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

A new species of Aspidiophorus (Gastrotricha: Chaetonotidae) from the Swedish west coast

A new species of marine Gastrotricha is describe from the west coast of Sweden

Probing gastrotrich taxonomy with DNA barcoding

Gastrotrichs represent a phylum of basal metazoans, living both in marine and freshwater environments, dimensionally comprised between 80 µm and 3 mm. Though taxonomic and biogeographic knowledge has been improved in the last years, little is known about the molecular aspects of this group. The aim of this study was to analyze these organisms by means of DNA barcoding which is a well-known technique consisting in the use of a gene sequence to affiliate an organism to a known species or to a new taxon. In this research, mitochondrial gene cytochrome oxidase I (COI) was used to identify gastrotrichs. It’s important to notice that no Gastrotrich COI sequence has been deposited in GenBank so far. Sampling of different populations of Turbanella cornuta and Paraturbanella teissieri, species considered to have a wide distribution, was carried out in Adriatic, Ligurian and Tyrrhenian Sea (Italy), Baltic Sea (Sweden), Atlantic Ocean (Canary Islands) and Arabian Gulf (Kuwait). DNA was extracted from some specimens, COI sequence amplified through PCR, and in the end the product was purified and sequenced. The obtained sequences were analyzed with NJ, MP and Bayesian Inference. It was possible to group in monophyletic clades, morphologically similar specimens belonging both to the same population and to diversely geographically distant populations. In particular, analyses revealed that specimens of T. cornuta from Adriatic, Ligurian, and Baltic Sea and Arabian Gulf can be considered distinct species, although similar. These results show that barcoding allows a more precise specific identification of Gastrotrichs; therefore this technique appears to be clearly useful when dealing with cryptic species, not easily distinguishable just by means of morphological characters. The wide application of this method will be of true interest also in reconsidering on new bases the paradoxical cosmopolitan distribution of several species

Meiofauna of the Koster-area, results from a workshop at the Sven Lovén Centre for Marine Sciences (Tjärnö, Sweden)

During a two-week workshop held at the Sven Lovén Centre for Marine Sciences on Tjärnö, an island on the Swedish west-coast, meiofauna was studied in a large variety of habitats using a wide range of sampling techniques. Almost 100 samples coming from littoral beaches, rock pools and different types of sublittoral sand- and mudflats yielded a total of 430 species, a conservative estimate. The main focus was on acoels, proseriate and rhabdocoel flatworms, rotifers, nematodes, gastrotrichs, copepods and some smaller taxa, like nemertodermatids, gnathostomulids, cycliophorans, dorvilleid polychaetes, priapulids, kinorhynchs, tardigrades and some other flatworms. As this is a preliminary report, some species still have to be positively identified and/or described, as 157 species were new for the Swedish fauna and 27 are possibly new to science. Each taxon is discussed separately and accompanied by a detailed species list