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Cigarette butts have become one of the most common and persistent forms of debris in marine coastal areas, where they pose significant toxicity risks. This study investigated cigarette butt pollution along beaches of the Yellow Sea and used laboratory experiments to assess the toxicity of their leachate and fibers on the euryhaline rotifer Brachionus plicatilis. A pollution index confirmed pollution by this debris across all eight beaches surveyed, where the density of cigarette butts averaged 0.23 butts/m2. In controlled laboratory experiments, both the fibers and leachates from cigarette butts exhibited negative impacts on the development, reproduction, and population growth of rotifers. Unique abnormalities observed under different exposure treatments indicated toxicity specific to certain chemicals and particles. Continuous exposure to cigarette butts initially reduced rotifer fecundity, but this effect diminished over successive generations. However, the exposure induced transgenerational reproductive toxicity in the rotifers. Adaptive responses in rotifers after repeated exposure led to relative reduction in reproductive inhibition in the F3 and F4 generations. Furthermore, rotifers were capable of ingesting and accumulating cigarette butts, and maternal transfer emerged as an alternative pathway for uptake of this material in the offspring. These results increase our understanding of the ecological risks posed by cigarette butts in aquatic environments. [Display omitted] • Marine and coastal environments along the Yellow Sea are threatened cigarette butt pollution. • The fecundity and survival of B. plicatilis altered with diverse cigarette butt concentrations. • Cigarette butts induce trans-generational reproductive toxicity in B.plicatilis. • Maternal transfer was verified as a relevant uptake route of chemicals from cigarette butts. [ABSTRACT FROM AUTHOR]

• Microplastics adversely affected demographic variables of brachionus calyciflorus. • The adverse effect was more pronounced at 25° than at 20 °C. • Ingestion rates declined significantly in the presence of the microplastics. • Pre-exposure improved the survivorship of the rotifers to microplastics. Microplastics (MPs) are becoming increasingly common in freshwater ecosystems. Rotifers may involuntarily ingest MPs through non-selective filtration, thus causing non-real satiety, leading to adverse effects on their demography. Here, we evaluated the acute and chronic effects of MPs (30 µm) on two successive generations of Brachionus calyciflorus s.s. at 20 and 25 °C. Demographic variables and ingestion rates were compared in the absence and presence of microplastics (550 spheres mL-1). For the life table experiments, cohorts of twenty neonates were introduced into 20 mL medium with four replicates per treatment. Ingestion rates of the rotifer were tested at both test temperatures in the absence and presence of the microplastics in 20 mL containers with 1 ind. mL-1 per container. The rotifer population growth rates ranged from 0.55 to 1.05 d-1 depending on the treatment. MPs decreased the fecundity by 20–24 %. The average lifespan of rotifers exposed to MPs in the F 0 generation was lower than that in the F 1 generation at both temperatures, indicating that pre-exposure of mothers may offer some protection to the offspring. The population growth rate was higher at 25 °C. The ingestion rates were significantly lower in the presence of the microplastics. Our observations indicated that this strain of B. calyciflorus was better adapted to 20 °C; microplastics and higher test temperature resulted in a pronounced changes in the demographic variables of the rotifer. [Display omitted] [ABSTRACT FROM AUTHOR]

To assess the toxicity of Hexabromocyclododecane (HBCD), the population, individual, and cellular biochemical parameters of the rotifer Brachionus plicatilis exposed to different concentrations of HBCD were investigated. The results showed that the population growth rate, reproductive period, and offspring number in B. plicatilis significantly decreased under 324 μg/L and 648 μg/L HBCD. Antioxidant enzyme activity and mRNA expression of CAT and Mn-SOD were promoted at low concentrations (32 μg/L and 64 μg/L) and inhibited at high concentrations (324 μg/L and 648 μg/L), while MDA content accumulated continuously with increasing HBCD concentrations, indicating that HBCD induced oxidation imbalance in rotifers. Further evidence was provided by the correlation between DNA fragmentation and physiological changes. The increased intercellular concentration of Ca2+ and the expression of CaM mRNA suggested that HBCD activated pathways related to calcium signaling. In summary, the excessive production of ROS induced by HBCD was considered to be the main cause of reproductive toxicity. [Display omitted] • HBCD has adverse effects on population growth and reproduction. • The antioxidative capacity of B.plicatilis was activated by low dose of HBCD. • ROS were the MIE of HBCD-induced reproductive toxicity. • HBCD causes stress at multiple levels in B.plicatilis. [ABSTRACT FROM AUTHOR]

As microplastics (MPs) are particulate pollutants, their size and shape, and the presence of prey in the media can affect their toxicity. However, the size- and shape-dependent toxicities of MPs and their prey-dependent ingestion patterns in marine zooplankton are not well understood. Thus, we investigated the ingestion and egestion patterns, and toxicity of different shapes and sizes of MPs on two marine zooplankton, Brachionus koreanus and Diaphanosoma celebensis , under different prey conditions. The ingestion assay showed that smaller MPs were ingested more frequently, regardless of their shape. However, fragmented MPs showed higher toxicity than spherical MPs of comparable size. Prey in the media reduced the uptake and toxicity of MPs in both species depending on the taxa's feeding strategy. Our findings demonstrate that the size and shape of MPs are important factors in determining toxicity and that the presence of prey should also be considered when assessing MP toxicity. [Display omitted] • Smaller-sized MPs were readily ingested by both marine zooplankton. • Fragmented MPs induced significant mortality of marine zooplankton. • Prey in the media reduced MP ingestion and toxicity. • Effect of prey on MP toxicity depended on feeding strategy of biota. [ABSTRACT FROM AUTHOR]

The rotifer-specific exogenic biopolymer, named Rotimer and its related molecular processes are affected by physical and chemical factors (e.g., temperature, pH or metal ions); however, the study of biological influences (e.g., the presence protozoa) concerning the particle-dependent reproduction (egg laying) and 'biopolymer producing capacity' (BPC) of rotifers is the objective of the present work. Non-planktonic rotifer species (Philodina acuticornis , Adineta vaga , Euchlanis dilatata , and Lecane bulla) were studied in paired micrometazoa-protozoa co-cultures involving Paramecium , Diplonema , and Amoeba. These protozoa can be beneficial food sources, enhancing reproduction, or even toxic factors for the above-mentioned animals, but can also function as particle-like mechanical stimulators. Furthermore, current studies reveal that bdelloids, similarly to monogonants, produce filamentous exudate; moreover, the body of bdelloids is covered by their exudate, unlike that of monogonants, especially in the case of A. vaga. A mathematical formula was developed as an improved version of a previously published viability marker to characterize the BPC and the relative amount of produced exudate in different conditions. Rotifer species secreting biopolymers appear to be a general trait indicating a common evolutionary background (e.g., calcium- and particle dependency) of such molecules; therefore, the BPC becomes an experiential sublethal influencing marker to these micrometazoans. • Rotifers selectively consume protozoa in different species-specific combinations. • The presence of protozoa may ambivalently affect the reproduction of rotifers. • Laying eggs by rotifers depends on biopolymer-microparticle conglomerate formation. • The biopolymer production of rotifers depends on the type of protozoa being present. • Bdelloids also create filamentous viscoelastic biopolymer, such like monogonants. [ABSTRACT FROM AUTHOR]

Temperature plays an important role in the occurrence and performance of organisms in aquatic ecosystems and is also one of the main environmental factors affecting species' survival and growth in aquaculture. As an important species for aquaculture sustainability, the rotifer Brachionus sp. benefits from inducible phenotypic traits that allow the organisms to cope with environmental stress. The exposure to high temperature has shown to increase production of heat shock proteins (HSPs) and histone modifications in several organisms, resulting in induced thermotolerance. This study aimed to evaluate the potential of non-lethal heat shock (NLHS) to induce thermotolerance in two strains of B. koreanus and pinpoint some of the molecular mechanisms involved in the process. Exposure of organisms to 42 °C for 30 min, with a subsequent recovery at 25 °C for 8 h demonstrated to increase thermotolerance in up to three-fold when organisms were, in a posterior phase, subjected to a lethal temperature. This study also showed that one of the strains is tendentially more thermotolerant than the other. Indeed, NLHS exposure resulted in increased mRNA expression of different Hsp genes and production of HSP70 in general, but different patterns of expression were observed between strains. However, a single NLHS showed to have no effects in epigenetic mechanisms, suggesting that the induced capacity to tolerate heat stress was transient and some more cycles of NLHS may be needed to promote a persistent effect. [Display omitted] • Exposure to NLHS induced thermotolerance in two strains of B. koreanus. • NLHS resulted in increased mRNA expression of several Hsp genes and production of HSP70. • Studied strains showed different patterns of alterations of molecular mechanisms. • A single NLHS showed to have no effects in epigenetic mechanisms. [ABSTRACT FROM AUTHOR]

The impact of leachates from micronized beached plastics of the Mediterranean Sea and Atlantic Ocean on coastal marine ecosystems was investigated by using a multidisciplinary approach. Chemical analysis and ecotoxicological tests on phylogenetically distant species were performed on leachates from the following plastic categories: bottles, pellets, hard plastic (HP) containers, fishing nets (FN) and rapido trawling rubber (RTR). The bacteria Alivibrio fischeri , the nauplii of the crustaceans Amphibalanus amphitrite and Acartia tonsa , the rotifer Brachionus plicatilis , the embryos of the sea urchin Paracentrotus lividus , the ephyrae of the jellyfish Aurelia sp. and the larvae of the medaka Oryzias latipes were exposed to different concentrations of leachates to evaluate lethal and sub-lethal effects. Thirty-one additives were identified in the plastic leachates; benzophenone, benzyl butyl phthalate and ethylparaben were present in all leachates. Ecotoxicity of leachates varied among plastic categories and areas, being RTR, HP and FN more toxic than plastic bottles and pellets to several marine invertebrates. The ecotoxicological results based on 13 endpoints were elaborated within a quantitative weight of evidence (WOE) model, providing a synthetic hazard index for each data typology, before their integrations in an environmental risk index. The WOE assigned a moderate and slight hazard to organisms exposed to leachates of FN and HP collected in the Mediterranean Sea respectively, and a moderate hazard to leachates of HP from the Atlantic Ocean. No hazard was found for pellet, bottles and RTR. These findings suggest that an integrated approach based on WOE on a large set of bioassays is recommended to get a more reliable assessment of the ecotoxicity of beached-plastic leachates. In addition, the additives leached from FN and HP should be further investigated to reduce high concentrations and additive types that could impact marine ecosystem health. [Display omitted] • Beached-plastic leachate toxicity was assessed in aquatic organisms. • Chemical analyses detected a cocktail of leached compounds. • Leachate toxicity was found in marine zooplankton and not in bacteria and fish. • Weight of Evidence estimated environmental hazards in fishing nets and hard plastics. • Additives leached from certain plastics should be further monitored. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • BPA delays offspring production in B. plicatilis. • Oxidative stress is increased by BPA in rotifers. • BPA reduces fatty acid, Nile red staining area • New MGAT and DGAT genes in Brachionus species were found. • Food availability impacts MGAT and DGAT gene expression. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • HT boosts offspring production but decrease lifespan. • HTHS and HTHSNP stresses significantly reduce lifespan and reproduction. • Stress elevates reactive oxygen species and antioxidant enzymes. • All stress conditions decrease fatty acid profiles. • Recovery from HT is swift; HTHS and HTHSNP need four generations. [ABSTRACT FROM AUTHOR]

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 (R C) or Phaeocystis globosa (R P). Results indicated purple ALAN promoted R C development, white ALAN inhibited R C development, while 3-Flash and white ALAN promoted R P development. Under red and white ALAN, R P 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. [Display omitted] • Purple promotes but white inhibits development of rotifer experiencing Chlorella. • The 3-Flash and white ALAN promote development of rotifer experiencing Phaeocystis. • Red and white ALAN increase fecundity and decrease lifespan of rotifer. • High-quality food experience enhances rotifer to resist negative impact of ALAN. • Blue ALAN has similar effect on rotifer as the normal light cycle. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Toxic effects of PET fragments as environmentally relevant MPs were investigated. • PET MP was not acutely toxic to the marine rotifer Brachionus koreanus. • PET MP increased intracellular ROS levels and antioxidant enzyme activity. • Multiomics analysis showed immunotoxicity and metabolic disorder induced by PET MP. • PET MPs are potentially toxic to immune system and energy metabolism in rotifers. [ABSTRACT FROM AUTHOR]

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 (TiO 2 NPs), on the rotifer Brachionus plicatilis. We exposed B. plicatilis to multiple combinations of different concentrations of EHMC and TiO 2 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 TiO 2 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. [Display omitted] • EHMC delays sexual maturation and decreases the reproduction of rotifer. • TiO 2 NPs promotes sexual maturation and decreases the reproduction of rotifer. • EHMC upregulates expression of genes related to reproduction and stress of rotifer. • TiO 2 NPs can alleviate the toxic effect of EHMC to rotifer. • Effect of EHMC and TiO 2 on rotifer reproduction can be transmitted to offspring. [ABSTRACT FROM AUTHOR]

In aquatic systems, littoral zones provide heterogeneous environments where turbellarians can reach densities of up to 40,000 ind. m−2. To reach such high densities turbellarians need to feed on a variety of prey items. Very little information is available on the feeding ecology of Stenostomum spp. in natural conditions. The objective of this work was to determine the food preference of Stenostomum virginianum based on the density and physical characteristics of prey present in the littoral zone of the Benito Juárez reservoir (Mexico) associated with the macrophyte Egeria densa by analyzing the gut content of the turbellarians. We found that 58% of turbellarians contained rotifers in their gut. The thickness of rotifer lorica did not limit the selection, but the size and availability of the species did. The preferred rotifer prey included Trichocerca porcellus, Lecane closterocerca and Colurella obtusa. This work demonstrates that turbellarians feed on rotifers but are often overlooked in freshwater trophic analyses. They need be considered together with other invertebrate predators such as Asplanchna and cyclopoid copepods because of their impact on rotifer communities in tropical and temperate water bodies. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) and nanoplastics (NPs) are emerging pollutants in the ocean, but their transfer and toxicity along the food chains are unclear. In this study, a marine rotifer (Brachionus plicatilis)-marine medaka (Oryzias melastigma) food chain was constructed to evaluate the transfer of polystyrene MPs and NPs (70 nm, 500 nm, and 2 μm, 2000 μg/L) and toxicity of 70 nm PS-NPs (0, 20, 200, and 2000 μg/L) on marine medaka after long-term food chain exposure. The results showed that the amount of 70 nm NPs accumulated in marine medaka was 1.24 μg/mg, which was significantly higher than that of 500 nm NPs (0.87 μg/mg) and 2 μm MP (0.69 μg/mg). Long-term food chain exposure to NPs caused microflora dysbiosis, resulting in activation of toll-like receptor 4 (TLR4) pathway, which induced liver inflammation. Moreover, NPs food chain exposure increased liver and muscle tissue triglyceride and lactate content, but decreased the protein, sugar, and glycogen content. NPs food chain exposure impaired reproductive function and inhibited offspring early development, which might pose a threat to the sustainability of marine medaka population. Overall, the study revealed the transfer of MPs and NPs and the effects of NPs on marine medaka along the food chain. [Display omitted] • MPs and NPs could transfer along the rotifer-marine medaka food chain. • NPs (70 nm) were more easily accumulated in marine medaka along the food chain. • NPs (70 nm) caused intestinal damage and microbial dysbiosis in marine medaka. • Metabolism of marine medaka liver and muscle were disturbed after feeding rotifers. • Early development of marine medaka offspring was inhibited after feeding rotifers. [ABSTRACT FROM AUTHOR]

The yellow-striped cardinalfish (Ostorhinchus cyanosoma) can be found in the Indo-West Pacific region. It possesses great potential for the ornamental aquarium market due to its vibrant body coloration and tendency of group swimming. This study aims to investigate the spawning frequency and larval morphological ontogeny, and develop first feeding techniques of O. cyanosoma reared in capacity. From April 2021 to August 2022, a total of 70 spawning events were documented for the broodstock. These spawning events did not exhibit specific patterns related to seasonal or lunar cycles. The effects of four live prey treatments (mono-feeding and co-feeding of SS-type rotifer Brachionus sp. and nauplii of copepod Bestiolina coreana) on the mouth opening rate, prey ingestion rate, and prey selectivity of the 0 day-post-hatch (dph) larvae were investigated. The O. cyanosoma larvae displayed significantly higher mouth opening rate, ingestion rate and prey selectivity on the copepod nauplii over the rotifer. In the 7-d larviculture experiment, the larvae showed significant higher survival rate in the copepod feeding treatment (68%) than the rotifer feeding treatment (0%). For ontogeny, O. cyanosoma larvae appeared to be altricial (at pre-flexion stage with no gas bladder and poor-developed fins) and small-mouthed (235.94 μm) when leaving the mouthbrood. The standard length increased from 2.64 to 6.51 mm during 0 to 21dph. Ntochord flexion initiated at 12 dph, and the metamorphosis was completed by 21 dph. This study is the first attempt to document the broodstock management, first feeding protocol and larval ontogeny of O. cyanosoma. The findings could have implications for larviculture of cardinalfishes. • Broodstock and larviculture of cardinalfish Ostorhinchus cyanosoma are established. • Nauplii of Bestiolina coreana is suitable live prey for O. cyanosoma larvae. • The larval morphological ontogeny of O. cyanosoma is documented. [ABSTRACT FROM AUTHOR]

Rapid, anthropogenic activity–induced global warming is a severe problem that not only raises water temperatures but also shifts aquatic environments by increasing the bioavailability of heavy metals (HMs), with potentially complicated effects on aquatic organisms, including small aquatic invertebrates. For this paper, we investigated the combined effects of temperature (23 and 28 °C) and methylmercury (MeHg) by measuring physiological changes, bioaccumulation, oxidative stress, antioxidants, and the mitogen-activated protein kinase signaling pathway in the marine rotifer Brachionus plicatilis. High temperature and MeHg adversely affected the survival rate, lifespan, and population of rotifers, and bioaccumulation, oxidative stress, and biochemical reactions depended on the developmental stage, with neonates showing higher susceptibility than adults. These findings demonstrate that increased temperature enhances potentially toxic effects from MeHg, and susceptibility differs with the developmental stage. This study provides a comprehensive understanding of the combined effects of elevated temperature and MeHg on rotifers. Methylmercury (MeHg) is a widespread and harmful heavy metal that can induce lethal effects on aquatic organisms in even trace amounts. The toxicity of metals can vary depending on various environmental conditions. In particular, rising temperatures are considered a major factor affecting bioavailability and toxicity by changing the sensitivity of organisms. However, there are few studies on the combinational effects of high temperatures and MeHg on aquatic animals, especially invertebrates. Our research would contribute to understanding the actual responses of aquatic organisms to complex aquatic environments. [Display omitted] • Combined effects of increased temperature and MeHg were measured in B. plicatilis. • High temperature and MeHg adversely caused the physiological change of the rotifers. • Bioaccumulation and biochemical responses depend on the stages of the rotifers. • Susceptibility to high temperature and MeHg differed with the developmental stage. [ABSTRACT FROM AUTHOR]

Climbing perch, A. testudineus (Bloch, 1792), is a widely consumed fish in Asian nations due to its high nutritional value and delicate meat. The main obstacles to the spread of its cultural practises are a scarcity of high-quality seed and larval rearing due to the low survival rates in the initial stages of larval development. The key to improving the seed production of this species may lie in strategies to improve larval survival in the early stages. As a result, the goal of current study was to evaluate the impact of vitamin C, selenium, and highly unsaturated fatty acid (HUFA) enriched Brachionus calyciflorus on the development, nutrient availability, and fatty acid profile of climbing perch larvae. A total of 180 numbers of 3 days post-hatch (dph) larvae (0.021 ± 0.001 mg) were uniformly distributed among five treatments in triplicates. The larvae were fed thrice a day for 15 days with selenium (D 1), vitamin-C (D 2), HUFA (D 3) and combination of selenium-vitamin C- HUFA enriched (D 4) and non-enriched rotifer (C). The proximate analysis of various enriched and unenriched B. calyciflorus groups revealed that the vitamin C and HUFA-enriched treatment groups, respectively, had the highest percentages of crude protein (7.50%) and crude lipid (2.51%). Whereas, larvae fed a combination of selenium-vitamin C- HUFA enriched (D 4) rotifer showed the highest percentages of crude protein (12.40%) and crude lipid (1.81%). The findings of the fatty acid analysis demonstrate that feeding Se-VC-HUFA enriched B. calyciflorus to larvae resulted in significantly greater concentrations of Eicosapentaenoic acid (9.38%) and Docosahexaenoic acid (11.05%) that are 3.07 and 7.67 times higher, respectively, than feeding unenriched B. calyciflorus to larvae. The highest DHA/EPA ratio (1.18) was also observed with larvae fed Se-VC-HUFA enriched B. calyciflorus. The survivorship analysis revealed that the D 4 treatment group fed a combination of Se-VC-HUFA-enriched B. calyciflorus had the highest survival (37.41%) and the lowest (18.70%) observed in the control group. The highest average body weight gain and increased growth (30.79 ± 1.11 mg) were seen in the fishes given the rotifer supplemented with D 4 group, which performed substantially better than the other treatment groups (P < 0.05). Weight-specific growth rate (W-SGR) and Length-specific growth rate (L-SGR) of the fish exhibited similar trends across all treatment groups, whereas significantly (P < 0.05) lowest condition factor was observed in D 4 (2.63 ± 0.01) and highest in control group (3.21 ± 0.01). The results showed that larvae fed with enriched rotifer had significantly higher (P < 0.05) growth, nutrient availability, and fatty acid profile compared to un-enriched rotifer. The ideal first food for A. testudineus larval growth and survival must be a combination of Se-VC-HUFA enriched B. calyciflorus. • Enrichment of rotifer with nutraceuticals such as selenium, HUFA and vitamin C will improve the nutritional profile of rotifer as well as improves the larvae performance. • Better larval growth and survival could be achieved by feeding with enriched B. calyciflorus. • Feeding B. calyciflorus enriched with Selenium-Vitamin C-HUFA leads to increased body weight gain and specific growth rate in climbing perch larvae. • Higher larval growth and survival rates are positively correlated, suggesting that dietary DHA and EPA levels are essential for the proper development of climbing perch larvae. [ABSTRACT FROM AUTHOR]

• HBCD belongs to the highly toxic pollutants. • HBCD affected the reproductive characteristics of Brachionus plicatilis. • ROS were the MIE of HBCD-induced reproductive toxicity. • IBR and AOP were effective methods for evaluating the toxicity of HBCD. Hexabromocyclododecane (HBCD), third-generation brominated flame retardants (BRFs), has aroused worldwide concern because of its wide application and potentially negative impacts on marine ecosystems, but an information gap still exists regarding marine low-trophic organisms. Brachionus plicatilis , the model marine zooplankton, was used in the present study, and its reproductive responses were used as the endpoint to indicate HBCD-induced toxicity. HBCD was suggested to be extremely highly toxic compounds regarding the 96 h-LC 50 of 0.58 mg L −1. The sublethal exposure of HBCD injured the reproduction of B. plicatilis : The total number of offspring per female and the key population index calculated from the life table, including the intrinsic rate of population increase (r m) and net reproductive rate (R 0), were significantly influenced in a concentration-dependent manner. The reproductive process was also altered, as indicated by the first spawning time, first hatching time and oocyst development time. At the same time, individual survival and growth (body length) were also negatively affected by HBCD. Reactive oxygen species (ROS) were suggested to be responsible for reproductive toxicity mainly because the total ROS contents as well as the main components of •OH and H 2 O 2 greatly increased and resulted in the oxidative imbalance that presented as malondialdehyde (MDA) elevation. Simultaneous activation of the glutathione antioxidant system was accompanied by the apoptosis marker enzymes Caspase-3 and 9, as well as the correlation between ROS content, physiological alteration and cell apoptosis, providing further evidence for this. The integrated biomarker response (IBR) and adverse outcome pathway (AOP) showed that HBCD had a significant toxic effect on B. plicatilis near the concentration range of 96 h-LC 50. The establishment of this concentration range will provide a reliable reference for future environmental concentration warning of HBCD in marine. [ABSTRACT FROM AUTHOR]

While wastewater discharged from in-water cleaning process of ship hulls on rotifer consistently released into aquatic ecosystem, its detrimental effects on non-target animals are largely unclear. In this study, we provide evidence on detrimental effects of hull cleaning wastewater in the monogonont rotifer Brachionus manjavacas by analyzing biochemical and physiological parameters in its oxidative status, survival, lifespan, growth, fecundity, and population. The wastewater contained high concentrations of metals (Zn and Cu) and metal–based antifoulants (CuPT and ZnPT). Significant oxidative stress was observed in response to two wastewater samples [1) raw wastewater (RW) and 2) mechanical filtrated in the cleaning system (MF)]. Higher detrimental effects in survival, lifespan, fecundity, and population growth for 10 days were measured in the RW-exposed rotifers than those results analyzed in the MF-exposed rotifers. Two growth parameters, lorica length and width were also significantly modulated by both wastewater samples. These results indicate that even filtered hull cleaning wastewater would have deleterious effects on the maintenance of the rotifer population when they exposed constantly. [Display omitted] • Filtrated wastewater contained high concentrations of metals and metal-based antifoulants. • Filtered wastewater acutely increased mortality and induced significant oxidative stress. • Chronic exposure to filtered wastewater inhibited reproduction across generations. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) and nanoplastics (NPs) have gained global concern due to their detrimental effects on marine organisms. We investigated the effects of 80 nm polystyrene (PS) NPs on life history traits, ingestion, and dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP) production in the rotifer Brachionus plicatilis. Fluorescently labeled 80 nm PS NPs were ingested by the rotifer B. plicatilis and accumulated in the digestive tract. The lethal rates of B. plicatilis exposed to NPs were dose-dependent. High concentrations of PS NPs exposure had negative effects on developmental duration, leading to prolonged embryonic development and pre-reproductive periods, shortened reproductive period, post-reproductive period, and lifespan in B. plicatilis. High concentrations of PS NPs exposure inhibited life table demographic parameters such as age-specific survivorship and fecundity, generation time, net reproductive rate, and life expectancy. Consequently, the population of B. plicatilis was adversely impacted. Furthermore, exposure to PS NPs resulted in a reduced ingestion rate in B. plicatilis , as well as a decreased in DMS, particulate DMSP (DMSP p) concentration, and DMSP lyase activity (DLA), which exhibited a dose-response relationship. B. plicatilis grazing promoted DLA and therefore increased DMS production. PS NPs exposure caused a decline in the increased DMS induced by rotifer grazing. Our results help to understand the ecotoxicity of NPs on rotifer and their impact on the biogeochemical cycle of dimethylated sulfur compounds. [Display omitted] • The lethal rate of Brachionus plicatilis exposed to PS NPs was dose-dependent. • High concentrations of PS NPs had detrimental effects on life history of rotifers. • PS NPs had negative effects on ingestion and DMS and DMSP concentrations. [ABSTRACT FROM AUTHOR]

Mercury (Hg), a heavy metal pollutant worldwide, can be transformed into methylmercury (MeHg) by various aquatic microorganisms in water, thus accumulating along the aquatic food chain and posing a particular challenge to human health. Zooplankton plays a crucial role in aquatic ecosystems and serves as a major component of the food chain. To evaluate the effects of MeHg on the rotifer Brachionus plicatilis and reveal the underlying mechanism of these effects, we exposed B. plicatilis to MeHg by either direct immersion or by feeding with MeHg-poisoned Chlorella pyrenoidesa , respectively, and conducted a transcriptomic analysis. The results showed that B. plicatilis directly exposed to MeHg by immersion showed significant enrichment of the glutathione metabolism pathway for detoxification of MeHg. In addition, the exposure to MeHg by feeding induced a significant enrichment of lysosome and notch signaling pathways of rotifers, supporting the hypothesis that MeHg can induce autophagy dysfunction in cells and disturb the nervous system of rotifers. In two different routes of MeHg exposure, the pathway of cytochrome P450 in rotifers showed significant enrichment for resisting MeHg toxicity. Our results suggest further studies on the potential mechanism and biological responses of MeHg toxicity in other links of the aquatic food chain. [Display omitted] • We explored the changes in transcriptome regulations in B. plicatilis under MeHg stress. • B. plicatilis exposed to MeHg by immersion showed significant enrichment of the glutathione metabolism pathway for detoxification of MeHg. • ·The exposure to MeHg by feeding induced the significant enrichment of lysosome and notch signaling pathways of B. plicatilis. • In two exposure routes, the pathway of cytochrome P450 in B. plicatilis showed significant enrichment for resisting MeHg toxicity. [ABSTRACT FROM AUTHOR]

Chicken manure is rich in various nutrients, and it is used to improve the nutritional status of microalgae, which subsequently affects the production and nutrition of rotifers. The investigation of the effect of chicken manure on Chlorella and rotifer cultivation is therefore critical for practical production. Here, to investigate the effects of chicken manure extract (CME) on the continuous culture of the biological bait " Chlorella -rotifer", different concentrations of CME (Groups 1–5: 0, 5, 10, 15, and 20 mL·L−1, respectively) were added to the culture medium for cultivating Chlorella vulgaris , assessed the growth of C. vulgaris , and the optimal amount of CME for culturing Chlorella was determined; and the effects of the cultured Chlorella as food for rotifer cultivation and fatty acid composition of Chlorella and rotifers were analyzed. In 12 days of continuous culture, no significant difference in Chlorella population density was noted among G3, G4, and G5 (P > 0.05). Following completion of the culturing period, the specific growth rate of Chlorella in G3 (0.14 ± 0.01) and G5 (0.14 ± 0.01) showed no significant difference (P > 0.05), and chlorophyll a (Chl a) content in G3 (3.79 ± 0.06 mg·mL−1) was significantly higher than that in G5 (3.30 ± 0.12 mg·mL−1) (P < 0.05). Hence, we chose G3-cultured Chlorella for rotifer cultivation. In the 120-h rotifer cultivation period, the longevity of G3-bred rotifers (G-CME) (15.06 ± 0.82 d) was significantly more than that of the control group (G-BG11) (13.13 ± 1.27 d) (P < 0.05), and the offspring number of rotifer in G-CME (24.75 ± 3.45) was significantly higher than that in G-BG11 (17.75 ± 3.06) (P < 0.05). Rotifer population density and fecundity were significantly improved by G-CME than by G-BG11. Regarding fatty acid composition, the principal component analysis showed that Chlorella cultured by CME (CME-C) and BG11 (BG11-C) and rotifers that used them as diet (CME-R and BG11-R, respectively) exhibited a variation in principal components, with LC-PUFAs (12.66% ± 0.42%) and n-6 LC-PUFAs (3.99% ± 0.17%) being significantly higher in CME-R than in BG11-R (LC-PUFAs: 9.76% ± 0.81%, n-6 LC-PUFAs: 2.17% ± 0.32%) (P < 0.01). In conclusion, CME can promote the growth and alter the fatty acid composition of Chlorella , thus indirectly improving the growth condition and fatty acid content of rotifers; the optimal amount of CME for the continuous cultivation of the bio-bait " Chlorella -rotifer" was 10 mL·L−1. [Display omitted] • The optimum dosage of CME for Chlorella cultivation is 10 mL·L−1. • CME-cultured Chlorella can promote the growth and change life history of rotifers. • CME can change the component of fatty acids in Chlorella. • CME can indirectly increase the content of LC-PUFAs and n-6 LC-PUFAs in rotifers. [ABSTRACT FROM AUTHOR]

Using appropriate zooplankton to transfer the primary productivity of harmful algae to higher trophic levels through food chain is an eco-friendly mode to remove harmful algae. To assess the top-down efficiency of rotifer removing Phaeocystis and the salinity effect, we adopted a series of salinities to carry out Phaeocystis -rotifer population dynamics and rotifer life-history experiments. Results showed that the time for rotifers to remove Phaeocystis population was the shortest when the salinity was ≤20 ‰. With salinity rising to above 25 ‰, although the clearance time of Phaeocystis population by rotifer was significantly prolonged, ultimately the Phaeocystis population were almost completely eliminated at all salinities. Additionally, rotifer matured and reproduced earlier at low salinity, while high salinity significantly delayed first reproductive time and decreased the total offspring. The above findings are helpful to assess the impacts of external environmental factors on the application of zooplankton to control harmful algae. [Display omitted] • The fecundity of rotifer is weakened significantly at high salinity. • The efficiency of rotifer to remove Phaeocystis is decreased with rising salinity. • Top-down effect of rotifer on controlling harmful algae is salinity dependent. • Using rotifer to remove Phaeocystis is a promising way for managing coastal waters. [ABSTRACT FROM AUTHOR]

Triclosan (TCS) poses an ecological health risk due to its lipophilic nature, long half-life, and bioconcentration. To evaluate the toxicity of TCS on aquatic organisms, the life history parameters, population dynamics, and transcriptome regulation of Brachionus plicatilis exposed to TCS were investigated. In this study, the fecundity of rotifers was promoted by 25 μg/L of TCS and inhibited by higher concentrations (100 μg/L, 200 μg/L). The reproductive period of rotifers was shortened by 46.24 % but the post-reproductive period was prolonged by 176.47 % in 200 μg/L TCS. Both population growth and life table parameters indicated that a high concentration of TCS (200 μg/L) had negative impacts on population growth. Transcriptomic analysis showed that the effects of TCS on the life history parameters and population dynamics of rotifers were determined by regulating the expression of functional genes in cilium organization and cilium assembly and involved in pathways of focal adhesion. [Display omitted] • Rotifers had different energy allocation strategies under different doses of TCS. • TCS had a hormesis effect on the population growth of rotifers. • Rotifers were affected by TCS through pathways involving the cytoskeleton. [ABSTRACT FROM AUTHOR]

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

The rotifer-specific biopolymer, namely Rotimer, is a recently discovered group of the biomolecule family. Rotimer has an active role in the biofilm formation initiated by rotifers (e.g., Euchlanis dilatata or Adineta vaga) or in the female-male sexual interaction of monogononts. To understand the Ca2+- and polarity-dependent formation of this multifunctional viscoelastic material, it is essential to explore its molecular composition. The investigation of the rotifer-enhanced biofilm and Rotimer-inductor conglomerate (RIC) formation yielded several protein candidates to predict the Rotimer-specific main components. The exudate of E. dilatata males was primarily applied from different biopolimer-containing samples (biofilm or RIC). The advantage of males over females lies in their degenerated digestive system and simple anatomy. Thus, their exudate is less contaminated with food and endosymbiont elements. The sequenced and annotated genome and transcriptome of this species opened the way for identifying Rotimer proteins by mass spectrometry. The predicted rotifer-biopolymer forming components are SCO-spondins and 14–3-3 protein. The characteristics of Rotimer are similar to Reissner's fiber, which is found in the central nervous system of vertebrates and is mainly formed from SCO-spondins. This molecular information serves as a starting point for its interdisciplinary investigation and application in biotechnology, biomedicine, or neurodegeneration-related drug development. [Display omitted] • The rotifer-initiating biofilm formation is closely related to Ca2+ and humidity. • Male rotifers, like females, produce rotifer-specific biopolymer, namely Rotimer. • The female-male sexual interaction is also Ca2+-dependent and assisted by Rotimer. • Predicted components of Rotimer are SCO-spondins, associated with 14–3-3 protein. • The Rotimer-candidate protein is exclusively a rotifer species-specific SCO-spondin. [ABSTRACT FROM AUTHOR]

Taurine appears to be a crucial nutrient for teleosts, especially top predator species such as Atlantic bluefin tuna (Thunnus thynnus , L.; ABT). While dietary taurine supplementation has been highly recommended, there is a lack of studies on taurine assimilation and biosynthesis for this iconic species. The present study aims to provide insight into the molecular mechanisms involved in taurine biosynthesis and transport in ABT by studying tissue distribution and ontogenetic development of expression of cysteine dioxygenase (cdo), cysteine sulfinic acid decarboxylase (csad), 2-aminoethanethiol dioxygenase (ado) and taurine transporter (tauT) in response to graded levels of dietary taurine supplementation. The full open reading frame (ORF) for cdo and partial sequences for csad , ado and tauT were obtained, with the translated polypeptides being 202, 176, 166 and 324 amino acids, respectively. All three showed characteristics such as cupin motifs in Cdo and predicted N-glycosylation sites in Taut that are common to these genes in other species. Phylogenetic analysis showed that the ABT sequences clustered with sequences of other teleosts, and separately from mammals and molluscs. Tissue distribution varied, with adipose tissue, kidney, white muscle and testis/brain showing highest expression of cdo , csad , ado and tauT , respectively. Whole larvae expression of csad peaked at 15 dah, whereas the other genes generally increased throughout development to show highest expression at 25 dah. The nutritional trial was carried out by feeding ABT larvae from mouth opening to 14 days after hatching (dah) with rotifers (Brachionus rotundiformis) enriched with 4 different levels of taurine: 0.0 (tau0), 0.5 (tau0.5), 1.0 (tau1), and 2.0 g taurine per 106 rotifers (tau2). Rotifers effectively accumulated taurine with ABT larvae fed on treatment tau2 attaining the highest concentration of taurine. However, ABT larvae fed tau1 displayed higher growth and survival, and flexion index at 14 dah, than larvae fed the other taurine levels. Larvae fed tau1 also showed generally higher expression of tauT and cdo and digestive and antioxidant enzyme genes. While this study showed that larval ABT express taurine metabolism genes, suggesting possible synthesis that could contribute to the taurine pool in the fish, larval performance was enhanced by a level of dietary taurine (3.7 mg taurine g−1 rotifer) supplied by enrichment of rotifers at 1 g taurine per 106 rotifers. • Tissue distribution, ontogeny and expression of taurine metabolism genes were evaluated in Atlantic Bluefin tuna • Tissue distribution varied, with adipose tissue, kidney, white muscle and testis/brain showing highest expression levels • Whole larvae expression of csad peaked at 15 dah, whereas the other genes generally showed the highest expression at 25 dah • Atlantic Bluefin tuna larvae fed 3.7 mg taurine g-1 rotifer displayed the best growth and expression levels of tauT and cdo [ABSTRACT FROM AUTHOR]

Euryhaline rotifer belonging to the genera Brachionus are often used as live feed for first feeding marine finfish larviculture. Two common rotifer enrichments, a single usage of docosahexaenoic acid (DHA)-enriched Chlorella vulgaris and a combination of DHA-enriched C. vulgaris and salmon roe emulsion oil were used to assess: (i) nutritional status of rotifers and, (ii) performance when rotifers were fed to Pagrus major and Paralichthys olivaceus larvae from 2 to 15 days after hatching (DAH). Both rotifer enrichment treatments were found to be nutritionally effective with high unsaturated fatty acid (HUFA) content, especially in the combined treatment with significantly higher eicosapentaenoic acid (EPA). Despite deficient levels of EPA, DHA-enriched C. vulgaris was found to be a suitable enrichment for rotifer and also had positive response in survival, growth and trypsin activity in both P. major and P. olivaceus. DHA-enriched C. vulgaris only treatment had higher rotifer population growth (13% higher), egg bearing capacity (7% higher), almost double the soluble protein content and generally higher free amino acid content. Oxidation of lipids in the combined diet due to its high-saturated fatty acid content could be a possible cause to the inferior performance of the combined treatment. Both P. major (20.1 ± 10.1%) and P. olivaceus (12.3 ± 3.87%) suffered low survival and lower gut content in the combined treatment especially during periods of significant growth in both species (7–11 DAH). Despite high HUFA content in the combined treatment, this study revealed that consideration of free amino acids and soluble protein content as parameters of nutritional indicators for first feeding P. major and P. olivaceus should not be discounted. • Despite being important culture species, little is known of the effects of emulsion oils on the feeding response in first feeding Japanese flounder and red sea bream. • Dosages of oil-based enrichments on rotifer need to be regulated if oxidation of lipids, production of low quality rotifers with too high lipid content and associated low viability of cultured larvae is to be avoided. • Critical phase of exponential growth during first feeding observed between 7 and 11 DAH in both species of larvae with increased growth and feed utilization as reflected in gut content. • Consideration of free amino acids and soluble protein content as a parameters of nutritional suitability for first feeding marine fish despite importance of highly unsaturated fatty acids. [ABSTRACT FROM AUTHOR]

To understand the lipid metabolism in invertebrate species, identification of the fatty acid (FA) synthesis gene families in invertebrate species is important, since some FA are unable to be synthesized in the organisms by themselves. In the study, to identify the elongation of very long chain fatty acid (Elovl) genes in the marine rotifer Brachionus koreanus , the genome-wide identification and phylogenetic analysis of Elovl genes have been conducted with the expression profile of Elovl genes on the alga Tetraslemis suecica -fed B. koreanus. A total 10 Elovl genes have been identified from the genome of B. koreanus , with conserved HXXHH motif. Synteny analysis showed that tandem duplication event has occurred (Elovl3/6a and b , Elovl9a and b , and Elovl9c and d) in the ancestor. Phylogenetic analysis have clearly revealed that Brachionus spp. has only 2/5 and 3/6 subfamilies, and two novel Elovl classes have been revealed, namely Elovl9 and 10. Transcriptional data showed that the 10 Elovl genes were differently expressed and their expression could be regulated by feeding the alga T. suecica. From fatty acid (FA) profile data of the alga Tetraslemis suecica -fed B. koreanus , we revealed that the marine rotifer B. koreanus may synthesize very long chain fatty acid (VLCFA; >22 carbons) by themselves, as VLCFA was hardly detected in the alga T. suecica. The study provides a better understanding of FA metabolism of the marine rotifer B. koreanus after feeding the T. suecica. Unlabelled Image • Total 10 Elovl genes have been identified from the genome of B. koreanus. • Tandem duplication event has occurred (Elovl3/6a and b , Elovl9a and b , and Elovl9c and d). • Brachionus spp. has only 2/5 and 3/6 subfamilies with two novel Elovl classes Elovl9 and 10. • 10 Elovl genes were differently expressed and their expression could be regulated by feeding the alga T. suecica. • B. koreanus may synthesize very long chain fatty acid (VLCFA; > 22 carbons) by themselves. [ABSTRACT FROM AUTHOR]

Highlights • Fecundity and lifespan were decreased significantly (P < 0.05) in B[α]P-exposed B. rotundiformis. • Total intracellular ROS level and GST activity were significantly increased (P < 0.05). • Transcriptional regulation of GST s and ABC transporters were significantly upregulated and downregulated (P < 0.05). • B[α]P-exposed B. rotundiformis showed the increased levels of the p-JNK and p-p38. Abstract To examine the adverse effects of the benzo[α]pyrene (B[α]P), the monogonont rotifer Brachionus rotundiformis was exposed to various concentration of B[α]P (0 [control], 1, 10, and 100 μg/L) and measured life cycle parameters (e.g., mortality, fecundity [cumulated number of offspring], and lifespan), reactive oxygen species (ROS), antioxidant enzymatic activity of glutathione S -transferase (GST). In addition, defense-related transcripts (e.g., glutathione S -transferases [GSTs], ATP binding cassette [ABCs] transporters) and Western blot analysis of mitogen-activated protein kinase (MAPK) signaling pathway were investigated in B[α]P-exposed rotifer. In this study, the total intracellular ROS level and GST activity were significantly increased (P < 0.05), while fecundity and lifespan were also significantly (P < 0.05) reduced in a concentration dependent manner in B[α]P-exposed B. rotundiformis. In addition, transcriptional regulation of GST s and ABC transporters were significantly upregulated and downregulated (P < 0.05), respectively, suggesting that B[α]P can induce oxidative stress leading to induction of antioxidant system and detoxification mechanism. In addition to detoxification-related genes, B[α]P-exposed B. rotundiformis showed the increased levels of the p-JNK and p-p38, suggesting that B[α]P can activate MAPK signaling pathway in B. rotundiformis. [ABSTRACT FROM AUTHOR]

• Heterocapsa bohaiensis showed sighificant toxic effects on Brachionus plicatilis by being ingested. • The results of hemolytic activity were consistent with the toxic effect on rotifers. • Increased fluorescence intensity was found in the stomach, indicating the alteration of calcium homeostasis and membrane permeability. The algae Heterocapsa bohaiensis is a newly described species of dinoflagellate associated with Penaeus japonicus and larvae of Eriocheir sinensis in a coastal pond of Liaodong Bay China. The rotifer Brachionus plicatilis is used as live feed for aquaculture organisms including prawns and crabs larvae. To evaluate the potential toxicity of H. bohaiensis , the effects on Brachionus plicatilis and haemolytic activity were investigated in this study. The results showed that H. bohaiensis had significant toxic effect on B. plicatilis , and this effect was dependent on the cell concentration. Significant rotifer growth suppression was observed in the ruptured cells of H. bohaiensis with ultrasonic. Relatively similar rotifer mortalities were induced both in the light and in the dark. Interestingly, haemolysis to erythrocytes was also caused in a cell density-dependent and time-dependent manner, which meant the results of haemolytic activity were consistent with the toxicity. Therefore, haemolytic toxins were considered to be involved in the toxic mechanism of H. bohaiensis against rotifers. Then, the concentrations of calcium were measured in the mastax, stomach and ovary of B. plicatilis. Obviously increased fluorescence intensity was found in the stomach, which indicated the alteration of calcium homeostasis and membrane permeability after ingesting H. bohaiensis. These results implicated haemolytic activity as a causative factor linked to the toxicity of H. bohaiensis against B. plicatilis. The results contributed to research the production and control of H. bohaiensis toxins. [ABSTRACT FROM AUTHOR]

Abstract Cytochrome P450s (CYPs) are a large gene superfamily that are found in all living organisms. CYPs have a key role in detoxification of xenobiotics and endogenous chemicals. Although aquatic invertebrate CYPs and their detoxification mechanisms have been reported, little is known about interspecific comparison of CYPs and their detoxification mechanism in the rotifer Brachionus spp. The aim of this study was to identify the entire CYP s in the rotifer Brachionus rotundiformis (B. rotundiformis) and compare B. rotundiformis -CYPs to the previously reported CYPs in other model Brachionus spp. (B. koreanus , B. plicatilis , and B. calyciflorus). To validate the model, the rotifer, specifically Brachionus rotundiformis was exposed to various concentrations of B[α]P, which is widely used PAH xenobiotic, and analyzed gene expression in response to B[α]P. Here, in silico analysis results showed the total of 26 CYP s from the rotifer B. rotundiformis. Based on the phylogenetic analysis, the 26 B. rotundiformis -CYPs were separated into five different clans: 2, 3, 4, mitochondrial, and 46 clans in comparison to three rotifers species, B. koreanus , B. plicatilis , and B. calyciflorus. To understand the detoxification mechanisms of 26 B. rotundiformis -CYPs, we investigated transcriptional expression of 26 CYP s and found that five CYP s (CYP3045A2 , CYP3045B4 , CYP3045C10 , CYP3049A5 , and CYP3049E8) were significantly increased (P < 0.05) in response to 10 and 100 μg B[α]P. In addition, we identified the aryl hydrocarbon receptor (AhR) and aryl hydrocarbon receptor nuclear translocator (ARNT) and observed slight up-regulation of B. rotundiformis - AhR and - ARNT , indicating that these CYPs are likely associated with detoxification mechanism and could be used as potential molecular biomarkers of B[α]P in B. rotundiformis. Overall, this study will be helpful for expanding our knowledge of invertebrate CYPs on detoxification mechanisms associated with AhR signaling pathway in rotifers. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Highlights • Body size-dependent tolerance to Cd toxicity was shown in three Brachionus spp. • Metabolic rate and Cd bioaccumulation support the body size-dependent tolerance in Brachionus spp. • MAPK signaling pathways and antioxidant enzymatic activities showed different activation patterns depending on the species. Abstract Although several studies have reported on different interspecific sensitivities in response to various toxicants, the response mechanisms are still poorly understood. Here, we investigate the interspecific toxicity of cadmium (Cd) and its mechanism using three marine rotifer Brachionus spp. that are distinguishable by body size, which is considered the most significant indicator of phenotypic difference. The body sizes of B. plicatilis , B. koreanus , and B. rotundiformis are significantly different throughout their life cycles (egg, neonate, and adult), with the smaller rotifer exhibiting higher sensitivity to Cd. To investigate the mechanisms that result in body size-dependent tolerance to Cd, metabolic and Cd bioaccumulation rates were investigated. Both rates have shown a significant correlation with body size, indicating that body size and its variables are important factors in determining Cd tolerance in Brachionus spp. In addition, similar patterns that further explain body size-dependent tolerance are shown in the phosphorylation status of mitogen-activated protein kinases, reactive oxygen species level, and antioxidant enzymatic activities. Our study provides valuable insight into size- and species-dependent toxicity mechanisms of species in the same genus. [ABSTRACT FROM AUTHOR]

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

Recently, dinoflagellate blooms have frequently occurred in the coastal waters of Fujian, East China Sea. In June 2022, a fish-killing bloom of Kareniaceae species occurred in this region. In this study, four species of Kareniaceae, namely, Karenia longicanalis , K. papilionacea , Karlodinium veneficum , and Karl. digitatum were identified from this bloom event based on the results of single-cell PCR and clone libraries, and intraspecies genetic diversity was found in the Karl. veneficum population. The results of acute toxicity assays of the bloom water to two zooplankton species (Brachionus plicatilis and Artemia salina) demonstrated this bloom event strongly inhibited their swimming capacities and survival. The results of this study suggested that the bloom events caused by multiple species of Kareniaceae in the Fujian coastal waters had adverse impacts on the local fishery resources and zooplankton community. • A fish-killing bloom of Kareniaceae multiple species outbroke in Fujian coast in June 2022. • The bloom was dominated by Karenia longicanalis , K. papilionacea , Karlodinium veneficum , and Karl. digitatum. • Karl. veneficum population has intraspecies genetic diversity. • The bloom strongly inhibited the survival of Brachionus plicatilis and Artemia salina. [ABSTRACT FROM AUTHOR]

This study assessed the eco-genotoxic impact of diclofenac (DCF) in sentinel species of the freshwater ecosystem. DCF residues are found in freshwater from few ng/L to tens of μg/L due to the inability of conventional wastewater treatment plants to ensure removal efficiency of the drug. An ample body of literature reports on the acute toxicity of DCF in non-target organisms without addressing potential chronic long-term effects on organisms at actual, environmental concentrations. Herein, assessment for acute and chronic toxicity was performed on organisms in vivo exposed to DCF, specifically on the green alga Raphidocelis subcapitata , the rotifer Brachionus calyciflorus and the crustacean Ceriodaphnia dubia. Furthermore, potential DNA damage and expression of antioxidant genes (MnSOD, Cu/ZnSOD and CAT) were evaluated in crustacean neonates. The toxicological risk of DCF was assessed as well as its. The acute toxicity was observed at concentrations far from those of environmental concern. Rotifers and crustaceans were much more chronically sensitive than the algae to DCF, observing besides, the median effect concentrations at tens of μg/L. In crustaceans, DNA damage was noted at units of μg/L, revealing concentrations of environmental concern. The dysregulated activity of SOD and CAT also showed the ability of DCF to provoke oxidative stress. On assessment of environmental risk, the chronic Risk Quotient (RQ) was above the threshold value of 1. Nevertheless, the genotoxic RQ was significantly greater than the chronic RQ, thus, the need of regulatory bodies to acknowledge the genotoxic impact as an environmental risk factor. To our knowledge, this study is the first investigation to perform environmental genotoxic risk assessment of DCF. [Display omitted] • Freshwater producers and consumers were exposed in vivo to diclofenac. • Primary consumers were more sensitive than primary producer to diclofenac. • Chronic Risk Quotient was above the threshold value of 1. • Genotoxicity was found in C. dubia at units of μg/L. • Dysregulation of the expression of antioxidant genes was observed. [ABSTRACT FROM AUTHOR]

Because nanoplastics (NPs) can transport pollutants, the absorption of surrounding pollutants into NPs and their effects are important environmental issues. This study shows a combined effect of high concentrations of NPs and copper (Cu) in the marine rotifer Brachionus plicatilis. Co-exposure decreased the growth rate, reproduction, and lifespan. The highest level of NP ingestion was detected in the co-treated group, but the Cu concentration was higher in the Cu single-exposure group. ERK activation played a key role in the downstream cell signaling pathway activated by the interaction of NPs and Cu. The increased sensitivity of B. plicatilis to Cu could be due to the impairment of MXR function caused by a high concentration of NPs, which supports our in vivo experiment results. Our results show that exposure to NPs could induce the dysfunction of several critical molecular responses, weakening resistance to Cu and thereby increasing its physiological toxicity in B. plicatilis. • The toxicity of NPs was dose-dependent, and adverse in vivo effects were increased with Cu. • In the combined exposure group of NPs and Cu, the ingestion of NPs increased while the Cu concentration decreased. • The interaction of NPs and Cu reduced ROS and increased antioxidant activity, implying destroyed redox homeostasis. • ERK pathway was activated by co-exposure to high-concentration NPs and Cu, with increasing antioxidant enzyme activities. • NPs could induce cell damage and inhibit P-gp and MRP activity, reducing the ability to defend against Cu toxicity. [ABSTRACT FROM AUTHOR]

Highlights • Low concentrations of two pharmaceuticals APAP and OTC elicited oxidative stress through the generation of ROS.. • Low concentrations of two pharmaceuticals APAP and OTC increased glutathione S-transferase activity. • APAP and OTC have no-observed effect in in-vivo population growth. • CYP3045A2 and GSTs1 , GSTs4 , and GSTo1 were responsible in detoxification of APAP and OTC. • These led no significant changes in the population growth and undetermined NOEC in rotifer. Abstract To investigate the adverse effect of two widely used pharmaceuticals, paracetamol (acetaminophen [APAP]) and oxytetracycline (OTC) on the marine rotifer Brachionus rotundiformis (B. rotundiformis), the animals were exposed to various environmentally-relevant concentrations. Up to date, acetaminophen and oxytetracycline have been considered as toxic, if used above threshold concentration, i.e. overdosed. However, this study demonstrated these two pharmaceuticals even at low concentration (i.e. , μg/L scale) elicited oxidative stress through the generation of reactive oxygen species (ROS) along with the increased glutathione S -transferase activity, despite no-observed effect in in-vivo population growth. To validate the adverse effects of the two pharmaceuticals at relatively low concentrations, mRNA expression analysis was performed of the entire set of genes encoding 26 cytochrome P450s (CYPs) of phase I and 19 glutathione S -transferases (GSTs) of phase II of the rotifer B. rotundiformis. The mRNA expression analysis suggested specific genes CYP3045A2 and GSTσ1 , GSTσ4 , and GSTω1 take part in detoxification of APAP and OTC, resulting in no significant changes in the population growth and undetermined no observed effect concentration (NOEC) in the marine rotifer B. rotundiformis. [ABSTRACT FROM AUTHOR]

Triadimefon, a broad-spectrum, systemic fungicide used to protect agricultural crops is popular in China. However, sub-lethal effects of triadimefon on aquatic organisms remained poorly understood, and its risks to aquatic organisms were unclear. In the current study, thresholds for chronic toxicity to five aquatic organisms were determined and a PNEC based on reproductive fitness of nine aquatic organisms was derived through use of a species sensitivity distribution (SSD). NOECs, based on reproduction or inhabitation of growth, for Oryzias latipes , Daphnia magna , Brachionus calyciflorus , Heterocypris incongruens and Soirodela polyrhiza were 5, 25, 80, 320 and 500 μg L −1 , respectively, and the final PNEC derived was 3.66 μg L −1 . A screening-level hazard assessment of surface water based on both measured environment concentrations (ND∼5.22 μg L −1 ) in 3 lakes, 2 reservoirs and 1 river and predicted environment concentrations (0.36–65 μg L −1 ) in a simulated river and pond, identified unacceptable hazard to aquatic organisms posed by triadimefon, with maximum hazard quotients (HQs) of 1.43 and 17.8, respectively. Potential deleterious effects and hazards or risks of exposure of aquatic organisms from current patterns of use of triadimefon in surface water if of concern. Since HQs were relatively small and the benefits large, it is suggested that mitigations be applied to allow use while minimizing potential for adverse effects on aquatic organisms. [ABSTRACT FROM AUTHOR]

Treatment of dredged materials is a critical issue, since management and disposal of these products requires considerable investment of monetary resources, time, and space. The high concentration of pollutants in dredged materials, along with high water content and many fine particles make recycling these materials particularly difficult. In order to solve this problem, solidification/stabilization has been considered as a potentially viable solution for recycling dredged marine sediments. However, there are currently no guidelines that address potential biological and environmental impacts. To evaluate the stability of treated materials and their biological impacts, dredged marine sediments, which were polluted with heavy metals, were treated by solidification/stabilization using two different solidifying agents. To assess potential impacts, toxicity characteristic leaching procedures (TCLP, USEPA) and a bioassay (with the rotifer, Brachionus sp.) were performed with treated materials. In a TCLP test, we found that treatment with a solidification agent decreased the leaching concentration of heavy metals from sediment compared to the control. The rotifer bioassay showed no change in the survival rate during 24 h of exposure to both agents. However, survival differed between the two agents after 48 h of exposure. Screening physiological status using gene expression, showed that oxidative stress genes were significantly altered. These results suggest that more studies are needed to provide guidelines for deciding the usability of treated materials created by the solidification or stabilization of dredged materials. [ABSTRACT FROM AUTHOR]

Autophagy originated from the common ancestor of all life forms, and its function is highly conserved from yeast to humans. Autophagy plays a key role in various fundamental biological processes including defense, and has developed through serial interactions of multiple gene sets referred to as autophagy-related ( Atg ) genes. Despite their significance in metazoan life and evolution, few studies have been conducted to identify these genes in aquatic invertebrates. In this study, we identified whole Atg genes in four Brachionus rotifer spp., namely B. calyciflorus , B. koreanus , B. plicatilis , and B. rotundiformis , through searches of their entire genomes; and we annotated them according to the yeast nomenclature. Twenty-four genes orthologous to yeast genes were present in all of the Brachionus spp. while three additional gene duplicates were identified in the genome of B. koreanus , indicating that these genes had diversified during the speciation. Also, their transcriptional responses to cadmium exposure indicated regulation by cadmium-induced oxidative-stress–related signaling pathways. This study provides valuable information on 99 conserved Atg genes involved in autophagosome formation in Brachionus spp., with transcriptional modulation in response to cadmium, in the context of the role of autophagy in the damage response. [ABSTRACT FROM AUTHOR]

The development of strategies to improve the quality and to optimize the costs of rotifer production for fish larval feeding, particularly those related to microalgal supply, are highly desirable. In the present work, three different rations (80,000, 130,000 or 200,000 cells rotifer −1 ) of Nannochloropsis gaditana were assessed as enrichment diets for the marine rotifer Brachionus sp. The microalga was cultured in semi-continuous regime with two different daily renewal rates, 10% and 40%, which provided nutrient-depleted or nutrient-sufficient conditions respectively and resulted in strong differences in biochemical composition. Protein and arachidonic acid (ARA) content were twice higher and eicosapentaenoic acid (EPA) was three times higher in N. gaditana from nutrient-sufficient cultures. After 24-h enrichment, rotifers fed N. gaditana cultured in nutrient-sufficient conditions showed higher dry weight, as well as higher contents of protein, lipids and carbohydrates. Total polyunsaturated fatty acids (PUFAs) and ARA contents increased >50%, whereas EPA content doubled in rotifers fed N. gaditana from nutrient-sufficient conditions. As for feed ration, the increase from 80,000 to 130,000 cells individual −1 enhanced the accumulation of protein, lipids, carbohydrates, total PUFAs, ARA and EPA, but a further increase to 200,000 cells individual −1 only enhanced the accumulation of lipid content. Our results show that the nutritional quality of microalgae, rather than concentration, is the most important factor influencing biomass productivity and biochemical composition of rotifer cultures. Since microalgal biomass is in general a limited resource for aquaculture, the improvement of its nutritional value through the optimization of culture conditions should be considered as an adequate and cost-efficient strategy to produce high-quality live feed. [ABSTRACT FROM AUTHOR]

The demand for the rotifers Brachionus spp., which is considered indispensable for larviculture, has increased considerably in the tropical countries. Although freshly cultured microalga is the common rotifer diet, the culture protocols are laborious and costly, thus limit sufficient production of rotifers, and consequently disrupt fish seedling production programs in the microalgae-based hatcheries. This study aimed at developing an alternative low-cost and stable fishwaste diet (FWD), for the rotifers. The diets i.e. FWD 1 (fishwastes only), FWD 2 (FWD 1 + carbon source) and control ( Chlorella vulgaris only) were used to determine the population density, specific growth rate and dietary value of the rotifer Brachionus rotundiformis (SS-type) in 30 l tanks of sea water (22 ppt), in which 20 rotifers ml − 1 were stocked and semi-continuously cultured for 18 days at 28 ± 1 °C without aeration. The coefficient of variation (CV) of the mean specific growth rate was calculated to determine the stability of the cultures. The culture medium and rotifer gut were aseptically screened for bacteria, which were counted and reported as colony-forming units (CFU ml − 1 ). The rotifers and microflora were harvested and analyzed for total lipids. FWD 2 produced significantly higher rotifer density than FWD 1 and control diet ( p < 0.05), but no significant difference was detected between FWD 1 and control cultures ( p > 0.05). Up to 1188 ± 70 rotifers ml − 1 were obtained on day 13 day with FWD 2 . There was no significant effect of FWD on the CV of the cultures, which were 0.11 ± 0.05, 0.07 ± 0.02 and 0.08 ± 0.04 for FWD 1 , FWD 2 and control cultures, respectively ( p > 0.05). There was significantly higher DO in the control- than in the FWD-tanks, and higher NH 3 -N in the FWD- than in the control-tanks ( p < 0.05). There was no significant effect of FWD on the pH in the diets ( p > 0.05). However, the water quality values were within the acceptable limits for aquaculture. The FWD-rotifers ingested significantly higher CFU ml − 1 of bacteria (1.02 ± 0.12 × 10 7 ) than the control-rotifers (8.25 ± 2.19 × 10 6 CFU ml − 1 ). About 0.35 and 0.39 mg/g of DHA and EPA, respectively was obtained in the FWD 2 -fed rotifers, and both were under detectable limit in the control-rotifers. The FWD may have contained essential nutrients and probiotics, which explains the higher rotifer population density in the FWD cultures than in the control cultures. This study offers an opportunity to reduce or eliminate the need for the expensive on-site microalgal production, and rotifer enrichment emulsions, toward a more cost-effective aquaculture, especially in the tropical countries. [ABSTRACT FROM AUTHOR]

P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) are ATP-binding cassette (ABC) transporters that confer multixenobiotic resistance (MXR) via their efflux activity, which enables a variety of xenobiotics to be expelled from cells. MXR has been proposed as the first line of defense against xenobiotics. In this study, the protective roles of P-gp and MRP in the rotifer Brachionus koreanus were examined in response to four biocides (alachlor, chlorpyrifos, endosulfan, and molinate) using fluorescent substrates and inhibitors specific to P-gp and MRP. Exposure of rotifers to the four biocides resulted in increased P-gp and MRP activity. Moreover, the rotifers became more sensitive to the biocides with a reduced tendency in survival and slower population growth rates, when P-gp or MRP was inhibited. These findings suggest that P-gp and MRP are involved in the defense system in response to biocide exposure. Furthermore, the transcriptional levels of the genes encoding P-gp and MRP were examined to uncover the mechanism by which MXR is regulated. Our results demonstrate a crucial role of the MXR efflux system in the defense response to biocides, thereby providing a better understanding of rotifer defense mechanisms on the molecular level. [ABSTRACT FROM AUTHOR]

Salinity is a critical key abiotic factor affecting biological processes such as lipid metabolism, yet the relationship between salinity and lipid metabolism has not been studied in the rotifer. To understand the effects of salinity on the monogonont rotifer B. koreanus , we examined high saline (25 and 35 psu) conditions compared to the control (15 psu). In vivo life cycle parameters (e.g. cumulative offspring and life span) were observed in response to 25 and 35 psu compared to 15 psu. In addition, to investigate whether high salinity induces oxidative stress, the level of reactive oxygen species (ROS) and glutathione S -transferase activity (GST) were measured in a salinity- (15, 25, and 35 psu; 24 h) and time-dependent manner (3, 6, 12, 24 h; 35 psu). Furthermore composition of fatty acid (FA) and lipid metabolism-related genes (e.g. elongases and desaturases ) were examined in response to different salinity conditions. As a result, retardation in cumulative offspring and significant increase in life span were demonstrated in the 35 psu treatment group compared to the control (15 psu). Furthermore, ROS level and GST activity have both demonstrated a significant increase ( P < 0.05) in the 35 psu treatment. In general, the quantity of FA and mRNA expression of the lipid metabolism-related genes was significantly decreased ( P < 0.05) in response to high saline condition with exceptions for both GST - S4 and S5 demonstrated a significant increase in their mRNA expression. This study demonstrates that high salinity induces oxidative stress, leading to a negative impact on lipid metabolism in the monogonont rotifer, B. koreanus . [ABSTRACT FROM AUTHOR]

Unlike temperate regions, tropical ecosystems are characterized by high temperatures (>18 °C) all year, promoting blooms of cyanobacteria which often produce secondary metabolites toxic to zooplankton. Nabor Carillo and the Recreational Lake are part of the saline, Lake Texcoco, in Central Mexico which is filled nowadays with treated waste water. Both water bodies are dominated by Planktothrix , Anabaenopsis , Spirulina and Microcystis . In this study we present the concentration of microcystins in these waterbodies over an annual cycle. We also evaluated the chronic effects of cyanobacterial crude extracts from both lakes on two clones of the rotifer Brachionus calyciflorus , one from Nabor Carrillo Lake and the other from a canal in the shallow, Lake Xochimilco. The experiments on population growth were performed, beginning with 10 individuals per container for each of the following treatments: control (no crude extract), concentrated crude extract, and diluted crude extract (50:50) with moderately hard water and Chlorella vulgaris in a concentration of 0.5 × 10 6 cells ml −1 . The cyanotoxin levels were measured using an ELISA test and ranged between 0.20 and 2.4 μg L −1 in the lake water. The results showed that the Recreational Lake extracts were more toxic, killing the rotifers in less than five days. The r values ranged from −1.74 to 0.48 in the presence of the crude extracts and 0.16 and 0.24 in the controls. The results have been discussed with emphasis on the importance of conducting regular studies to test ecotoxicological impacts of cyanobacterial blooms in tropical waters. [ABSTRACT FROM AUTHOR]

Nanoplastics have received a great deal of attention as evidence of their potential harmful effects on aquatic biota. In zooplankton, ingestion is known as a major uptake route of nanoplastics due to the low feeding selectivity of filter-feeding organisms. In this study, we propose maternal transfer as an alternative uptake route of nanoplastic in the rotifer Brachionus koreanus. Exposure to nanoplastics in parental rotifers induced maternal transfer in offspring, as revealed by fluorescence in rotifer eggs. We further verified that egg shells are not permeable to nanoplastics, and the observed fluorescence was associated with nanoplastic particles, not leached fluorescent dye, supporting the idea that nanoplastics can be transferred through an intrinsic maternal transfer route. This maternal transfer induced adverse effects on life-cycle parameters, including development and reproduction, in offspring rotifers, and was associated with oxidative stress. The results of this study shed light on the ecological impacts of nanoplastics in marine environments. [Display omitted] • Maternal transfer was verified as an alternative uptake route of nanoplastic. • Maternally transferred nanoplastic induced transgenerational toxicity in offspring. • Oxidative stress was induced in offspring by maternal transfer of nanoplastic. • Parental exposure to nanoplastic can induce transgenerational toxicity. [ABSTRACT FROM AUTHOR]

The ingredients of tire-rubber products include a complex range of chemicals additives, most of which are leached into surrounding water as unmeasured toxicants with unexplored ecotoxicological impacts. The present study summarizes the reported species-specific acute toxicity of N-(1,3-dimethylbutyl)- N ′-phenyl- p -phenylenediamine-quinone (6PPD-Q), the ozonation product of anti-oxidant 6PPD used in tire rubber. Also, chronic toxicity and oxidative response of 6PPD-Q and another tire-rubber derivative, 2′,2′′′-dithiobisbenzanilide (DTBBA), in rotifer Brachionus koreanus were investigated. Although 6PPD-Q has been reported to be highly toxic to several species of salmonids, only moderate chronic toxicity was observed in B. koreanus. In contrast, DTBBA significantly retarded the population growth and fecundity. The varying toxicity of 6PPD-Q and DTBBA was linked to the level of reactive oxygen species in which DTBBA exposure caused a significant concentration-dependent increase. Our results imply unanticipated risks to aquatic species posed by chemical additives in tire-rubber which may be considered emerging contaminants of toxicological concern. • The species sensitive to 6PPD-Q did not have evolutionary relationship. • 6PPD-Q exhibited only moderate toxicity on the marine rotifer B. koreanus. • DTBBA retarded population growth and fecundity of the rotifer B. koreanus. • The toxicity of 6PPD-Q and DTBBA was shown to be mediated by oxidative stress. [ABSTRACT FROM AUTHOR]

• Autophagy was induced in the marine rotifer brachionus plicatilis upon BDE-47 exposure. • ROS mediated autophagy in B. plicatilis exposed to BDE-47. • Induced autophagy relieved oxidative stress in B. plicatilis under BDE-47 exposure. • Autophagy is a newly discovered protective mechanism in B. plicatilis. 2,2′,4,4′-Tetrabromodiphenyl ether (BDE-47) is a persistent organic pollutant that spreads widely in the marine environment. Our previous studies found that it had adverse effects on the marine rotifer Brachionus plicatilis and caused a series of stress responses. The present study was performed to verify the occurrence of autophagy and explore its role in B. plicatilis ' coping with BDE-47 exposure. Rotifers were exposed to 0.05, 0.2, 0.8, and 3.2 mg/L BDE-47 for 24 h, respectively. Detections of the autophagy marker protein LC3 by western blot and autophagosomes by MDC staining demonstrated the occurrence of autophagy. The levels of autophagy were significantly increased in BDE-47-treated groups with a peak in 0.8 mg/L group. A series of indicators responded to BDE-47 exposure, including reactive oxygen species (ROS), GSH/GSSG ratio, superoxide dismutase (SOD) activity, and malonaldehyde (MDA), collectively indicating the occurrence of oxidative stress. The potential interplay between autophagy and oxidative stress in B. plicatilis was explored in the 0.8 mg/L group through a series of additions. The ROS level was significantly decreased by the addition of the ROS generation inhibitor diphenyleneiodonium chloride, to a level even lower than that in the blank control, and concomitantly, autophagosome was almost undetectable, indicating that a certain level of ROS was essential for the occurrence of autophagy. Autophagy was weakened by the addition of the autophagy inhibitor 3-methyladenine coincident with the great elevation of ROS, indicating that activated autophagy contributed to reducing the ROS level. Additional proof of this relation was obtained from the direct opposite effects of the autophagy inhibitor bafilomycin A1 and the autophagy activator rapamycin: the former increased the MDA content significantly, whereas the latter decreased it significantly. The combined results suggested that autophagy alleviated oxidative stress and might be a newly discovered protective mechanism in B. plicatilis coping with BDE-47 exposure. [Display omitted] [ABSTRACT FROM AUTHOR]

Toxicants released during the degradation of cyanobacterial blooms, such as microcystin-LR (MC-LR) and nitrite (NO 2 -N), affect the growth of aquatic organisms. The freshwater rotifer Brachionus calyciflorus was exposed to solutions with different combined concentrations of MC-LR (0, 10, 50, 100, and 200 μg L −1 ) and NO 2 -N (0, 2, 4, 6, and 8 mg L −1 ) to assess the combined effects of MC-LR and NO 2 -N on life cycle parameters and oxidative stress. Single solutions of MC-LR 200 μg L −1 and NO 2 -N 8 mg L −1 were toxic to rotifers. MC-LR combined with NO 2 -N decreased population growth rate ( r ), survival, and reproduction, but increased reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH) contents ( p < 0.01). Superoxide dismutase (SOD) and catalase (CAT) activities and mRNA expression levels of MnSOD , CuZnSOD , and CAT significantly decreased under high concentrations of MC-LR or NO 2 -N ( p < 0.05). ROS levels had negative correlations with antioxidant enzyme activities and expression levels of antioxidant genes ( p < 0.01). MC-LR and NO 2 -N had interactive effects on r , reproduction, ROS levels, MDA content, SOD activity, and expression levels of MnSOD and CAT ( p < 0.05). By contrast, these effects were antagonistic on survival, CAT activity, GSH content, and expression level of CuZnSOD ( p > 0.05). Results showed that cyanobacterial metabolites act synergistically and antagonistically to cause toxicity to B. calyciflorus . ROS-mediated toxicity was considered the mechanism by which MC-LR and NO 2 -N induce damage. [ABSTRACT FROM AUTHOR]