Integrated data analysis allows the establishment of a new, cosmopolitan genus of marine Macrodasyida (Gastrotricha).

Macrodasyida (phylum Gastrotricha) comprises 365 species distributed across 34 genera and 10 families. However, current classification is under revision due to the contradictory results of molecular and morphological cladistic analyses. Studies aimed at bridging the gaps took advantage of supplementary assessments of poorly known species and particularly from observations of new taxa showing original traits that could help to identify plesiomorphic character states in these anatomically diverse micrometazoa. We follow this path by describing three new interesting macrodasyidan species respectively from Italy, Brazil and Sweden. In many respects, the new species resemble most closely species of the genus Macrodasys; however, details of the external morphology, in combination with the different lay-out of the reproductive system and the tiny spermatozoa lacking a visible flagellum, suggest they belong to a new genus, possibly in the family Macrodasyidae. These hypotheses are supported by the phylogenetic relationships of 47 taxa inferred from analyses of the 18S rRNA gene, which found the new species clustering with Thaidasys tongiorgii in a subset of a larger clade containing Macrodasys. Accordingly, the establishment of the following taxa is proposed: Kryptodasys gen. nov., K. marcocurinii sp. nov., K. carlosrochai sp. nov. and K. ulfjondeliusi sp. nov.

Contribution to the freshwater gastrotrich fauna of wetland areas of southwestern Ontario (Canada) with redescriptions of seven species and a check-list for North America.

This study gives additional, detailed information on the freshwater gastrotrich species described and reported from the southwestern regions of Ontario and New Brunswick, Canada by Schwank (1990). Aspidiophorus ontarioniensis, Chaetonotus (Chaetonotus) furculatus, Chaetonotus (Chaetonotus) ontariensis, Chaetonotus (Primochaetus) annae, Ichthydium malleum, Lepidodermella forficulata and Setopus lemnicola are all redescribed. In addition, a complete list of freshwater species currently known from North America is given.

New species and records of freshwater Chaetonotus (Gastrotricha: Chaetonotidae) from Sweden.

Chaetonotus is the most speciose genus of the family Chaetonotidae within Gastrotricha, a small phylum of aquatic acoelomate invertebrates. The freshwater gastrotrich fauna of Sweden has been studied during the last five years and so far 44 species have been reported in the literature from the country. This study describes the new species, Chaetonotus (Primochaetus) veronicae n. sp., and reports 9 species new to the Swedish fauna raising the known number of freshwater species from the country to 54. Some records stand out from a biogeographic point of view: Chaetonotus (Primochaetus) soberanus is reported for the first time from Europe and Chaetonotus (Chaetonotus) arethusae, Chaetonotus (Chaetonotus) naiadis and Chaetonotus (Hystricochaetonotus) euhystrix are reported for the first time outside the countries from which they were originally described.

Four new species of Acoela from Chile.

Acoels are with few exceptions marine worms and a common component of the interstitial meiofauna. In this study we present new species to science belonging to Isodiametridae and Solenofilomorphidae. The new species, Isodiametra finkei n. sp., Postaphanostoma nilssoni n. sp., Pseudaphanostoma hyalinorhabdoida n. sp. and Solenofilomorpha pellucida n. sp. were all collected in Chile during March 2012. Nucleotide sequences for the ribosomal genes 18S rDNA and 28S rDNA as well as COI mtDNA have been determined for the new species and used in a maximum likelihood analysis to further support their classification.

Gastrotricha: a marine sister for a freshwater puzzle.

BACKGROUND: Within 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 FINDINGS: Specimens 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/SIGNIFICANCE: A 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.

Phylogeny of Thaumastodermatidae (Gastrotricha: Macrodasyida) inferred from nuclear and mitochondrial sequence data.

BACKGROUND: Phylogenetic 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 FINDINGS: In 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/SIGNIFICANCE: Results 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.