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Phylogenetic relationships of 43 Gastrotricha Macrodasyida inferred from Bayesian analysis of 18 S rDNA. The outgroup is represented by Xenotrichula intermedia (Chaetonotida, Xenotrichulidae). Number at nodes represents posterior probabilities.
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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...
Citations
... The Tropical Northwestern Atlantic (TNWA) is one of the most biodiverse areas for marine gastrotrichs with more than 70 species reported from its five regions (renaud-Debyser, 1963;Thane-Fenchel, 1970;hummon, 1974;Schöpfer-Sterrer, 1974;ruppert, 1978b;Kisielewski, 1984;Decho et al., 1985;Evans & hummon, 1991;Evans, 1992Evans, , 1994Todaro, 1994;Todaro et al., 1995;hochberg, 2008, 2010hummon, 2010b, 2010ahochberg & Atherton, 2011;Atherton & hochberg, 2012;Todaro et al., 2012;Atherton, 2014;Kånneby et al., 2014;Schuster et al., 2017;Araújo & hochberg, 2023). The TNWA includes the type locations for three species: C. miniceratus hummon, 1974, C. pacificus Schmidt, 1974 and C. interinsularis Kieneke, Schmidt-rhaesa & hochberg, 2015. ...
A new gastrotrich species of the genus Cephalodasys (Macrodasyida: Cephalodasyidae) is described from Capron Shoal, Florida, USA. The new species is up to 630 μm long. There are six TbA that arises directly from a fleshy hand-like base. up to 26 TbVL per side. 11 pairs of TbV running from u28 to u65. 12 pairs of TbP arranged symmetrically along the posterior margin from u90 to u100. Animals are simultaneous hermaphrodites with a rounded frontal organ and a putative caudal organ. on the other hand, the new species is unique and differs from its congeners by the arrangement of anterior, posterior and ventrolateral adhesive tubes and by exclusive series of TbV, first time reported in Cephalodasys. A complete set of longitudinal, circular and helicoidal muscles are described for the first time for a Cephalodasys species using Confocal Laser Scanning Microscopy (CLSM). The muscular analysis added important novelties to the knowledge of muscular architecture of Macrodasyida group and to the phylum.
... The first encompasses up to 380 species distributed in nine families and 37 genera with a large variation of body shape and cuticular ornamentations, bearing multiple adhesive tubes along the body, almost exclusively marine, with some freshwater exceptions (e.g. Kisielewski (1987); Garraffoni et al. 2010Garraffoni et al. , 2019aTodaro et al. (2012); Araújo et al. (2013); Kånneby and Wicksten (2014). The latter, Chaetonotida, is composed of seven families, totaling 490 species divided into 31 genera of tenpin-body shaped animals, usually with only a single pair of adhesive tubes in the posterior region (except for those with two pairs, or even absent) (Kånneby et al. 2013;Garraffoni and Araújo 2020;Araújo et al. 2022). ...
... The result of these networks increases the quality of scientific publications because it allows the development of more sophisticated research due to the use of integrative approaches (e.g. phylogeny, ultrastructure with transmission electron microscopy, and 3D anatomical reconstruction with laser confocal microscopy, molecular analysis) (Todaro et al. 2012;Kånneby et al. 2013;Kånneby and Wicksten 2014;Araujo et al. 2016;Garraffoni et al. , 2019aSchnier et al. 2019;Kieneke and Todaro 2021;Minowa and Garraffoni 2021;Araújo et al. 2022). In our opinion, the possible next step to engage even more the Gastrotrichologist community is to organize an International Symposium on Gastrotricha, that could represent the greatest scientific forum on this taxon. ...
... Most of the papers are related to species description (e.g., Kisielewski (1987), Araújo and Hochberg (2017), , Bosco et al. (2020), Campos et al. (2020), Minowa and Garraffoni (2021), Araújo et al. (2022) and in the past years new publications have started to investigate a few internal relationships among the taxon (e.g. Hochberg and Litvaitis (2000); Todaro et al. (2012); Kånneby et al. (2013); ; Garraffoni et al. 2019a);Campos et al. (2020) and new techniques to investigate the ultrastructure start to be used to understand the physiology (e.g., Hochberg and Litvaitis (2001), Guidi et al. (2002), Kieneke and Ostmann (2012), Schnier et al. (2019). ...
Since the discovery of the first Gastrotricha at the end of the eighteenth century, the study of this taxon has proven to be notoriously difficult due to the fragility of the body and its diminutive size. Consequently, this microinvertebrates group is considered part of the less-known metazoan taxa and its biodiversity knowledge is still far from being understood. To bring light to the past, present, and future understanding of Gastrotricha biodiversity literature, we conducted the first study aimed to quantitatively and qualitatively evaluating the global research productivity on this clade by carrying out a bibliographic survey in Web of Science and Scopus databases using bibliometric tools. We found 523 studies published between 1904 and 2022 and detected i) a high prevalence of “new species’’ as a keyword in the literature, indicating the youth of our knowledge on biodiversity of this phylum; ii) the formation of clusters of interacting researchers around well-established veterans’ researchers in Europe; but also, iii) the formation of new research centers training new research-ers in recent decades around the world. However, we also found that there are gaps in the accessibility of past literature in the main search tools. We believe that it is time to explore new facets of Gastrotricha research and we hope that our study can provide a guide for future research development to shape more effective policies for biodiversity discovery and conservation initiatives.
... The order Macrodasyida includes four freshwater species distributed in two genera whose species have been found either at a single site, such as Marinellina flagellata Ruttner-Kolisko, 1955 in Austria [14] or at a few sites, such as Redudasys fornerise and R. brasiliensis in Brazil [15][16][17], and R. neotemperatus Kånneby & Kirk, 2017 in the USA [18,19]. Resting eggs are not reported for these parthenogenetic species. ...
Gastrotricha are microscopic benthic animals found in almost all water bodies. To date, over 890 species distributed in 71 genera, 18 families, and two orders are known. There are 376 freshwater species, and several are also found in Italy; however, a compendium of the studies carried out so far, and a georeferenced distribution of the species, still need to be provided. This project summarizes information about the diversity and geographic distribution of Italian gastrotrichs. Diversity data, acquired over 239 years, were reviewed and corrected based on taxonomic and nomenclatural updates and, in addition to distribution information, were organized into a data matrix valuable for statistical analysis. The data were fed into geographic information system software to understand the overall figures more easily. The results indicated that Italy is one of the best-known countries regarding freshwater gastrotrichs. With 92 species in 17 genera and three families from 61 investigated localities, Italy counts 17 type localities and 19 endemic species. Despite this high biodiversity, many Italian regions still need to be investigated, and should, therefore, be the focus of future research. The implementation of a web-mapping plugin enabled the creation of interactive maps for an easy and modern method for sharing the work done, and the information acquired.
... The order Macrodasyida includes four freshwater species distribute in two genera whose species have been found either at a single site, such as Marinellina flagellata Ruttner-Kolisko, 1955 in Austria [12] or at a few sites, such as Redudasys fornerise and R. brasiliensis in Brazil [13][14][15], and R. ...
Gastrotricha are microscopic benthic animals found in almost all water bodies. To date, about 870 species distributed in 71 genera, 18 families, and two orders are known. Known freshwater species are 359, several of which found also in Italy; however, a compendium of the studies carried out so far and a georeferenced distribution of the species still needs to be provided. This project aims to summarize information about Italian gastrotrichs' diversity and geographic distribution. Diversity data, acquired over 239 years, were reviewed and corrected based on taxonomic and nomenclatural updates and, in addition to distribution information, were organized into a data matrix useful for statistical analysis and to be feed to a Geographic Information System software to easily understand the overall figures. Results indicate Italy as one best-known country regarding freshwater gastrotrich, with 88 species in 16 genera and 3 families from 59 investigated localities; the Nation counts 16 type localities and 19 endemic species. Despite its censed biodiversity, many Italian regions remain still poorly or not investigated where future research should focus. Implementing a web mapping plugin enabled the creation of interactive maps for an easy and modern sharing of the work done and information acquired.
... The Tropical Northwestern Atlantic (TNWA) has seen an increase in descriptions of new species of marine Gastrotricha ever since Hummon (2010) published his review of Caribbean species. To date, more than 70 species have been reported from the five regions that compose the TNWA (Renaud-Debyser 1963;Thane-Fenchel 1970;Hummon 1974;Schöpfer-Sterrer 1974;Kisielewski 1984;Decho et al. 1985;Evans & Hummon 1991;Evans 1992Evans , 1994Todaro 1994;Todaro et al. 1995;Hochberg 2008Hochberg , 2010Hummon 2010;Hochberg & Atherton 2011;Atherton & Hochberg 2012;Kånneby et al. 2012;Todaro et al. 2012a;Atherton 2014). ...
A new gastrotrich species of the genus Crasiella (Macrodasyida: Planodasyidae) is described from Capron Shoal, Florida, USA. The new species is up to 520 μm long and differs from its congeners in the position of adhesive tubes and the structure of its spermatozoa. There are nine TbA that insert ventrally on the head plus an additional pair of TBA that insert medially. Up to 42 TbVL per side. Six pairs of TbP insert on a pair of caudal pedicles. Animals are simultaneous hermaphrodites with an elongated frontal organ and large caudal organ. The spermatozoa have a tripartite acrosome unlike others in the genus that have a four-part acrosome.
... Semiplanktonic gastrotrichs show a high dependence on the periphytic environment, between roots of floating and submerged aquatic plants (Nesteruk 2000;Balsamo et al. 2014;Kånneby 2016;Minowa & Garraffoni 2017. However, most of the inland sampling done in Brazil was concentrated in the upper layer of sandy sediment (psammon) on benthic and interstitial biotopes (Kisielewski 1987(Kisielewski , 1991Todaro et al. 2012;Araújo et al. 2013Araújo et al. , 2016Garraffoni et al. , 2017aGarraffoni et al. , 2019bGarraffoni & Melchior 2015) totalling 73 coordinates across the country (distributed in 13 sampling sites) where only 18 reports came from periphyton environments (5 sites) (Table S3) (Kisielewski 1991;Garraffoni & Melchior 2015;Minowa & Garraffoni 2017Guidetti et al. 2021). ...
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.
... Morphology-based identification of gastrotrichs is, however, hampered by (1) the lack of standardized methods for species descriptions in the past, (2) a great disparity of species descriptions among authors, (3) the briefness and generality of 'old' descriptions, (4) the over-schematization and simplification of illustrations, and (5) the necessity of detailed examination of living specimens (Kisielewski 1991;Balsamo et al. 2008;Garraffoni & Melchior 2015;Kieneke & Nikoukar 2017;Magpali et al. 2021 and references cited therein). Nowadays, an integrative approach combining detailed morphological observations (e.g., differential interference contrast optics, confocal laser scanning microscopy, SEM) with multi-gene data is the preferred way for the description of new gastrotrich species (e.g., Kånneby 2011;Todaro et al. 2012;Garraffoni et al. 2017Garraffoni et al. , 2019aKolicka et al. 2016Kolicka et al. , 2018Kolicka 2019aKolicka , 2019bBosco et al. 2020;Magpali et al. 2021). Molecular data are, indeed, crucial for the recognition of cryptic and near-cryptic species, as it is the very definition of cryptic species that it is difficult, if not impossible, to find morphological characters that distinguish among them. ...
The subgenus Hystricochaetonotus Schwank, 1990 is one of the most species-rich subgenera of Chaetonotus Ehrenberg, 1830. It has a worldwide distribution and encompasses 37 species predominantly living in the benthos and periphyton of limnetic habitats. We have discovered further nine new species in running and stagnant waters in Slovakia (Central Europe): Ch. (H.) arcanus sp. nov., Ch. (H.) avarus sp. nov., Ch. (H.) gulosus sp. nov., Ch. (H.) iratus sp. nov., Ch. (H.) luxus sp. nov., Ch. (H.) mirabilis sp. nov., Ch. (H.) optabilis sp. nov., Ch. (H.) slavicus sp. nov., and Ch. (H.) superbus sp. nov. Their morphology was studied using differential interference contrast microscopy and subsequent morphometric analyses were carried out. In addition, the primary and secondary structures of their 18S, ITS2, and 28S rRNA molecules as well as their barcoding mitochondrial gene encoding for cytochrome c oxidase (COI) were analyzed. Species boundaries were tested also using the compensatory base change analysis. The new species could be well separated both morphologically and molecularly. The present barcoding analyses revealed that the nuclear ITS2 sequences represent a powerful DNA barcode in addition to the mitochondrial COI gene. According to the multi-gene phylogenetic analyses, the lineage leading to the last common ancestor of the ‘Hystricochaetonotus’ clade is the longest internal branch within the family Chaetonotidae Gosse, 1864. Since members of the subgenus Hystricochaetonotus are morphologically highly heterogeneous, parallel evolution of Chaetonotus-like and/or Hystricochaetonotus-like characters of scales and spines occurred during its radiation.
... The phylum comprises nearly 880 valid species, which are classified into two orders (Balsamo et al. 2015;Kieneke & Schmidt-Rhaesa 2015): Macrodasyida Remane, 1925(Rao & Clausen 1970 and Chaetonotida Remane, 1925(Rao & Clausen 1970. The first order currently contains 384 nominal species, mostly marine, with a vermiform body plan and many adhesive tubes distributed along the length of the body ; only four freshwater species are known (Ruttner-Kolisko 1955;Kisielewski 1987;Todaro et al. 2012;Kånneby & Kirk 2017;Garraffoni et al. 2019a). The second order, Chaetonotida, is composed of approximately 494 species of tenpin-like organisms, most with only one pair of posterior adhesive tubes (Balsamo et al. 2014;Kieneke & Schmidt-Rhaesa 2015). ...
The majority of meiofaunal organisms have limited abilities to disperse over long distances, yet they may still have disjointed distributions. Many studies have found evidence of long distance meiofauna dispersal due to passive transport by wind and/or animals that serve as vectors for these widespread distributions. Our research on an archipelago in northeast Brazil uncovered a species of freshwater gastrotrich that at fi rst sight appeared to be a 'cosmopolitanʼ species that had surpassed the connectivity constraint to occupy an island more than 350 km from the mainland. However, through an integrative approach using molecular sequences and morphology, we have uncovered evidence of a pseudo-cryptic species in this freshwater gastrotrich. Polymerurus insularis sp. nov. closely resembles its congeners and can easily be mistaken for similar species such as P. nodicaudus, a cosmopolitan gastrotrich. Unique to P. insularis sp. nov. are (1) a cuticular armature composed of simple spined scales with polygonal shape (Type 1 scales), (2) a single, spineless dorsal scale with a triangular shape located terminally next to the furca base (Type 2 scale), (3) a spineless zone composed by a patch lacking cuticular ornamentation and fl at, rounded or polygonal scales without spines (Type 4 scales) (4) particular sets of terminal spined or keeled scales located both dorsally and ventrally around the furca base (Types 3, 5, 6, 7 and 8 scales). The presence of this species on a volcanic island is discussed, as is the relationship between pseudocryptism and dispersal in gastrotrichs and other meiofauna.
... Currently, the first order comprises 10 families, 36 genera and 377 described species (Todaro, 2019a), with strap-shaped bodies, the presence of pharyngeal pores and, usually, numerous adhesive tubes present in the anterior, lateral and posterior body regions (Todaro & Hummon, 2008;Kånneby & Hochberg, 2015). The majority of macrodasyids are marine species; only four species have been reported in freshwater from the Swiss Alps, Brazilian streams and a reservoir and aquifer from the USA (Ruttner-Kolisko, 1955;Kisielewski, 1987;Garraffoni et al., 2010Garraffoni et al., , 2019aTodaro et al., 2012;Araújo, Alcantara & Garraffoni, 2013;Kånneby & Wicksten, 2014;Kånneby & Kirk, 2017). Within Chaetonotida, eight families, 32 genera with nearly 483 species (Todaro, 2019b) are interstitial or epibenthic in marine and brackish water, and 2/3 of the species live in freshwater habitats ( Balsamo et al., 2008Balsamo et al., , 2014). ...
Information regarding the records of Brazilian marine gastrotrichs is presented. We systematized and organized the existing information associated with approximately 23 species (belonging to the genera Aspidiophorus , Chaetonotus , Crasiella , Dactylopodola , Dendrodasys , Draculiciteria , Halichaetonotus , Heteroxenotrichula , Kryptodasys , Macrodasys , Pseudostomella , Ptychostomella , Urodasys and Xenotrichula ) from the Brazilian coast (eight endemic) and their 1,581 records from 36 marine ecoregions of the world. A link is provided to an on-line interactive map where all occurrences for each species are shown, accompanied by geographic coordinates, oceans, countries, cities, granulometric characteristics and ecoregions. Furthermore, a critical analysis of the geographical distribution of Brazilian marine gastrotrichs, an estimate of the number of undescribed species, a summary of the existence and status of taxonomical collections are also presented.
... The following key, modified from [35], encompasses the valid families and genera of described to date [24]. Two families (Redudasyidae and Hummondasyidae, belonging to Macrodasyida) and five genera (Bifidochaetus and Cephalionotus belonging to Chaetonotida and Anandrodasys, Hummondasys, Thaidasys, and Kryptodasys belonging to Macrodasyida) included herein have been established since the publication of the previous keys [12][13][14][15]36,37]. For the inclusion of Megadasys among the Planodasyidae (order Macrodasyida), see [18]. ...
Gastrotricha is a group of meiofaunal-sized, free-living invertebrates present in all aquatic ecosystems. The phylum includes over 860 species globally, of which 505 nominal species have been recorded in marine sandy sediments; another 355 taxa inhabit the freshwater environments, where they are recurrent members of the periphyton and epibenthos, and, to a lesser degree, of the plankton and interstitial fauna. Gastrotrichs are part of the permanent meiofauna and, in general, they rank among the top five groups for abundance within meiobenthic assemblages. The diversity, abundance, and ubiquity of Gastrotricha allow us to suppose an important role for these animals in aquatic ecosystems; however, ecological studies to prove this idea have been comparatively very few. This is mainly because the small size and transparency of their bodies make gastrotrichs difficult to discover in benthic samples; moreover, their contractility and fragility make their handling and morphological survey of the specimens rather difficult. Here we offer an overview, describe the basic techniques used to study these animals, and provide a key to known genera in an attempt to promote easy identification and to increase the number of researchers who may be interested in conducting studies on this understudied ecological group of microscopic organisms.
