Kånneby, T., . Phylogeny of Chaetonotidae and other Paucitubulatina (Gastrotricha: Chaetonotida) and the colonization of aquatic ecosystems. -Zoologica Scripta, 42, 88-105. Chaetonotidae is the largest family within Gastrotricha with almost 400 nominal species represented in both freshwater and marine habitats. The group is probably non-monophyletic and suffers from a troubled taxonomy. Current classification is to a great extent based on shape and distribution of cuticular structures, characters that are highly variable. We present the most densely sampled molecular study so far where 17 of the 31 genera belonging to Chaetonotida are represented. Bayesian and maximum likelihood approaches based on 18S rDNA, 28S rDNA and COI mtDNA are used to reconstruct relationships within Chaetonotidae. The use of cuticular structures for supra-specific classification within the group is evaluated and the question of dispersal between marine and freshwater habitats is addressed. Moreover, the subgeneric classification of Chaetonotus is tested in a phylogenetic context. Our results show high support for a clade containing Dasydytidae nested within Chaetonotidae. Within this clade, only three genera are monophyletic following current classification. Genera containing both marine and freshwater species never form monophyletic clades and group with other species according to habitat. Marine members of Aspidiophorus appear to be the sister group of all other Chaetonotidae and Dasydytidae, indicating a marine origin of the clade. Halichaetonotus and marine Heterolepidoderma form a monophyletic group in a sister group relationship to freshwater species, pointing towards a secondary invasion of marine environments of these taxa. Our study highlights the problems of current classification based on cuticular structures, characters that show homoplasy for deeper relationships.

Ribbon worms (phylum Nemertea) have traditionally been described and classified based on a combination of internal and external morphological characters. The extent, and wealth of details, of these descriptions vary both over time and amongst authors. In addition, definitions of characters and character states are in many cases vague, causing problems both for identification and in phylogenetic analyses. Here, we suggest a system of describing nemerteans based on a list of characters and their states with the actual description in the form of a vector of character state symbols. We argue that this system makes it easier for other systematists to extract the necessary characters/character states for comparative and phylogenetic analyses. The proposed list of characters can also act as a checklist for nemertean description, whereby hopefully ambiguities (such as does the nonmentioning of a character actually mean 'missing' or just not looked for) can be avoided in the future. We describe two new species and one new genus Carinina ochracea sp. nov. and Raygibsonia bergi gen. et sp. nov. using this concept in combination with molecular analyses based on 18S and cytochrome oxidase I (COI) DNA sequences.

BackgroundPhylogenetic relationships within Gastrotricha are poorly known. Attempts to shed light on this subject using morphological traits have led to hypotheses lacking satisfactory statistical support; it seemed therefore that a different approach was needed.Methodology/Principal FindingsIn this paper we attempt to elucidate the relationships within the taxonomically vast family Thaumastodermatidae (Macrodasyida) using molecular sequence data. The study includes representatives of all the extant genera of the family and for the first time uses a multi-gene approach to infer evolutionary liaisons within Gastrotricha. The final data set comprises sequences of three genes (18S, 28S rDNA and COI mtDNA) from 41 species, including 29 thaumastodermatids, 11 non-thaumastodermatid macrodasyidans and a single chaetonotidan. Molecular data was analyzed as a combined set of 3 genes and as individual genes, using Bayesian and maximum likelihood approaches. Two different outgroups were used: Xenotrichula intermedia (Chaetonotida) and members of the putative basal Dactylopodola (Macrodasyida). Thaumastodermatidae and all other sampled macrodasyidan families were found monophyletic except for Cephalodasyidae. Within Thaumastodermatidae Diplodasyinae and Thaumastodermatinae are monophyletic and so are most genera. Oregodasys turns out to be the most basal group within Thaumastodermatinae in analyses of the concatenated data set as well as in analyses of the nuclear genes. Thaumastoderma appears as the sister taxon to the remaining species. Surprisingly, Tetranchyroderma is non-monophyletic in our analyses as one group of species clusters with Ptychostomella while another appears as the sister group of Pseudostomella.Conclusions/SignificanceResults in general agree with the current classification; however, a revision of the more derived thaumastodermatid taxa seems necessary. We also found that the ostensible COI sequences from several species do not conform to the general invertebrate or any other published mitochondrial genetic code; they may be mitochondrially derived nuclear genes (numts), or one or more modifications of the mitochondrial genetic code within Gastrotricha.

Gastrotricha is a cosmopolitan group ofaquatic invertebrates. To date, approximately 765species have been described. This study is the first todeal with species delimitation and cryptic species offreshwater Gastrotricha. Three commonly encounteredspecies, Heterolepidoderma ocellatum, Lepidochaetuszelinkai, and Lepidodermella squamata, areinvestigated for cryptic speciation. Most of thematerial is based on Swedish specimens but closelyrelated species from other parts of the world are alsoincluded. Taxonomic revisions are supported byphylogenies based on 18S rRNA, 28S rRNA, andCOI mtDNA of freshwater Chaetonotidae from severalgenera and inferred from Bayesian and maximumlikelihood approaches. Heterolepidoderma ocellatumf. sphagnophilum is raised to species level, under thename H. acidophilum n. sp. Moreover, genetic databased on COI indicate large variation between twomorphologically very similar groups of Lepidodermellasquamata. The extent of cryptic speciation inL. zelinkai appears low. Based on the phylogenetichypothesis presented in this article, the new species,Lepidodermella intermedia n. sp., from northernSweden is also described. The phylogenetic hypothesisgenerated shows that Chaetonotidae is a nonmonophyleticgroup

BackgroundWithin an evolutionary framework of Gastrotricha Marinellina flagellata and Redudasys fornerise bear special interest, as they are the only Macrodasyida that inhabit freshwater ecosystems. Notwithstanding, these rare animals are poorly known; found only once (Austria and Brazil), they are currently systematised as incertae sedis. Here we report on the rediscovery of Redudasys fornerise, provide an account on morphological novelties and present a hypothesis on its phylogenetic relationship based on molecular data.Methodology/Principal FindingsSpecimens were surveyed using DIC microscopy and SEM, and used to obtain the 18 S rRNA gene sequence; molecular data was analyzed cladistically in conjunction with data from 42 additional species belonging to the near complete Macrodasyida taxonomic spectrum. Morphological analysis, while providing new information on taxonomically relevant traits (adhesive tubes, protonephridia and sensorial bristles), failed to detect elements of the male system, thus stressing the parthenogenetic nature of the Brazilian species. Phylogenetic analysis, carried out with ML, MP and Bayesian approaches, yielded topologies with strong nodal support and highly congruent with each other. Among the supported groups is the previously undocumented clade showing the alliance between Redudasys fornerise and Dactylopodola agadasys; other strongly sustained clades include the densely sampled families Thaumastodermatidae and Turbanellidae and most genera.Conclusions/SignificanceA reconsideration of the morphological traits of Dactylopodola agadasys in light of the new information on Redudasys fornerise makes the alliance between these two taxa very likely. As a result, we create Anandrodasys gen. nov. to contain members of the previously described D. agadasys and erect Redudasyidae fam. nov. to reflect this novel relationship between Anandrodasys and Redudasys. From an ecological perspective, the derived position of Redudasys, which is deeply nested within the Macrodasyida clade, unequivocally demonstrates that invasion of freshwater by gastrotrichs has taken place at least twice, in contrast with the single event hypothesis recently put forward.