Phlorizin alleviates deltamethrin-induced oxidative stress in brine shrimp Artemia

Deltamethrin(DEL),a commonly used pyrethroid pesticide,results in higher reactive oxygen species(ROS)levels in aquatic animals,which consequently unbalance the redox state.Phlorizin(PHL)is a flavonoid and a natural product promising to prevent or reduce pesticide-induced oxidative stress.Artemia is a micro-crustacean widely used in marine hatcheries and an experimental aquatic organism for environmental toxicology research.This research aimed to evaluate the toxicity of DEL on Artemia and the antioxidative effect of PHL against the toxicity.Results show that 0.08-mg/mL PHL exerted its antioxidative effects on hatching percentage of the cysts in 24-h incubation and on body length and survival rate of Artemia in 12-d culture.After 12-d culture,12-,24-,and 36-h DEL exposure showed significant drops in SOD,CAT,and GSH-Px enzyme activities,and significant increases in ROS and malondialdehyde(MDA)levels in Artemia(P<0.05).On the contrary,0.08-mg/mL PHL application improved the enzyme activities and decreased the ROS and MDA levels(P<0.05).Moreover,0.08-mg/mL PHL significantly increased mRNA expression levels of Cu/Zn SOD,CAT,GST,HO-1,NQO1,and Nrf2,and decreased mRNA expression level of Keap1 in the DEL-exposed Artemia(P<0.05).Therefore,DEL is toxic to Artemia,while PHL alleviates DEL-induced oxidative damage by possibly regulating the Nrf2signaling pathway.This study provided a theoretical basis for PHL to reduce pesticide-induced toxicity in aquatic animals.

Halomonas-PHB protects gnotobiotic Artemia against Vibrio and m odifies Artemia gut microbiota in xenic culture conditions

The prokaryotic cell storage compound ploy-β-hydroxybutyrate(PHB)has been considered as prebiotics that can be applied in aquaculture.In this paper,the dietary effect of a PHB-accumulating Halomonas strain(HM·PHB)identified from our previous work were studied in Artemia under gnotobiotic and xenic culture conditions,in comparison of Halomonas without PHB accumulation(HM)and microalgae Isochrysis(ISO)feeding.Under gnotobiotic condition,both HM·PHB and HM served as sole food supporting Artemia survival.Although both HM·PHB and HM feeding had no significant difference on Artemia survival percentage(P>0.05),HM·PHB significantly improved their resistance against Vibrio anguillarum challenge(P<0.05).Mass Artemia culture were further performed in xenic condition.Compared to ISO,HM·PHB feeding protected Artemia against V.anguillarum challenge(P<0.05),and HM·PHB and HM feeding resulted in increased T-AOC,pepsin,T-SOD and CAT activities(P<0.05).High throughput sequencing analysis showed that HM·PHB and HM feeding resulted in a lower Artemia gut microbial diversity(P<0.05),and modified the gut microbial community by remarkably reducing the Vibrio proportion.The outcome of the paper confirmed the beneficial effect of Halomonas-PHB in Artemia culture,which supports the use of Halomonas-PHB in the production of bio-secured live feed Artemia.

Effect of carbon and nitrogen ratio control on Artemia growth, water quality, biofloc microbial diversity under high salinity and zero-water exchange culture condition

Biofloc technology has been applied successfully in the intensive aquaculture of several fish and shrimp species. The growth of heterotrophic microorganisms can be stimulated through adding extra carbon, which reduces the nitrogen level in the water and provides microbial protein to the animals. However, most of the studies and practical applications have been conducted in freshwater and marine environment. This paper focused on brine shrimp Artemia that lives in high salinity environment together with other halophilic or halotolerant microorganisms. The effect of carbon supplementation on Artemia growth, water quality, and microbial diversity of biofl ocs was studied in the closed culture condition without any water exchange. The salinity of the culture medium was 100. A 24-d culture trial was conducted through supplementing sucrose at carbon/nitrogen (C/N) ratio of 5, 15, and 30 (Su5, Su15, and Su30), respectively. The culture without adding sucrose was used as a control. Artemia was fed formulated feed at a feeding ration of 60% recommended feeding level. The results showed that sucrose supplementation at higher C/N ratio (15 and 30) signifi cantly improved the Artemia survival, growth and water quality ( P <0.05). Addition of sucrose at C/N ratio of 15 and 30 significantly increased biofloc volume (BFV)( P <0.05). The Illumina MiSeq sequencing analysis showed that supplementing carbon at C/N ratio of 15 had a better total bacterial diversity and richness, and shaped the microbial composition at genera level. This study should provide information for studying the mechanism of biofloc technology and its application in high salinity culture conditions.

Eff ect of polystyrene microplastics and temperature on growth,intestinal histology and immune responses of brine shrimp Artemia franciscana

Microplastics pollution and seawater temperature rise have been the major environmental issues,threatening the survival and biodiversity of marine organisms.This study evaluated the combined effect of temperature and polystyrene microplastics(MP)on Artemia,a filter-feeding crustacean that is widely used for environmental toxicology studies.Brine shrimp Artemia franciscana were exposed to three MP concentrations(0,0.2,and 2.0 mg/L)and three temperatures(22,26,and 30℃)for 14 d.In general,higher MP concentration and temperature led to a decreased survival rate and growth.Two-way ANOVA analysis indicated that the survival rate of Artemia was significantly impacted by both MP concentration and temperature(P<0.05),but there was no significant interaction between two factors(P>0.05).Growth of Artemia was significantly impacted by temperature(P<0.05),and with a significant interaction between two factors(P<0.05).Furthermore,the enzymatic activity,intestinal histological analyses,and immune gene expression were determined for Artemia reared at 30℃ with three MP concentrations(0,0.2,and 2.0 mg/L).The results showed that 2.0-mg/L MP resulted in reduced Artemia intestinal microvilli and exfoliated epithelia cells,significantly increased acid phosphatase(ACP)activity(P<0.05)and immunerelated gene ADRA1 B and CREB3 expression,revealing that higher MP concentration could induce oxidative and immunological stress on Artemia at 30℃.Overall,our study suggests that MP and temperature have combined adverse effect on Artemia,especially at relatively high temperature and polystyrene MP concentration.These findings are important to understand the potential ecological risks posed by these two factors on the organisms in marine environment.

Transcriptomes of Litopenaeus vannamei reveal modulation of antioxidant system induced by dietary archaeal carotenoids

Oxidative stress induced by factors such as ammonia nitrogen has become a major issue in shrimp farming.The effects of carotenoids on the growth and antioxidant capability of Litopenaeus vannamei juveniles were investigated in this study using dietary archaeal carotenoids supplementation.For four weeks,shrimp were given diets containing 0 mg/kg(Ctrl)and 55.98 mg/kg(Car)archaeal carotenoids.Dietary archaeal carotenoids significantly enhanced the astaxanthin content in shrimp muscles and carapaces,as well as the superoxide dismutase(SOD)and glutathione peroxidase(GSH-Px)activity(P<0.05).The malonaldehyde(MDA)content in Car group significantly decreased(P<0.05).The transcriptome analysis was conducted to determine the molecular processes in response to archaeal carotenoids supplementation.A total of 1536 differentially expressed genes(DEGs)were detected,including 538 upregulated DEGs and 998 downregulated DEGs.GO functional enrichment analysis between Ctrl and Car indicated that 26 GO terms including extracellular region,metabolic process,and proteolysis were enriched.The KEGG pathway enrichment analysis revealed that the amino sugar and nucleotide sugar metabolism,cysteine and methionine metabolism,glycine serine and threonine metabolism,and amino acid biosynthesis were enriched.Archaeal carotenoids influenced the expression of several important genes involved in reactive oxygen species(ROS)generation,Nrf2 signaling,and antioxidant enzymes.Seven DEGs were chosen to confirm the RNA-Seq data using qRT-PCR.The genes and pathways discovered in this work assist to elucidate the molecular processes through which archaeal carotenoid enhances L.vannamei antioxidative system.

Diversity and connectedness of brine shrimp viruses in global hypersaline ecosystems

Brine shrimp(Artemia)has existed on Earth for 400 million years and has major ecological importance in hypersaline ecosystems.As a crucial live food in aquaculture,brine shrimp cysts have become one of the most important aquatic products traded worldwide.However,our understanding of the biodiversity,prevalence and global connectedness of viruses in brine shrimp is still very limited.A total of 143 batches of brine shrimp(belonging to seven species)cysts were collected from six continents including 21 countries and more than 100 geographic locations worldwide during 1977–2019.In total,55 novel RNA viruses were identified,which could be assigned to 18 different viral families and related clades.Eleven viruses were dsRNA viruses,16 were+ssRNA viruses,and 28 were−ssRNA viruses.Phylogenetic analyses of the RNA-directed RNA polymerase(RdRp)showed that brine shrimp viruses were often grouped with viruses isolated from other invertebrates and fungi.Remarkably,most brine shrimp viruses were related to those from different hosts that might feed on brine shrimp or share the same ecological niche.A notable case was the novel brine shrimp noda-like virus 3,which shared 79.25%(RdRp)and 63.88%(capsid proteins)amino acid identity with covert mortality nodavirus(CMNV)that may cause losses in aquaculture.In addition,both virome composition and phylogenetic analyses revealed global connectedness in certain brine shrimp viruses,particularly among Asia and Northern America.This highlights the incredible species diversity of viruses in these ancient species and provides essential data for the prevalence of RNA viruses in the global aquaculture industry.More broadly,these findings provide novel insights into the previously unrecognized RNA virosphere in hypersaline ecosystems worldwide and demonstrate that human activity might have driven the global connectedness of brine shrimp viruses.