New data on Brazilian semiplanktonic gastrotrichs (Gastrotricha: Chaetonotida).

Gastrotricha are free-living aquatic microinvertebrates with a ubiquitous distribution. With almost two centuries of accumulated knowledge, currently there are more than 860 described species, but our knowledge on Brazilian Gastrotricha is still far from complete. This statement is even more precise when considering freshwater semiplanktonic gastrotrichs. We aim to contribute to biodiversity knowledge of Brazilian gastrotrichofauna with new records of Dasydytes lamellatus Kisielewski, 1991, Haltidytes pseudosquamosus Minowa & Garraffoni, 2017 and Neogossea acantholla Kisielewski, 1991. We provide morphometric, molecular and phylogenetic data for these species, and the first electron microscopy record of D. lamellatus revealing previously inaccessible characters.

Assessing biodiversity shortfalls of freshwater meiofauna from the Atlantic Forest: New species, distribution patterns and the first total-evidence phylogeny of semiplanktonic Gastrotricha.

The Brazilian Atlantic forest is a tropical rainforest recognized as a hotspot of biodiversity, with high species richness and endemicity. This forest extends over a wide latitudinal range, bordering the entire Brazilian coastline, from sea level to high mountains over 2000 m.a.s.L., and presents a variety of environmental conditions and forest physiognomy. Despite many years of intense studies on animal biodiversity in the biome, there is a lack of information on meiofauna taxa causing several shortfalls in biodiversity knowledge of these tiny organisms. In this study, we address some of these shortfalls by describing a new species of Neogossea (Gastrotricha: Chaetonotida) from a lentic ecosystem in southeastern Brazil, surrounded by fragments of Atlantic Forest by using an integrative approach combining different morphological techniques and molecular data. We also point out new hypotheses of homologous structures due to scanning electron microscope observations of the new species. Additionally, we used two numerical methods to assess distribution patterns and historical regionalization of four freshwater meiofaunal taxa (Gastrotricha, Rotifera, Copepoda and Cladocera). For the first time, we accessed the areas of endemism in this biological hotspot based on aquatic fauna with a very peculiar life history. Due to sampling issues and meiofauna species being widespread, our results raise incongruences with previous endemism analyses on vertebrates and arthropods. Finally, we performed the first total-evidence phylogenetic analyses of benthic and semiplanktonic gastrotrichs based on 59 morphological characters and three molecular markers, employing a parsimony approach. The phylogenetic reconstruction supports the hypothesis of a single origin of semiplanktonic gastrotrichs, and both Dasydytidae and Neogosseidae families are monophyletic taxa as well as four non-monotypic genera.

Redescription of the dasydytid gastrotrich Haltidytesooëides (Brunson, 1950) based on type material.

The semi-pelagic gastrotrich species Haltidytesooëides (Brunson, 1950) is redescribed based on original type material deposited at the Smithsonian National Museum of Natural History. Herein we present a new diagnosis and figures of the species, detailing the insertion position of the lateral spines, misinterpreted in the original description. Furthermore, we reassess the taxonomic key for the genus Haltidytes Remane, 1936 based on our new findings.