[Plankton Community Stability and Drive Factor Identification Guizhou Plateau Reservoir].

In order to understand the stability of the zooplankton and phytoplankton communities in the Guizhou plateau reservoir environment, the process of reservoir water quality change affecting the stability of plankton was studied. The changes in the plankton community and water quality in three different nutrient reservoirs （Huaxi Reservoir, Goupitan Reservoir, and Hailong Reservoir） were studied from October 2020 to August 2021. The stability of the zooplankton and phytoplankton communities was studied using time-lag analysis （TLA）. Variance decomposition analysis （VPA） was used to explore the response of the two communities to environmental changes. The driving factors of plankton community changes in reservoirs were also revealed. The results showed that Huaxi Reservoir and Goupitan Reservoir were mesotrophic reservoirs, and Hailong Reservoir was a eutrophic reservoir. The average comprehensive nutrition indices of the three reservoirs were 44.07, 44.68, and 50.25. A total of 51 species of zooplankton rotifers, 39 species of rotifers, three species of copepods, and nine species of cladocera were identified. Among them, the abundance of rotifers was the highest, accounting for 85.96%. A total of seven phyla and 73 species of phytoplankton were identified, including 16 species in the phylum Cyanophyta, 32 species in the phylum Chlorophyta, 16 species in the phylum Diatoma, three species in the phylum Chlorophyta, four species in the phylum Euglenophyta, and one species each in the phyla Cryptophyta and Chrysophyta. Among them, the abundance of cyanobacteria and diatoms was the highest, accounting for 66.2% and 27.35%, respectively. The median absolute deviation （MAD） of the Bray-Curtis distance of zooplankton and phytoplankton community in the three reservoirs were 0.67 and 0.65 in Huaxi Reservoir, 0.80 and 0.69 in Goupitan Reservoir, and 0.85 and 0.47 in Hailong Reservoir, respectively. The larger the value, the greater the variation in the community. The absolute value of the slope of zooplankton was greater than that of phytoplankton in the TLA results, and the absolute values of the slopes were 0.018 and 0.004, respectively. The larger the absolute value of the slope, the faster the community variability. The zooplankton community in the three reservoirs was less stable than the phytoplankton community and more sensitive to environmental changes, and the degree of variation was greater. The higher the degree of eutrophication of the reservoir, the more obvious this phenomenon. VPA showed that the changes in plankton communities in Huaxi Reservoir and Hailong Reservoir were mainly influenced by water temperature and eutrophication factors. The changes in planktonic community in Goupitan Reservoir were mainly influenced by water temperature and chemical factors. The driving factors of Huaxi Reservoir were water temperature, TP, permanganate index, and SD. The driving factors of Goupitan Reservoir were water temperature, NO3-- N, and pH. The driving factors of Hailong Reservoir were water temperature and TP. Nutrients and water temperature were the main factors affecting the stability of plankton communities in reservoirs.

Bdelloid rotifers deploy horizontally acquired biosynthetic genes against a fungal pathogen.

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.

Contrasting toxicity response to a mixture of azithromycin and ivermectin between a freshwater and a euryhaline rotifer.

Organisms are usually exposed to mixtures of emerging pollutants in aquatic environments. Due to their widespread use and environmental relevance, the individual and combined effects of the drugs azithromycin (AZT) and ivermectin (IVM) on the freshwater rotifer Lecane papuana and the euryhaline rotifer Proales similis were investigated. Rotifers showed greater sensitivity to IVM compared to AZT. The LC50 values of IVM and AZT for L. papuana and P. similis were 0.163 and 0.172 mg/L, and 13.52 and 20.00 mg/L, respectively. Population growth rates, assessed in chronic toxicity assays, responded negatively to increasing concentrations of both toxicants, either individually or in combination. Our results revealed two distinct combined toxicity responses: a strong synergistic effect in the freshwater rotifer and a marked antagonistic impact of the AZT-IVM mixtures in the euryhaline rotifer.

Ecotoxicological assessment, oxidative response, and enzyme activity disorder of the rotifer Brachionus asplanchnoidis exposed to a toxic cocktail of spent lithium-ion battery leachate.

Spent lithium-ion batteries (LIBs) have emerged as a major source of waste due to their low recovery rate. The physical disposal of spent LIBs can lead to the leaching of their contents into the surrounding environment. While it is widely agreed that hazardous substances such as nickel and cobalt in the leachate can pose a threat to the environment and human health, the overall composition and toxicity of LIB leachate remain unclear. In this study, a chemical analysis of leachate from spent LIBs was conducted to identify its primary constituents. The ecotoxicological parameters of the model organism, rotifer Brachionus asplanchnoidis, were assessed to elucidate the toxicity of the LIB leachate. Subsequent experiments elucidated the impacts of the LIB leachate and its representative components on the malondialdehyde (MDA) level, antioxidant capacity, and enzyme activity of B. asplanchnoidis. The results indicate that both the LIB leachate and its components are harmful to individual rotifers due to the adverse effects of stress-induced disturbances in biochemical indicators, posing a threat to population development. The intensified poisoning phenomenon under combined stress suggests the presence of complex synergistic effects among the components of LIB leachate. Due to the likely environmental and biological hazards, LIBs should be strictly managed after disposal. Additionally, more economical and eco-friendly recycling and treatment technologies need to be developed and commercialized.

Effects of microplastics on reproductive characteristics and mechanisms of the marine rotifer Brachionus plicatilis.

Microplastic pollution, especially secondary microplastics (MPs), poses a significant threat to marine ecosystems. Despite its prevalence, the impact of natural-aged MPs on marine organisms, hindered by collection challenges, remains poorly understood. This study focused on 1-3 µm natural-aged MPs collected from Japan's coastal sea, investigating their effects on the rotifer Brachionus plicatilis sensu stricto and its reproductive mechanisms. Rotifers exposed to varying MP concentrations (0, 20, and 200 particles/mL) over 14-day batch cultures exhibited reduced population growth and fertilization rates. Down-regulation of reproductive genes and up-regulation of oxidative stress-related genes were observed, indicating MP-induced disruptions. Enhanced activities of superoxide dismutase and acetylcholinesterase and elevated malondialdehyde levels further emphasized oxidative stress. These findings underscore the detrimental impact of MPs on rotifer reproductivity, shedding light on the underlying mechanisms.

The impact of artificial light pollution at night on the life history parameters of rotifer Brachionus plicatilis with different food experiences.

Artificial light at night (ALAN) may pose threat to rotifer Brachionus plicatilis. Additionally, the food of rotifer, i.e. algal community composition, often fluctuates. Thus, we selected five wavelengths of ALAN (purple, blue, green, red, white) and a three-colored light flashing mode (3-Flash) to test their impacts on life history traits of B. plicatilis with different food experiences, including those feeding Chlorella vulgaris (RC) or Phaeocystis globosa (RP). Results indicated purple ALAN promoted RC development, white ALAN inhibited RC development, while 3-Flash and white ALAN promoted RP development. Under red and white ALAN, RP increased fecundity but decreased lifespan. High-quality food enhanced rotifer's resistance to the impact of ALAN on lifespan. ALAN and food experience interacted on B. plicatilis. The effect of blue ALAN has less negative effects on B. plicatilis, based on hierarchical cluster analysis. Such findings are helpful to evaluate the potential impact of ALAN on marine zooplankton.

Effects of bisphenol A on reproduction, oxidative stress, and lipid regulation in the marine rotifer Brachionus plicatilis.

This study reports the effects of bisphenol A (BPA) on the rotifer Brachionus plicatilis, focusing on growth performance, reproductive output, oxidative stress responses, and lipid metabolism genes. High BPA levels disrupted peak daily offspring production and led to oxidative stress and increased superoxide dismutase and catalase activity. The research identified distinctive monoacylglycerol O-acyltransferase (MGAT) and diacylglycerol O-acyltransferase (DGAT) genes in B. plicatilis, B. rotundiformis, and B. koreanus, enhancing understanding of lipid metabolism in these species. BPA exposure significantly altered MGAT and DGAT expression, and feeding status affected these regulatory patterns. When food was unavailable, BPA reduced DGAT2 and MGAT2a expression. However, under feeding conditions, DGAT2 and MGAT1 levels increased, indicating that nutritional status and BPA exposure interact to affect gene expression.

Multigenerational resilience of the marine rotifer Brachionus plicatilis to high temperature after additive exposure to high salinity and nanoplastics.

To study multigenerational resilience to high temperature (HT) conditions, we exposed Brachionus plicatilis marine rotifers to HT, high salinity (HS), and nanoplastics (NPs), and measured reproductive and life-cycle endpoints. After exposure to HT, rotifer lifespans were reduced, but daily production of offspring increased. However, both combined HT/HS and HT/HS/NP exposure led to additional decreases in longevity and reproductive ability; the antioxidant defense mechanisms of the rotifers were also notably upregulated as measured by reactive oxygen species levels. Fatty-acid profiles were reduced in all conditions. In multigenerational experiments, the negative effects of HT dissipated rapidly; however, the effects of HT/HS and HT/HS/NPs required four generations to disappear completely. The findings indicated that B. plicatilis were able to recover from these environmental stressors. This study demonstrated the resilience of aquatic organisms in response to changing environmental conditions and provides insights into the complex interactions of different abiotic stressors.

Energy strategy alteration, rather than toxicity itself, interferes with the population fluctuation of Brachionus plicatilis exposed to water-accommodated fractions (WAFs) of crude oil.

Oil spills are reported to have conflicting impacts of either injury or resilience on zooplankton communities, and physiological plasticity is speculated to be the possible causative factor. But how? An explanation was sought by exposing the marine rotifer Brachionus plicatilis to a series of water-accommodated fractions (WAFs) of crude oil under controlled laboratory conditions, and population dynamics, which is the core issue for zooplankton facing external stress, were analyzed. The total hydrocarbon concentration of WAFs was quickly degraded from a concentration of 5.0 mg L-1 to half within 24 h and then remained stable. No acute lethality was observed; only motion inhibition was observed in the group treated with 10 %, 50 % and 100 % WAFs, which occurred simultaneously with inhibition of feeding and filtration. However, sublethal exposure to the WAFs concentration series presented stimulation impacts on reproduction and even the population of B. plicatilis. The negative correlation between motion and reproduction seemed to indicate that a shift in the distribution of individual energy toward reproduction rather than motion resulted in increased reproduction after exposure to WAFs. More evidence from transmission electron microscopy (TEM) revealed ultrastructural impairment in both the ovaries and cilia in each treated group, and imbalance in mitochondrial numbers was one of the distinct features of alteration. WAFs stress may alter the energy utilization and storage paradigm, as indicated by the significant elevation in glycogen and the significant decrease in lipid content after WAFs exposure. Further evidence from metabolomics analysis showed that WAFs stress increased the level of lipid metabolism and inhibited some of the pathways in glucose metabolism. Sublethal acute toxicity was observed only in the first 24 h with WAFs exposure, and an energy strategy consisting of changes in the utilization and storage paradigm and reallocation is responsible for the population resilience of B. plicatilis during oil spills.

Ice-inhabiting species of Bdelloidea Rotifera reveal a pre-Quaternary ancestry in the Arctic cryosphere.

Historical climate data indicate that the Earth has passed through multiple geological periods with much warmer-than-present climates, including epochs of the Miocene (23-5.3 mya BP) with temperatures 3-4°C above present, and more recent interglacial stages of the Quaternary, for example, Marine Isotope Stage 11c (approx. 425-395 ka BP) and Middle Holocene thermal maximum (7.5-4.2 ka BP), during which continental glaciers may have melted entirely. Such warm periods would have severe consequences for ice-obligate fauna in terms of their distribution, biodiversity and population structure. To determine the impacts of these climatic events in the Nordic cryosphere, we surveyed ice habitats throughout mainland Norway and Svalbard ranging from maritime glaciers to continental ice patches (i.e. non-flowing, inland ice subjected to deep freezing overwinter), finding particularly widespread populations of ice-inhabiting bdelloid rotifers. Combined mitochondrial and nuclear DNA sequencing identified approx. 16 undescribed, species-level rotifer lineages that revealed an ancestry predating the Quaternary (> 2.58 mya). These rotifers also displayed robust freeze/thaw tolerance in laboratory experiments. Collectively, these data suggest that extensive ice refugia, comparable with stable ice patches across the contemporary Norwegian landscape, persisted in the cryosphere over geological time, and may have facilitated the long-term survival of ice-obligate Metazoa before and throughout the Quaternary.

Acyclovir eco-geno-toxicity in freshwater organisms.

This study explores the eco-geno-toxic impact of Acyclovir (ACV), a widely used antiviral drug, on various freshwater organisms, given its increasing detection in surface waters. The research focused on non-target organisms, including the green alga Raphidocelis subcapitata, the rotifer Brachionus calyciflorus, the cladoceran crustacean Ceriodaphnia dubia, and the benthic ostracod Heterocypris incongruens, exposed to ACV to assess both acute and chronic toxicity. The results indicate that while acute toxicity occurs at environmentally not-relevant concentrations, a significant chronic toxicity for C. dubia (EC50 = 0.03 µg/L, NOEC = 0.02·10-2 µg/L), highlighted substantial environmental concern. Furthermore, DNA strand breaks and reactive oxygen species detected in C. dubia indicate significant increase at concentrations exceeding 200 µg/L. Regarding environmental risk, the authors identified chronic exposures to acyclovir causing inhibitory effects on reproduction in B. calyciflorus at hundreds of µg/L and hundredths of µg/L for C. dubia as environmentally relevant environmental concentrations. The study concludes by quantifying the toxic and genotoxic risks of ACV showing a chronic risk quotient higher than the critical value of 1and a genotoxic risk quotient reaching this threshold, highlighting the urgent need for a broader risk assessment of ACV for its significant implications for aquatic ecosystems.

Changes in life history parameters and expression of key genes of Brachionus plicatilis exposed to a combination of organic and inorganic ultraviolet filters.

The increasing use of ultraviolet filters has become an emerging contaminant on the coast, posing potential ecological risks. Rotifers are essential components of marine ecosystems, serving as an association between primary producers and higher-level consumers. These organisms frequently encounter ultraviolet filters in coastal waters. This study aimed to assess the comprehensive effects of organic ultraviolet filters, specifically 2-ethylhexyl-4-methoxycinnamate (EHMC), and inorganic ultraviolet filters, namely, titanium dioxide nanoparticles (TiO2 NPs), on the rotifer Brachionus plicatilis. We exposed B. plicatilis to multiple combinations of different concentrations of EHMC and TiO2 NPs to observe changes in life history parameters and the expression of genes related to reproduction and antioxidant responses. Our findings indicated that increased EHMC concentrations significantly delayed the age at first reproduction, reduced the total offspring, and led to considerable alterations in the expression of genes associated with reproduction and stress. Exposure to TiO2 NPs resulted in earlier reproduction and decreased total offspring, although these changes were not synchronised in gene expression. The two ultraviolet filters had a significant interaction on the age at first reproduction and the total offspring of rotifer, with these interactions extending to the first generation. This research offers new insights into the comprehensive effects of different types of ultraviolet filters on rotifers by examining life history parameters and gene expression related to reproduction and stress, highlighting the importance of understanding the impacts of sunscreen products on zooplankton health.

Range of trait variation in prey determines evolutionary contributions to predator growth rates.

Evolutionary and ecological dynamics can occur on similar timescales and thus influence each other. While it has been shown that the relative contribution of ecological and evolutionary change to population dynamics can vary, it still remains unknown what influences these differences. Here, we test whether prey populations with increased variation in their defence and competitiveness traits will have a stronger impact on evolution for predator growth rates. We controlled trait variation by pairing distinct clonal lineages of the green alga Chlamydomonas reinhardtii with known traits as prey with the rotifer Brachionus calyciforus as predator and compared those results with a mechanistic model matching the empirical system. We measured the impact of evolution (shift in prey clonal frequency) and ecology (shift in prey population density) for predator growth rate and its dependency on trait variation using an approach based on a 2-way ANOVA. Our experimental results indicated that higher trait variation, i.e., a greater distance in trait space, increased the relative contribution of prey evolution to predator growth rate over 3-4 predator generations, which was also observed in model simulations spanning longer time periods. In our model, we also observed clone-specific results, where a more competitive undefended prey resulted in a higher evolutionary contribution, independent of the trait distance. Our results suggest that trait combinations and total prey trait variation combine to influence the contribution of evolution to predator population dynamics, and that trait variation can be used to identify and better predict the role of eco-evolutionary dynamics in predator-prey systems.

Toxic effects of fragmented polyethylene terephthalate particles on the marine rotifer Brachionus koreanus: Based on ingestion and egestion assay, in vivo toxicity test, and multi-omics analysis.

Microplastics (MPs) are a major concern in marine ecosystem because MPs are persistent and ubiquitous in oceans and are easily consumed by marine biota. Although many studies have reported the toxicity of MPs to marine biota, the toxicity of environmentally relevant types of MPs is little understood. We investigated the toxic effects of fragmented polyethylene terephthalate (PET) MP, one of the most abundant MPs in the ocean, on the marine rotifer Brachionus koreanus at the individual and molecular level. No significant rotifer mortality was observed after exposure to PET MPs for 24 and 48 h. The ingestion and egestion assays showed that rotifers readily ingested PET MPs in the absence of food but not when food was supplied; thus, there were also no chronic effects of PET MPs. In contrast, intracellular reactive oxygen species levels and glutathione S-transferase activity in rotifers were significantly increased by PET MPs. Transcriptomic and metabolomic analyses revealed that genes and metabolites related to energy metabolism and immune processes were significantly affected by PET MPs in a concentration-dependent manner. Although acute toxicity of PET MPs was not observed, PET MPs are potentially toxic to the antioxidant system, immune system, and energy metabolism in rotifers.

Adaptation and potential culture of wild Amphipods and Mysids as potential live feed in aquaculture: a review.

Live foods such as phytoplankton and zooplankton are essential food sources in aquaculture. Due to their small size, they are suitable for newly hatched larvae. Artemia and rotifer are commonly used live feeds in aquaculture; each feed has a limited dietary value, which is unsuitable for all cultured species. Whereas, copepod and cladocerans species exhibit favorable characteristics that make them viable candidates as sources of essential nutrients for hatchery operations. Due to their jerking movements, it stimulates the feeding response of fish larvae, and their various sizes make them suitable for any fish and crustacean. Even though Artemia is the best live feed due to its proficient nutritional quality, the cost is very expensive, which is about half of the production cost. A recent study suggests the use of amphipods and mysids as alternative live feeds in aquaculture. High nutritional value is present in amphipods and mysids, especially proteins, lipids, and essential fatty acids that are required by fish larvae during early development. Amphipods and mysids are considered abundant in the aquatic ecosystem and have been used by researchers in water toxicity studies. However, the culture of amphipods and mysids has been poorly studied. There is only a small-scale culture under laboratory conditions for scientific research that has been performed. Thus, further research is required to find a way to improve the mass culture of amphipods and mysids that can benefit the aquaculture industry. This review article is intended to provide the available information on amphipods and mysids, including reproductive biology, culture method, nutritional value, feed enhancement, and the importance of them as potential live feed in aquaculture. This article is useful as a guideline for researchers, hatchery operators, and farmers.

Differential Roles of Diet on Development and Spinal Cord Regeneration in Larval Zebrafish.

The zebrafish is a powerful model organism for studying development and regeneration. However, there is a lack of a standardized reference diet for developmental and regeneration experiments. Most studies evaluate the rate of growth, survival, and fecundity. In this study, we compare three diets and their effects on growth and regeneration after a spinal cord injury (SCI). Fish were fed daily for 1 week with daily measurements of overall length and width of spinal injury. Fish fed a live rotifer diet grew 32%, whereas a commercially available diet only led to a 4% increase in body length. Similarly, differences in rate of regeneration were observed with over 80% of rotifer-fed larvae forming a glial bridge after injury compared to <10% of zebrafish fed with the commercial diet. Our data highlight the need for establishing a standardized diet for regeneration studies to improve research reproducibility.

An artificial intelligence-based model for predicting reproductive toxicity of bisphenol analogues mixtures to the rotifer Brachionus calyciflorus.

The joint toxicity effects of mixtures, particularly reproductive toxicity, one of the main causes of aquatic ecosystem degradation, are often overlooked as it is impractical to test all mixtures. This study developed and evaluated the following models to predict the concentration response curve concerning the joint reproductive toxicity of mixtures of three bisphenol analogues (BPA, BPF, BPAF) on the rotifer Brachionus calyciflorus: concentration addition (CA), independent action (IA), and two deep neural network (DNN) models. One applied mixture molecular descriptors as input variables (DNN-QSAR), while the other applied the ratios of chemicals in the mixtures (DNN-Ratio). Descriptors related to molecular mass were found to be of greater importance and exhibited a proportional relationship with toxic effects. The results indicate that the range of correlation coefficients (R2) between predicted and measured values for various mixture rays by CA and IA models is 0.372 to 0.974 and - 0.970 to 0.586, respectively. The R2 values for DNN-Ratio and DNN-QSAR were 0.841 to 0.984 and 0.834 to 0.991, respectively, demonstrating that models developed by DNN significantly outperform traditional models in predicting the joint toxicity of mixtures. Furthermore, DNN-QSAR not only predicts mixture toxicity but also provides accurate toxicity predictions for BPA, BPF, and BPAF, with R2 values of 0.990, 0.616, and 0.887, respectively, while DNN-Ratio yields values of 0.920, 0.355, and - 0.495. The study also found that the joint effects of mixtures are primarily influenced by the total concentration of the mixtures, and an increase in total concentration shifts the joint effects towards addition. This study introduces a novel approach to predict joint toxicity and analyze the influencing factors of joint effects, providing a more comprehensive assessment of the ecological risk posed by mixtures.

Is there potential for estradiol receptor signaling in lophotrochozoans?

Estrogen receptors (ERs) are thought to be the ancestor of all steroid receptors and are present in most lophotrochozoans studied to date, including molluscs, annelids, and rotifers. A number of studies have investigated the functional role of estrogen receptors in invertebrate species, although most are in molluscs, where the receptor is constitutively active. In vitro experiments provided evidence for ligand-activated estrogen receptors in annelids, raising important questions about the role of estrogen signalling in lophotrochozoan lineages. Here, we review the concordant and discordant evidence of estradiol receptor signalling in lophotrochozoans, with a focus on annelids and rotifers. We explore the de novo synthesis of estrogens, the evolution and expression of estrogen receptors, and physiological responses to activation of estrogen receptors in the lophotrochozoan phyla Annelida and Rotifera. Key data are missing to determine if de novo biosynthesis of estradiol in non-molluscan lophotrochozoans is likely. For example, an ortholog for the CYP11 gene is present, but confirmation of substrate conversion and measured tissue products is lacking. Orthologs CYP17 and CYP19 are lacking, yet intermediates or products (e.g. estradiol) in tissues have been measured. Estrogen receptors are present in multiple species, and for a limited number, in vitro data show agonist binding of estradiol and/or transcriptional activation. The expression patterns of the lophotrochozoan ERs suggest developmental, reproductive, and digestive roles but are highly species dependent. E2 exposures suggest that lophotrochozoan ERs may play a role in reproduction, but no strong dose-response relationship has been established. Therefore, we expect most lophotrochozoan species, outside of perhaps platyhelminths, to have an ER but their physiological role remains elusive. Mining genomes for orthologs gene families responsible for steroidogenesis, coupled with in vitro and in vivo studies of the steroid pathway are needed to better assess whether lophotrochozoans are capable of estradiol biosynthesis. One major challenge is that much of the data are divided across a diversity of species. We propose that the polychaetes Capitella teleta or Platyneris dumerilii, and rotifer Brachionus manjavacas may be strong species choices for studies of estrogen receptor signalling, because of available genomic data, established laboratory culture techniques, and gene knockout potential.

Population growth of two limno-terrestrial Antarctic microinvertebrates in different aqueous soil media.

Terrestrial microinvertebrates provide important carbon and nutrient cycling roles in soil environments, particularly in Antarctica where larger macroinvertebrates are absent. The environmental preferences and ecology of rotifers and tardigrades in terrestrial environments, including in Antarctica, are not as well understood as their temperate aquatic counterparts. Developing laboratory cultures is critical to provide adequate numbers of individuals for controlled laboratory experimentation. In this study, we explore aspects of optimising laboratory culturing for two terrestrially sourced Antarctic microinvertebrates, a rotifer (Habrotrocha sp.) and a tardigrade (Acutuncus antarcticus). We tested a soil elutriate and a balanced salt solution (BSS) to determine their suitability as culturing media. Substantial population growth of rotifers and tardigrades was observed in both media, with mean rotifer population size increasing from 5 to 448 ± 95 (soil elutriate) and 274 ± 78 (BSS) individuals over 60 days and mean tardigrade population size increasing from 5 to 187 ± 65 (soil elutriate) and 138 ± 37 (BSS) over 160 days. We also tested for optimal dilution of soil elutriate in rotifer cultures, with 20-80% dilutions producing the largest population growth with the least variation in the 40% dilution after 36 days. Culturing methods developed in this study are recommended for use with Antarctica microinvertebrates and may be suitable for similar limno-terrestrial microinvertebrates from other regions.

Resilience of rotifers and cladocerans communities in four reservoirs with eutrophication pollution and lead concentrations in Aguascalientes, Mexico.

Pollution in aquatic ecosystems has been increasing drastically worldwide changing their water quality. Therefore, species must be adapted to these new scenarios. In Aguascalientes City, four representative urban reservoirs contain lead in the water column and extremely high concentrations of sediments. Therefore, an analysis was conducted to evaluate the resilience of zooplankton species to lead exposure in each reservoir using dormant and organisms. Results demonstrated a decrease range from 57.5 to 22.5% in overall diapausing egg hatching rate, while survivorship rate also decreased from 98 to 54% when organisms were exposed to the water of the four reservoirs and increasing lead concentrations. When Pb exposure increased, results showed a global negative effect on both hatching rate (decreasing from 58 to 30% at 0.09 mg L-1) and survivorship levels (decreasing from 100% to 0.07% at 0.09 mg L-1). We provide Species Sensitivity Distribution for both water reservoir dilutions and lead concentration to analyze diapausing eggs hatching and survivorship of offspring in the presence of same polluted conditions or lead of the autochthonous species found in reservoirs. Furthermore, specific analysis with two populations of the cladoceran Moina macrocopa showed clear dissimilar hatching patterns that suggested a different adaptive mechanism. Niagara population shows a hatching rate of approximately 25% in the first two days of reservoir water exposure, while UAA population drastically increased hatching rate to 75% on exposure at day seven. We provide the first record of bioaccumulation in ephippia of M. macrocopa.