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Rotifers are widely used as a live prey for finfish larvae, although their content in minerals such as selenium and zinc is lower than in fish. In the present study, mixed microalgae (i.e., Isochrysis aff. galbana and Nannochloropsis oculata) were enriched with different amounts of Se and Zn either alone (45, 90, and 135 mg L−1 of Zn, 60, 120, and 180 mg L−1 of Se) or mixed (22.5, 45, and 90 mg Zn L−1 and 30, 60, and 120 mg Se L−1). The content of minerals in the microalgae was analysed after 1 and 3 h enrichment and their effect on the growth and mineral composition of the rotifer. Based on the results, 1 h enrichment time and 90 and 120 mg L−1 of Zn and Se, respectively, resulted in the highest amount of Se and Zn in enriched microalgae. The maximum Zn content was detected in the rotifers fed 90 mg L−1 Zn and 90 mg L−1 Zn +120 mg L−1 of Se, but the maximum Se was observed in rotifers fed with 120 and 180 mg L−1 Se. Thus, Se- and Zn-enriched rotifers can be used as a mineral delivery method to cover marine fish larvae nutritional requirements. info:eu-repo/semantics/acceptedVersion

The modulation of antioxidant responses and onset of oxidative stress is due to several factors, including temperature, diets, and hypoxia followed by re-oxygenation in several aerobic organisms including rotifers. In this context, the aims of this study were (1) to establish a protocol for evaluating in vivo ROS (reactive oxygen species) concentration in rotifer Brachionus plicatilis and (2) to determine the effects on population growth and oxidative stress responses in rotifers fed with different diets: commercial baker’s yeast (Saccharomyces cerevisiae) or concentrated microalgae Nannochloropsis oculata. The rotifers were stocked in five densities (200, 400, 660, 800, and 1000 rotifers mL−1) and exposed to four concentrations of dichlorofluorescein diacetate (H2DCF-DA) (4.4, 8.7, 17.5, and 35 nmol L−1) to optimize a protocol for in vivo ROS determination. The methodology was standardized using 8.7 nmol H2DCF-DA L−1 and it is effective when rotifer density lies within 400 and 1000 rotifers mL−1. In the second experiment, rotifers were fed with 55 × 109 microalgae cells or 0.6 g yeast per million rotifers for 4 days in quadruplicate. Rotifers fed with yeast showed poorer oxidative condition as shown by (a) a higher in vivo ROS concentration; (b) a higher GST (glutathione S-transferase) activity; and (3) a reduced total antioxidant capacity. In conclusion, the methodology to measure in vivo ROS concentration using the H2DCF-DA was efficiently standardized for the first time to rotifers B. plicatilis. Although the yeast-fed rotifers showed higher population growth comparing with this concentration of microalgae, the rotifers fed with N. oculata faced a safer pro-oxidant scenario and presented a higher percentage of egg-carrying females throughout the experiment indicating a better physiological condition.

In the presence of the predatory rotifer Asplanchna, some Brachionus and Keratella species develop inducible morphological, behavioral, and life history defenses that enable prey to survive predation pressure. However, whether clones belonging to the same rotifer species but with different behaviors (attached and free-swimming) exhibit divergent responses in morphology and life history remains largely unknown. In this study, neonates of an attached and a free-swimming clone of B. dorcas were exposed to media conditioned by A. brightwellii neonates at densities of 0 (control), 40, 80, and 160 ind l−1 for 24 h, and their morphological and life-table demographic parameters were measured and calculated. We showed that the Asplanchna kairomone significantly increased the propensity to attach in the attached clone only, with attached individuals effectively protected from Asplanchna predation. In response to increasing Asplanchna kairomone concentration, the attached clone did not show any morphological changes, but it did exhibit a decreased net reproductive rate and intrinsic rate of population increase. The free-swimming clone developed elongated posterolateral spines and a decreased intrinsic rate of population increase, as well as a decrease in the proportion of sexual offspring. Thus, both clones exhibited reproductive costs.

This investigation aimed to analyze the effects of different diets and determine the optimal feed on the growth performance of guppy Poecilia reticulata (Peters, 1859). In the present study, juvenile guppies were procured from commercial fish breeders, Kolathur, Chennai, and fed with four experimental diets, namely Diet I (Control-Pellet feed), Diet II (Formulated feed), Diet III (Dry Tubifex), and Diet IV (Live feed Brachionus plicatilis) to examine the effects on growth and survival rates. In the experiment, 12 glass circular tanks with a volume of 10 L were used, and ten juveniles having an average body length and weight of 0.8 cm and 0.01 g were randomly introduced into each aquarium (80 cm×30 cm×35 cm) in triplicates. During the experimental study, the fish were fed two times a day ad libitum for 90 days. The various growth parameters and proximate composition of the diets were calculated by following standard methods. The findings showed significant differences (p

The species composition of zooplankton in mineralized water bodies located in the Ulug-Khem basin (Republic of Tuva) was studied. These lakes have the status of natural monuments of regional significance. In total we recorded 53 species of microscopic Custaceans and Rotifers from 32 genera, 13 families, and 8 orders. Cladocera comprises 53% of the species. The dependence of the species diversity on the level of mineralization was revealed; 89% of the species were found in brackish water bodies. The zooplankton composition of the hyperhaline lakes Dus-Khol (Svatikovo) and Cheder has remained constant for many dozen years. The zooplankton includes some species known only from Republic of Tuva in Russia, namely, Microcyclops afganicus and Macrotrix tabrizensis. M. asiaticus and Alona irinae, rare for the fauna of Russia, live in the lake Haak-Hol. A decrease in the total numbers of zooplankton is observed in the lakes, namely: in the lake Dus-Khol, it has decreased by 4 times, in the lake Khadyn it has decreased by 10–19 times as compared to the middle of the last century. Despite the lack of intermediate information, we regard this as a consequence of anthropogenic impact. The emergence of an indicator of pollution (Brachionus nilsoni) in the lake Khadin confirms this version. At the same time, the stable finding of species rare for the fauna of Russia indicates the presence of favorable conditions for their development and life, which increases the value of the reservoirs themselves, which are already unique natural objects.

In order to discover the plankton distribution patterns and its relationship with environment gradients and hydrological connectivity in wetlands, samples from Yellow River Delta that span gradients in salinity and hydrological connectivity were analyzed in this study. Plankton community composition, abundance and biomass were determined and correlated with water variables and hydrological connectivity indexes to gain information about the forces that structure the plankton community in this dynamic environment. Phytoplankton with a total of 88 species and zooplankton with a total of 49 species were observed at an average abundance of 4.11 × 107 cells/L and 951.27 ind./L, respectively. Predominant species were Merismopedia minima G.Beck/Merismopedia elegans A. Braun ex Kutzing (Cyanobacteria) and Trichocerca pusilla (Jennings) (Rotifera), accounting for over 10% of the total abundance of phytoplankton and zooplankton, respectively. The dominant species of phytoplankton communities were shifted from freshwater Chlorophyta (e.g., Oocystis sp.) to brackish Cyanobacteria (e.g., Merismopedia minima and Merismopedia elegans) and then to marine cyanobacterium (e.g., Oscillatoria sp. and Pseudoanabaena sp.); That shift in zooplankton community was from freshwater rotifers Trichocerca pusilla and Polyarthra trigla (Ehrenberg) to brackish rotifer Brachionus urceus (Linnaeus) and copepod Thermocyclops spp. and then to marine copepods Sinocalanus spp. and Microsetella spp. toward the river mouth. However, abundance, biomass and community similarity of plankton decreased with increasing water salinity and decreasing hydrological connectivity from upper reaches to river mouth. Salinity gradient could be major force for the shift of plankton community while the increasing hydrological connectivity between freshwater and saline habitats promoted the similarity of plankton distribution patterns within the wetland network.

In larviculture of marine finfish, Tisochrysis lutea cultured cells have a potential to be a sustainable enrichment diet for rotifers due to its de novo synthesis of docosahexaenoic acid (DHA). To improve its effectiveness in rotifer enrichment for later larviculture, we determined which growth phase of T. lutea can enhance DHA in polar lipids (PLs) in Brachionus plicatilis sp. complex rotifers without reducing their vigor. Tisochrysis lutea was harvested at logarithmic growth phase, deceleration growth phase, and stationary phase. The ambient concentrations of phosphorus (P) and nitrogen (N), and fatty acid composition of microalgae were measured. P was limited between logarithmic and deceleration growth phases, followed by N starvation in stationary phase. Total lipid DHA was lowest in logarithmic growth phase, whereas DHA levels increased in deceleration growth phase and maintained at high levels even in stationary phase. PL-DHA also increased during deceleration growth phase, although its abundance dropped during stationary phase. In a rotifer enrichment trial, T. lutea harvested in each phase were fed to B. plicatilis sp. complex rotifers for 12 h. The highest PL-DHA value for cells in deceleration growth phase reflected the concentrations of the rotifers. No significant differences were found in rotifer growth rate and egg ratio. Rotifers fed cells in deceleration growth phase exhibited higher swimming speeds than those fed the other cells, potentially linking to increased larval capture success. Therefore, we recommend the deceleration growth phase as an optimal timing for T. lutea harvest for the effective enrichment of B. plicatilis sp. complex rotifers.

The study tested a new feeding protocol to find out the best program using cheap and available products to enhancement the mass culture and the nutritional value of B. plicatilis. The feeding regime was six artificial treatments formulated from dried yeast (Saccharomyces cervisiae) with sucrose sugar and yeast with molasses in different concentrations. Additionally, a live Cyclotella sp. had been applied as supplementary food to each treatment and as independent treatment (control). B. plicatilis was cultured in small scale to find the best food regime and technique to apply it in the large one. B. plicatilis attained its highest density in the small scale culture (370 Ind.ml1 ) with T1 (30 % yeast, 70 % sugar and Cyclotella sp.) at the 12th day, while the highest population growth rate (PGR) (0.65) was calculated at the 9th day. According to the analysis of variance (ANOVA) and PGR, T1 had been applied in the large scale culture. B. plicatilis samples were composed of 51.6% total protein with 16 amino acids and 33.01% total lipid with 19 identified fatty acids. The study concluded that the treatment (T1) is a suitable diet for enrichment the mass culture and the nutritional value of B. plicatilis.

La creciente demanda de proteína acuícola sugiere buscar alternativas biotecnológicas que mejoren el cultivo de especies de interés comercial. En este estudio se evaluó Bacillus firmus C101 como promotor del crecimiento y potencial probiótico, el cual fue caracterizado y posteriormente administrado (106 UFC mL-1 * día) en poslarvas de camarón blanco (Litopenaeus vannamei) y en rotíferos (Brachionus plicatilis sensu stricto). Se observó que B. firmus C101 tiene tolerancia a sales biliares, fuerte actividad fosfatasa y actividad antimicrobiana frente a patógenos como Vibrio alginolyticus y Aeromonas hydrophila, entre otros. Por otro lado, tras su administración por tres semanas a poslarvas de camarón causó un aumento significativo (p < 0,05) en la tasa específica de crecimiento (TEC = 3,8 ± 0,7 % día-1), el incremento de peso diario (ADG = 1,5 ± 0,1 mg día-1) y en la tasa de conversión alimenticia (TCA = 1,5 ± 0,1 %) en comparación con los controles sin adición de esta bacteria (PBS estéril). Así mismo, la administración de B. firmus C101 (106 UFC mL-1 * día) a rotíferos causó un aumento en la tasa de crecimiento poblacional (TC = 20,2 ± 1,5 % día-1), fecundidad (F = 0,4 ± 0,03 huevos individuos-1) y productividad (R = 16,0 ± 0,7 individuos mL-1 * día), después de 48 h de cultivo. Con base en lo anterior y en comparación con otros estudios, se sugiere a B. firmus C101 como potencial probiótico y promotor del crecimiento en poslarvas de camarón, y como primer reporte del efecto de su administración en rotíferos. No obstante, se precisan estudios sobre los posibles mecanismos de acción, y pruebas a escala piloto y comercial para validar estos resultados y su posible transferencia al sector productivo.

A method of assessing the quality of seawater using the rotifer Brachionus plicatilis Muller is described. Relevance of developing a new bioassay of marine aquatic environment is emphasized, and the choice of the saltwater rotifer B. plicatilis as a test organism is justified considering its biological characteristics, specific structural features, reproduction, and development. A detailed protocol of maintaining rotifer cultures under laboratory conditions is presented, including feeding, breeding, and testing their sensitivity to standard toxicants; the list of necessary materials, reagents, and equipment is provided, and the procedures of biotesting and assessing seawater quality are described. Application of this bioassay is illustrated on several samples of seawater contaminated with heavy metals (copper and zinc) and organic compounds (ethanol and isopropanol). Some specific features of chronic and acute seawater pollution were determined. In particular, continuous contamination with a small concentration of a toxic substance and short-term exposure to high concentrations of pollutants can have different consequences. The results of the bioassay substantiate the need for laboratory experiments simulating different modes of contamination of aquatic environments with toxic pollutants.

Background/Objective: Present study was carried out to identify zooplankton density at Baburpukur pond along with physicochemical properties. In India. Planktonic richness reflects the biodiversity stock. The present study assumes greater importance for biodiversity conservation/ pollution indicator and aquaculture of fish and prawns. Methods/Statistical analysis: Statistical analysis in this experiment was performed by Student\'s t-test. In this test, 0.05 probability, degree of freedom, critical t-value, and calculated t-values were recorded. Here zooplankton number along with physico-chemical parameters was recorded. From these t-values, significant seasonal variations were found in the respective water body. The zooplankton density and physiochemical parameters were recorded during the period of Jun 2018 to February 2020. Diversity of zooplankton has been counted using Sedgwick-Rafter counting chamber. Findings: Four different species of zooplankton were studied such as Daphnia, Cyclops, Cypris and Brachionus. Zooplankton community structure generally changes with temperature, pH of water, free CO2 level, dissolved O2. This study also reveals that zooplanktons have their own peak periods of density which is influenced by the above environmental conditions. Application: At present, this water reservoir is suitable for fish culturing. So several management practices are necessary to conserve this zooplankton density for proper healthy situation of water body. This study is also helpful in understanding the zooplankton diversity of Baburpukur Pond with proper maintaining of aquaculture. Keywords: Zooplankton; biodiversity conservation; pollution indicator; aquaculture

Nannochloropsis is widely used in aquaculture as a feed source. However, large-scale cultivation of Nannochloropsis usually fails due to rotifer contamination. In order to identify an effective technique for reducing rotifer contamination, the effect of Brachionus plicatilis contamination on photosynthetic characteristics in Nannochloropsis oculata and the efficacy of the celangulin (CA):toosendanin (TSN) (1:9) combination for rotifer extermination were investigated using chlorophyll a fluorescence transient. B. plicatilis could directly devour microalgal cells and sharply reduced N. oculata density to very low levels. B. plicatilis also inhibited activities of PSII reaction centers, both acceptor and donor side, thereby damaging the photosynthetic performance of surviving N. oculata cells. However, the CA:TSN (1:9) combination could completely eliminate B. plicatilis, thereby preventing rotifers from devouring microalgae cells and protecting the photosynthetic performance of the surviving algal cells against rotifers damage. Therefore, the binary combination of CA:TSN (1:9), is considered to be a good candidate of botanical pesticide for controlling rotifer contamination.

To evaluate the nutritional quality of the Teleaulax/Plagioselmis/Geminigera (TPG) clade species over the conventional prey species of the Rhodomonas/Rhinomonas/Storeatula (RHO) clade for the enrichment of a rotifer, Brachionus plicatilis, two strains of Teleaulax amphioxeia (TA), CR‐MAL07 and CR‐MAL08‐02, and a Chroomonas sp. strain CR‐MAL10 from Korean coastal waters were mass cultured in 500 L photobioreactors. When harvested from the stationary growth phase, the composition of all three macronutrients and three n‐3 highly unsaturated fatty acids (UFAs) exhibited large deviations among strains and culture media. The composition of essential amino acids and UFAs was higher in CR‐08‐02 by up to 1.1 and 22.2 times, respectively, than that in a commercially available Chlorella sp. strain. For the enrichment of B. plicatilis cultures previously grown with the Chlorella concentrates, high‐density cultures of CR‐08‐02 were offered. After a 3‐hr enrichment, the compositions of eicosapentaenoic acid, n‐3 FA (fatty acids), and n‐6 FA in B. plicatilis increased by 331, 19.5, and 10.48%, respectively, which might reflect the relevant quality compositions in the TA cells. Thus, TA in the TPG clade can be another novel type of prey to enrich rotifer cultures for the marine larviculture.

Abundance and diversity of zooplankton with relation to physicochemical parameters in three ponds at Chittagong University campus was conducted for two years period from January 2017 to December 2018. A total of 72 samples were collected from the three ponds, whereby 33 zooplankton species belonging to five classes were identified. Among the 5 classes, Rotifera was the most dominant and abundant group which contributed 54.17%-72.73% of the total zooplankton population. The overall contribution of Rotifera was 72.73%, 54.17% and 61.90% in ponds 1, 2 and 3 respectively and among Rotifera, Brachionus was the most dominant and abundant genus. Copepoda (8.33- 14.29%) and Cladocera (9.09-25.0%) were moderately abundant and Nematoda (4.17-4.76%) and Protozoa (4.55-8.33%) were the least abundant groups in all the three ponds. Significant direct or inverse relationships of zooplankton were observed with some physicochemical parameters. Zooplankton in Pond 1 showed positive significant relationship with air temperature (r = 0.61, P

Summer and perennial planktonic rotifers from temperate regions can vary greatly in their ability to reproduce at low temperatures. The population growth rate (r day−1) of a Patagonian Keratella tropica was 0.025 at 3.9 °C and gradually increased to 0.083 at 9.3 °C. The ability of this rotifer to survive and reproduce at low winter temperatures suggests that populations in permanent waters with cold winters may have life cycles with little or no commitment to sexually produced diapausing eggs. In contrast, three Brachionus taxa from two localities in southeastern Australia reproduced poorly at low temperatures. At 3.9 °C, all females died before reproducing. At 6.1 °C, only a single amictic female of the Darling Brachionus (B. calyciflorus species complex) from Lake Littra survived to produce a few offspring. At 9.3 °C, amictic females of the Darling Brachionus from both Lake Littra and a billabong produced many more offspring (7–9 offspring female−1) than those of the Lake Littra B. calyciflorus and the billabong B. rubens (1–2 offspring female−1). At 14.9 °C, amictic females of the latter two taxa, and the Darling Brachionus from Lake Littra, produced many (14–17) offspring female−1. Seasonal changes in temperature occurring in natural populations of these Brachionus taxa should have important ecological and evolutionary implications. Low temperatures likely favor the occurrence and reproduction of the Darling taxon. The inability of active individuals to survive and reproduce at low winter temperatures may be a factor favoring selection for sexual reproduction and production of resting eggs in both permanent and temporary water bodies.

The complete mitochondrial genome of Brachionus rubens was sequenced using primers design, clone culture, DNA extraction, LONG-PCR amplification, purification and clone sequencing. We found that it is composed of two circular chromosomes, designated mtDNA I (11,398 bp) and mtDNA II (12,820 bp). The gene content of the B. rubens mitochondrial genome was similar to that of the previously reported mitochondrial genome of B. plicatilis. It contained 22 tRNA genes, 2 rRNA genes and 12 protein-coding genes (PCGs). Four of the 12 PCGs had an incomplete stop codons, TA（cob, atp6, nd3）or T(cox3). The A + T content of B. rubens mitochondrial genome was apparently higher (mtDNA-I 70.2% and mtDNA II 70.4%) than that of the mitochondrial genome of B. plicatilis (mtDNA-I 63.9% and mtDNA-II 62.9%).

The purpose of this study was to look at the diversity and abundance of rotifers in Chakki talab, Bodhan, Telangana, in relation to dissolved oxygen. Rotifer distribution and diversity is influenced by deteriorating quality of water in freshwater ecosystems and eutrophication. From October 2015 to September 2016, rotifers from seven genera were studied, and their density was altered by a little shift in dissolved oxygen levels. The eutrophic state of Chakki talab was shown by the dominance of the genera Brachionus and Keratella.

Zooplankton assemblages in the confined coastal lagoons of La Pletera salt marshes (Baix Ter wetlands, Girona, Spain) are dominated by two species: one calanoid copepod (Eurytemora velox) and the other rotifer (Brachionus gr. plicatilis). They alternate as the dominant species (more than 80% of total zooplankton biomass), with the former being dominant in winter and the latter in summer. Shifts between these taxa are sudden, and intermediate situations usually do not last more than 1 month. Although seasonal shifts between zooplankton dominant species appear to be related with temperature, other factors such as trophic state or oxygen concentration may also play an important role. Shifts between species dominances may be driven by thresholds in these environmental variables. However, according to the alternative stable states theory, under conditions of stable dominance a certain resistance to change may exist, causing that gradual changes might have little effect until a tipping point is reached, at which the reverse change becomes much more difficult. We investigated which are the possible factors causing seasonal zooplankton shifts. We used high-frequency temperature and oxygen data provided by sensors installed in situ to analyse if shifts in zooplankton composition are determined by a threshold in these variables or, on the other hand, some gradual change between stable states occur. Moreover, following the postulates of the alternative stable states theory, we looked at possible hysteresis to analyse if these seasonal zooplankton shifts behave as critical transitions between two different equilibriums. We also examined if top-down or bottom-up trophic interactions affect these zooplankton shifts. Our results show that shifts between dominant zooplankton species in La Pletera salt marshes are asymmetric. The shift to a Eurytemora situation is mainly driven by a decrease in temperature, with a threshold close to 19 °C of daily average temperature, while the shift to Brachionus does not. Usually, the decrease in water temperature is accompanied by a decrease in oxygen oscillation with values always close to 100% oxygen saturation. Moreover, oxygen and temperature values before the shift to calanoids are different from those before the reverse shift to Brachionus, suggesting hysteresis and some resistance to change when a critical transition is approaching. Top-down and bottom-up forces appear to have no significant effect on shifts, since zooplankton biomass was not negatively correlated with fish biomass and was not positively related with chlorophyll, in overall data or within shifts Financial support was provided by the Ministerio de Economia, Industria y Competitividad (refs. CGL2017- 86515-P and CGL2016-76024-R AEI/FEDER/UE), the Generalitat de Catalunya (ref. 2017 SGR 548) and the University of Girona (MPCUdG2016-049) Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

We determined numerical response, functional response, and prey selection by the predator Asplanchna girodi using 4 brachionid rotifer species, varying in size and lorica spines. We hypothesized th...

Modern methodological approaches were applied to analyze the zooplankton community spatial distribution (with the example of the middle river part of the Cheboksary Reservoir). Zooplankton communities were sampled in the middle river part of the Cheboksary Reservoir (from the city of Nizhny Novgorod to Vasilsursk town) in the summer low-water period in 2018. The boundaries between the communities in the Cheboksary Reservoir were gradually changing during the history of the Cheboksary Reservoir from the time of its construction to present. In the middle river part of the Cheboksary Reservoir there are two distinct spatially stable zooplankton communities associated to the Oka and Volga streams. The distinction between these two zooplankton communities was demonstrated by hierarchical cluster analysis. Redundancy analysis has shown that chlorophyll- a and pH were the main factors influencing the specific zooplankton structure. Chlorophyll- a concentration reflects the meso-scale heterogeneity of the horizontal phytoplankton distribution and hence the distribution of the zooplankton’s food sources. The relation of zooplankton to pH level reflects the high sensitivity of the species of the genus Brachionus Pallas, 1766 to high acidity. The influence of pH as an environmental factor was less evident. However, this variable is well known as one of the leading factors determining the structure of zooplankton communities. Its role in zooplankton community assembly of lowland reservoirs deserves further investigation.

Information on the distribution of three genera of rotifers, Anuraeopsis, Brachionus, and Notholca of the family Brachionidae in the Ural region is summarized based on the author’s research and the analysis of published sources. Data on their localities, biology, and quantitative development in water bodies of the Ural region are presented.

Multidisciplinary research was carried out to verify the best approach for a reliable assessment of sediment quality in marine areas affected by strong metal enrichment. The study was carried out on Sulcis-Iglesiente marine coastal areas (Sardinia, Italy), where a long-lasting past mining operation strongly contaminated marine sediments with heavy metals (Cd, Pb and Zn). Surface sediments were analysed for grain size and mineralogical content, total organic carbon, total metal concentrations and sequential extractions. Additionally, ecotoxicological bioassays were performed using Vibrio fischeri (Microtox®) on the solid phase and elutriate, Dunaliella tertiolecta on elutriate and Brachionus plicatilis on elutriate. Analysed sediments were nearly exclusively sand (98.5–100%) with a very low TOC content; their texture and mineralogy indicated a N-S drift affecting the dispersion of mining contributions. The total concentrations of Cd, Pb and Zn, which are positively correlated, exceeded background and Environmental Quality Standards (EQS) values by up to two orders of magnitude, while sequential extractions revealed their high mobility because Cd and Pb were mainly extracted in the first phase (up to 77 and 82%, respectively) and Zn in the second phase (up to 99%). In spite of this, bioassays recorded the absence of toxicity in all the samples. These apparently conflicting results suggest that ecotoxicological tests cannot replace chemical analyses in sediment quality assessments because they could fail to provide reliable information on the bioavailability of contaminants over time.

This study deals with the determination of availability of sugar beet molasses as a nutritional enrichment factor for rotifer cultures. A series of experiments under varying conditions such as ratio of sugar beet molasses in the nutrient complex were carried out in order to determine the effectiveness of sugar beet molasses as a carbohydrate and mineral source for the purpose of aquacultural operations. The culture water of Brachionus plicatilis with the salinity of 38% was treated through mechanical filtration and UV sterilization. 1 T cylindro-conical tanks are utilized for rotifer culture. Parameters of culture water were stabilized at values as following; Oxygen concentration:5 to 10 ppm, temperature: 27 0 C and pH:6.8 to 7.4. Rotifers were counted by using Sedgewick Rafter Cell on a daily basis in order to determine increase of number of individuals. The study was conducted as 3 different trial groups, each consisting three separate tanks, so triplicate determinations were obtained. For the Group I, 10% molasses by weight of Culture Selco Plus (200 gr Selco Plus+20 gr molasses per tank) was added 6 times a day with 4 hours’ intervals. For the Group II, 20% molasses by weight of Culture Selco Plus (200gr Selco Plus+40gr molasses per tank) was added and lastly for the control group, Group III, no molasses has been added and 200 gr Culture Selco Plus was only added per tank. The addition of molasses to nutritive complex has a decreasing effect on the number of rotifer and increasing effect on the number of ciliate. From the study, it is clear that sugar beet molasses should not be used as an additional nutritional factor for rotifer cultures due to its decreasing effect on the number rotifers and stimulating effect on the ciliate booming. Addition of 10% and 20% molasses resulted in 31.4% and 23.3% decrease in number of rotifers at the time of T3, respectively. On the other hand, it was observed that addition of molasses in the nutritive complex has not affected on the percentage of rotifers bearing eggs.

Ecological stoichiometry predicts that the extent to which herbivores are limited by nutrients depends on their metabolic demands. Nonconsumptive effects (NCEs) caused by predators have been demonstrated to trigger not only inducible defenses but also physiological stresses in prey. Stressed prey always exhibit increased metabolism and decreased nutrient deposition (e.g., nitrogen and phosphorus) as physiological stress responses to their predators. Consequently, prey exposed to predation risk should reduce demands for nutrients intake and become adaptive to nutrient limitations. In this study, results obtained from classic Brachionus–Asplanchna model revealed that Brachionus calyciflorus fed with full nutrient algal food showed energetic costs, e.g., reduced investment in asexual (lifetime fecundity) and sexual (mixis ratio) reproductions, in response to predation risk. However, reduction in sexual and asexual reproductions diminished when herbivorous Brachionus were supplied with nitrogen- or phosphorus-limited algal food. Moreover, long posterolateral spines and high posterolateral spine-body length ratio developed in either nitrogen- or phosphorus-deficient conditions containing Asplanchna kairomones, indicating an additive effect of nutrient limitation and predation risk on posterolateral spine development in Brachionus. The findings of this study highlighted predator-facilitated adaptation of prey to nutrient limitations of primary producers, which may have implications in understanding roles of NCEs in regulating trophic interactions.

Exposure of prey to predation risk usually leads to increased metabolism and decreased nutrient deposition as physiological stress responses (PSRs) of prey to their predators. Many studies using freshwater animals as models failed to find evidences as predicted from PSRs. One possible reason is that energetic costs during development of inducible defenses may lower the quantity of resources, which can be allocated to production of costly PSRs. Results obtained from the classic Brachionus-Asplanchna model indicated that inducible defenses did not alleviate PSRs in B. calyciflorus, which were manifested as increased respiration and enhanced body molar ratios of carbon (C) to nitrogen (N) and C to phosphorus (P). Moreover, activities of antioxidant systems also increased in defended B. calyciflorus. There were no alterations in somatic growth and swimming activity in B. calyciflorus when they were exposed to Asplanchna kairomones; however, we observed predator-induced –reduction of food intake in Brachionus. Our results suggest that enhanced metabolisms of defended prey in support of fight-or-flight responses are likely to be the physiological adaptation of prey to diminish hydrodynamic costs accompanied with morphological alterations (e.g., decreased swimming speed) and maintain their fitness under predation risk.

The effects of the cell separation method and the biomass processing of Nannochloropsis oculata were evaluated with respect to the cultivation performance of rotifers (Brachionus sp.). The algal culture was harvested by centrifugation or flocculation, and the biomass separation efficiency and the concentration factor were determined. The biomass was processed by chilling, freezing, heat-drying, or freeze-drying; and the cell integrity, resuspension percentage, and sedimentation profile of the diets were evaluated. The zootechnical performance (maximum rotifer density, growth rate, maximum egg production, fecundity, and feed ingestion rate) of rotifer cultures that fed the concentrated diets was compared with feeding the fresh culture of N. oculata (control treatment). Centrifugation resulted in 97% separation efficiency and a concentration factor of 578 and flocculation followed by centrifugation showed an efficiency of ~ 100% and concentration factor of 444. The harvesting technique did not have a significant influence on the characteristics of the diets and also on the zootechnical performance of the rotifers. The characteristics of the chilled concentrates (cell integrity, resuspension percentage, and sedimentation profiles) were similar to the control treatment, and the rotifers fed on those diets had the highest growth performances. Rotifers fed on frozen diets presented the worst performances. The heat-dried diets presented the lowest cell viability percentages, lowest resuspension percentages, and higher sedimentation rates. The feed ingestion rates of these diets were the lowest, resulting on inferior growth performance of the rotifers. In summary, both harvesting methods could be used, and chilling is the most recommended method for processing N. oculata biomass.

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.

This study aimed to optimize the use of euryhaline rotifer Brachionus plicatilis for rearing larval pikeperch Sander lucioperca L. We assessed motility of rotifers under salinities of 0‰, 2‰, 4‰, 8‰, and 16‰ over a 6-h period. Rotifers stocked into freshwater were completely immotile within 2 h. The motility of rotifers after 6 h was 10 ± 2.27% at 2‰, 35 ± 5.58% at 4‰, 79 ± 30.35% at 8‰, and 92 ± 1.98% at 16‰. A second trial quantified the effect of the target salinity levels on pikeperch gut fullness over the course of 11 h. The gut fullness of larvae fed with rotifers was significantly lower at 8‰ salinity than in other tested groups. Salinity of 16‰ resulted in 100% mortality. Survival and growth of pikeperch larvae from 4 to 11 days post-hatching (DPH) was analyzed at low (2‰ and 4‰) and medium (8‰) salinity. Differences in larval performance under tested salinities were found in survival (S), total length, SGR, eye diameter, myotome height, and gut fullness. The highest mean survival (S) and specific growth rate (SGR) were obtained at 2‰ (S = 64%; SGR = 10 ± 5.4% day−1) and 4‰ (S = 65%; SGR = 8.23 ± 3.4% day−1) salinity and significantly differed from 8‰ (S = 36%; SGR = 5 ± 2.3% day−1) and control (S = 34%; SGR = 7 ± 3% day−1) at 11 DPH. At the conclusion of the trial (11 DPH), larvae of all exposures and control presented normal histology with no signs of pathology. Morphometric analyses revealed significant differences in brush border and fold height of anterior intestine among treatment groups. Larvae at 2‰ salinity showed significantly higher intestinal fold height (31.2 ± 5.40 μm) compared to those at 4‰ (26.5 ± 6.11 μm), 8‰ (26.3 ± 4.52 μm), and control (22.8 ± 5.13 μm) (p ˂ 0.05). Larvae at 4‰ salinity had significantly higher brush border height (2.50 ± 0.73 μm) compared to those at 2‰ (2.27 ± 0.63 μm) and 8‰ (1.87 ± 0.44 μm) salinity and control (1.66 ± 0.56 μm) (p < 0.05). The results showed 2‰ and 4‰ salinity supported higher numbers of motile B. plicatilis and higher larval survival and growth rate to 11 DPH.

Most coastal waters are at risk from microplastics, which vary in concentration and size. Rotifers, as important primary consumers linking primary producers and higher trophic consumers, usually coexist with the harmful alga Phaeocystis and microplastics in coastal waters; this coexistence may interfere with rotifer life-history traits and ingestion of Phaeocystis. To evaluate the effects of microplastics on rotifers, we designed a series of experiments concerning rotifer Brachionus plicatilis life-history traits and rotifer-Phaeocystis (predator-prey) population dynamics under different concentrations and sizes of microplastics. The results showed that small-sized microplastics (0.07 μm) at high levels (≥5 μg mL-1) decreased rotifer survival and reproduction, prolonged the time to maturation, and reduced the body size at maturation, whereas large-sized microplastics (0.7 and 7 μm) had no effect on rotifer life-history traits. For rotifer-Phaeocystis population levels, small-sized microplastics (0.07 μm) significantly delayed the elimination of Phaeocystis by rotifers; this is the first study to test the effects of microplastics on predator-prey dynamics. The results of rotifer-Phaeocystis population dynamics are consistent with the changes in the life-history traits of rotifers and further confirm the negative effects of small-sized microplastics (0.07 μm) on rotifers. These findings help to reveal the effect of pollutants on predator-prey population dynamics.

The paper presents the possibility of applying combined chemical oxidation processes using potassium ferrate(VI) (K2FeO4) and Fe(III)/H2O2 for the treatment of real wastewater from the textile industry characterised by an increased content of organic substances (COD = 1920 mg O2/L). The use of both processes under optimal conditions included the use of the RSM method (Response Surface Methodology) in order to make it possible to decrease the COD of the wastewater by 75.4% (final COD = 472 mg O2/L). The toxicity of wastewater treated under the most favourable conditions, determined using two test organisms (Aliivibrio fischeri and Brachionus plicatilis), decreased by 33 and 45%, respectively. In some cases the method described can be used on a larger scale.

Monogonont rotifers constitute, depending on the moment of the year, most of the zooplankton in many freshwater ecosystems. Sexual reproduction is essential in the development cycle of these organisms as it enables them to constitute stocks of cysts which can withstand adverse environmental conditions and hatch when favorable conditions return. However, endocrine disrupting compounds (EDCs) can interfere with the reproduction of organisms. The present work aimed to investigate the effects of cyproterone acetate (CPA, anti-androgen and progestogen synthetic steroid) at 0.5 mg L−1, on the sexual reproduction of Brachionus calyciflorus in a cross-mating experiment. Results show no impact on mixis whereas the fertilization rate and resting egg production were higher in females exposed to CPA (from embryogenesis to adult stage), regardless of the treatment applied to the males with which they were mating (i.e. males hatched from CPA-treated females or from control females). Moreover, neonate females which mothers has been exposed to 0.5 mg L−1 CPA had more oocytes in their germarium than control neonates. Our results suggest that the effects of CPA observed are not related to toxicity but rather are consistent with an endocrine disruption-related impact, probably through disturbance of the mate recognition protein (MRP) production and through interference with a steroid receptor. Moreover, the absence of effect on mixis rate indicates that mixis induction on the one hand and mating process and resting production on the other hand are not controlled by the same hormonal pathways.

Glutathione S-transferases (GSTs) play an important role in phase II of detoxification to protect cells in response to oxidative stress generated by exogenous toxicants. Despite their important role in defense, studies on invertebrate GSTs have mainly focused on identification and characterization. Here, we isolated omega and sigma classes of GSTs from the freshwater rotifer Brachionus calyciflorus and the marine rotifer Brachionus koreanus and explored their antioxidant function in response to metal-induced oxidative stress. The recombinant Bc- and Bk-GSTs were successfully transformed and expressed in Escherichia coli. Their antioxidant potential was characterized by measuring kinetic properties and enzymatic activity in response to pH, temperature, and chemical inhibitor. In addition, a disk diffusion assay, reactive oxygen species assay, and morphological analysis revealed that GST transformed into E. coli significantly protected cells from oxidative stress induced by H2O2 and metals (Hg, Cd, Cu, and Zn). Stronger antioxidant activity was exhibited by GST-S compared to GST-O in both rotifers, suggesting that GST-S plays a prominent function as an antioxidant defense mechanism in Brachionus spp. Overall, our study clearly shows the antioxidant role of Bk- and Bc-GSTs in E. coli and provides a greater understanding of GST class-specific and interspecific detoxification in rotifer Brachionus spp.

A strain of Pseliodinium pirum was isolated from Jiaozhou Bay, China, identified based on a recently emended classification, and further characterized for its morphology using light, scanning electron, and transmission electron microscopy, and phylogeny based on SSU and partial LSU rDNA sequences. The pigment composition, life history, and potential effects on aquatic animals were also examined. We observed the typical characteristics of Ceratoperidiniaceae, in which its apical structure complex (ASC) formed a circular loop, and the ASC of our isolate comprised four to five rows of vesicles, and connected with sulcal intrusion. Epifluorescence and transmission electron microscopy revealed a bean‐shaped, centrally located nucleus, with at least 76 chromosomes. Numerous rod‐shaped chloroplasts were in connection to the irregularly shaped pyrenoids. Pigment analysis showed that peridinin was the most abundant among all carotenoids and other pigments. Phylogenetic analyses using maximum likelihood and Bayesian inference indicated that our isolate is conspecific with the entity Cochlodinium cf. helix (accession No. KF245459), but different from Ceratoperidinium, Kirithra, and other unidentified species of the family Ceratoperidiniaceae. Pseliodinium pirum could produce sexual, thin‐walled cyst, with subspherical and spherical shape and smooth surface (without spines or rough projections). The cyst could germinate within 3 days. Bioassays did not show adverse effects of P. pirum on the finfish Oryzias melastigma and the rotifer Brachionus plicatilis, indicating it may not be a harmful species.

The rotifer Brachionus plicatilis is the first live feed in larviculture of marine fish species. Rotifer diets differ in their biochemical composition, physical properties, and production technology while feeding protocols largely vary among facilities. The objective of the present study was to determine the effects of two different forms of Nannochloropsis oculata and commonly used commercial diets on growth performance and biochemical composition of rotifers produced under commercial conditions. Rotifers were fed one of five different types of feed: Algome® (dried Schizochytrium sp.), Protein Plus® (PP), Inactive Baker’s Yeast® (INBY), spray-dried Nannochloropsis oculata (SDN), or freshly cultured Nannochloropsis oculata (FN). Rotifers fed SDN diet resulted in significantly higher rotifer biomass during 16 days of semi-continuous culture, with an increasing biomass trend that lasted 11 days, high egg production, and egg-carrying female numbers, whereas rotifers fed PP showed highest ∑n-3, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid contents. Amino acid profiles of rotifers were enhanced by utilization of both INBY and SDN diets. Overall, the results indicated that SDN is optimal for long-term biomass production of rotifers. However, their nutritional profile needs to be enriched by feeding PP (EFA source) and INBY (EAA source) once desired biomass production is obtained.

Penelitian ini bertujuan untuk menentukan parameter lingkungan perairan berdasarkan faktor fisik-kimia, keanekaragaman zooplankton, dan hubungan kelimpahan zooplankton pada hasil tangkapan togok. Pengambilan sampel dilakukan 3 kali dengan interval 1 minggu. Berdasarkan nilai DO perhatikan bahwa stasiun 1 dikategorikan sebagai polusi sedang, sedangkan stasiun 2 dan 3 masih dalam kategori polusi rendah. Selama penelitian ada 8 jenis zooplankton yang terdiri dari Brachionusdimidiatus, Brachionus quadratus, Calanus gracilis, Calanus minor, Euterpina acutifron, Oikopleura laboradoriensis, Oithona attenuate, dan Nauplius. Nilai indeks rata-rata zooplankton sebesar 1,12-1,44 menunjukkan bahwa keragaman sedang dengan distribusi individu sedang dan tingkat polusi yang terkontaminasi adalah sedang. Nilai indeks dominansi zooplankton menunjukkan bahwa tidak ada tipe dominan dengan nilai 0,29-0,34. Hasil korelasi Pearson menunjukkan tidak ada hubungan antara kelimpahan zooplankton dari tangkapan togok, dengan nilai 0,882.

A feeding study was conducted to determine the effects of defatted Haematococcus pluvialis meal (DHPM) on the growth performance of rotifers (Brachionus plicatilis). To assess the efficiency of DHPM as a new additive for rotifer enrichment, the effects of DHPM supplementation on carotenoid and astaxanthin concentrations of the rotifers were investigated. The results showed that the addition of DHPM (125 mg l−1) increased the total number of rotifers (TR), the number of egg-bearing rotifers (EBR), and the number of rotifer eggs (RE). The large proportion of total egg-bearing rotifers indicated that DHPM was good for rotifer growth and reproduction. After feeding on DHPM, rotifers had significant increases (P

Although many efforts have been made to understand the toxic effects of metals in aquatic invertebrates, there are limited data regarding metal toxicity in natural ecosystems, as most previous studies were conducted under controlled laboratory conditions. To address this data gap, we analyzed toxic effects and molecular responses in the marine rotifer Brachionus koreanus and the marine copepod Tigriopus japonicus following in vivo exposure to a seawater sample collected from a polluted region in South Korea. Inductively coupled plasma-mass spectrometry (ICP-MS) analysis of the field seawater sample found a variety of metals. Exposure to several dilutions of the field seawater sample impacted several endpoints in both species, including mortality and reproduction. Interestingly, the rotifer and copepod test species exhibited different patterns of effects on reactive oxygen species (ROS) and antioxidant enzymatic activities, suggesting that different regulatory mechanisms may be activated in the two species in response to exposure to toxic chemicals. Our study helps to better understand the defense mechanisms activated in aquatic invertebrates in response to metal-induced oxidative stress induced by contaminated seawater.

To investigate the effects of five different foods on fatty acid metabolism in the monogonont marine rotifer Brachionus koreanus, we measured life cycle parameters, analyzed the area of Nile red staining, fatty acid composition, and mRNA expression of fatty acid desaturase (Fads) and elongation of very long chain fatty acid (Elovl) genes. Among the five different foods (Tetraselmis suecica, Chlorella sp., Isochrysis galbana, Chaetoceros sp., and Nannochloropsis oculata), life span of I. galbana-fed group was significantly increased compared to the other groups. However, the reproduction parameters (cumulative offspring and daily reproduction) were the highest in T. suecica-fed group, and the lowest in Chlorella sp.-fed group. The area of Nile red staining analysis showed similar trends, in respect to the content of total fatty acid. The single fatty acid analysis result clearly indicated that not only the most of the content of fatty acid was highly dependent on the food types, especially in omega-6 fatty acids group, but also, B. koreanus could newly synthesize some specific fatty acids by themselves (e.g. omega-3 and -9 families). Lastly, the mRNA expression of Elovl and Fads genes were modulated by food types indicating the lipid metabolism could be controlled by food in B. koreanus and probably very small amount of 18:3n-3 fatty acids was utilized and synthesized omega-3 fatty acids through the increase in Elovl and Fads gene expression in Chaetoceros sp. and N. oculata-fed groups. In conclusion, this study revealed that although B. koreanus could modulate fatty acid metabolism by itself, some nutrient values (e.g. omega-6 fatty acids) should be considered, therefore, it is important to understand the essential nutrient through both the molecular and quantitative analysis.

Danau Ebony merupakan danau hias buatan yang di sekitarnya terdapat aktivitas domestik yang menghasilkan limbah yang dapat mempengaruhi kualitas perairan dan biota yang ada didalamnya, salah satunya zooplankton. Danau Ebony dijadikan objek studi untuk melihat keterkaitan antara komunitas zooplankton dengan kualitas air. Penelitian dilakukan pada bulan April-Agustus 2014 pada 5 stasiun pengambilan contoh dengan interval satu bulan. Berdasarkan hasil, komunitas zooplankton di perairan Danau Ebony terdiri atas kelompok Rotifera (7 genera), Crustacea (3 genera), dan Protozoa (2 genera). Kelimpahan tertinggi adalah genus Brachionus dari kelompok Rotifera. Kelompok Rotifera berkorelasi negatif kuat dengan TSS, kekeruhan, ammonia dan berkorelasi positif kuat dengan pH. Hal ini menandakan tingginya TSS, kekeruhan, ammonia diikuti oleh rendahnya kelimpahan Rotifera, sedangkan tingginya pH diikuti oleh tingginya kelimpahan Rotifera. Kelompok Protozoa berkorelasi positif kuat dengan TSS dan berkorelasi negatif kuat dengan suhu.

The complete mitochondrial genome of Brachionus rubens was sequenced using primers design, clone culture, DNA extraction, LONG-PCR amplification, purification and clone sequencing. We found that it is composed of two circular chromosomes, designated mtDNA I (11,398 bp) and mtDNA II (12,820 bp). The gene content of the B. rubens mitochondrial genome was similar to that of the previously reported mitochondrial genome of B. plicatilis. It contained 22 tRNA genes, 2 rRNA genes and 12 protein-coding genes (PCGs). Four of the 12 PCGs had an incomplete stop codons, TA（cob, atp6, nd3）or T(cox3). The A + T content of B. rubens mitochondrial genome was apparently higher (mtDNA-I 70.2% and mtDNA II 70.4%) than that of the mitochondrial genome of B. plicatilis (mtDNA-I 63.9% and mtDNA-II 62.9%).

Much of the recent literature concerning the threat posed by anthropogenic microscopic pollution has focussed on marine organisms although freshwater environments face the same degree of pollution and therefore risk. Although several studies have documented the ingestion of nanoparticles (NPs) in species of the pelagic freshwater rotifer genus Brachionus, unambiguous evidence for its cellular uptake in this group remains lacking. We therefore used transmission electron microscopy (TEM) of ultrathin sections through the digestive tract of individuals of Brachionus calyciflorus exposed in vitro to citrate stabilized gold nanoparticles (AuCit NPs) in their culture medium to provide the first concrete evidence for the cellular uptake of NPs in rotifers, a group of organisms that comprise an important part of the zooplankton community. Using this method, AuCit NPs with average diameters of 8.5 ± 1.4 nm and 12.5 ± 1.5 nm could be localized clearly within large vacuoles within the stomach cells. Moreover, the occasional presence of pits containing AuCit NPs in the outer membranes of these cells hints that the particles are taken up by some form of endocytosis. In all cases, the ingestion of AuCit NPs showed lethal effects after only one day with virtually no individuals surviving more than two days of exposure. Combined with the TEM evidence above, we hypothesize that death might derive from some form of lysosomal overload. In total, our results document the potential threat that microscopic pollution also poses for freshwater organisms. Through this, we hope that additional emphasis in this context will be directed toward freshwater environments and the potential for such pollution both to enter as well as to move up the food chain via trophic transfer events.

Brachionus spp. rotifers have been proposed as model organisms for ecotoxicological studies. We analyzed the whole-genome sequence of B. paranguensis through NextDenovo, resulting in a total length of 106.2 Mb and 71 contigs. The N50 and the GC content were 4.13 Mb and 28%, respectively. A total of 18,501 genes were predicted within the genome of B. paranguensis. Prominent detoxification-related gene families of phase I and II detoxifications have been investigated. In parallel with other Brachionus rotifers, high gene expansion was observed in CYP clan 3 and GST sigma class in B. paranguensis. Moreover, species-specific expansion of sulfotransferase (SULTs) and gain of UDP-glucuronosyltransferases (UGTs) through horizontal gene transfer has been specifically found within B. plicatilis complex. This whole-genome analysis of B. paranguensis provides a basis for molecular ecotoxicological studies and provides useful information for comparative studies of the evolution of detoxification mechanisms in Brachionus spp.

Sorption of organic pollutants on microplastics can be an alternative uptake route for organic pollutants in aquatic organisms. To assess the combined effects of microplastics and organic pollutants, we employed phenotypic and transcriptomic analyses to the responses of the marine rotifer Brachionus koreanus to environmentally relevant concentrations of nano-sized microplastic (0.05 µm), water-accommodated fractions of crude oil, and binary mixtures thereof. Our multigenerational in vivo experiments revealed more than additive effects on population growth of B. koreanus in response to combined exposure, while a single exposure to nano-sized microplastic did not induce observable adverse effects. Synergistic transcriptome deregulation was consistently associated with dramatically higher numbers of differentially expressed genes, and increased gene expression was associated with combined exposure. The majority of synergistic transcriptional alteration was related to metabolism and transcription, with impaired reproduction resulting from energetic reallocation toward adaptation. As further supported by chemistry analysis for polycyclic aromatic hydrocarbons sorption on microplastic, our findings imply that nano-sized microplastics can synergistically mediate the effects of organic pollutants in aquatic organisms.