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Background: The family Proalidae Harring & Myers, 1924, includes four genera and 53 species, distributed across all eight biogeographic realms and inhabiting various environments, including freshwater, saltwater and terrestrial environments. The genus Proales, the largest within Proalidae, encompasses 41 species characterised by diverse morphological traits. In Korea, the presence of Proalidae has been documented with five known species: Bryceella perpusilla Wilts, Martínez Arbizu & Ahlrichs, 2010, B. stylata (Milne, 1886), B. tenella (Bryce, 1897), Proales fallaciosa Wulfert, 1937 and Proalinopsis caudatus (Collins, 1872). New information: A new species, Proales amplus sp. nov., is the 42nd species within the genus Proales. This species exhibits unique morphological characteristics in the trophi, particularly in the epipharynx, which are distinctive enough to prevent misidentification with other Proales species. The habitus of the new species bears some resemblance to P. phaeopis Myers, 1933, sharing features, such as an elongated and fusiform body, two eyespots, a single foot pseudosegment, two short toes and the absence of a dorsal papilla between the toes. However, the epipharynx of the two species is markedly different. The unique epipharynx characteristic of this new species is unparalleled within the genus Proales. [ABSTRACT FROM AUTHOR]

The family Proalidae Harring & Myers, 1924, includes four genera and 53 species, distributed across all eight biogeographic realms and inhabiting various environments, including freshwater, saltwater and terrestrial environments. The genus Proales, the largest within Proalidae, encompasses 41 species characterised by diverse morphological traits. In Korea, the presence of Proalidae has been documented with five known species: Bryceella perpusilla Wilts, Martínez Arbizu & Ahlrichs, 2010, B. stylata (Milne, 1886), B. tenella (Bryce, 1897), Proales fallaciosa Wulfert, 1937 and Proalinopsis caudatus (Collins, 1872).A new species, Proales amplus sp. nov., is the 42nd species within the genus Proales. This species exhibits unique morphological characteristics in the trophi, particularly in the epipharynx, which are distinctive enough to prevent misidentification with other Proales species. The habitus of the new species bears some resemblance to P. phaeopis Myers, 1933, sharing features, such as an elongated and fusiform body, two eyespots, a single foot pseudosegment, two short toes and the absence of a dorsal papilla between the toes. However, the epipharynx of the two species is markedly different. The unique epipharynx characteristic of this new species is unparalleled within the genus Proales.

We present a data set reporting the checklist of the species of the phylum Rotifera for Italy, updating the one previously published in the series ‘Checklist delle Specie della Fauna d'Italia’ in 1995. The records of the updated checklist refer to the 483 taxa at the species and subspecies level currently known from national Italian territories (119 Bdelloidea, 362 Monogononta, 2 Seisonacea) at the regional level (22 terrestrial and nine marine geographical units). The records refer to various freshwater, limno-terrestrial, and marine coastal habitats. The previous checklist reported 245 taxa (54 Bdelloidea, 189 Monogononta, 2 Seisonacea): three taxa were removed because currently considered not valid and 241 were added, scanning 21 papers we found that were published between 1993 and 2020, expanding the regional records and including four papers older than 1993 with overlooked records in the previous checklist. The Rotifera data are part of the updated Checklist of the Italian Fauna, which is viewable on the LifeWatch Italy platform at https://www.lifewatchitaly.eu/en/initiatives/checklist-fauna-italia-en/checklist and is freely available on the LifeWatch Italy Data Portal (https://dataportal.lifewatchitaly.eu/data). The checklist will be dynamically updated with new records; this paper describes the state of the art of the data set regarding Rotifera on May 2021.

We present a data set on Antarctic biodiversity for the phylum Rotifera, making it publicly available through the Antarctic Biodiversity Information facility. We provide taxonomic information, geographic distribution, location, and habitat for each record. The data set gathers all the published literature about rotifers found and identified across the Continental, Maritime, and Subantarctic biogeographic regions of Antarctica. A total of 1455 records of rotifers in Antarctica found from 1907 to 2018 is reported, with information on taxonomic hierarchies, updated nomenclature, geographic information, geographic coordinates, and type of habitat. The aim is to provide a georeferenced data set on Antarctic rotifers as a baseline for further studies, to improve our knowledge on what has been considered one of the most diverse and successful groups of animals living in Antarctica.

Springs are often considered as "hotspots" of aquatic biodiversity. However, small organisms, such as rotifers, substantially contribute to secondary production, but they are rarely investigated in springs. We surveyed the rotifer fauna of 47 springs in the Knyszyn Forest (north-eastern Poland) in summer and autumn 2014–2015. We hypothesized that stream communities of Rotifera may be specific to this habitat. Rotifer samples were taken using a Plexiglas tube in the spring current. Concurrently, water temperature, pH, conductivity, water redox potential and phosphorus and nitrogen concentrations were determined. The springs did not differ statistically in water quality and were stable regarding their temperature and conductivity. Rotifer densities and mean number of monogonont species were very low both in summer and autumn. Nevertheless, the total number of species recorded in all springs was relatively high and accounted for 101 in total. Although strongly differentiated, the rotifer fauna contained a set of several species common to most of the springs. Most of the recorded species are eurytopic and widely spread in water ecosystems. Only the concentration of magnesium and chloride ions had an impact on Monogononta numbers. [ABSTRACT FROM AUTHOR]

Background: The family Proalidae Harring & Myers, 1924, includes four genera and 53 species, distributed across all eight biogeographic realms and inhabiting various environments, including freshwater, saltwater and terrestrial environments. The genus Proales , the largest within Proalidae, encompasses 41 species characterised by diverse morphological traits. In Korea, the presence of Proalidae has been documented with five known species: Bryceellaperpusilla Wilts, Martínez Arbizu & Ahlrichs, 2010, B.stylata (Milne, 1886), B.tenella (Bryce, 1897), Proalesfallaciosa Wulfert, 1937 and Proalinopsiscaudatus (Collins, 1872)., New Information: A new species, Proalesamplus sp. nov., is the 42 nd species within the genus Proales . This species exhibits unique morphological characteristics in the trophi, particularly in the epipharynx, which are distinctive enough to prevent misidentification with other Proales species. The habitus of the new species bears some resemblance to P.phaeopis Myers, 1933, sharing features, such as an elongated and fusiform body, two eyespots, a single foot pseudosegment, two short toes and the absence of a dorsal papilla between the toes. However, the epipharynx of the two species is markedly different. The unique epipharynx characteristic of this new species is unparalleled within the genus Proales ., (Hee-Min Yang, Gi-Sik Min.)

Abstract Background 18S rRNA is a major component of the small subunit of the eukaryotic ribosome and an important phylogenetic marker for many groups, often to the point of being the only marker available for some. A core structure across eukaryotes exists for this molecule that can help to inform about its evolution in different groups. Using an alignment of 18S rDNA for Rotifera as traditionally recognized (=Bdelloidea, Monogononta, and Seisonacea, but not Acanthocephala), I fitted sequences for three exemplar species (Adineta vaga, Brachionus plicatilis, and Seison nebaliae, respectively) to the core structure and used these maps to reveal patterns of evolution for the remainder of this diverse group of microscopic animals. Results The obtained variability maps of the 18S rRNA molecule revealed a pattern of high diversity among the three major rotifer clades coupled with strong conservation within each of bdelloids and monogononts. A majority of individual sites (ca. 60%) were constant even across rotifers as a whole with variable sites showing only intermediate rates of evolution. Although the three structural maps each showed good agreement with the inferred core structure for eukaryotic 18S rRNA and so were highly similar to one another at the secondary and tertiary levels, the overall pattern is of three highly distinct, but conserved motifs within the group at the primary sequence level. A novel finding was that of a variably expressed deletion at the 3' end of the V3 hypervariable region among some bdelloid species that occasionally extended into and included the pseudoknot structure following this region as well as the central “square” of the 18S rRNA molecule. Compared to other groups, levels of variation and rates of evolution for 18S rRNA in Rotifera roughly matched those for Gastropoda and Acanthocephala, despite increasing evidence for the latter being a clade within Rotifera. Conclusions The lack of comparative data for comparable groups makes interpretation of the results (i.e., very low variation within each of the three major rotifer clades, but high variation between them) and their potential novelty difficult. However, these findings in combination with the high morphological diversity within rotifers potentially help to explain why no clear consensus has been reached to date with regard to the phylogenetic relationships among the major groups.

Springs are often considered as “hotspots” of aquatic biodiversity. However, small organisms, such as rotifers, substantially contribute to secondary production, but they are rarely investigated in springs. We surveyed the rotifer fauna of 47 springs in the Knyszyn Forest (north-eastern Poland) in summer and autumn 2014–2015. We hypothesized that stream communities of Rotifera may be specific to this habitat. Rotifer samples were taken using a Plexiglas tube in the spring current. Concurrently, water temperature, pH, conductivity, water redox potential and phosphorus and nitrogen concentrations were determined. The springs did not differ statistically in water quality and were stable regarding their temperature and conductivity. Rotifer densities and mean number of monogonont species were very low both in summer and autumn. Nevertheless, the total number of species recorded in all springs was relatively high and accounted for 101 in total. Although strongly differentiated, the rotifer fauna contained a set of several species common to most of the springs. Most of the recorded species are eurytopic and widely spread in water ecosystems. Only the concentration of magnesium and chloride ions had an impact on Monogononta numbers.

Background: 18S rRNA is a major component of the small subunit of the eukaryotic ribosome and an important phylogenetic marker for many groups, often to the point of being the only marker available for some. A core structure across eukaryotes exists for this molecule that can help to inform about its evolution in different groups. Using an alignment of 18S rDNA for Rotifera as traditionally recognized (=Bdelloidea, Monogononta, and Seisonacea, but not Acanthocephala), I fitted sequences for three exemplar species (Adineta vaga, Brachionus plicatilis, and Seison nebaliae, respectively) to the core structure and used these maps to reveal patterns of evolution for the remainder of this diverse group of microscopic animals. Results: The obtained variability maps of the 18S rRNA molecule revealed a pattern of high diversity among the three major rotifer clades coupled with strong conservation within each of bdelloids and monogononts. A majority of individual sites (ca. 60%) were constant even across rotifers as a whole with variable sites showing only intermediate rates of evolution. Although the three structural maps each showed good agreement with the inferred core structure for eukaryotic 18S rRNA and so were highly similar to one another at the secondary and tertiary levels, the overall pattern is of three highly distinct, but conserved motifs within the group at the primary sequence level. A novel finding was that of a variably expressed deletion at the 3' end of the V3 hypervariable region among some bdelloid species that occasionally extended into and included the pseudoknot structure following this region as well as the central "square" of the 18S rRNA molecule. Compared to other groups, levels of variation and rates of evolution for 18S rRNA in Rotifera roughly matched those for Gastropoda and Acanthocephala, despite increasing evidence for the latter being a clade within Rotifera. Conclusions: The lack of comparative data for comparable groups makes interpretation of the results (i.e., very low variation within each of the three major rotifer clades, but high variation between them) and their potential novelty difficult. However, these findings in combination with the high morphological diversity within rotifers potentially help to explain why no clear consensus has been reached to date with regard to the phylogenetic relationships among the major groups. [ABSTRACT FROM AUTHOR]

This work was involved DNA extraction from cultured Brachionus calyciflorus subjected to PCR .The PCR reaction was performed with Brachionus calyciflorus which having identical sequences of 18S rDNA and recorded as a global isolates of Brachionus calyciflorus in the (NCBI of USA, ENA of Europe and DDBJ of Japan) with Genbank ID: KM191796.1. [ABSTRACT FROM AUTHOR]

This study investigated the zooplankton composition of Ogbei Stream. Fortnightly samples of zooplankton were sampled for twelve months (May 2018 - April 2019). A total of 1457 specimens belonging to 3 phyla, 5 classes and 7 orders were caught using plankton net with 80µm mesh size. Rotifera (706, 48.46%) was the dominant phylum and Monogononta was the most abundant class. Ploima (590, 40.49%) was the most abundant rotiferan order while Bdelloidea (47, 3.23%) was the least abundant order. Monthly abundance of zooplankton was highest in September (465, 31.91%) during the wet season and lowest in March (56, 3.84%). Seasonally, zooplankton occurred most in the wet season and least in the dry season. [ABSTRACT FROM AUTHOR]

In the course of examination of the zooplankton of Han Stream (Malatya, Turkey) between September 2012 and August 2013, 20 zooplankton species-group taxa were identified. These were 13 species and 1 subspecies of the Rotifera, four species of the Cladocera and two species of the Copepoda. Among rotifers, there are two new geographical records for Turkey: Proales gigantea (Glascott, 1893), a species parasitizing eggs of aquatic snails, and Ascomorpha saltans indica Wulfert, 1966. Among all zooplankton was represented with Rotifera 70%, Cladocera 20% and Copepoda 10%. This new records that discovered are monogonont rotifer. Photo of the new recorded species were illustrated using light microscopy. Scanning electron microscope image was taken for trophi of Ascomorpha saltans indica. [ABSTRACT FROM AUTHOR]

The presence of the rotifer species Brachionus rotundiformis from the B. plicatilis species complex in Lake Arcturo, a saline lake in the Genovesa Island of the Galápagos Islands, is here reported. This is the first record of the species for the rotifer fauna of Ecuador as well as of the species complex to the Galápagos Islands. This finding is consistent with the idea of high dispersion capacity, and of cosmopolitan distribution of this species complex. Because Genovesa Island is uninhabited, passive transport by wind currents and zoochory by migrant birds seem to emerge as the most plausible factors in this process of colonization. Integrative studies on the morphological variations, genetic, molecular, and ecological aspects are still required to further understand the process of dispersion and the ecology of this member of the B. plicatilis species complex in this remote and isolated locality, and the exact taxonomical position of the island's population to the other members of the complex. [ABSTRACT FROM AUTHOR]

A comprehensive re-description of the monogonont rotifer Synchaeta oblonga Ehrenberg, 1832 is presented with the aim of creating a specific and robust suite of characters to identify this species that takes account of its morphological intraspecific variability. To accomplish this, we used an integrative approach that combined morphological data of the habitus and trophi (light and scanning electron microscopy) together with ecological and molecular data to generate a data set that clearly delineates S. oblonga from the morphologically similar Synchaeta tremula (Müller, 1786) with which it is often confused. In addition, by comparing S. oblonga to all remaining members of the genus Synchaeta, we found that the literature descriptions of Synchaeta rufina Kutikova and Vasiljeva, 1982, a Lake Baikal endemic species, and Synchaeta littoralis Rousselet, 1902, a species whose taxonomic status with respect to S. oblonga had already been called into question, to both lie entirely within the range of intraspecific morphological variability present in S. oblonga. Thus, we conclude that S. oblonga can be clearly demarcated from S. tremula, but that no unambiguous morphological differences exist to delineate it from either S. rufina or S. littoralis. Because our molecular data indicate S. oblonga to be a single species despite the morphological intraspecific variability that is present, we recommend that thorough re-examinations of the taxonomic statuses of both S. rufina and S. littoralis should be performed on topotypes sampled from their type localities (Lake Baikal, Russia and Dundee, Scotland, respectively). [ABSTRACT FROM AUTHOR]

Abstract Temperature‐Size Rule (TSR) is a phenotypic body size response of ectotherms to changing temperature. It is known from the laboratory studies, but seasonal patterns in the field were not studied so far. We examined the body size changes in time of rotifers inhabiting activated sludge. We hypothesize that temperature is the most influencing parameter in sludge environment, leading sludge rotifers to seasonally change their body size according to TSR, and that oxygen content also induces the size response. The presence of TSR in Lecane inermis rotifer was tested in a laboratory study with two temperature and two food‐type treatments. The effect of interaction between temperature and food was significant; L. inermis followed TSR in one food type only. The seasonal variability in the body sizes of the rotifers L. inermis and Cephalodella gracilis was estimated by monthly sampling and analyzed by multiple regression, in relation to the sludge parameters selected as the most influential by multivariate analysis, and predicted to alter rotifer body size (temperature and oxygen). L. inermis varied significantly in size throughout the year, and this variability is explained by temperature as predicted by the TSR, but not by oxygen availability. C. gracilis also varied in size, though this variability was explained by both temperature and oxygen. We suggest that sludge age acts as a mortality factor in activated sludge. It may have a seasonal effect on the body size of L. inermis and modify a possible effect of oxygen. Activated sludge habitat is driven by both biological processes and human regulation, yet its resident organisms follow general evolutionary rule as they do in other biological systems. The interspecific response patterns differ, revealing the importance of taking species‐specific properties into account. Our findings are applicable to sludge properties enhancement through optimizing the conditions for its biological component.

The discovery and exploration of cryptic species have been profoundly expedited thanks to developments in molecular biology and phylogenetics. In this study, we apply a reverse taxonomy approach to the Brachionus calyciflorus species complex, a commonly studied freshwater monogonont rotifer. By combining phylogenetic, morphometric and morphological analyses, we confirm the existence of four cryptic species that have been recently suggested by a molecular study. Based on these results and according to an exhaustive review of the taxonomic literature, we name each of these four species and provide their taxonomic description alongside a diagnostic key. [ABSTRACT FROM AUTHOR]

Swimming is of vital importance for aquatic organisms because it determines several aspects of fitness, such as encounter rates with food, predators, and mates. Generally, rotifer swimming speed is measured by manual tracking of the swimming paths filmed in videos. Recently, an open-source package has been developed that integrates different open-source software and allows direct processing and analysis of the swimming paths of moving organisms. Here, we filmed groups of females and males of Keratella cochlearis separately and in a mixed experimental setup. We extracted movement trajectories and swimming speeds and applied the classification method random forest to assign sex to individuals of the mixed setup. Finally, we used advanced statistical methods of movement ecology, namely a hidden Markov model, to investigate swimming states of females and males. When not discriminating swimming states, females swam faster than males, while when discriminating states males swam faster. Specifically, females and males showed two main states of movement with many individuals switching between states resulting in four modes of swimming. We suggest that switching between states is related to predator avoidance. Males of K. cochlearis especially exhibited switching between turning in a restricted area and swimming over longer distances. No mating or other male-female interactions were observed. Our study elucidates the steps necessary for automatic analysis of rotifer trajectories with open-source software. Application of sophisticated software and analytical models will broaden our understanding of zooplankton ecology from the individual to the population level. [ABSTRACT FROM AUTHOR]

Abstract: Monogononta is the most speciose class of rotifers, with more than 2,000 species. The monogonont genus Brachionus is widely distributed at a global scale, and a few of its species are commonly used as ecological and evolutionary models to address questions related to aquatic ecology, cryptic speciation, evolutionary ecology, the evolution of sex and ecotoxicology. With the importance of Brachionus species in many areas of research, it is remarkable that the genome has not been characterized. This study aims to address this lacuna by presenting, for the first time, the whole‐genome assembly of the freshwater species Brachionus calyciflorus. The total length of the assembled genome was 129.6 Mb, with 1,041 scaffolds. The N50 value was 786.6 kb, and the GC content was 24%. A total of 16,114 genes were annotated with repeat sequences, accounting for 21% of the assembled genome. This assembled genome may form a basis for future studies addressing key questions on the evolution of monogonont rotifers. It will also provide the necessary molecular resources to mechanistically investigate ecophysiological and ecotoxicological responses. [ABSTRACT FROM AUTHOR]

Autophagy is a ‘self-eating’ system that regulates the degradation of cellular components and is involved in various biological processes including survival and development. However, despite its crucial role in organisms, the regulatory mechanism of autophagy remains largely unclear, particularly in invertebrates. In this study, conserved autophagy in the rotifer Brachionus koreanus in response to cadmium (Cd) exposure was verified by measuring acidic vesicle organelles using acridine orange (AO) and neutral red (NR) staining, and by detecting LC3 I/II on Western blot and immunofluorescence. We also demonstrated activation of p38 mitogen-activated protein kinase (MAPK) in response to Cd-induced oxidative stress, leading to the induction of autophagy in B. koreanus . This was further verified by analysis of MAPK protein levels and immunofluorescence of LC3 I/II after treatment with reactive oxygen species (ROS) scavengers and inhibitors specific to MAPKs. We propose a p38 MAPK-mediated regulatory mechanism of autophagy in B. koreanus in response to Cd-induced oxidative stress. This study will contribute to a better understanding of autophagic processes in invertebrates and its modulation by environmental stressors. [ABSTRACT FROM AUTHOR]

Facultative sexual species employ a dual reproductive strategy (heterogony) comprising primarily asexual reproduction with intermittent sexual reproduction. Given the higher relative costs of sexual reproduction, elucidating the triggers underlying these transitions might help our understanding of the evolution of (obligate) sex in general. Existing hypotheses into how and when facultative sexuals invest into sex focus largely either on environmental (habitat-deterioration and resource-demanding hypotheses) or genetic factors (condition-dependent hypothesis), but tend to lack experimental evidence, especially with respect to within-population variation. To address this deficit, we examined the influence of several variables that potentially affect fitness (food quality, water temperature, physiological acclimation, and all combinations thereof) on both the lifetime reproduction (total number of offspring) and investment into sexual offspring per female in a clonal population of the monogonont rotifer Brachionus rubens. Investment into sex, both absolutely and relative to lifetime reproduction, was tied most closely to and positively correlated with individual fitness (i.e., lifetime reproduction): individuals with higher fitness invested more into sexual reproduction. These results run contra to the condition-dependent hypothesis and indicate an energy-budget analogue of the resource-demanding hypothesis. Furthermore, investment into sex increased after a period of physiological acclimation to the new conditions, probably because of the amelioration of short-term stress effects or clonal selection. Our results underscore that life history and general phenotypic considerations-here, energetic provisioning of offspring, the presence of a sexual resting stage, and the relative timing of sexual versus asexual reproduction-can modify existing hypotheses based either on environmental or genetic factors alone. [ABSTRACT FROM AUTHOR]

This study investigates the influence of limnological parameters that are known to influence rotifer species richness and composition in temperate areas on two families of monogonont rotifers in a tropical area. We analysed species richness and diversity of the two families from 133 samples taken from several habitat types in Thailand. Coordinates, elevation, pH, temperature, conductivity, salinity and dissolved oxygen were measured and their effect on rotifers assessed. A total of 60 species in 5 genera was recorded from the two families. Latitude and temperature had an effect on species richness of Brachionidae. None of the variables affected species richness of Lecanidae, except habitat type, albeit not significantly. Habitat type and conductivity had an effect on species composition of the two families, whereas latitude had an effect only on species composition of Lecanidae. Species richness and composition of the two rotifer families are well documented in Thailand and no or only few additional species are expected. The limnological correlates of rotifer diversity seem to be in part comparable to and in part different from those known from temperate areas, suggesting that there may be general trends in rotifer species richness and composition across different latitudes.

We studied the accumulation of lead as Pb(NO3)2 in the freshwater rotifer Lecane quadridentata using Leadmium Green and x-ray microanalysis by energy dispersion. The results indicate that lead is bioaccumulated in great amounts in the stomach after the rotifer is exposed for 24 h to 0.5 mg L-1 of Pb(NO3)2. When the exposure concentration of Pb(NO3)2 is increased to 1.0 mg L-1, lead was detected mostly in the cuticle after 24 h. Analysis of x-ray microanalysis by energy dispersion suggests a loss of calcium and rubidium, and an increase of aluminum, niobium, and silicon. A discussion comparing bioaccumulation between the rotifers Brachionus calyciflorus and Lecane quadridentata is included. [ABSTRACT FROM AUTHOR]

Two morphologically distinct Brachionus calyciflorus hatched from Lake Littra sediment: a typical B. calyciflorus Pallas and B. (calyciflorus) "Darling", a reproductively isolated, globular taxon without posteromedian spines. The Darling taxon is well defended against Asplanchna by its large size (adult lorica length ≥ 310 μm) and short (~50 μm) Asplanchna-induced posterior spines that protect small, vulnerable neonates. The typical B. calyciflorus is smaller (adult lorica length 169-195 μm) and is a mixture of interbreeding clones with or without constitutive posterolateral spines. In one of the former clones, adult posterolateral spine length increased significantly with maternal age, from ~62 to 78 μm. Asplanchna induced increased lorica length and pronounced spine development in all clones and its effect on females with constitutive posterolateral spines was additive. With Asplanchna, posterolateral spine length was 159 μm for a clone without constitutive posterolateral spines and 207 μm in a clone with 74μm-long constitutive posterolateral spines. Coexistence of clones with and without constitutive posterolateral spines suggests a trade-off between the benefit of long defensive spines and some cost to spine development. It likely is maintained by fluctuating directional selection in response to changing Asplanchna abundance and by a sediment bank of diapausing eggs produced by sexual reproduction. [ABSTRACT FROM AUTHOR]

Anticipatory parental effects modulate population responses to environmental conditions and so are predicted to play a large role in the responses of organisms to global change., In response to one such aspect of global change, the eutrophication of freshwaters and associated blooms of the toxin-producing cyanobacteria species Microcystis aeruginosa, the rotifer Brachionus calyciflorus produces larger offspring., We hypothesized that rotifers, with their short generational times, exposed to highly predictable cyanobacteria bloom conditions, may adaptively increase offspring investment and offspring fitness (i.e. the maternal match hypothesis)., We explicitly tested the consequences of this differential investment by rearing offspring produced by rotifers reared under Microcystis and the nontoxigenic green alga Chlamydomonas, in a full factorial design, where offspring were raised under the maternal diet or the opposite food source., We measured age-specific fecundity, survival and population growth rates under these conditions and found that maternal exposure to Microcystis decreased offspring survival and fecundity, regardless of offspring diet. Population growth rates, tested using aster models, differed significantly among maternal and neonate diets, but there was no significant interaction between the two factors., Our evidence thus leads us to reject the maternal match hypothesis in this case of rotifer-toxigenic algal bloom interactions and provides further support that toxigenic algal blooms may have extensive effects on grazer populations in ways that are not evaluated using traditional, single-generation experimental methods., A is available for this article. [ABSTRACT FROM AUTHOR]

Four species of the genus Synchaeta were identified in the waters of Liepaja harbour (coastal Eastern Gotland Basin, Baltic Sea). Synchaeta baltica and S. monopus are common in the Baltic Sea and they co-dominated most of the samples. Synchaeta fennica was abundant during spring, but S. triophthalma was detected in October 2014 for the first time in Latvian waters. During sample analysis particular attention was paid to insufficiently described trophi of S. monopus and S. fennica. Subsequently, brief descriptions were made during analysis and complemented with images. [ABSTRACT FROM AUTHOR]

A better understanding of the ability of organisms to adapt to local selection conditions is essential for a better insight in their ecological dynamics. The study of micro-evolutionary adaptation and its eco-evolutionary consequences is challenging for many reasons and the choice of a suitable model organism is particularly important. In this paper, we explain why monogonont rotifers, through their unique combination of traits, are ideal study organisms for this purpose. With a literature review, we demonstrate the capacity of monogonont populations to adapt to a variety of selection conditions (e.g., salinity, food shortage, elemental limitation, and disturbance regimes) within very short-time frames and highlight some potential eco-evolutionary implications. Although monogononts are increasingly used in eco-evolution-oriented studies, their potential is still underappreciated compared to other model organisms. No doubt the high prevalence of cryptic species complexes and the lack of genomic tools form important obstacles that may discourage researchers to work with this group. Here, we argue that none of these difficulties should prevent monogonont rotifers from becoming commonly used model organisms in micro-evolutionary studies and make suggestions for future research. [ABSTRACT FROM AUTHOR]

Rotifers are ubiquitous freshwater animals for which many complexes of cryptic species (i.e. distinct species that are morphologically difficult to distinguish) are described. Keratella cochlearis occurs globally and shows a wide phenotypic diversity indicating the potential presence of a species complex. We sampled lakes of the Trentino-South Tyrol region (Italy) and investigated mitochondrial genetic diversity in K. cochlearis in relation to detailed lorica measurements. We sequenced the mitochondrial cytochrome c oxidase subunit I and used the generalised mixed Yule coalescent approach, Poisson tree process model and automatic barcode gap discovery to delimit mitochondrial groups, associated with putative evolutionary significant units (ESUs). Based on 248 sequences, eight putative ESUs were indicated that could only partially be delimited by lorica morphology. Specifically, several morphological characteristics (i.e. spinelets, bended median ridge, and posterior spine) were found in specimens of different putative ESUs, and thus, these characters seem to be of poor discriminatory value. Furthermore, different putative ESUs of K. cochlearis were found in the same lake. We conclude that the high mitochondrial genetic diversity may be linked to tolerance of K. cochlearis to varying environmental conditions. [ABSTRACT FROM AUTHOR]

In this contribution, we review our knowledge on bet-hedging strategies associated with rotifer diapause. First, we describe the ecological scenario under which bet hedging is likely to have evolved in three diapause-related traits in monogonont rotifer populations: (1) the timing of sex (because diapausing eggs are produced via sexual reproduction), (2) the sexual reproduction ratio (i.e. the fraction of sexually reproducing females) and (3) the timing of diapausing egg hatching. Then, we describe how to discriminate among bet-hedging modes and discuss which modes and mechanisms better fit the variability observed in these traits in rotifers. Finally, we evaluate the strength of the empirical evidence for bet hedging in the scarce studies available, and we call for the need of research at different levels of biological complexity to fully understand bet hedging in rotifer diapause. [ABSTRACT FROM AUTHOR]

We present a survey of the literature documenting sexuality in monogonont rotifers, including reports of diapausing embryos (DEs), males, and/or hatchlings from dry sediments. Of 30 families, 27 possess species with documented occurrences of sex. Information on DEs is lacking in 41 genera. Of ~300 species with evidence of sexuality (~20% of ~1500 monogononts), only 172 had direct observations of DEs; in the others, DE production was inferred from observations of males and/or hatchlings. DEs are sufficiently widespread to affirm that their presence is plesiomorphic, however few DE characteristics show a phylogenetic signature. They differ widely in volume (~0.11-100 × 10 µm) and have a varied surface morphology (smooth to highly structured and ornamented). Some species retain DEs within their bodies; others carry them, deposit them on or attach them to surfaces, or release them free into the water. To better understand the evolutionary forces that influence monogonont sexuality and DE biology, a more comprehensive and uniform reporting scheme is needed. To enhance information dissemination, we propose that new and existing data on sex in monogonont rotifers (DEs, males, and hatchlings from dry sediments) be placed in an Internet-based repository. [ABSTRACT FROM AUTHOR]

This study investigates the influence of limnological parameters that are known to influence rotifer species richness and composition in temperate areas on two families of monogonont rotifers in a tropical area. We analysed species richness and diversity of the two families from 133 samples taken from several habitat types in Thailand. Coordinates, elevation, pH, temperature, conductivity, salinity and dissolved oxygen were measured and their effect on rotifers assessed. A total of 60 species in 5 genera was recorded from the two families. Latitude and temperature had an effect on species richness of Brachionidae. None of the variables affected species richness of Lecanidae, except habitat type, albeit not significantly. Habitat type and conductivity had an effect on species composition of the two families, whereas latitude had an effect only on species composition of Lecanidae. Species richness and composition of the two rotifer families are well documented in Thailand and no or only few additional species are expected. The limnological correlates of rotifer diversity seem to be in part comparable to and in part different from those known from temperate areas, suggesting that there may be general trends in rotifer species richness and composition across different latitudes. [ABSTRACT FROM PUBLISHER]

The ATP-binding cassette ( ABC ) transporter family is one of the largest gene family in animals, and members of this family are known to be involved in various biological processes due to their ability to transport a wide range of substrates across membranes using ATP cleavage-derived energy. We identified 61 ABC transporters in the genome of the monogonont rotifer Brachionus koreanus , and classified these into eight distinct subfamilies (A–H) by phylogenetic analysis. ABC transporters in the rotifer B. koreanus are comprised of 11 ABCA genes, 19 ABCB genes, 14 ABCC genes, 3 ABCD genes, 1 ABCE gene, 3 ABCF genes, 8 ABCG genes, and 2 ABCH genes. Extensive gene duplication and loss events in synteny were observed in several subfamilies. In particular, massive gene duplications of P-glycoproteins ( P-gps ), multidrug resistance proteins ( MRPs ), and Bk-Abcg-like proteins were observed. The ability of these B. koreanus proteins to function as multixenobiotic resistance (MXR) ABC transporters was validated using specific fluorescence substrates/inhibitors. The ABC transporter superfamily members identified in this study will be useful in future toxicological studies, and will facilitate comparative studies of the evolution of the ABC transporter superfamily in invertebrates. [ABSTRACT FROM AUTHOR]

In this study, 39 rotifer species from the families Lecanidae and Lepadellidae were identified after examination of samples collected from 47 different localities in Turkey. Lecane acanthinula, L. thalera, and L. unguitata are new records for the Turkish rotifer fauna. [ABSTRACT FROM AUTHOR]

The meiofauna assemblages inhabiting the bryophyte-covered tufa barriers were investigated in the barrage system of Plitvice Lakes (Croatia). The main aims of the present study were: (1) to analyse the structure of the rotifer community and other meiofaunal communities in the bryophytes and the hyporheic tufa zone; and (2) to determine the influence of food sources on the meiofauna. Our results indicate that meiofauna were a constant and abundant component in bryophytes and tufa. Of the nine identified groups (Catenulida, Gastrotricha, Nematoda, Rotifera, Hydrachnidia, Oligochaeta, Copepoda, Tardigrada and Chironomidae (Diptera)), rotifers (50%) and nematodes (40%) were most abundant. Rotifers were the most diverse meiofaunal group and reached their highest numbers within the bryophytes. Also, the highest amount of ultrafine particulate organic matter, as a potential food source for rotifers, was recorded in this layer. Nematodes were the dominant meiofaunal group in deeper tufa layers. They are an omnivorous trophic group and different food sources (such as phytal remains or other meiofauna) were available in tufa layers. Meiofaunal assemblages were significantly nested and their composition was under the influence of community established in surface bryophyte mats. Information on these often overlooked faunal groups is essential for estimates of overall abundance, species richness and productivity in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

In contrast to the highly conserved mitogenomic structure and organisation in most animals (including rotifers), the two previously sequenced monogonont rotifer mitogenomes were fragmented into two chromosomes similar in size, each of which possessed one major non-coding region (mNCR) of about 4–5 Kbp. To further explore this phenomenon, we have sequenced and analysed the mitogenome of one of the most studied monogonont rotifers, Brachionus calyciflorus. It is also composed of two circular chromosomes, but the chromosome-I is extremely large (27 535 bp; 3 mNCRs), whereas the chromosome-II is relatively small (9 833 bp; 1 mNCR). With the total size of 37 368 bp, it is one of the largest metazoan mitogenomes ever reported. In comparison to other monogononts, gene distribution between the two chromosomes and gene order are different and the number of mNCRs is doubled. Atp8 was not found (common in rotifers), and Cytb was present in two copies (the first report in rotifers). A high number (99) of SNPs indicates fast evolution of the Cytb-1 copy. The four mNCRs (5.3–5.5 Kb) were relatively similar. Publication of this sequence shall contribute to the understanding of the evolutionary history of the unique mitogenomic organisation in this group of rotifers. [ABSTRACT FROM AUTHOR]

In this study, we evaluated accumulation and adverse effects of ingestion of microplastics in the monogonont rotifer (Brachionus koreanus). The dependence of microplastic toxicity on particle size was investigated by measuring several in vivo end points and studying the ingestion and egestion using 0.05-, 0.5-, and 6-µm nonfunctionalized polystyrene microbeads. To identify the defense mechanisms activated in response to microplastic exposure, the activities of several antioxidant-related enzymes and the phosphorylation status of mitogen-activated protein kinases (MAPKs) were determined. Exposure to polystyrene microbeads of all sizes led to significant size-dependent effects, including reduced growth rate, reduced fecundity, decreased lifespan and longer reproduction time. Rotifers exposed to 6-µm fluorescently labeled microbeads exhibited almost no fluorescence after 24 h, while rotifers exposed to 0.05- and 0.5-µm fluorescently labeled microbeads displayed fluorescence until 48 h, suggesting that 6-µm microbeads are more effectively egested from B. koreanus than 0.05- or 0.5-µm microbeads. This observation provides a potential explanation for our findings that microbead toxicity was size-dependent and smaller microbeads were more toxic. In vitro tests revealed that antioxidant-related enzymes and MAPK signaling pathways were significantly activated in response to microplastic exposure in a size-dependent manner. [ABSTRACT FROM AUTHOR]

Triclosan (TCS) and Triclocarban (TCC) are used as antimicrobial agents and have been widely dispersed and detected in the marine environment. However, the toxicities of TCS and TCC have been poorly investigated in marine invertebrates. In this study, the effects of TCS and TCC on mortality, population growth, lifespan, and fecundity were examined in the monogonont rotifer ( Brachionus koreanus ) using cellular ROS levels, GST enzymatic activity, and gene expression of defensomes. The median lethal concentration (LC50) of TCS (393.1 μg/L) and TCC (388.1 μg/L) was also determined in the same species. In TCS- and TCC-exposed B. koreanus , growth retardation and reduced fecundity were observed and were shown to have a potentially deleterious effect on the life cycle of B. koreanus . In addition, time-dependent increases in ROS content (%) and GST enzymatic activity were shown in response to TCS and TCC exposure. Additionally, transcript levels of detoxification proteins (e.g., CYP s), antioxidant proteins (e.g., GST-sigma , Cu / ZnSOD , CAT ), and heat shock proteins ( Hsp s) were modulated in response to TCS and TCC exposure over a 24 h period. Our results indicate that TCS and TCC induce oxidative stress and transcriptional regulation of detoxification, antioxidant, and heat shock proteins, resulting in changes in lifespan and fecundity. [ABSTRACT FROM AUTHOR]

We provide here a checklist of species of Monogononta rotifers from lentic and lotic environments in Argentina, 25 years after the initial catalogue compiled by Susana B. José de Paggi. This new inventory now includes the reports on rotifers documented in 93 studies produced after 1990. The majority of the investigations were carried out in three of the 24 Argentine provinces. In addition, the presence of 13 species in samples from three water bodies within Buenos Aires province are now cited here for the first time in Argentina. In this updated checklist, a total of 351 species are catalogued, the majority being representatives of the Lecanidae, Brachionidae, and Lepadellidae. [ABSTRACT FROM AUTHOR]

To examine the toxic effects of multi-walled carbon nanotubes (MWCNTs) in the marine environment, we first exposed the monogonont rotifer ( Brachionus koreanus ) to MWCNTs in the presence of copper. The acute toxicity of copper decreased significantly with a decrease in copper bioavailability resulting from MWCNT exposure. Furthermore, we examined the effects of MWCNT exposure on reproductive capacity, population growth rate, growth patterns, antioxidant systems, and mitogen-activated protein kinase (MAPK) activation. Reproductive capacity, population growth rate, and body growth rate were significantly suppressed in B. koreanus in response to 1.3–4 mg/L MWCNT exposure. Furthermore, MWCNTs induced the generation of reactive oxygen species (ROS) and decreased the antioxidant enzymatic activities of catalase (CAT) and glutathione reductase (GR). However, the enzymatic activity of glutathione S -transferase (GST) was up-regulated after a 24 h-exposure to 100 mg/L MWCNTs. Exposure to 100 mg/L MCWNTs induced extracellular signal-regulated kinase (ERK) activation in B. koreanus , suggesting that p-ERK may mediate the adverse effects of MWCNTs in B. koreanus via the MAPK signaling pathway. Our results provide insight into the mechanistic basis of the ecotoxicological effects of MWCNTs in the marine environment. [ABSTRACT FROM AUTHOR]

Phthalate esters are widespread contaminants that can cause endocrine disruption in vertebrates. Studies showed that molecules with hormonal activities in vertebrates and invertebrates can affect asexual and sexual reproduction in rotifers. We investigated the impact of di-hexylethyl phthalate (DEHP), di-butyl phthalate (DBP) and butylbenzyl phthalate (BBP), on the asexual and sexual reproduction of the freshwater monogonont rotifer Brachionus calyciflorus in order to determine a potential environmental risk for sexual reproduction. We observed that DEHP has no significant impact on both asexual and sexual reproduction up to 2 mg/L. DBP has a positive effect on asexual reproduction at concentrations from 0.05 to 1 mg/L, but depresses it at 2 mg/L. Sexual reproduction is only affected at 2 mg/L and the impact observed is negative. BBP displayed a negative impact on both asexual and sexual reproduction at 1 and 2 mg/L. However we showed that the impacts of BBP on mixis and fertilization rates observed are due to the decrease in population growth rates at these concentrations and not to a direct impact of BBP on the mixis and the fertilization processes. Our results show that sexual reproduction in B. calyciflorus is not more sensitive than asexual reproduction to any of the substances tested which indicates the mode of action of these molecules is related to general toxicity and not to an interference with potential endocrine regulation of sexual reproduction. Comparison of effect concentrations and surface water contamination by phthalate esters suggests these compounds do not constitute a risk for primary consumers in these environments. [ABSTRACT FROM AUTHOR]