Freshwater Gastrotricha Research Articles

Status of the Italian Freshwater Gastrotricha Biodiversity, with the Creation of an Interactive GIS-Based Web Map

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.

Gastrotrichs and tardigrades in a remnant of Atlantic Forest (Serra do Japi, SP, Brazil)

Abstract: Serra do Japi, located in the southeast of São Paulo State, is considered a priority area for conservation, as it houses original Atlantic Forest cover remains. Despite the significant number of studies about vertebrates and invertebrates that were carried out in this region, the meiofauna biodiversity is completely unknown. Thus, the present study aimed to investigate for the first time freshwater Gastrotricha and limnoterrestrial Tardigrada in Serra do Japi Biological Reserve. Samples of sediments, periphyton and floating vegetation in reservoirs and natural lagoons, and mosses growing on native and non-native tree trunks were collected in May 2019. At least five gastrotrichs morphotypes were identified and three of them were formally described: Chaetonotus acanthocephalus, C. dadayi (first record in Brazil), and Heterolepidoderma mariae (first record outside the type locality). In regards to tardigrades, twelve morphotypes were identified and four of them were formally described: Pseudechiniscus juanitae, Minibiotus cf. acontistus, Echiniscus dreyfusi and Itaquascon umbellinae (last two species reported for the first time outside the type locality). This study reinforces that meiofaunal diversity and distribution have been underestimated, even in one of the five largest hotspots in the world.

New Arctic Gastrotricha — ThreeChaetonotus(Chaetonotidae) from Longyearbyen (Spitsbergen, Svalbard Archipelago)

Gastrotricha is a cosmopolitan phylum of aquatic and semi-terrestrial invertebrates comprising over 820 described species. Virtually no taxonomic or faunistic data exist on freshwater Gastrotricha of the Arctic. So far, 10 studies have recorded Gastrotricha from the entire area of the Svalbard Archipelago; only in two were gastrotrichs determined to the genus and species levels. The remaining studies only reported the presence of Gastrotricha as a phylum. In this article, I present the results of research on freshwater Gastrotricha from the area of fjord Isfjorden (Spitsbergen, Arctic). The collected material contained representatives of 8 species, 2 subgenera of Chaetonotus namely Chaetonotus (Chaetonotus) Erhenberg, 1830 and Chaetonotus (Hystricochaetonotus) Schwank, 1990, two genera namely Chaetonotus Erhenberg, 1830 and Bifidochaetus Kolicka et Kisielewski, 2016, both belonging to the family Chaetonotidae Gosse, 1864 (sensu Leasi and Todaro, 2008). I describe 3 new species from the Chaetonotidae: Chaetonotus (Chaetonotus) jaceki sp. nov., C. (C.) gelidus sp. nov., and C. (C.) svalbardi sp. nov., together with data on the range, frequency and abundance of all noted species. Furthermore, a record abundance of Gastrotricha was noted, amounting to more than one thousand specimens per 1 cm3 of bottom sediment.

A new genus and new species of freshwater Chaetonotidae (Gastrotricha: Chaetonotida) from Brazil with phylogenetic position inferred from nuclear and mitochondrial DNA sequences

Most studies of South American freshwater Gastrotricha have focused on the inland waters of Brazil including São Paulo State, Mato Grosso do Sul State, and Pará State. In this paper, we describe a new genus and species, Cephalionotus kisielewskii gen. et. sp. nov. (Chaetonotida, Chaetonotidae), from Minas Gerais State using morphological data and DNA sequence data (18S rDNA and COI genes). The new genus contains a single psammic species collected from high altitude streams. Cephalionotus gen. nov. exhibits a set of autapomorphic characters that easily distinguish it from all other genera of Chaetonotida: extremely large cephalion and hypostomium that completely cover the dorsal and ventral sides of the head, respectively; a single pair of pleurae; peculiar shape and arrangement of dorsal and ventral scales in the posterior trunk region; one paired, very large, keeled scale at the ventral posterior end; and very long adhesive tubes divided into three parts. Affinity of Cephalionotus kisielewskii gen. et sp. nov. with other Chaetonotida (Paucitubulatina) is discussed from morphological and molecular perspectives.http://zoobank.org/urn:lsid:zoobank.org:pub:5E324696-AB33-42C2-A27A-609B1983D540

Structure, function and evolution of somatic musculature in Dasydytidae (Paucitubulatina, Gastrotricha)

The musculature of two species of the gastrotrich taxon Dasydytidae, Dasydytes (Dasydytes) goniathrix and Haltidytes crassus, was investigated and described using phalloidin staining, confocal microscopy and computer-aided three-dimensional data analysis. Dasydytidae is a peculiar taxon of freshwater Gastrotricha, containing species that are characterized by different adaptations to a semiplanktonic lifestyle, a rather uncommon feature among primarily benthic Gastrotricha. Like other dasydytid species studied so far, D. goniathrix and H. crassus possess a system of movable cuticular spines with an associated system of somatic oblique and segmented lateral muscles. The presence of other somatic (dorsodermal muscles R1 and R2) and visceral muscles (musculi ventrales, m. ventrolaterales, m. dorsales, m. helicoidales) known from a wide range of gastrotrich species was confirmed. Regarded from a functional perspective, the earlier proposed antagonistic role of oblique muscles (as spine abductors) and segmented lateral muscles (as adductors) is questioned for the species studied herein. Alternatively, our structural and behavioral observations suggest that muscular spine abduction in D. goniathrix is brought about by synergistic contraction of the musculi obliqua and m. laterales, and a passive adduction due to muscle relaxation and elastic recoil of the trunk and cuticle. For H. crassus, we hypothesize active muscular spine abduction by contraction of the musculi obliqua plus the last segment of m. laterales accompanied by severe cuticle deformations close to the spine insertions. Adduction is achieved by cuticle reformation due to elasticity and increase in tissue pressure brought about by muscle action, possibly of enforced dorsodermal muscles. The newly obtained and published muscular data of further gastrotrich species were gathered in a species-character matrix. Based on this data set, a maximum parsimony analysis of representatives of the Dasydytidae has been conducted. According to this analysis, there are three well-supported monophyletic lineages within likewise monophyletic Dasydytidae. The first lineage comprises the taxa Anacanthoderma, Stylochaeta and Chitonodytes, the second comprises Dasydytes, Setopus and Ornamentula, and the third represents the taxon Haltidytes. Relationships between these clades could be resolved but are only weakly supported. The new phylogenetic hypothesis is used to reconstruct the ancestral character pattern and to infer possible evolutionary transformations within the Dasydytidae.

A phylogenetic approach to species delimitation in freshwater Gastrotricha from Sweden

Gastrotricha is a cosmopolitan group of aquatic invertebrates. To date, approximately 765 species have been described. This study is the first to deal with species delimitation and cryptic species of freshwater Gastrotricha. Three commonly encountered species, Heterolepidoderma ocellatum, Lepidochaetus zelinkai, and Lepidodermella squamata, are investigated for cryptic speciation. Most of the material is based on Swedish specimens but closely related species from other parts of the world are also included. Taxonomic revisions are supported by phylogenies based on 18S rRNA, 28S rRNA, and COI mtDNA of freshwater Chaetonotidae from several genera and inferred from Bayesian and maximum likelihood approaches. Heterolepidoderma ocellatum f. sphagnophilum is raised to species level, under the name H. acidophilum n. sp. Moreover, genetic data based on COI indicate large variation between two morphologically very similar groups of Lepidodermella squamata. The extent of cryptic speciation in L. zelinkai appears low. Based on the phylogenetic hypothesis presented in this article, the new species, Lepidodermella intermedia n. sp., from northern Sweden is also described. The phylogenetic hypothesis generated shows that Chaetonotidae is a non-monophyletic group.

New data on freshwater psammic Gastrotricha from Brazil

Current knowledge of freshwater gastrotrich fauna from Brazil is underestimated as only two studies are available. The present communication is a taxonomic account of the first-ever survey of freshwater Gastrotricha in Minas Gerais State. Samplings were carried out yielding six species of three Chaetonotidae genera: Aspidiophorus cf. pleustonicus, Ichthydium cf. chaetiferum, Chaetonotus acanthocephalus, Chaetonotus heideri, Chaetonotus cf. succinctus, Chaetonotus sp., and also an undescribed species belonging to the genus Redudasys (incertae sedis): this is the first finding of specimens of Redudasys outside of original type locality. These preliminary observations suggest that the knowledge of the biodiversity of Gastrotricha in the Minas Gerais State, as well as in the whole Brazil, will certainly increase as further investigations are undertaken, and that freshwater Macrodasyida may be more common than previously thought.

Taxonomic and nomenclatural notes on freshwater Gastrotricha

Taxonomic and nomenclatural notes on freshwater Gastrotricha

One new species and records of Ichthydium Ehrenberg, 1830 (Gastrotricha: Chaetonotida) from Sweden with a key to the genus

The freshwater gastrotrich fauna of Sweden is poorly known. Only seven species of freshwater gastrotrichs have been reported so far. This paper is the first in a series of contributions about the Swedish freshwater gastrotrich fauna. Here we describe one new species, Ichthydium skandicum n. sp., from Jämtland, northern Sweden. The new species falls within the boundary of the subgenus Forficulichthys and is morphologically closest to Ichthydium tanytrichum from which it can be differentiated based on the presence of four pairs of dorsal, keeled scales in the posterior trunk region. Moreover, we provide morphometric data for three additional Ichthydium species: I. diacanthum, I. squamigerum and I. tanytrichum, Italian species all of which are reported for the first time outside Italy. Considering the accompanying fauna, a total of thirteen freshwater Gastrotricha are reported for the first time from Sweden. Finally we present a dichotomous key for Ichthydium along with distributional data of the species considered.

Taxonomic and nomenclatural notes on freshwater Gastrotricha

Some taxonomic and nomenclatural remarks concerning freshwater species of Gastrotricha Chaetonotida are presented. In the family Chaetonotidae, the subgenus Chaetonotus (Hystricochaetonotus) is synonimized with the subgenus C. (Chaetonotus sensu stricto). The genus Lepidochaetus is moved to a subgeneric rank into the genus Chaetonotus, and the subgenus Nudichaetonotus Schwank, 1990 is synonymized with C. (Lepidochaetus). Chaetonotus (Lepidochaetus) brasilianus is proposed as a replacement name for Chaetonotus brasilense Kisielewski, 1991, which has become a secondary junior homonym of Chaetonotus brasiliensis Schwank, 1990. Emended diagnoses of the genus Chaetonotus and of the subgenera C. (Chaetonotus sensu stricto), and Chaetonotus (Lepidochaetus) are given. The 3 subgenera of the genus Ichthydium introduced by Schwank (1990) have not been introduced in the present list. In the family Dasydytidae, the subgenus Dasydytes (Setodytes) is synonymized with the genus Setopus. Six new species by Schwank (1990) (Aspidiophorus ontarionensis, Chaetonotus (C.) furculatus, Chaetonotus (Zonochaeta) annae, Ichthydium malleum, Lepidodermella forficulata and Dasydytes (Setodytes) lemnicola) are nomina nuda. An updated list of the reliable world freshwater species of Gastrotricha is reported.

Nouvelles observations sur les Gastrotriches d'eau douce de Guyane française

Finding in French Guyana of three species of freshwater gastrotrichs considered up to now as endemic from Paraguay. Anyone of these species is known from Brazil. Biogeographical remarks on the freshwater Gastrotricha from South America.

Marine and freshwater Gastrotricha from the Island of Montecristo (Tuscan Archipelago, Italy), with the description of new species

Abstract Marine and freshwater gastrotrich fauna from the Island of Montecristo (Tuscan Archipelago) is reported. Thirteen macrodasyid and six chaetonotid species were found in marine sandy sediments from four collecting sites. The new species Lepidodasys unicarenatus and Tetranchyroderma insulare ate described. Nine chaetonotid species were collected from the inland waters of the island, and the new species Chaetonotus (Schizochaetonotus) oplites is described. A comparison between the gastrotrich fauna of Montecristo and that of other islands in the archipelago and of the Tuscan littoral is drawn.

On Some Freshwater Gastrotricha from North-Eastern Region, with Remarks on Indian Taxa

On Some Freshwater Gastrotricha from North-Eastern Region, with Remarks on Indian Taxa

Freshwater Gastrotricha of Poland. II. Gastrotricha from the seaside lakes in the Słowiński National Park

Freshwater Gastrotricha of Poland. II. Gastrotricha from the seaside lakes in the Słowiński National Park

Freshwater Gastrotricha of Poland. I. Gastrotricha from the Tatra and Karkonosze Mountains

Res\ilts of the research on gastrotrichan fauna of the Tatra and Karkonosze Moun­ tains. 39 species were recorded, solely of the fam ily Chaetonotidae. Out of the identified 33 species, 3 species (Chaetonotus sudeticus, Aspidiophorus tatraensis and A. tetrachaetus) are new' to science, Ch. formosus is new to the fauna of Europe, w hile Ch. uncinus and A. ophiodermus are new to the fauna of Poland.

Freshwater Gastrotricha of Poland. IV. Gastrotricha from fish ponds in the vicinity of Siedlce

A b str a ct. In the course of studies carried out on gastrotriclis of fish ponds in the vicin ity of Siedlce (central-east Poland), 39 species were recorded, including 5 very lik ely new to science. Id en tity of Chaetonotus magnus w ith Ch. robustus was evidenced. The present studies provided the third record ever of the occurrence of Ichthydium bifurcatum. Ch. multisetosus, Ch. acanthocephalus and Heterolepidoderma tenuisquamatum were for the third tim e re­ ported from Poland in the course of the present research.

Freshwater Gastrotricha of Poland. V. Gastrotricha of alder woods

Freshwater Gastrotricha of Poland. V. Gastrotricha of alder woods

Freshwater Gastrotricha of Poland. VI. Gastrotricha of small astatic water bodies with rush vegetation

Freshwater Gastrotricha of Poland. VI. Gastrotricha of small astatic water bodies with rush vegetation

Freshwater Gastrotricha of Poland. VII. Gastrotricha of extremely eutrophicated water bodies

Freshwater Gastrotricha of Poland. VII. Gastrotricha of extremely eutrophicated water bodies

Taxonomic notes on some freshwater Gastrotricha from West Bengal, India

The present paper is a taxanomic account of seven species of gastrotrichs (Gastrotricha: Chaetonotidae) collected from Calcutta and its adjacent areas (Lower Bengal). All the reported species represent new records from the north-eastern region of this subcontinent and three of them are new records from India.