are currently being used for morphological studies. In order to increase the morphological knowledge on this challenging group, we study the germline in Nemertodermatida, in comparison to that of Acoela. As the structure of the gonads in Acoela and Nemertodermatida is variable and complex, light and transmission electron microscopy are used to define the spatial arrangement, characteristics and organization of the testes and ovaries in different species. We assess the potential of the morphological characteristics of the germline as a complement to the molecular data in the discussion of the evolutionary relationships within and between these intriguing groups