Brachionus Species Research Articles

Effects of salinity on life history traits and fatty acid-binding proteins in the marine rotifer, Brachionus plicatilis

We present a comprehensive analysis of the impact of increased salinity on Brachionus plicatilis, focusing on growth, reproduction, behavior, and fatty acid-binding protein (FABP) gene expression. We discovered delays in maturation and potential disruptions in the reproductive process under conditions of high salinity. Experiments demonstrated that while the total number of B. plicatilis offspring remained unchanged across different salinity levels, the peak daily offspring count was delayed, and the pace of reproduction was slower at higher salinity. However, the pre-reproductive and reproductive periods at 35 practical saline units were extended, contributing to longer timeframes to produce all offspring, but the post-reproductive period was shortened, thus balancing the overall lifespan across different salinity levels. Furthermore, we noted that high salinity impedes the growth of B. plicatilis and causes alterations in swimming behavior. Our findings also demonstrated five pairs of FABPs within the three Brachionus species (B. plicatilis, B. rotundiformis, and B. koreanus) with distinctive sequences. Phylogenetic analysis revealed that Brachionus FABPs diverged before the speciation of the three species and were found outside the vertebrate FABP group. The results contribute to our understanding of the impact of high salinity on B. plicatilis and the evolutionary positioning of FABPs in these species, while also highlighting the need for further research into specific FABP differentiation and expression patterns in Brachionus species.

New record of six Brachionus species from the South of Iraq

In this survey, six species of Brachionus genus are indexed as new record in the south Iraqi water resource at the first time in Iraq depending on the sequence of 18S rRNA gene, these species were registered as a new record in Iraq and the other two species which are HH1 and HH2 were registered in the National Center for Biotechnology Information (NCBI), The European Nucleotide Archive (ENA) and DNA Data Bank of Japan (DDBJ) sequentially.

Environmental Characterization of Two Ecologically Distinct Gangetic Oxbow Lakes using Zooplankton Taxonomic Indices Through Comparative Approach for Wetland Monitoring

The present investigation is an attempt for environmental characterization of two ecologically distinct oxbow lakes using zooplankton taxonomic indices following a comparative approach. These closed and seasonally open oxbow lakes are subjected to eutrophication, impacting their nutrient concentration and eco-hydrological characteristics. The zooplankton are closely linked with environment throughout their life cycle, hence are a potential indicator of eutrophication. The study examined the assemblage pattern of zooplankton community and trophic state of two ecologically distinct oxbow lakes based on eco-hydrological factors and community structure of rotifers and planktonic crustaceans. Comprehensive trophic state index (mTSI), rotifer trophic state indices (mTSIROT) and crustacean based indices (TSICR) were used to assess the degree of eutrophication. The Kruskal–Wallis test confirmed the heterogeneity in eco-hydrological factors between the oxbow lakes. The studied lakes were in transition from high meso-eutrophic to moderately eutrophic state. The mTSI, mTSIROT and mTSICR for Khalsi (seasonally open) and Akaipur (closed) were 54.90 ± 11.71, 56.95 ± 15.64, 59.55 ± 4.54 and 60.26 ± 4.48, 55.79 ± 4.76, 60.00 ± 4.03 respectively. The Canonical Correspondence Analysis (CCA) revealed NO3−N, water temperature and pH positively impacted abundance of eutrophication indicator species Brachionus and Keratella. An overview of worldwide use of rotifer and crustacean based indices in assessment of TSI has also been discussed. The use of these zooplankton indices to evaluate the trophic status of the ecologically distinct lakes is highly recommended for water quality assessment and management.

The genome of the freshwater monogonont rotifer Brachionus rubens: Identification of phase I, II, and III detoxification genes

Monogonont rotifers are common species in aquatic environments and make model species for ecotoxicology studies. Whole genomes of several species of the genus Brachionus have been assembled, but no information on the freshwater rotifer Brachionus rubens has been reported. In this study, the whole-genome sequence of B. rubens was successfully assembled using NextDenovo. The total length of the genome was 132.7 Mb (N50 = 2.51 Mb), including 122 contigs. The GC contents accounted for 29.96% of the genome. Aquatic organisms are always exposed to various external stresses, and a comprehensive genomic analysis is needed to better understand the adverse effects on organisms. This paper focuses on the ecotoxicological aspect and conducted genome analysis of representative gene families involved in detoxification mechanisms against environmental stressors. Specifically, we identified cytochrome P450 genes (CYPs) of phase I, glutathione S-transferase genes (GSTs) of phase II, and ATP-binding cassette transporter genes (ABCs) of phase III in the genome of B. rubens. Gene duplications were found in CYP, GST, and ABC genes, as is the case for other Brachionus rotifers. Our results suggest that these detoxification-related gene families have evolved in a species-specific and/or lineage-specific manner. This paper improves our understanding of how the freshwater Brachionus rotifers respond to environmental stressors in a molecular ecotoxicology context.

Hydrological Characteristics and Trophic Status as Dominant Drivers of Rotifer Community Composition in Artificially Created Riverine Wetlands.

Simple SummaryIncreased public awareness of wetlands and the importance of their conservation stipulated various preservation or improvement projects. In 2012, riverine wetlands were created in the Nakdong River in Korea to replace those damaged or destroyed by the River Refurbishment Project, but they could not be maintained as functional wetlands, owing to the long-term neglect and lack of management. A previous survey detected various problems in these wetlands, including insufficient in/outflow function, shore instability, and difficulty in introducing appropriate water sources, which cause nutrient accumulation and algal blooms. The in/outflow functions of the mainstream and tributaries were hampered by soil and plant deposition. These chemical changes influenced the community composition of rotifers. In particular, three rotifer species—Brachionus, Keratella, and Trichocerca—were mainly distributed in wetlands with relatively high nutrient concentrations (total nitrogen and phosphorus). Therefore, the rotifer community can be used as an indicator of the nutritional status of a wetland, and the functional state of the wetland can be understood through continuous monitoring of rotifers.Hydrological characteristics of freshwater ecosystems are powerful determinants of the distribution of biological communities and changes in environmental factors. This study identified relationships between the wetland environment, rotifer community, and hydrological factors for 48 wetlands, to determine their impact on wetland conservation and management. Different hydrological factors produced different wetland environments, which influenced the rotifer community composition. The wetlands with “poor” “in/outflow function” and “shore stability” levels showed high conductivity, turbidity, depth, and concentrations of total nitrogen, total phosphorus, and chlorophyll a. In contrast, the dissolved oxygen levels and velocity were the highest in wetlands with “good” in/outflow function and shore stability variables. The nutritional status of each wetland affected the composition of the rotifer community. Some genera (Keratella, Brachionus, Anuraeopsis, Trichocerca, and Philodina) were found in wetlands with high concentrations of total nitrogen, total phosphorus, and chlorophyll a, and high turbidity and depth. In contrast, Ascomorpha and Ploesoma were found in wetlands with high dissolved oxygen levels and flow velocity. High densities of Lepadella, Lecane, and Testudinella were found in wetlands completely covered by macrophytes. The rotifer community distribution can be used to understand the trophic, current functional, and environmental status of wetlands.

Community structure of two rotifer populations and ecological assessment of water quality in Miyun Reservoir

In order to understand the changes in the ecological environment of Miyun Reservoir after the South-to-North Water Transfer Project, our study investigated the changes in the composition and structure of two indicator species in the Miyun Reservoir and applied the rotifer biological assessment method to analyse the changes of water ecological environment. Our results showed that a total of 10 species of the genera Trichocerca and Brachionus were identified during the investigation with an average annual abundance of 542.124 ind./L and 102.68 ind./L, respectively. Among them, T. pusilla and T. cylindrica were the dominant species of the genus Trichocerca, and the majority of Brachionus species were B. diversicornis, B. angularis, B. caudatus. Variance results showed that there were significant differences in the abundance of these two rotifer pupations at different inter-annual and spatial scales during the survey. The biological evaluation indicated that the water quality has gradually changed from eutrophication to oligotrophication after the South-to-North Water Transfer Project, and the ecological environment was maintained well. Our results will provide necessary ecological parameters for water environment protection and ecological safety management of Miyun Reservoir.

Species Diversity of selected Flora and Fauna in the river Yamuna at Kalpi (U.P.) India

To evaluate the pollution status species diversity of selected flora and fauna of the Yamuna river at Kalpi stretch was studied for a period of one year. Four sampling stations were selected for sampling purpose. Collected samples are evaluated for flora and fauna specially phytoplankton, aquatic macrophytes, zooplankton and fishes. Selected flora and fauna of studied water are presented by phytoplankton members of Chlorophyceae, Euglenophyceae, Bacillariophyceae and Cyanophyceae, aquatic macrophytes of 8 families, zooplankton members of Protozoa, Rotifera, Cladocera and Copepoda and fishes of 10 families. In these recorded species of different groups of flora and fauna, some pollution indicator species like Scenedesmus quadricauda, Stigeoclonium tenue,Ankistrodesmus falcatus, Chlorella vulgaris, Euglena viridis, Synedra ulna, Cyclotella meneghiniana, Navicula viridula, Nitzschia, Oscillatoria limosa, O. tenuis, O. chlorina, Phormidium uncinatum,Microcystis aeruginosa of phytoplanton, Eichhornea, Potamogeton and Cyperus species of aquatic macrophytes, Brachionus species and Keratella species of zooplankton and Clarias batrachus fish are also presented along with clean water species. Presence of both pollution indicator and clean water species show that water of Yamuna river at Kalpi stretch is moderately polluted. Sustaining the diversity of flora and fauna it is necessary to maintain living status of this river.

Evaluation of the trophic status in three reservoirs in Algeria (north west) using physicochemical analysis and rotifers structure.

The aim of this study is to examine the trophic state of three reservoirs located in the northwest of Algeria based on the physicochemistry of water and the community of rotifers. The measurements of the physicochemical variables were carried out monthly over a 2-year period from December 2015 to November 2017. The rotifers were sampled simultaneously. Abiotic and biotic indices such as the Carlson index, QB/T, and TSIROT were determined in order to classify the three reservoirs according to their trophic state. Thus, the diversity indices of Shannon-Wiener (H'), Margalef richness index (D), Pielou evenness (J'), and the density were calculated in order to study the structure of the rotifers. The Kruskal-Wallis test confirmed the heterogeneity of the physicochemical quality (P value < 0.05) among the three reservoirs. A total of 71 species were identified during this study. The result of the various indices affirms this heterogeneity and indicates a trophic state hypereutrophic for the Hammam Boughrara reservoir, eutrophic for the Bakhadda reservoir and meso-oligotrophic for Sidi Yacoub. The use of canonical correspondence analysis (CCA) has shown that the structure of rotifers is influenced by local environmental factors. Some species such as the genus Brachionus species have shown their preference for extreme conditions. The use of biotic indices is highly recommended for the trophic state evaluation of reservoirs for a better water resources management.

Effects of Temperature on Life History Strategy of the Rotifer Euchlanis dilatata.

The cosmopolitan littoral rotifer Euchlanis dilatata is a potential model species in eco-toxicological and ecological studies, owing to its unique characteristics, such as periphytic benthic living, sensitivity to toxicity, and laying eggs on substrates instead of carrying them on the mother's body. However, studies about the life history strategy of this species, in contrast to the intensely studied planktonic Brachionus species, are relatively scarce. Temperature is an important factor that affects the rotifer's life history traits, and is well known to induce phenotypic plasticity in planktonic rotifers. The present study measured life table parameters of the rotifer E. dilatata originating from one clonal population local to Beijing under three temperature treatments: 14°C, 20°C and 26°C (10 females/replicate × 4 replicates for each treatment). We also examined trade-offs between egg size and egg number, as well as current reproduction and future survival to evaluate the life history strategy of the rotifer. In contrast to cold conditions, in which mothers produced a few large eggs with similar egg sizes, in warm environments, mothers produced many smaller eggs and a few larger eggs, thus resulting in a clear variation in egg sizes. With increasing temperature, the pre-mature period, reproductive period, life span and generation time shortened, while the net reproductive rate and population growth rate increased. Temperature also affected the trade-off between current reproduction and future survival. This work provides basic data for the potential model species E. dilatata.

Utilizing Brachionus biodiversity in marine finfish larviculture

Mouth gape sizes of marine finfish larvae determine the size of rotifer prey that can be ingested, so providing appropriate size rotifers controls the success of larval rearing. It is difficult for hatcheries to maintain pure cultures of multiple rotifer species by long-term serial dilution without cross-contamination. In this paper, we describe a technique for utilizing multiple rotifer species in larviculture that uses rotifer diapausing eggs as inocula, enabling hatcheries to supply larval predators with optimally sized rotifers. Biodiversity in the Brachionus plicatilis species complex is extensive, including considerable variation in body size. In this paper, we show that large quantities of diapausing eggs can be produced from many Brachionus species. Using the full range of body size diversity from seven Brachionus species, we can produce adult female rotifers with mean body lengths as small as 137 μM, or as large as 305 μM, and neonate females with body lengths ranging from 103 to 206 μM. The length of diapausing eggs for small Brachionus species averaged 100 μM, and 166 μM for large species. Diapausing egg production varied by 3.6 fold among 14 strains. Using diapausing eggs of the very small rotifer Proales similis (88 μM) to inoculate mass cultures also is described.

Genome-wide identification of the entire 90 glutathione S-transferase (GST) subfamily genes in four rotifer Brachionus species and transcriptional modulation in response to endocrine disrupting chemicals

Genome-wide identification of glutathione S-transferase (GST), a major phase II detoxification enzyme, was investigated in four different aquatic model rotifer species Brachionus koreanus, B. plicatilis, B. rotundiformis, and B. calyciflorus. GSTs are ubiquitous antioxidant enzymes that play versatile function including cellular detoxification, stress alleviation, and production of the radical conjugates. Among the four rotifers, B. rotundiformis was found with the least number of GST genes (total 19 GST genes), whereas the other three species shared 23 to 24 GST genes. Among the identified GST genes, belonging to the cytosolic GST superfamily, the expansion of GST sigma classes mainly occurs through tandem duplication, resulting in tandem-arrayed gene clusters on the chromosomes. Overall, the number of genes discovered in this study was highest in the sigma class, zeta, alpha, and omega in descending order. With integration of phylogenetic analysis and xenobiotic-mediated GST mRNA expression patterns along with previous enzymatic activities, the functional divergence among species-specific GST genes was clearly observed. This study covers full identification of GST classes in three marine rotifer and one fresh-water rotifer species and their important role in marine environmental ecotoxicology.

Life-history strategies in zooplankton promote coexistence of competitors in extreme environments with high metal content

The toxicity of pollutants on aquatic communities is determined by the specific sensitivities and by the ecological relationships between species, although the role of ecological interactions on the specific sensitivity to pollutants is complex. We tested the effect of exposure to copper on the life-history strategies of two coexisting rotifer species of the genus Brachionus from Inca-Coya lagoon, an isolated water body located in Atacama Desert. The experiments looked at differences in the response to the stress by chemical pollution mimicking field conditions of copper exposure, levels of food, and salinity, between single-species cultures and coexisting species. Under single species cultures, B. ‘Nevada’ had lower densities, growth rates, and resting eggs production than B. quadridentatus; when in competition, B. ‘Nevada’ performed better than B. quadridentatus in most life-history traits. B. ‘Nevada’ was a copper-tolerant species, which outcompeted B. quadridentatus, more copper-sensitive, with higher levels of copper. Species-specific responses to environmental conditions and pollution, plus differential relationships between population density and production of resting eggs, resulted in reduced niche overlap between species, allowing stabilized coexistence. The extreme environmental conditions and the isolation of the Inca-Coya lagoon, make it an excellent model to understand the adaption of aquatic organisms to stressed environments.

DISTRIBUTION OF MONOGONONT ROTIFERS, Branchionus spp IN NORTH SULAWESI

In order to characterize the distribution pattern of rotifers Brachionus spp. in North Sulawesi, sample collections have been conducted at four locations, two at east coast and other two at west coast of North Sulawesi peninsula, which are connected to Maluku and Sulawesi Seas, respectively. At each location, a 40 p.m mesh size plankton net with a 0.3 m opening diameter was horizontally towed at three sites to represent coastal water, estuary and brachkiswater pond. Sampling periods were in January and August 2005 to represent west monsoon and east monsoon, respectively. Each sampling was performed twice a day during high and low tide. Some environmental factors were also measured in situ during the sampling. Three species of Brachionus were found during the survey, Brachionus rotundiformis, B. caudatus and B. quadridentatus. Their abundances were significantly different, both between locations and sampling sites. However, among the similar habitat such as between Manembo-nembo and Minanga brachkishwater ponds, B. rotundiforms abundance was not significantly different. This species was the most abundant compared to the other two species, in average 1984,4 ind/m3, while the other species was as low as 26,1 ind/m3 and 212,9 ind/m3 for B. caudatus and B. quadridentatus, respectively. The abundance of rotifers in northern areas connected to Molluccas Sea is higher compared to those in the southern areas connected to Sulawesi Sea. Distribution of B. caudatus is very similar to those of B. rotundiformis, while B. quadridentatus appears to have its specific pattern. Results of this study suggest that the abundance and species composition of the rotifers reflect trophic status of the aquatic ecosystem in the area. It is still awaiting future studies to elaborate the impacts of the trophic gradients in horizontal distribution of rotifers. Therefore, it is necessary to conduct a long term monitoring with emphasis on the structure of rotifer assemblages in a variety of sites subjected to environmental perturbations, including anthropogenic contaminant inputs.

The genome of the freshwater monogonont rotifer Brachionus calyciflorus.

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 129.6Mb, with 1,041 scaffolds. The N50 value was 786.6kb, 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.

Combined Effects of Temperature and the Microcystin MC-LR on the Feeding Behavior of the Rotifer Brachionus calyciflorus.

The aim of this study was to investigate the responses in filtration and grazing rates of five rotifer strains of the species Brachionus calyciflorus under different temperatures and MC-LR concentrations. The results showed that strain identity, MC-LR concentration, temperature, and the interactions of these factors significantly affected both response variables, with the exception of the interaction of strain and MC-LR on the grazing rates. At low MC-LR concentrations and for the control group, the filtration and grazing rates increased with increasing temperature. The filtering and grazing rates of B. calyciflorus exposed to higher MC-LR concentrations, however, showed no evident enhancement with increasing of temperature. At high temperatures, the filtration and grazing rates of all rotifer strains decreased significantly with increasing concentration of MC-LR, however B. calyciflorus exhibited a refractory stability in the presence of increased MC-LR levels at lower temperatures.

Selectividad de los renacuajos de Incilius valliceps (Anura: Bufonidae) sobre el zooplancton de agua dulce

The dietary preferences of tropical tadpoles and the way they interact with zooplankton often go unstudied in aquatic ecosystems. Goals. We investigated the interactions between Incilius valliceps tadpoles and a freshwater zooplankton community found in an artificial aquatic pond located on Cozumel Island in Quintana Roo, Mexico. Methods. We determined zooplankton abundance, richness, the Shannon-Wiener diversity index, and the proportion of each zooplankton species in the environment. We also evaluated characteristics of the tadpole population such as body size, abundance, and proportion of prey ingested as determined by stomach content analysis. We used the Jacobs selectivity index to determine tadpole prey of preference. Results. The rotifers Anuraeopsis fissa and an unidentified species of Bdelloidea group were dominant among the eight zooplankton species consumed. The selectivity index showed that I. valliceps tadpoles preferred to consume macro-zooplankton (ostracods and cladocerans) instead of the rotifer species available. Tadpoles positively chose Cypridopsis vidua throughout their growth and development and Moina wierzejskii during their early developmental stages, and negatively selected the rotifer species of the one unidentified species of Bdelloidea, A. fissa, and Epiphanes brachionus. In the presence of tadpoles, Keratella americana, Lepadella patella, and Lecane luna were either present in extremely low abundances or not found in the aquatic community, and M. wierzejskii produced males and resistant eggs. Conclusions. The findings of this study clarify the dietary needs of tropical tadpoles and their role in aquatic ecosystems.

Biodiverse rotifer assemblage (Rotifera: Eurotatoria) of floodplain lakes of the Brahmaputra basin of lower Assam, northeast India: composition and ecosystem diversity

The study aims to ascertain the hypothesis on the rich rotifer biodiversity of the floodplain lakes (beels) of the Brahmaputra river basin and to use these metazoans to assess trophic status or to characterize habitat variations of wetlands. The plankton samples collected from four beels of lower Assam revealed 160 Rotifera species belonging to 35 genera and 19 families. The richness is of biodiversity value as ~38.0% and ~57.0% of the rotifer species known till date from India and northeast India (NEI), respectively. One species each is new to the Oriental region and NEI, and three species are new to Assam; 23 species merit global biogeography interest and several exhibit distribution values in the Indian sub-region. The diverse Lecanidae > Brachionidae > Lepadellidae > Trichocercidae and speciose littoral-periphytic Lecane > Lepadella > Trichocerca, and richness of Brachionus spp. following removal of aquatic macrophytes are noteworthy. Overall rotifer composition showed homogeneity amongst beels while lower monthly richness and community similarities affirmed heterogeneity within individual beels. We propose L/B quotient based on Lecane: Brachionus species ratios to characterize habitat variations of the sampled wetlands. Sladecek’s B/T quotient based on Brachionus: Trichocerca species ratios affirmed general’ meso-trophic’ status of different beels. Our results provided little insight on the influence of individual abiotic factors but the canonical correspondence analyses asserted higher cumulative influence of ten abiotic parameters on Rotifera richness in each beel.

Seasonal Changes in Zooplankton and Macro-fauna Populations of the East Calcutta Wetland Fish Ponds

The current study was to explore the seasonal variation in the zooplankton and aquatic macroinvertebrate population in India’s oldest and largest sewage fed fish ponds of East Kolkata Wetlands and whether they show different trends from the natural ponds. Zooplankton diversity was significantly higher in fish ponds whereas macroinvertebrate diversity was higher in natural ponds. Zooplanktons showed significant seasonal variation in the natural ponds but did not show any variation throughout the year in sewage fed fisheries. Among zooplankton species Brachionus spp., Keratella tropica which are pollution (eutrophy) indicator were found in greater abundance in EKW fisheries than natural ponds. Chironomid larvae which thrive and flourish in highly organically polluted or eutrophicated waters were dominant in EKW. The regular input of sewage provides a certain high level of nutrient to the fisheries which help to maintain greater and consistent population density and diversity of zooplanktons forming a strong base for the food webs in the EKW ponds.

LA VARIACIÓN Y FRECUENCIA DE ALGUNAS ESPECIES DE ROTÍFEROS PROVENIENTES DE LA CIÉNAGA GRANDE DE SANTA MARTA (COLOMBIA)

This report is about six species of Rotifers belonging to three families follow: Brachionidae: three species of the genus Brachionus and one of the genus Platyias; Lecanidae: one species of Lecane, and Testudinelidae: one species of the genus Filinia. The report attempts to show how these species vary in quantity over a specified period according to the very considerable ÿchanges salinity in the Ciénaga Grande. Also indicated is the occurence of other genera of Rotifers in this region of Colombia.

Development time of male and female rotifers with sexual size dimorphism

Dwarfism in males is a common phenomenon in planktonic monogonont rotifers. Considering the small body size of males, some studies suggested that the development time of male rotifers is faster than that of females. However, empirical studies associated with such a speculation are scarce. In this study, we used two common rotifer species, Brachionuscalyciflorus and Brachionusplicatilis (each with two geographical populations), to test the hypothesis that the development time of dwarf males is significantly shorter than that of females. Results showed that male eggs (embryos) were deposited much faster than female eggs (embryos) in both Brachionus species. However, the embryonic development time of these small male eggs (embryos) was longer than that of large female eggs (embryos). As a result, males needed significantly longer total development time than females. The total development time of males was 2–3 h longer than that of females in both Brachionus species. Male-producing and female-producing females in the two Brachionus species did not show any difference in development time. Because sexual reproduction begins at high population densities in both species, postponement of development in males will be advantageous by decreasing mating costs in male rotifers.