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Predator–prey interactions are crucial components of populations and communities. Their dynamics depend on the covariation of traits of the interacting organisms, and there is increasing evidence that intraspecific trade‐off relationships between defense and competitive traits are important drivers of trophic interactions. However, quantifying the relevant traits forming defense–competitiveness trade‐offs and how these traits determine prey and predator fitness remains a major challenge. Here, we conducted feeding and growth experiments to assess multiple traits related to defense and competitiveness in six different strains of the green alga Chlamydomonas reinhardtii exposed to predation by the rotifer Brachionus calyciflorus. We found large differences in defense and competitive traits among prey strains and negative relationships between these traits for multiple trait combinations. Because we compared trait differences among strains whose ancestors evolved previously in controlled environments where selection favored either defense or competitiveness, these negative correlations suggest the presence of a trade‐off between defense and competitiveness. These differences in traits and trade‐offs translated into differences in prey and predator fitness, demonstrating the importance of intraspecific trade‐offs in predicting the outcome of predator–prey interactions. [ABSTRACT FROM AUTHOR]

In mammals, mixed lineage kinase domain-like protein (MLKL) is the executor of necroptosis. MLKL comprises an N-terminal domain (NTD), which alone suffices to trigger necroptosis by forming pores in the plasma membrane, and a C-terminal domain that inhibits the NTD activity. Evolutionarily, MLKL is poorly conserved in animals and not found in Protostomia. Although MLKL orthologs exist in invertebrate Deuterostomia, the biological activity of invertebrate MLKL is unknown. Herein, we examined 34 metazoan phyla and detected MLKL not only in Deuterostomia but also in Protostomia (Rotifera). The Rotifera MLKL exhibited low identities with non-Rotifera MLKL but shared relatively high identities with non-metazoan MLKL. In invertebrates, MLKL formed two phylogenetic clades, one of which was represented by Rotifera. In vertebrates, MLKL expression was tissue-specific and generally rich in immune organs. When expressed in human cells, the MLKL-NTD of Rotifera, Echinodermata, Urochordata, and Cephalochordata induced strong necroptosis. The necroptotic activity of Rotifera MLKL depended on a number of conserved residues. Together these findings provided new insights into the evolution of MLKL in Metazoa and revealed the biological activity of invertebrate MLKL. [ABSTRACT FROM AUTHOR]

The present study was conducted in one of the most significant water sources in Iraq, the Tigris River in Misan Province. The aim was to examine the zooplankton community, specifically Cladocera, Copepoda, and Rotifera. Samples were collected 30cm below the water surface using a plankton haul net with a mesh size of 64μm from September 2023 to February 2024. Sampling took place at three stations: the first in Kumait, located in the north of Misan Province; the second in Amarah City, the capital of Misan Province, and the third about 20km south of Amarah City. The results revealed seventeen species of zooplankton, belonging to two phyla, three classes, four orders, and eight families. A comparison between the historical and current status in the study area indicated a noticeable shift in zooplankton composition toward species more tolerant of pollution. For instance, the appearance of the family Brachionidae and its common species Brachionus sp. in the study area, alongside the absence of Daphnia species, suggests ecological degradation in the inland waters of Iraq, particularly in Misan Province. This study recommends incorporating zooplankton into water quality monitoring programs (WQMPS) in Iraq. [ABSTRACT FROM AUTHOR]

Biodiversity records are of great importance, especially in light of the biodiversity crisis. Here, we present a study on the diversity of rotifers in Bolivia based on an extensive investigation of the literature published so far. Through this approach and an analysis of samples from 207 water bodies of the country, we updated the checklist of reported species. This study revealed a total of 195 species of rotifers previously reported; we identified 153 species in our samples, with 84 of them being reported for the first time in Bolivia. Thus, a total of 279 species are known at present in this country. Our findings suggest that Bolivia has a rich and diverse rotifer community, with many species likely to be unique to the region. [ABSTRACT FROM AUTHOR]

Zooplankton may represent a considerable part of plankton in large rivers, but little is known about the factors that control it. We hypothesized that (1) significant longitudinal increase of zooplankton abundance, biomass, taxonomic richness, and diversity will occur along a free-flowing river section; (2) the residence time of water is more important for zooplankton population growth than environmental variables such as water temperature, oxygen saturation, and food concentration; and (3) the influence of tributaries on the longitudinal dynamics of zooplankton is insignificant or only has a local effect. A Lagrangian survey was applied in the free-flowing section of the River Elbe (Germany) in spring 2022. The abundances and biomass of the dominant rotifers as well as of cladocerans and copepods increased significantly downstream due to the population growth of zooplankton. The water residence time was the most important factor for zooplankton increment. One of the tributaries increased zooplankton abundance and biomass in the River Elbe, while other tributaries did not but the introduction of new species increased taxonomic richness and decreased the evenness of zooplankton in the main river so that diversity remained nearly constant. [ABSTRACT FROM AUTHOR]

This study investigates the effects of tidal cycles on the zooplankton community within the Cotonou Channel, an important waterway connecting the large Nokoué Lagoon to the Atlantic Ocean in Benin. From the determination of zooplankton composition from 25-hour samples collected in July 2020, alpha diversity indices and abundance were assessed, while relationships between biotic and abiotic parameters were analyzed through Pearson correlation, analysis of variance, and principal component analysis. A total of 66 zooplankton taxa were identified, with rotifers exhibiting the highest species richness (35 taxa), while copepods dominated in abundance (71%). Zooplankton abundance varied significantly, ranging from 2 to 95 ind L−1 depending on the tidal phase. A negative correlation was found between species richness (r = −0.51, p < 0.01) and increasing salinity (3–37), indicating that higher salinity reduced diversity (r = 0.06, p > 0.05). Resilient species like Synchaeta bicornis persisted despite salinity changes. The tidal cycle structurally altered the zooplankton community, with abundance and diversity peaking at different phases, notably higher at high tide (15 ind L−1.) These initial findings underscore the complex interactions between tidal dynamics and estuarine biodiversity, suggesting the need for further research across different tidal and seasonal conditions to inform effective management and conservation efforts. [ABSTRACT FROM AUTHOR]

Rotifers are microscopic metazoans which are generally predominant in freshwater ecosystems both in terms of species richness and species abundance. Despite their small size, they are crucial in maintaining ecological balance. In the present investigation, plankton samples collected during February 2019-January 2021 from two lentic water sources of Jammu region of Jammu & Kashmir revealed 58 species of rotifers belonging to 16 families, among which five species of monogonont rotifers from three genera were recorded to be the first reports from this region. These include three species from family Lecanidae: Lecane arcula, L. inermis, L. (Monostyla) unguitata; one species from family Brachionidae: Anuraeopsis coelata; and species Pompholyx sulcata of family Testudinellidae. Among these five monogonont species, Anuraeopsis coelata shows pantropical distribution, Lecane unguitata is a palaeotropical species, while other three are cosmopolitan in occurrence. Furthermore, comments are made on the diagnosis, seasonality, biogeographical, and ecological distribution of these species. [ABSTRACT FROM AUTHOR]

High larval and frymortality has been amajor challenge to the commercial culture of the African bony-tongue (Heterotis niloticus). Research indicates inadequate feeding to be a possible cause of the high mortality rates of larvae/fry grown in captivity. An experiment was conducted to first describe the developmental stages of H. niloticus eggs and larvae until schooling, 6 days after hatching (DAH), at 26°C. The morphological development, survival, growth (weight gain and length), and swimming behavior of the larvae were monitored. A follow-up feeding trial was conducted with H. niloticus fry from 6 to 27 DAH involving four treatments: feeding with Artemia nauplii; a combined feed of 50% Artemia nauplii and 50% rotifers (w/w); feeding with rotifers; and no feeding. The activities of three digestive enzymes (trypsin, lipase, and amylase)were assessed in fry exposed to the live feed treatments. At hatching, the larvae had a large, vascularized yolk sac filled with yolk platelets, which occupied approximately one-third of the total body length of the abdominal cavity. Yolk platelet reabsorption started at 1 DAH and was complete at 6 DAH. Metamorphosis was completed at 6 DAH, and schooling behavior was observed. For the feeding trial, the fry that received Artemia nauplii underwent the fastest development until 27 DAH. Similarly, the survival rate was considerably higher in fry fed with Artemia nauplii than in those that received a combination of Artemia nauplii and rotifers or only rotifers. Overall, the survival rates for fry fed with Artemia nauplii and larvae co-fed were 72.7% ± 0.9% and 41.2% ± 3.3%, respectively. Fry did not survive until 27 DAH in the rotifer-fed and unfed treatment groups. Digestive enzyme activity differed significantly (p< 0.05) between treatments and sampling dates. All digestive enzymes were detectable at the onset of mouth opening (5 DAH) and fluctuated through the 7 and 9 DAH. Lower enzyme activity was observed when the fry were subjected to starvation or the rotifer treatment. Results indicate that Artemia nauplii is the best live feed organism for H. niloticus larviculture. [ABSTRACT FROM AUTHOR]

Understanding nutrition and its effect on growth is essential for developing diets in commercially important species. This study aimed to evaluate the larval development of Callinectes sapidus fed with rotifers (Brachionus plicatilis) enriched with Chlorella pyrenoidosa (Ch) as a main protein source and a lipid emulsion (Spr) rich in highly unsaturated fatty acids. The enriched compositions had seven ratios Ch/Spr (w/w): 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, and 40/60. The enriched rotifers with each ratio were called diets. Lipids increased progressively between 100/0 and 40/60 (7.48 to 11.30 g 100 g-1), as well as energy (21.88 to 23.16 kJ g-1), but the protein level did not show a clear trend (63.93 and 67.50 g 100 g-1). The production response of blue crab larvae showed significant differences within diets (P < 0.05). The highest survival (29 to 34%) was obtained in the 50/50 and 40/60 treatments. In the 40/60, 50/50, and 60/40 diets, the larval cycle was shorter (P < 0.05), and the megalopa stage was reached between 49 and 52 days of culture. Metamorphosis tomegalopa occurred between the fifth and eighthmolts; its corresponding weight varied from 0.72 to 1.33 mg, the length varied from 2,632 to 2,926 μm, and Le Cren's condition factor varied from 0.83 to 1.16. The most important factor in the production response was the diet lipid content, which was significantly correlated with the survival, weight, length, and condition factor of C. sapidus larvae. Findings of the present study can be applied in future efforts towardsmass culture of blue crab larvae in the Caribbean and can also potentially be used to study other crustacean species with similar characteristics. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are increasingly affected by rising annual mean temperatures and heatwaves. While heatwaves are expected to have more immediate effects than mean temperature increases on local communities, comparative experimental studies are largely lacking. We conducted a 1‐month mesocosm experiment to test the effect of different warming treatments, constantly raised temperatures (+3°C) and recurring heatwaves (+6°C), on plankton communities. We specifically tested how shifts in zooplankton trait composition and functional groups are reflected in ecosystem function (top‐down control on primary producers). We found that heatwaves had a stronger and more immediate effect on zooplankton trait composition (specifically on body length and body mass) and functional groups. Heatwaves led to the decrease of small‐bodied grazers (i.e., Rotifera) and the dominance of larger omnivorous Copepoda, and these shifts resulted in weaker top‐down control, leading to elevated phytoplankton biomass. Altogether, our results highlight the importance of the indirect effects of heatwaves via inducing shifts in zooplankton functional groups and trait composition, which may lead to algal blooms. [ABSTRACT FROM AUTHOR]

Herbivorous zooplankton potentially encounter temporal dietary heterogeneity in sterol, an essential group of lipids, over short or long time scales. There are a few studies showing that dietary sterol fluctuation will impact the short-term growth and reproduction of zooplankton, but life histories in response to dietary sterol fluctuation have not been studied. In this study, both short-term physical performances and life tables of the brackish rotifer Brachionus plicatilis were compared at a series of constant dietary cholesterol levels and under a diurnal switching-quality regime (SQ) between low-cholesterol (LQ) and high-cholesterol (HQ) diets. The ingestion rate, short-term reproduction rate and lifetime fecundity were correlated significantly with dietary cholesterol concentration in the Michaelis‒Menten function pattern. The short-term reproduction rate and lifetime fecundity were higher in the SQ treatment than in the nonlinear averaging prediction. Generally, rotifers under the SQ condition exhibited life history traits comparable to those groups under the medium and high cholesterol conditions, as did the cholesterol accumulation in mother rotifers. The maternal allocation of cholesterol per offspring, nevertheless, varied among different food regimes, and the SQ offspring had a higher sterol content than the HQ offspring. It is suggested that diurnal switching dietary cholesterol quality will not decrease the physiological performance of rotifers, unlike predictions based on the nonlinear averaging hypothesis, and the population can maintain their development under diurnal fluctuating dietary sterol conditions. Furthermore, the variable per offspring sterol investment may bear adaptive significance for rotifers under the fluctuating food environments. [ABSTRACT FROM AUTHOR]

The species richness is an essential component of biodiversity metrics and an ecological indicator for setting conservation actions. Phylum Rotifera consists of a specious group of conspicuous and minute animals, mainly in freshwater environments. In the Neotropical region, the knowledge of the biodiversity of rotifers is incomplete, with outdated and geographically restricted information. In this regard, we present a comprehensive inventory of rotifers from freshwater ecoregions in Rio de Janeiro. From the literature review and active surveillance, we detected 238 spp.; among these, 39 were previously unknown to the State. We also preliminarily examine the potential use of Rotifera for ecoregions delimitation. The extrapolated number of species shows an increasing richness for the Paraiba do Sul and Fluminense ecoregions, which were also significantly different regarding species composition. Registers from the Ribeira de Iguape and Northern Mata Atlantica ecoregions are still lacking in the State. We believe that future survey efforts will undoubtedly reveal additional records and taxa improving our understanding of biogeographical patterns such as dispersal and biological invasions. Ultimately, support future conservation policies and the potentialities of this group for ecoregion delimitations. [ABSTRACT FROM AUTHOR]

Coloniality may grant colony members an energetic advantage in the form of lower individual respiration rates as colony size increases. If this occurs it should be apparent as negative allometric scaling of respiration with colony size, and colonial organisms should have scaling factors < 1. However, colonial members from phylum Rotifera have yet to be examined. To test if colonial rotifers possess allometric scaling relationships between respiration rate and colony size, we measured respiration rates for four solitary and three colonial rotifer species; from these respiration rates we estimated scaling factors. We found mixed evidence for allometric scaling of respiration rate in colonial rotifers. Both rotifers with allometric scaling of respiration rate, Conochilus hippocrepis and Lacinularia flosculosa, have extensive mucilaginous coverings. These coverings may represent an investment of colony members into a shared structure, lowering individual metabolic costs and thus respiratory needs. Additionally, we determined which traits are associated with allometric scaling of respiration. We compiled known scaling factors for animal phyla from a wide phylogenetic spectrum with colonial representatives and conducted a hierarchical mixed regression that included attributes of colonies. Traits associated with allometric scaling in colonial animals included colony shape, the presence of shared extrazooidal structures, and planktonic lifestyle. There are many other colonial rotifers and animal taxa for which allometric scaling factors have yet to be estimated, knowing these may enhance our understanding of the benefits of coloniality in animals. [ABSTRACT FROM AUTHOR]

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The XVI International Rotifer Symposium took place in Zagreb, Croatia in 2022. The symposium was organized every four years instead of the usual three due to global and regional circumstances, and it was held in a hybrid format. The conference was supported by the University of Zagreb, the Faculty of Science, the Croatian Ecological Society, and sponsors such as Springer Nature and domestic companies/associations. The event included social events and excursions to cultural and natural sites in Croatia. A total of 141 participants from 25 countries attended, with 97 onsite and 44 online. The symposium featured invited lectures, presentations from young scientists, and special sessions and workshops on various topics related to rotifers. These included practical techniques for capturing images of rotifers, the importance of culturing rotifers for ecological experiments, and the establishment of a database for rotifer research. There were also sessions on the ecology of rotifers in specific regions and their reproductive processes. The special issue of Hydrobiologia includes 28 articles on rotifers, covering themes such as evolution, general ecology, biotic interactions, and environmental stressors. The article also pays tribute to prominent rotifer researchers who have passed away. [Extracted from the article]

In paleolimnological studies, rotifers are usually a very rare component in multiproxy research. These small invertebrates are identified from sediments by their loricas. Analysis of subfossil rotifers was conducted for sediment cores collected from three peatlands in within Poland: the Grel raised bog (S Poland, Carpathians, Orawa-Nowy Targ Basin), the Imszar raised bog (NE Poland, Podlasie Region), and the Podemszczyzna peatland (SE Poland, Sandomierz Basin). Results were compared with multiproxy analyses of peat deposits: pollen of aquatic and mire plants, non-pollen palynomorphs (NPPs), and geochemical analyses. Analysis of the rotifers indicated the occurrence of the bdelloid species Habrotrocha angusticollis (Murray, 1905). In all profiles of the studied peatlands, the occurrence of rotifers was not correlated with pollen of aquatic or mire plants or NPPs; they seem to be more related to geochemical indices. The highest densities of rotifers were found in profile sections without significant fluctuations of geochemical variables, i.e. those with higher Na/K (chemical denudation) ratios and stable redox conditions (Fe/Mn ratio). The study of subfossil rotifers supported by multiproxy analysis of peat deposits could be a useful tool for indication of periods with stable palaeohydrological conditions during the Late Glacial and Holocene. [ABSTRACT FROM AUTHOR]

The Mediterranean area includes a wide variety of shallow water bodies which are recognized as hotspots of biodiversity. Here, we present the results of our study conducted on twenty-two small ponds, divided in two groups, fish free and fish stocked, along the coast and islands of the Adriatic Sea, in the Mediterranean. The main aims covered (1) the assessment of zooplankton structural and functional traits; (2) the impact of top predators (invasive mosquitofish) and macrophyte coverage on zooplankton diversity, abundance, and biomass. Overall, rotifers dominated in zooplankton diversity and abundance; it is likely that due to their small size they were not under direct fish predation. Rotifers prevailed in fish-stocked ponds, where their assemblage was shaped by food availability and macrophyte coverage. Macrophytes had a dual influence on rotifers: dense macrophyte coverage supported a high density of littoral species, while low macrophyte coverage provided a profitable condition for planktonic rotifers. In fish-stocked ponds, cladoceran and copepod density, biomass, and diversity were strongly reduced in relation to fish-free ponds. This study revealed high zooplankton diversity (77 taxa) in a Mediterranean region, structured by habitat heterogeneity and predation. [ABSTRACT FROM AUTHOR]

The clade Syndermata includes the endoparasitic Acanthocephala, the epibiotic Seisonidea, and the free-living Bdelloidea and Monogononta. The phylogeny of Syndermata is highly debated, hindering the understanding of the evolution of morphological features, reproductive modes, and lifestyles within the group. Here, we use publicly available whole-genome data to re-evaluate syndermatan phylogeny and assess the credibility of alternative hypotheses, using a new combination of phylogenomic methods. We found that the Hemirotifera and Pararotatoria hypotheses were recovered under combinations of datasets and methods with reduced possibility of systematic error in concatenation-based analyses. In contrast, the Seisonidea-sister and Lemniscea hypotheses were recovered under dataset combinations with increased possibility of systematic error. Hemirotifera was further supported by whole-genome microsynteny analyses and species-tree methods that use multi-copy orthogroups after removing distantly related outgroups. Pararotatoria was only partially supported by microsynteny-based phylogenomic reconstructions. Hence, Hemirotifera and partially Pararotatoria were supported by independent phylogenetic methods and data-evaluation approaches. These two hypotheses have important implications for the evolution of syndermatan morphological features, such as the gradual reduction of locomotory ciliation from the common ancestor of Syndermata in the stem lineage of Pararotatoria. Our study illustrates the importance of combining various types of evidence to resolve difficult phylogenetic questions. [ABSTRACT FROM AUTHOR]

Aging is a significant internal factor influencing the sexual ability of rotifers. This study examined the effects of maternal aging on a rotifer's reproductive behavior (either sexual or asexual) and how the impacts were transmitted via generations (P − F1 − F2) in two marine species in the Brachionus plicatilis species complex: Brachionus plicatilis (large type) and Brachionus rotundiformis (super-small type). Based on the rotifer reproductive period, we established young and old lineages produced in the first and second halves of the period, respectively. The fecundity and longevity of the progeny in the two species and throughout the generations remained unaffected by maternal age. However, young amictic females in each species (especially in B. plicatilis) produced a larger ratio of mictic offspring. The multigenerational assessment revealed that the amictic offspring from old mothers produced more mictic daughters than those from young rotifers. This implies that aged rotifers may adopt an adaptive strategy (i.e., entering dormancy via sexual reproduction) for survival. [ABSTRACT FROM AUTHOR]

Aquatic organisms are constantly exposed to effluents which often contain microplastics. Microplastics adversely affect aquatic organisms as a result of mechanical damage during ingestion or intoxication by chemicals adsorbed on the microplastics. Sub-optimal temperatures may acerbate the adverse effects of microplastics on aquatic biota. Brachionid rotifers, such as Brachionus havanaensis and Brachionus calyciflorus, are common in tropical freshwaters. They are generalist filter feeders capable of consuming microplastic particles of a wide size range 0.05 to 40 µm, which can eventually affect growth and competitive interactions among species. Here, we evaluated the effect of 30 µm beads of polystyrene microplastics at 10 and 20 mg l−1 on the population growth and competition of B. havanaensis and B. calyciflorus at 20 and 25 °C using 0.5 × 106 cells ml−1Chlorella vulgaris as food. Population growth decreased in treatments with microplastics at both temperatures as compared to the controls. The population growth rates ranged between 0.21 and 0.38 d−1 for B. calyciflorus, and between 0.27 and 0.48 d−1 for B. havanaensis. The presence of the competing species significantly lowered the population growth rate for B. calyciflorus but not for B. havanaensis. On the other hand, while the presence of the microplastics had little impact on the population growth rate of B. calyciflorus in the presence of the competitor, the reverse was true for B. havanaensis, especially at 20 °C. Our results show that the presence of microplastics may affect rotifer community structure in natural water bodies. [ABSTRACT FROM AUTHOR]

Exceptional resistance to dehydration allows species of bdelloid rotifers to tolerate desiccation stress in unpredictable habitats. The roles of exogenous and endogenous factors in resistance to short-term dehydration were investigated in Rotaria rotatoria to better understand this capacity among bdelloid rotifers. As the dehydration period was increased and the relative humidity (RH) was reduced, the proportion of rotifers active after the dehydration period decreased. The RH and dehydration period substantially influenced the recovery rate of R. rotatoria under rehydration for 1 h but had less effect under 12-h or 24-h rehydration treatment. The recovery rate was lower in rotifers subjected to a long dehydration period and short rehydration time, but improved by shortening the dehydration period and extending the rehydration treatment. Strain ZJ27 showed higher survivability than strain HX8, appropriate to their habitat near the sea in a region where drought and tropical rainstorms are frequent. Accordingly, species or strains originating from different climate regions and habitats will have experienced different frequencies of desiccation over their adaptive evolutionary history, resulting in varying levels of resistance among species. In addition, RH is shown to be a key factor in resistance to desiccation. [ABSTRACT FROM AUTHOR]

Rotifer structure may serve as predictor of environmental features, including temperate subclimates between water bodies. The difference in latitude between two temperate regions (Poland vs. Croatia) affects the identification of particular environmental factors that subsequently influence the taxon-related indices of rotifers. A study on 10 water bodies found that taxon-trait indices were sensitive in identifying latitude differences, even though extreme weather conditions were not considered, and only two seasons (spring and autumn) were examined. A variable rotifer community, with a high share of rare species, was obtained. We found a distinctiveness of abiotic factors between both countries, indicating a higher trophic state in Poland. Although habitat conditions were more similar in spring compared to the autumn, the percentage of rotifer common taxa was alike in both seasons but variation in distinct species community was clear. Trophic state increase in Poland was reflected in the structure of dominant and distinct species, with a wide range of eutrophy indicators. Comparing how rotifer species respond to environmental conditions is important for developing methods to assess trophic state changes due to climate change. Single species, distinct or rare species, are often the first sign of changes. [ABSTRACT FROM AUTHOR]

We quantified the effect of two cyclopoids, an invasive (Mesocyclops pehpeiensis) and a native (Mesocyclops longisetus curvatus) species on the population growth of the rotifers Brachionus havanaensis and Brachionus calyciflorus. We hypothesized that the invasive copepod would have a greater adverse effect on the test rotifers. The population growth of B. havanaensis was tested in the indirect presence of B. calyciflorus (used as prey for the predatory copepods), and the predatory copepods, M. pehpeiensis and M. longisetus curvatus. For B. calyciflorus the experimental design was as above except that we used B. havanaensis as prey. The test rotifers were separated from the competitors and predators by mesh cages placed in the experimental jars. Rotifer density and the egg ratios were quantified, followed by a daily medium change, until the population density declined. The population growth rate of B. havanaensis ranged between 0.26 and 0.30 day−1, while that of B. calyciflorus between 0.19 and 0.21 day−1. The presence of the invasive copepod had an adverse effect on the smaller (< 110 µm) B. havanaensis, but not on the larger (> 180 µm) B. calyciflorus. The results are discussed with emphasis on the differences in the indirect impact invasive and native predatory copepods. [ABSTRACT FROM AUTHOR]

Short-chain chlorinated paraffins (SCCPs) are ubiquitous, persistent chemicals whose toxicity and potential impacts on aquatic ecosystems have been overlooked for many years. This study aims to determine the impact of these chemicals on rotifers. As sexual reproduction is often more sensitive to toxicants than amictic reproduction, this study focuses on endpoints describing sexual reproduction and on the impact on the gene expression of three receptors associated with reproduction: retinoid-x-receptor (rxr), retinoid activated receptor (rar) and membrane-associated progesterone receptor (mapr). Brachionus calyciflorus was exposed to environmental concentrations of SCCPs (10,100 and 1000 ng/L) and the impact on sexual reproduction (mixis rate, fertilization rate, resting egg production and viability, inter-generational effects) was assessed. Variations in the gene expressions of rxr, rar and mapr were also studied through RT-qPCR analysis. Our results show that SCCPs increase the mixis rate but decrease the fertilization rate, leading to unaltered resting egg production. Exposure to SCCPs also affected the mRNA levels of the studied receptors in ways which could be linked to observed changes in mixis and fertilization rates. [ABSTRACT FROM AUTHOR]

We quantified the population growth of the predatory heliozoan Actinosphaerium eichhornii fed separately four rotifer prey (Anuraeopsis fissa, Brachionus calyciflorus, Brachionus havanaensis and Plationus patulus) at three densities (0.5, 1 and 2 ind. ml−1 per day). All the four prey rotifer species were consumed by A. eichhornii. Regardless of the prey species, increasing rotifer prey density resulted in an increased population growth of the heliozoans. Higher cyst production in A. eichhornii occurred at higher prey densities on all prey species. A. fissa offered at the lower densities of 0.5–1.0 ind. ml−1 day−1 did not lead to cyst production by A. eichhornii. The predator did not survive beyond 2 days on Chlorella vulgaris alone. When cultured together with heliozoans, A. fissa, B. calyciflorus and B. havanaensis were eliminated within 4 days. However, the prey rotifer Plationus patulus continued to survive for about 10 days with heliozoans. The highest rate of population increase of heliozoans (0.91 day−1) was recorded when fed B. calyciflorus at a density of 2 ind. ml−1 day−1, while of those of prey varied from 0.30 to 0.41 day−1 when fed Chlorella vulgaris at 1 × 106 cells ml−1 day−1. We have analyzed the impact of heliozoan predation on rotifers. [ABSTRACT FROM AUTHOR]

Most information on rotifers living in lake sands comes from the 1930s, when the first reports on this subject by Jerzy Wiszniewski appeared. After some decline in the interest in lake psammon in the following years, research on lake psammon returned in the last decade of the twentieth century. The last comprehensive review of ecology of psammon Rotifera was included in the excellent 1998 publication by Schmid-Araya on Rotifera in interstitial sediments. More than 20 papers have been published since that time. So far, research conducted almost exclusively in the northern hemisphere have dealt with issues related to distribution of rotifers, their species structure and diversity as well as to their relation to abiotic and biotic factors. The aim of the present study was to collect all available information on psammon rotifers, assess the shortcomings in our knowledge and fill these gaps with the results of some of my recent research. The results of the study show that the species richness of this group in geographical terms is still unknown. It means we also do not know the level of endemism among the psammon rotifers. The role of psammon rotifers in benthic food webs is another issue requiring research. [ABSTRACT FROM AUTHOR]

Rotifers' presence and significance are being underestimated among marine zooplankton because rotifers are lost when using larger mesh size nets. Furthermore, samples' preservation often makes species identification difficult, creating a knowledge gap regarding their diversity and abundance in coastal ecosystems. Our study aimed to address this gap by documenting the biodiversity and distribution patterns of the rotifer species, exploring their relationships with the components of the zooplankton community and determining the environmental variables driving their seasonal dynamics. Samplings were carried out in an urban coastal area in the North Aegean Sea in Greece, within two sampling periods. Four coexisting Synchaeta species were encountered, whose temporal distribution patterns were mainly driven by temperature; S. neapolitana exhibited a preference for colder temperatures, contrary to the thermophilic distribution patterns of S. baltica and S. vorax. Network analysis unveiled several negative links among Synchaeta species and other zooplankton taxa, suggesting potential competitive trophic interactions. The present study is one of the very few dealing with marine rotifers across the Mediterranean Sea and thus provides a significant contribution to our understanding of the dynamics of this group of micrometazoans. [ABSTRACT FROM AUTHOR]

Predation is a well-known factor that structures rotifer communities. However, the role of protists as predators is relatively understudied. Here, we investigated predatory behavior of Actinosphaerium sp., a freshwater heliozoan, on seven rotifer species. Predators and prey were collected from a local playa; except for Brachionus calyciflorus that served as a naive prey control. Prey included large species (≥ 175 µm mean length: Asplanchna sieboldii, B. calyciflorus, Platyias quadricornis, and Lacinularia flosculosa) and small species (< 175 µm: Cephalodella gibba, Euchlanis dilatata, and Lepadella patella). Four experiments were conducted. (1) Single prey items of varying size and motility. Larger prey types were ~ 1.7 to 3.0 times more likely to be ingested than small prey. No L. flosculosa were ingested, contrary to field observations. No correlation was found between swimming speed and predation risk. (2) Preference tests. Asplanchna sieboldii and B. calyciflorus were favored prey. (3) Growth rate of Actinosphaerium on mixed diets, with and without Asplanchna. Highest population growth of Actinosphaerium was observed in presence of A. sieboldii. (4) Prey defenses. Susceptibility of spined versus unspined B. calyciflorus resulted in no significant difference in predation risk. Thus, size and being mobile (compared to sessility) are the primary risk factors influencing rotifer predation vulnerability. [ABSTRACT FROM AUTHOR]

The Brachionidae rotifer Kellicottia bostoniensis (Rousselet, 1908) is a transcontinental invader that continues to spread rapidly from the south to the north of the South American continent. We investigated the invasion of K. bostoniensis and its potential impact on the rotifer assemblage in a large tropical reservoir in southeast Brazil over a period of 9 years. The degree of K. bostoniensis invasion was confirmed by its frequency of occurrence (23%) and constant presence near to the main tributary, thus indicating propagule pressure from upstream. Differing environmental drivers regulated the invader in comparison with resident species. Nitrate and dissolved oxygen were important for native rotifers but not for K. bostoniensis, which negatively correlated with water temperature and positively with epilimnion depth. Total body length of K. bostoniensis increased from 2001 to 2009 as a result of an increase in size of most spines, which suggested a defensive strategy against predation. A functional approach applied to the rotifer assemblage indicated that the high species richness may be associated with high niche partitioning within the assemblage. The permanence of K. bostoniensis in the assemblage appears to be related to occupation of an empty niche. [ABSTRACT FROM AUTHOR]

Adaptation to different ecological niches is considered one of the main drivers of species diversification, also in cryptic species complexes, notwithstanding their morphological stasis. We here review all the published information on ecological differentiation within cryptic species complexes within the phylum Rotifera. We found 177 instances of cryptic species identified genetically, published in 101 papers. Only a subset of the papers contained available information on ecological differences and only for two of the 54 known complexes, namely Brachionus calyciflorus s.l. and Brachionus plicatilis s.l., sufficient data were available for analyses of ecological differences. For the B. calyciflorus complex, B. fernandoi consistently occurred at a significantly lower temperature than the other species in the complex; no differences were found for other environmental variables. For the B. plicatilis complex, B. paranguensis occurred in waters with higher pH than the other species; no differences were found for other environmental variables. These results, even if preliminary and based on scattered information, reveal that adaptation to different ecological niches exists also between closely related species. Our aim is to showcase this interesting field of research spurring further detailed studies to focus on the mechanisms of ecological speciation using rotifer cryptic species as a model system. [ABSTRACT FROM AUTHOR]

Zooplankton indicators based on rotifers (TSIROT) and an indicator based on Secchi disk visibility (TSISD) were used to assess trophic state changes in artificial, slow-flowing, and stagnant canal waters. The study was conducted in the summers of 2019, 2021, and 2022 in the Bydgoszcz Canal and the Noteć Canal (Poland). Water samples were taken from five sites once in the month of July and once in August. In terms of the species number and density, rotifers dominated among zooplankton (at almost all sites), which reflected the high trophic state. Our results showed statistically significant correlations between TSIROT and TSISD as well as between the individual indicators TSIROT1 (Rotifer numbers), TSIROT2 (Rotifer biomass), TSIROT3 (bacterivorous numbers of rotifers), TSIROT6 (rotifers indicating high trophic state), and TSISD. According to our study, the presented indices most likely determine the trends between TSIROT cumulative and TSISD in the studied canals. Similarly to previous studies performed on lakes and small reservoirs, zooplankton constituted a useful indicator of trophic state. It seems that, for stagnant and slowly flowing waters of canals such as the Bydgoszcz Canal and the Noteć Canal, the method of zooplankton trophic status indicators based on rotifers may be applied. [ABSTRACT FROM AUTHOR]

The basal splits within Syndermata probably date back hundreds of millions of years, and extant syndermatans greatly differ in reproduction modes (parthenogenesis, metagenesis, heterosexuality) and lifestyles (free-living, epizoic, endoparasitic). Against this background, the present investigation aims to reconstruct genome and transcriptome metrics in the last common ancestor (LCA) of Syndermata. We especially annotated nuclear genome assemblies of one representative, each, of monogononts (Brachionus plicatilis), bdelloids (Adineta vaga), seisonids (Seison nebaliae), and acanthocephalans (Pomphorhynchus laevis), S1 and additionally considered previously published data. Present results suggest that the syndermatan LCA possessed a compact nuclear genome of 50–100 Mb with a coding portion of ≥ 40%. Its ~ 17,000 protein-coding genes probably had about 4–6 exons and 3–5 introns on average. Long interspersed nuclear elements (LINEs) should have occupied 4–5% of the ancestral genome. Based on this, independent evolutionary trajectories involving gene loss, genome duplication, and repeat proliferation resulted in greatly varying genomes within the clade. Nevertheless, we identified 2114 clusters containing proteins of all four syndermatan taxa. About 200 of these clusters lacked sufficiently similar counterparts in the platyhelminths Macrostomum lignano and Schmidtea mediterranea. Gene ontologies assigned to these clusters might reference the muscular pharynx, light perception, and transposition, amongst others. [ABSTRACT FROM AUTHOR]

Dispersal success is crucial for the survival of species in metacommunities. Zooplankton species engage in dispersal through time (i.e., egg bank) and space (i.e., vectors) by means of resting eggs. However, dispersal to patches does not equate to successful colonization, as there is a clear distinction between dispersal rates and successful colonization. We performed a field mesocosm experiment assessing dispersal and colonization success of zooplankton from resting eggs or transport via directional wind/airborne and biotic vectors in the vicinity of three ponds. By using active vs. sterile pond sediments and mesh-covered vs. open mesocosms, we disentangled the two mechanisms of dispersal, i.e., from the egg bank vs. space. We found that for both rotifers and cladocerans, sediment type, mesh cover and duration of the experiment influenced species richness and species composition. The relative contribution of resting stages to dispersal and colonization success was substantial for both rotifers and cladocerans. However, wind/airborne dispersal was relatively weak for cladocerans when compared to rotifers, whereas biotic vectors contributed to dispersal success especially for cladocerans. Our study demonstrates that dispersal and colonization success of zooplankton species strongly depends on the dispersal mode and that different dispersal vectors can generate distinct community composition. [ABSTRACT FROM AUTHOR]

Coevolutionary antagonism generates relentless selection that can favour genetic exchange, including transfer of antibiotic synthesis and resistance genes among bacteria, and sexual recombination of disease resistance alleles in eukaryotes. We report an unusual link between biological conflict and DNA transfer in bdelloid rotifers, microscopic animals whose genomes show elevated levels of horizontal gene transfer from non-metazoan taxa. When rotifers were challenged with a fungal pathogen, horizontally acquired genes were over twice as likely to be upregulated as other genes — a stronger enrichment than observed for abiotic stressors. Among hundreds of upregulated genes, the most markedly overrepresented were clusters resembling bacterial polyketide and nonribosomal peptide synthetases that produce antibiotics. Upregulation of these clusters in a pathogen-resistant rotifer species was nearly ten times stronger than in a susceptible species. By acquiring, domesticating, and expressing non-metazoan biosynthetic pathways, bdelloids may have evolved to resist natural enemies using antimicrobial mechanisms absent from other animals. Fungi and bacteria fight coevolutionary wars using antimicrobial compounds that animal cells cannot usually produce. This study finds that bdelloid rotifers attacked by a fungal pathogen express genes acquired horizontally from bacteria, including some resembling antibiotic synthesis clusters. [ABSTRACT FROM AUTHOR]

Genus Pompholyx Gosse, 1851 (Rotifera; Monogononta; Testudinellidae) comprises three species described from freshwater plankton around the globe. Here we describe a new species of Pompholyx collected from a freshwater pond in Massachusetts, USA. The new species resembles its congeners with respect to the following characters: paired eyespots; a dorsally arched lorica with a dorsal occipital convexity behind the corona; lateral flared and rounded lorica surfaces; a ventral surface bearing an occipital concavity posterior of the mouth; a unique egg-gland system; and the absence of a foot. However, P. faciemlarvasp. n. differs from its congeners in possessing a transverse furrow on both the dorsal and ventral surfaces of the lorica. While the trophi of P. faciemlarvasp. n. generally resemble those of other species of Testudinellidae, they do have a symmetrical pattern of unci teeth (17/17) that differs from Pompholyx sulcata (17–20/18–21, right/left), the only other species in the genus with well-described trophi. The description of this new species enhances the floristic richness of freshwater in North America. [ABSTRACT FROM AUTHOR]

A high mortality rate in the gold rabbitfish larvae of Siganus guttatus has been found during the initial developmental phase. This condition is thought to be due to unprepared larvae obtaining exogenous feed. Various efforts have been conducted to prevent high mortality rates, such as nutrient enrichment. This study was performed to evaluate the combined effect of βcarotene and taurine on the growth performance and survival rate of the gold rabbitfish larvae of S. guttatus. This study had four treatments for rotifer enrichment, namely BT0 without β-carotene and taurine enrichment, B7.5 (7.5mg L -1 β-carotene), T50 (50mg L -1 taurine), and a combination of 7.5mg L -1 β-carotene and 50mg L -1 taurine (Com-BT). The S. guttatus larvae were reared for 10 days after hatching (DAH). The parameter observed was growth performance, which contained absolute growth (body length and weight), fin development (dorsal, pectoral, and caudal), visual development (eye diameter and retina), total prey intake, and survival rate. The results indicated that enrichment of the rotifers with β-carotene and taurine can improve the absolute growth rate, fin development, visual development, and total prey intake. These parameters obtained better values as both ingredients were combined together (P< 0.05) Com-BT. Nutrient enrichment with β-carotene and taurine had no significant difference (P< 0.05) on the survival rate of S. guttatus larvae, but significantly showed a better survival rate in the combination of β-carotene and taurine treatment (Com-BT). In conclusion, β-carotene and taurine can be applied to improve the growth and survival rate of S. guttatus larvae. [ABSTRACT FROM AUTHOR]

Studies on zooplankton in lakes, ponds, and rivers have always received more attention, while zooplankton from streams remains understudied worldwide. Therefore, the role of zooplankton in neotropical stream functioning is still poorly understood. In order to remedy this situation, we aimed to answer the following questions: (1) How many papers have been published on the zooplankton from Brazilian streams? (2) In which hydrographic regions were these studies conducted? (3) Are there specific patterns of zooplankton species occurrence in neotropical streams? (4) What are the main types of studies and what are the main environmental factors influencing zooplankton in streams? In order to answer these questions, we performed a systematic review of indexed scientific papers. We indeed observed a paucity of studies on zooplankton in Brazilian streams. But despite the low number of studies (24), many species (276 taxa) were reported from seven Brazilian hydrographic regions. The species composition showed great variability within the hydrographic regions and fourteen environmental variables (physical, chemical, and spatial), which can represent environmental filters and influence dispersion processes, were related to zooplankton occurrences. These bibliographic data helped to clarify patterns in species composition and community structure of zooplankton in these streams. More studies are needed to further investigate the role of zooplankton in neotropical streams, which can help to develop conservation strategies. [ABSTRACT FROM AUTHOR]

The spatial and temporal variations in the distribution, abundance, and assemblage structure of zooplankton were examined in the Chiffa Wadi River, north central Algeria. Samples were taken seasonally from autumn 2020 to summer 2022. Nine physical and chemical variables were recorded, and their relationship with the density of 39 zooplankton species was established using canonical correspondence analysis. In order to study the structure of the zooplankton, Shannon–Wiener diversity indices (H′), Margalef richness index (Dmg), Pielou evenness (E), and abundance were calculated. During the analysis, rotifera was the dominant group in the zooplankton community, represented by 27 taxa, followed by Cladocera (9 taxa) and Copepoda (3 taxa). The diversity index indicated the higher richness, abundance, and evenness of zooplankton at a eutrophic site (S2) compared with other sites. The canonical correspondence analysis (CCA) showed that the structure of zooplankton is influenced by local environmental factors. The present study demonstrates that anthropogenic activities including urban discharge and the construction of Algeria's Medea-Chiffa highway, which increased the nutrient load in the aquatic system, disrupted water quality. Consequently, the distribution and quantity of zooplankton were dramatically impacted by these changes in water quality. [ABSTRACT FROM AUTHOR]

The zooplankton community was analysed in two intermittent salt lakes in Serbia – Lake Velika and Lake Mala Rusanda. Samples were collected twice a month during the wet phase between March and May. A total of 15 zooplankton taxa were identified. Crustaceans were more diverse in Lake Mala Rusanda. The communities of both lakes were composed mainly of cosmopolitan, generalist, euryhaline species. Strictly haline species such as Brachionus asplanchnoidis and Arctodiaptomus spinosus were the dominant components of the zooplankton communities in both lakes. Arctodiaptomus spinosus was most abundant in March and April, accounting for up to 50% of all zooplankton specimens found in a sample. The proportion of juvenile stages of A. spinosus was highest in the March and early April samples. The ratio of males to females varied and was likely related to swarming behaviour as part of the species' reproductive strategy. [ABSTRACT FROM AUTHOR]

We quantified the feeding behavior (encounter, attack, capture and ingestion) and demographic parameters (survival and reproduction) of the predatory rotifer Asplanchna sieboldii fed on the prey Plationus patulus previously exposed to microplastics (MPs), Cd or their combination. As compared to controls, capture and ingestion rates of P. patulus by A. sieboldii decreased by 71 and 61%, respectively, with prey previously exposed to mixed MPs and Cd treatment. Life table data showed that the predator died earlier in controls than when fed on prey exposed to both Cd and microplastics. Regardless of the prey treatment, the offspring production by A. sieboldii increased as the available prey numbers increased (from 1 to 4 ind. ml−1). Compared to controls, the fecundity rate of the predator decreased when contaminated prey was offered as food. [ABSTRACT FROM AUTHOR]

Simple Summary: Larviculture is one of the major bottlenecks in current aquaculture, where infectious diseases are responsible for populational collapses and large economic losses. Consequently, the main goal of this study was to evaluate the suitability of rearing tanks of rotifers (Brachionus plicatilis) used as the first live feed in turbot (Scophthalmus maximus, L.) larviculture as a new environmental niche for the isolation of bacterial probiotic candidates in the context of a sustainable aquaculture. Furthermore, the probiotic potential of four lactobacilli (two Lacticaseibacillus paracasei and two Lactiplantibacillus plantarum) isolated from a rotifer-rearing tank was evaluated. Aquaculture is a rapidly expanding agri-food industry that faces substantial economic losses due to infectious disease outbreaks, such as bacterial infections. These outbreaks cause disruptions and high mortalities at various stages of the rearing process, especially in the larval stages. Probiotic bacteria are emerging as promising and sustainable alternative or complementary strategies to vaccination and the use of antibiotics in aquaculture. In this study, potential probiotic candidates for larviculture were isolated from a rotifer-rearing tank used as the first live feed for turbot larvae. Two Lacticaseibacillus paracasei and two Lactiplantibacillus plantarum isolates were selected for further characterization due to their wide and strong antimicrobial activity against several ichthyopathogens, both Gram-positive and Gram-negative. An extensive in vitro safety assessment of these four isolates revealed the absence of harmful traits, such as acquired antimicrobial resistance and other virulence factors (i.e., hemolytic and gelatinase activities, bile salt deconjugation, and mucin degradation, as well as PCR detection of biogenic amine production). Moreover, Enterobacterial Repetitive Intergenic Consensus-PCR (ERIC-PCR) analyses unveiled their genetic relatedness, revealing two divergent clusters within each species. To our knowledge, this work reports for the first time the isolation and characterization of Lactic Acid Bacteria (LAB) with potential use as probiotics in aquaculture from rotifer-rearing tanks, which have the potential to optimize turbot larviculture and to introduce novel microbial management approaches for a sustainable aquaculture. [ABSTRACT FROM AUTHOR]

This is the first study related to the zooplankton assemblage in the La García reservoir, an equatorial high Andean reservoir located in the central region of the department of Antioquia (Colombia). The main objective of the work was to know the composition and abundance of the zooplankton assemblage in the reservoir and to establish if there is any relationship between these and the physical and chemical variables measured. It was carried out during a monitoring program between the months of June and September 2014. Monthly samples were taken at three stations, from five depths throughout the water column, with a 10 L capacity sampling bottle. The collected material was filtered through a plankton net with a 30-mm of mesh size, identified and counted under an inverted microscope using a Sedgwick-Rafter counting cell. Depth and rainfall were the variables that exerted more influence on the zooplankton assemblages, reaching the highest density during the driest season, in the shallowest station and the least Secchi transparency. [ABSTRACT FROM AUTHOR]

Afrotropical inland waters are highly diverse ecosystems; however, they remain poorly studied, especially for rotifers. Here, we contributed to the knowledge of the rotifer species richness in the largely understudied African countries of Angola and Ghana. We assessed the roles of habitat type and a suite of abiotic environmental factors in determining rotifer species richness of Ghana. A total of 37 sites (Ghana 32, Angola 5) in 19 water bodies from a variety of aquatic habitat types were sampled. In Ghana, we identified 118 taxa (105 species or subspecies level, 13 identified to genus). We identified 15 taxa (13 species) in the Angola samples. For Ghana, 100 of 118 (~85%) taxa were new records for the country, of which 13 species (~11%) were also new records for Africa. Nearly all the species (~93%) were new records for Angola. Species richness was positively correlated with conductivity and reservoir habitat type and negatively with pH. Redundancy analysis (RDA), conducted at the species level for the Ghana dataset, indicated suites of species associated with latitude, longitude, temperature, TDS, or pH. We also evaluated the effect of climate on species distribution in 27 African countries by conducting a review of all reports from Africa to determine factors associated with species richness. A Spearman's correlation confirmed a significant positive correlation between the number of rotifer species and the number of climatic regions (R = 0.53, p < 0.001) for certain countries, based on species distributions in relation to Köppen–Geiger climate regions. This fact validates the environmental heterogeneity hypothesis for African rotifers. Lastly, we predicted that rotifer species richness in Ghana, as a country with a tropical climate, could approach ~190 taxa, while in climatically heterogeneous Angola we predict ~200 taxa. This study contributes to our knowledge of rotifer biogeography and species richness patterns in Africa. [ABSTRACT FROM AUTHOR]

Global warming has raised concerns regarding the potential impact on aquatic biosafety and health. To illuminate the adaptive mechanisms of bdelloid rotifers in response to global warming, the ecological and transcriptomic characteristics of two strains (HX and ZJ) of Rotaria rotatoria were investigated at 25°C and 35°C. Our results showed an obvious genetic divergence between the two geographic populations. Thermal stress significantly reduced the average lifespan of R. rotatoria in both strains, but increased the offspring production in the ZJ strain. Furthermore, the expression levels of genes Hsp70 were significantly upregulated in the HX strain, while GSTo1 and Cu/Zn‐SOD were on the contrary. In the ZJ strain, the expression levels of genes Hsp70, CAT2, and GSTo1 were upregulated under thermal stress. Conversely, a significant decrease in the expression level of the Mn‐SOD gene was observed in the ZJ strain under thermal stress. Transcriptomic profiling analysis revealed a total of 105 and 5288 differentially expressed genes (DEGs) in the HX and ZJ strains under thermal stress, respectively. The PCA results showed clear differences in gene expression pattern between HX and ZJ strains under thermal stress. Interestingly, compared to the HX strain, numerous downregulated DEGs in the ZJ strain were enriched into pathways related to metabolism under thermal stress, suggesting that rotifers from the ZJ strain prioritize resource allocation to reproduction by suppressing costly metabolic processes. This finding is consistent with the life table results. This study provides new insights into the adaptive evolution of aquatic animals in the context of global climate change. [ABSTRACT FROM AUTHOR]

Bavarian glassblower Herman Oscar Mueller (fl. 1900s–1960s) was employed for over forty years at the American Museum of Natural History, New York, in his role as a glassblower making intricate glass models of biological subjects. From 1903 to 1945 he produced over one thousand models of invertebrate organisms that combined beauty, morphological accuracy and exceptional glassblowing skill. His talent often surpassed that of the famous Blaschkas of Dresden. Mueller enjoyed worldwide fame in his lifetime, yet his life and models have since fallen into relative obscurity, and few publications record his achievements. In contrast, the Blaschkas are the subject of extensive documentation. To correct this imbalance, Mueller's life and work are here analyzed, drawing on the large collection of primary sources in the Research Library of the American Museum of Natural History, New York, the Library of Congress, Washington DC, and the Rakow Research Library of the Corning Museum of Glass, Corning, New York, amongst others. Mueller's life provides important insights into his highly-specialized role as a museum glassblower, the changing role of natural history collections in the early twentieth century, and the ways in which the lives of important figures can be obscured by a focus on other, better documented individuals. [ABSTRACT FROM AUTHOR]

Soft-water lakes are valuable natural habitats and an important aquatic ecosystems. Lobelia lakes, which are classified based on the occurrence of isoetids, are the most characteristic of this group. The aim of our research was to assess the species richness and structure of pelagic zooplankton communities in the epilimnion of 45 Polish soft-water lakes. The lakes analyzed included a wide range of trophic states from oligotrophic to eutrophic. We noted 79 species of zooplankton, including 49 rotifer, 23 cladoceran, and seven copepod species. The species composition of epilimnetic zooplankton communities in these soft-water lakes was poor, and the species richness and zooplankton biomass were low. In these lakes, the species with the highest frequencies accounted for an important part of the total zooplankton biomass of the zooplankton communities, but the species occurring at lower frequencies differed among the lakes. The most common rotifer taxa were: Keratella cochlearis, Keratella cochlearis var. hispida, Polyarthra euryptera, Gastropus stylifer , and Trichocerca similis. The most important crustacean species in the soft-water lakes were: Macrocyclops albidus, Ceriodaphnia quadrangula , and Eudiaptomus sp. The major factors influencing rotifer species richness were total phosphorus, conductivity, and the trophic state of the lakes. Cladoceran species richness was positively related to lake area and pH, while the species richness of copepod communities was negatively related to chlorophyll a concentrations. [ABSTRACT FROM AUTHOR]

The differences in environmental parameters and zooplankton community were studied in the epilimnion of the Carpathian Dobczyce Dam Reservoir on the Raba River (southern Poland) between hydrologically dry (HD), average (HA) and wet (HW) years distinguished on the basis of mean annual flow for 2000-2017. We found significant differences in water chemistry (conductivity, nutrients: P-tot, PO 4 3−, NH 4 +) in the epilimnion between the studied hydrological years. The total density and dry weight of zooplankton and the density of Rotifera: Keratella quadrata (Müller, 1786), Copepoda: Copepoda n. det. (immature stages), Cyclops strenuus Fischer, 1851, Eudiaptomus gracilis (Sars G.O., 1863) and Cladocera: Bosmina longirostris (O.F.Müller, 1776), Daphnia cucullata G.O. Sars, 1862, and D. longispina (O.F.Müller, 1776) were significantly higher in HA and HW years than in HD years. The highest densities of many Rotifera, Cladocera and Copepoda species were found in HA and HW years with high flows or floods in the river in spring or early summer. At these times, the epilimnion was rich in P-tot (diffuse pollution), considered as a limiting factor for algal growth in Carpathian reservoirs. The best Generalized Linear Models (GLM) for zooplankton density included 4-6 factors, among which P-tot, NO 3 −, and pH were always present. We found that river flows prevailing in a given year determine water chemistry and eutrophication processes, which has a significant impact on densities and dry weight of zooplankton communities in HD, HA and HW years. The results obtained have important implications for proper management in mountain catchments. [ABSTRACT FROM AUTHOR]

The River Nile is the artery of Egypt, as it presents more than 96% of the municipal, industrial, and irrigation necessities of Egypt. This study was dedicated to providing data about the effect of pollution at six stations on the River Nile at the Rosetta branch during the period from August 2019 to April 2020, using heavy metals analysis and zooplankton as biological indicators. It was found that the average of heavy metals concentration follows the descending order Al > Fe > Mn > Zn > Ni > Co. Most of the heavy metals recorded its highest values at El-Rahawy station. Zooplankton community was represented by 32 species in addition to 4 Meroplanktons. Five groups of zooplankton were recorded, viz. Rotifera (1717 org./L), Protozoa (552 org./L), Cladocera (54 org./L), Nematoda (46 org./L), and other Meroplankton (44 org./L), dominated by Rotifera followed by Protozoa, Cladocera, Nematoda, and other Meroplanktons contributing 71%, 23%, 2%, 2%, and 2%, respectively. The highest average density of total zooplankton was recorded during spring while the lowest was recorded during summer. The highest similarity of (79.12%) was observed between (Site 1) and (Site 5). Almost all diversity indices were conducted and showed its highest values in site 6. The principal component analysis conducted between heavy metals, and zooplankton showed a significant negative correlation was shown for the dominant zooplankton with the heavy metals except with cobalt. Nematoda and the rotifer Brachionus angularis recorded a positive correlation with heavy metals except cobalt. [ABSTRACT FROM AUTHOR]

The present study investigated the effect of environmental variables on the abundance and distribution of zooplankton in different habitats along the Nile River in Shattura Village. Zooplankton samples were collected from three distinct sites along the Nile River in Shattura Village, each exhibiting different environmental characteristics: Site 1 with vegetation, site 2 lacking vegetation, and site 3 being a drain canal. The study spanned from spring 2020 to winter 2021, during which the physico-chemical parameters of the water were analyzed. Rotifera constituted the majority of the zooplankton (54.73%), followed by Cladocera (20.59%), Copepoda (13.1%), and Ostracoda (8.9%). Among the 52 identified zooplankton species, Rotifera comprised 18 species, Cladocera 13 species, Copepoda 10 species, and Ostracoda 11 species. Site 1 exhibited the highest zooplankton density (44.08%), attributed to the presence of vegetation, followed by site 3 (37.18%), influenced by agricultural drains, and site 2 had the lowest density (18.73%). Zooplankton abundance peaked in summer and declined in winter. Notably, Rotifera abundance increased in populated sites (site 3), whereas other zooplankton groups thrived in less populated areas. Correlation analyses revealed positive associations between Rotifera and Cladocera with electric conductivity, total dissolved solids (TDS), chloride (Cl), calcium (Ca), and sulfate (SO4). Conversely, Copepoda showed positive correlations with water transparency, pH, dissolved oxygen, and biological oxygen demand (BOD). Overall, seasonal variations significantly impacted the zooplankton community, with Rotifera dominating and Ostracoda being the least abundant. High values of the Shannon–Weaver diversity index, richness, and evenness suggested ample food resources and favorable growth conditions. Transparency, conductivity, pH, dissolved oxygen, and BOD were identified as the key influencing parameters on zooplankton abundance. Additionally, vegetation and agricultural drains strongly influenced total zooplankton levels. [ABSTRACT FROM AUTHOR]