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Recently, accidental spills of heavy oil have caused adverse effects in marine organisms. Oil pollution can induce damages on development and reproduction, linking with detrimental effects on diverse molecular levels of genes and proteins in plankton and fish. However, most information was mainly focused on marine vertebrates and consequently, limited information was available in marine invertebrates. Furthermore, there is still a lack of knowledge bridging in vivo endpoints with the functional regulation of cytochrome P450 ( CYP ) genes in response to oil spill pollution in marine invertebrates. In this paper, adverse effects of oil spill pollution in marine invertebrates are summarized with the importance of CYP genes as a potential biomarker, applying for environmental monitoring to detect oil spill using marine copepods. [ABSTRACT FROM AUTHOR]

The mitogen-activated protein kinases (MAPKs) family is known to mediate various biological processes in response to diverse environmental pollutants. Although MAPKs are well characterized and studied in vertebrates, in invertebrates the cross-reactivities of MAPKs antibodies were not clearly known in response to environmental pollutants due to limited information of antibody epitopes with material resources for invertebrates. In this paper, we performed phylogenetic analysis of MAPKs genes in the marine rotifer Brachionus koreanus and the copepods Paracyclopina nana and Tigriopus japonicus . Also in rotifer and copepods, several studies of Western blot of MAPK signaling pathways were shown in response to environmental pollutants, including multi-walled carbon nanotubes (MWCNTs), water-accommodated fractions (WAFs) of crude oil, and microplastics. This paper will provide a better understanding of the underlying mechanistic scenario in terms of cross-reactivities of mammalian antibodies in rotifer and copepod. [ABSTRACT FROM AUTHOR]

Oil pollution has deleterious effects on marine ecosystems. However, the toxicity of crude oil towards Antarctic marine organisms has not been well studied. We compared the deleterious effects of water accommodated fractions (WAFs) of crude oil on reproduction, intracellular reactive oxygen species (ROS) levels, and antioxidant enzymatic activity in Antarctic ( Tigriopus kingsejongensis ) and temperate ( Tigriopus japonicus ) copepods. Reproductive rates of T. kingsejongensis and T. japonicus were significantly reduced ( P < 0.05) in response to WAFs. Furthermore, T. kingsejongensis showed elevated levels of ROS and higher antioxidant enzyme (glutathione peroxidase [GPx]) activity than T. japonicus in response to WAFs. CYP genes from congeneric copepods were identified and annotated to better understand molecular detoxification mechanisms. We observed significant up-regulation ( P < 0.05) of Tk-CYP3024A3 and Tj-CYP3024A2 in response to WAFs, suggesting that CYP genes may contribute to the detoxification mechanism in response to WAF exposure. These finding also suggest that WAFs may induce oxidative stress, leading to reproductive impairment in copepods. Furthermore, Tk-CYP3024A3 and Tj-CYP3024A2 genes can be considered as potential biomarkers of WAF toxicity in the congeneric copepods T. kingsejongensis and T. japonicus . This study will be helpful for enhancing our knowledge on the harmful effects of WAFs in Antarctic and temperate copepods and provides insight into the underlying molecular mechanisms. [ABSTRACT FROM AUTHOR]

Triclosan (TCS) is an antimicrobial agent that has been widely dispersed and detected in the marine environment. However, the effects of TCS in marine invertebrates are poorly understood. In this study, the effects of TCS on life cycle history (e.g. mortality and fecundity) along with cellular reactive oxygen species (ROS) levels, GSH content, antioxidant enzymatic activities, and mRNA expression levels of oxidative stress-mediated genes were measured in the copepod Tigriopus japonicus . The no observed effect concentration (NOEC) and median lethal concentration (LC50) of TCS in the adult stage were determined to be 300 μg/L and 437.476 μg/L, respectively, while in the nauplius stages the corresponding values were 20 μg/L, and 51.76 μg/L, respectively. Fecundity was significantly reduced ( P < 0.05 ) in response to TCS at 100 μg/L. Concentration- and time-dependent analysis of ROS, GSH content (%), and antioxidant enzymatic activities (e.g. GST, GPx, and SOD) were significantly increased ( P < 0.05 ) in response to TCS exposure. Additionally, mRNA expression of detoxification (e.g., CYP s) and antioxidant (e.g., glutathione S -transferase-sigma isoforms, Cu/Zn superoxide dismutase , catalase ) genes was modulated in response to TCS exposure at different concentrations over a 24 h period. Our results revealed that TCS can induce reduced fecundity and oxidative stress with transcriptional regulation of oxidative stress-mediated genes with activation of the antioxidant system in the copepod T. japonicus . [ABSTRACT FROM AUTHOR]

CYP20A1 is a member of the cytochrome P450 (CYP) superfamily, identified as an orphan P450 without any assigned biological function; hence, its continued status as an “orphan” gene. In order to address this shortcoming in our understanding of this superfamily, we sought to characterize the CYP20A1 gene in the copepods Tigriopus japonicus ( Tj-CYP20A1 ) and Paracyclopina nana ( Pn-CYP20A1 ) at their mRNA transcriptional level. We assessed the response of this gene's expression in various developmental stages and in response to treatment with bisphenol A (BPA), 2, 2′, 4, 4′-tetrabromodiphenyl ether (BDE-47), and water accommodated fractions (WAFs) of crude oil. As shown in the vertebrate CYP20A1 , both Tj-CYP20A1 and Pn-CYP20A1 contained characteristic conserved motifs and domain regions (I helix, K helix and heme-binding motifs) with unusual amino acid sequences apparent in their gene structure. Also molecular characterization of the putative responsive elements in the promoter regions was performed. We observed transcriptional up-regulation of these genes during post-embryonic developmental stages including sex-specific up-regulation in adults. In addition, concentration- and time-dependent mRNA transcripts in response to xenobiotics (BPA, BDE-47, and WAFs) were seen. This study focuses on the molecular elucidation of CYP20A1 genes and their interactions with xenobiotics in the copepods T. japonicus and P. nana that provides important insight into the biological importance of CYP20A1 in invertebrates. [ABSTRACT FROM AUTHOR]

Trimethoprim (TMP) is an antibiotic that has been detected in various environments including marine habitats; however, the toxic effects of TMP are poorly understood in non-target marine organisms. In this study, the effects of TMP on mortality, development, reproduction, intracellular reactive oxygen species (ROS) levels, and transcription levels of antioxidant and xenobiotic detoxification-related enzyme genes were investigated in the copepod Tigriopus japonicus . The TMP half lethal dose at 48 h (LC 50 -48 h) in nauplius and TMP LC 50 -96 h in adult T. japonicus copepods was determined as 156 mg/L and 200 mg/L, respectively. In TMP-exposed T. japonicus , delayed developmental time and impaired reproduction were observed as harmful effects on the life history parameters. Increased ROS levels were also shown in response to TMP exposure at the highest concentration (100 mg/L TMP) and the expression of antioxidant- (e.g. GST-kappa, GST-sigma ) and xenobiotic detoxification (e.g. CYP s)-related genes were upregulated in a time and/or dose-dependent manner in response to TMP. Particularly, significant upregulation of three CYP genes ( Tj-CYP3024A2 , Tj-CYP3024A3 and Tj-CYP3027C2 ) were examined, suggesting that these CYP genes are likely playing an important role in the TMP detoxification metabolism in T. japonicus . In summary, we found that TMP induced oxidative stress via the transcriptional regulation of antioxidant- and xenobiotic detoxification-related genes, leading to changes in life history parameters such as developmental delay and reproduction impairment. Three Tj-CYP genes ( Tj-CYP3024A2 , Tj-CYP3024A3 and Tj-CYP3027C2 ) could be useful as potential T. japonicus biomarkers in response to antibiotics. [ABSTRACT FROM AUTHOR]

De novo lipogenesis (DNL) is a fatty acid synthesis process that requires several genes, including sterol regulatory element binding protein (SREBP), ATP-citrate lyase (ACLY), and acetyl-CoA carboxylase (ACC). DNL up-regulation is able to induce fat accumulation through an increase in fatty acids. To investigate the relationship between DNL up-regulation and the accumulation of fatty acids and lipid droplets in response to 2,2′,4,4′ tetrabrominated diphenyl ether (BDE-47), we examined DNL in the copepod Tigriopus japonicus . Transcription levels of DNL-related genes were increased after exposure to 2.5 μg/L BDE-47 for 24 h. After exposure to 2.5 μg/L BDE-47, palmitic acid was significantly increased ( P < 0.05) at days 1 and 4, along with upregulation of fatty acid synthesis-related genes ( e.g. , desaturases and elongases). However, docosahexaenoic acid and arachidonic acid were down-regulated at days 1 and 4, showing an antagonistic effect. Lipid droplet area significantly increased in Nile red staining analysis after 24 h of exposure to 2.5 μg/L BDE-47 in T. japonicus , while DNL was down-regulated in response to 500 μM salicylate (a lipogenesis inhibitor), indicating that BDE-47 exposure is closely associated with an increase in fatty acids in this copepod. This study provides a better understanding of the effects of BDE-47 on DNL in copepods. [ABSTRACT FROM AUTHOR]

2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) and perfluorooctane sulfonate (PFOS) are widely dispersed persistent organic pollutants (POPs) in the marine ecosystem. However, their toxic effects on marine organisms are still poorly understood. In this study, we investigated the effects of BDE-47 and PFOS on development and reproduction at the organismal level and reactive oxygen species (ROS) production and gene expression patterns of the defensome at the cellular level in the intertidal copepod Tigriopus japonicus . In copepods exposed to BDE-47 and PFOS, we observed developmental retardation and reduced fecundity, suggesting repercussions on in vivo endpoints through alterations to the normal molting and reproduction system of T. japonicus . BDE-47 and PFOS increased levels of ROS in T. japonicus in a concentration-dependent manner, indicating that POPs can induce oxidative stress through the generation of ROS. Additionally, transcript profiles of genes related to detoxification ( e.g. , CYP s), antioxidant functions ( e.g. , GST- sigma , catalase , MnSOD ), apoptosis ( e.g. , p53 , Rb ), and cellular proliferation ( e.g. , PCNA ) were modulated over 72 h in response to BDE-47 (120 μg/L) and PFOS (1000 μg/L). These findings indicate that BDE-47 and PFOS can induce oxidative stress-mediated DNA damage repair systems with transcriptional regulation of detoxification, antioxidant, and apoptosis-related genes, resulting in developmental retardation and reduced fecundity in the copepod T. japonicus . [ABSTRACT FROM AUTHOR]

Highlights: [•] 52 CYP genes were found from T. japonicus. [•] Development, molting, and hatching rate were affected in response of WAF exposure in T. japonicus. [•] WAF exposure induced oxidative stress. [•] CYP3024A2, CYP3024A3, and CYP3027C2 were significantly induced by WAF. [•] Promoter regions of CYP genes are useful to understand the mode of action for detoxification. [Copyright &y& Elsevier]

Highlights: [•] Mortality rate was significantly increased in response to gamma radiation. [•] A dose-dependent reduction in fecundity of ovigerous females. [•] Growth retardation, particularly at the nauplius stage. [•] Upon gamma radiation, T. japonicus showed an increased ROS levels. [•] Antioxidant genes and Hsps genes were upregulated at sublethal doses. [Copyright &y& Elsevier]

The whole transcriptome of the Antarctic copepod ( Tigriopus kingsejongensis ) was sequenced using Illumina RNA-seq. De novo assembly was performed with 64,785,098 raw reads using Trinity, which assembled into 81,653 contigs. TransDecoder found 38,250 candidate coding contigs which showed homology to other species by BLAST analysis. Functional gene annotation was performed by Gene Ontology (GO), InterProScan, and KEGG pathway analyses. Finally, we identified a number of expressed gene catalog for T. kingsejongensis that is a useful model animal for gene information-based polar research to uncover molecular mechanisms of environmental adaptation on harsh environments. In particular, we observed highly developing lipid metabolism in T. kingsejongensis directly compared to those of the Far East Pacific coast copepod Tigriopus japonicus at the transcriptome level. [ABSTRACT FROM AUTHOR]

The study, for the first time, evaluated the leaching rate of zinc oxide nanoparticles (nZnO) from human skins which were applied with three commercial sunscreens containing nZnO as an active ingredient. The leaching rate of nZnO varied greatly among the sunscreens, with a range of 8–72% (mean ± SD: 45% ± 33%). We further investigated their toxicities to the marine copepod Tigriopus japonicus. We found that 96-h median lethal concentrations of the three sunscreens to T. japonicus were > 5000, 230.6, and 43.0 mg chemical L−1, respectively, equivalent to Zn2+ concentrations at >82.5, 3.2, and 1.2 mg Zn L−1, respectively. Exposure to the individual sunscreens at environmentally realistic concentrations for 96 h led to up-regulation of antioxidant genes in T. japonicus , while they triggered the release of reactive oxygen species based on the results of in vivo assays. Evidently, these nZnO-included sunscreens can cause oxidative stress and hence pose risk to marine organisms. • Leaching rates of nZnO from the sunscreens applied on human skin ranged from 8 to 72%. • At elevated levels, nZnO-included sunscreens were toxic to the copepod T. japonicus. • Their toxicities were associated with releases of nZnO and Zn2+ from the sunscreens. • Exposure to the sunscreens altered the expression of antioxidant genes in copepods. • Such exposures triggered the release of in vivo ROS and caused oxidative stress. [ABSTRACT FROM AUTHOR]

In this study, the whole transcriptome of Tigriopus japonicus was sequenced using next generation sequencing technology. De novo assembly was performed using Trinity, which assembled 140,130 contigs. Transdecoder found 54,761 candidate coding contigs, 39,507 of which showed homology to other species covering 15,310 genes by BLAST analysis. Functional gene annotation was performed by Gene Ontology, InterProScan, and KEGG pathway analyses. In addition to various metabolism-related pathways, xenobiotic biodegradation and metabolism were other interesting pathways in T. japonicus . Transcripts encoding various enzymes (e.g. superoxide dismutase, heat shock protein, and peroxidases) in response to a variety of stimuli were identified, which might be useful candidate biomarkers for ecotoxicology studies. [ABSTRACT FROM AUTHOR]

Ecdysteroid hormones are pivotal in the development, growth, and molting of arthropods, and the hormone pathway is triggered by binding ecdysteroid to a heterodimer of the two nuclear receptors; ecdysone receptors (EcR) and ultraspiracle (USP). We have characterized EcR and USP genes, and their 5′-untranslated region (5′-UTR) from the copepod Paracyclopina nana , and studied mRNA transcription levels in post-embryonic stages and in response to water accommodated fractions (WAFs) of crude oil. The open reading frames (ORF) of EcR and USP were 1470 and 1287 bp that encoded 490 and 429 amino acids with molecular weight of 121.18 and 105.03 kDa, respectively. Also, a well conserved DNA-binding domain (DBD) and ligand-binding domain (LBD) were identified which confirmed by phylogenetic analysis. Messenger RNA transcriptional levels of EcR and USP were developmental stage-specific in early post-embryonic stages (N3-4). However, an evoked expression of USP was observed throughout copepodid stage and in adult females. WAFs (40 and 80%) were acted as an ecdysone agonist in P. nana , and elicited the mRNA transcription levels in adults. Developmental stage-specific transcriptional activation of EcR and USP in response to WAFs was observed. USP gene was down-regulated in the nauplius in response to WAF, whereas up-regulation of USP was observed in the adults. This study represents the first data of molecular elucidation of EcR and USP genes and their regulatory elements from P. nana and the developmental stage specific expression in response to WAFs, which can be used as potential biomarkers for environmental stressors with ecotoxicological evaluations in copepods. [ABSTRACT FROM AUTHOR]

To identify and characterize CHH (TJ-CHH) gene in the copepod Tigriopus japonicus, we analyzed the full-length cDNA sequence, genomic structure, and promoter region. The full-length TJ-CHH cDNA was 716bp in length, encoding 136 amino acid residues. The deduced amino acid sequences of TJ-CHH showed a high similarity of the CHH mature domain to other crustaceans. Six conserved cysteine residues and five conserved structural motifs in the CHH mature peptide domain were also observed. The genomic structure of the TJ-CHH gene contained three exons and two introns in its open reading frame (ORF), and several transcriptional elements were detected in the promoter region of the TJ-CHH gene. To investigate transcriptional change of TJ-CHH under environmental stress, T. japonicus were exposed to heat treatment, UV-B radiation, heavy metals, and water-accommodated fractions (WAFs) of Iranian crude oil. Upon heat stress, TJ-CHH transcripts were elevated at 30°C and 35°C for 96h in a time-course experiment. UV-B radiation led to a decreased pattern of the TJ-CHH transcript 48h and more after radiation (12kJ/m2). After exposure of a fixed dose (12kJ/m2) in a time-course experiment, TJ-CHH transcript was down-regulated in time-dependent manner with a lowest value at 12h. However, the TJ-CHH transcript level was increased in response to five heavy metal exposures for 96h. Also, the level of the TJ-CHH transcript was significantly up-regulated at 20% of WAFs after exposure to WAFs for 48h and then remarkably reduced in a dose-dependent manner. These findings suggest that the enhanced TJ-CHH transcript level is associated with a cellular stress response of the TJ-CHH gene as shown in decapod crustaceans. This study is also helpful for a better understanding of the detrimental effects of environmental changes on the CHH-triggered copepod metabolism. [ABSTRACT FROM AUTHOR]

Highlights • The genome-wide identification of GSTs in T. japonicus and P. nana resulted in 32 and 20 GSTs in total. • GSTs sigma and delta/epsilon GSTs were the dominant form in T. japonicus. • Delta/epsilon and mu GSTs classes were dominant cytosolic GSTs in P. nana. • Both copepods were exposed to copper and the ROS level and GST activity were measured. • Functional divergence among species-specific GST genes was clearly observed with GST enzymatic activities. Abstract In this study, the entire glutathione S -transferases (GSTs), the major phase II detoxification enzyme, were identified in two marine copepod species Tigriopus japonicus and Paracyclopina nana. The genome-wide identification of GSTs in T. japonicus and P. nana resulted in 32 and 20 GSTs in total, respectively. Among the identified GSTs, two specific classes of GSTs, specifically sigma and delta/epsilon GSTs were the dominant form of cytosolic GSTs in T. japonicus , while delta/epsilon and mu classes were dominant cytosolic GSTs in P. nana. In addition, Membrane-Associated Proteins in Eicosanoid and Glutathione metabolism (MAPEG) family were found in relatively higher proportion compared to other classes. Moreover, sigma, delta/epsilon, and microsomal GSTs have shown to expand through tandem duplication. To validate the detoxification function of the identified GSTs, both copepods were exposed to copper (Cu2+) and the reactive oxygen species (ROS) level and GST activity were measured. 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 two marine copepod species and their important role in marine environmental ecotoxicology. [ABSTRACT FROM AUTHOR]

Oil pollution is considered being disastrous to marine organisms and ecosystems. As molting is critical in the developmental process of arthropods in general and copepods, in particular, the impact will be adverse if the target of spilled oil is on molting. Thus, we investigated the harmful effects of water accommodated fractions (WAFs) of crude oil with an emphasis on inhibition of chitin metabolic pathways related genes and developmental retardation in the copepod Tigriopus japonicus. Also, we analysed the ontology and domain of chitin metabolic pathway genes and mRNA expression patterns of developmental stage-specific genes. Further, the developmental retardation followed by transcriptional modulations in nuclear receptor genes ( NR ) and chitin metabolic pathway-related genes were observed in the WAFs-exposed T. japonicus . As a result, the developmental time was found significantly ( P < 0.05) delayed in response to 40% WAFs in comparison with that of control. Moreover, the NR gene, HR3 and chitinases ( CHT9 and CHT10 ) were up-regulated in N4–5 stages, while chitin synthase genes (CHS-1, CHS-2-1, and CHS-2-2) down-regulated in response to WAFs. In brief, a high concentration of WAFs repressed nuclear receptor genes but elicited activation of some of the transcription factors at low concentration of WAFs, resulting in suppression of chitin synthesis. Thus, we suggest that WAF can lead molting retardation of naupliar stages in T. japonicus through down-regulations of chitin metabolism. These findings will provide a better understanding of the mode of action of chitin biosynthesis associated with molting mechanism in WAF-exposed T. japonicus. [ABSTRACT FROM AUTHOR]

In marine ecosystems, salinity fluctuations are critical in modulating energy balance, inducing stress proteins, providing reproductive success and affecting the distribution of copepods. Salinity induces osmotic stress in organisms when they are not in their optimal condition and the stressful status increase the energy demand required for osmoregulation, which in turn reflects in all biological processes. Effects of salinity stress on life history traits and tolerance are species-specific. In this study, we used the estuarine cyclopoid copepod Paracyclopina nana to understand the responses towards the hypo (5 ppt) and hypersalinity (25 and 30 ppt) conditions, and compared that with the control (15 ppt). We investigated the life cycle parameters (e.g. growth and fecundity), fatty acid (FA) synthesis, lipid accumulation (as lipid droplets [LDs]) and modulation of heat shock proteins ( hsps ) in response to salinity stress. As a result, life cycle parameters and FA synthesis, LDs, and modulation of hsps were found highly dependent on salinity changes in P. nana . Particularly, hypersalinity resulted in developmental retardation, reduced fecundity, decreased FA synthesis, a drop in lipid accumulation, and modulation of stress response proteins, suggesting that P. nana devoted increased energy to cope with the osmotic imbalance due to salinity stress in hypersalinity conditions. This finding provides a better understanding of how salinity affects in vivo endpoints and the relevant molecular responses in estuarine copepods. Statement of relevance We envisage that this manuscript will be helpful to understand salinity-dependent lipid composition changes in copepods and optimize the optimal salinity for the mass culture for this species. Considering the small size (~ 600 μm) of P. nana and its potential as live feeds for finfish larviculture, the present findings have considerable importance for the aquaculture industry. [ABSTRACT FROM AUTHOR]

To evaluate the effects of ultraviolet B (UV-B) radiation at the developmental, reproductive, and molecular levels in aquatic invertebrates, we measured UV-B-induced acute toxicity, impairments in developmental and reproductive traits, and UV-B interaction with the entire family of cytochrome P450 ( CYP ) genes in the intertidal benthic copepod Tigriopus japonicus . We found a significant, dose-dependent reduction ( P < 0.05) in the survival of T. japonicus that began as a developmental delay and decreased fecundity. The 48 h LD10 and LD50 were 1.35 and 1.84 kJ/m 2 , and the CYP inhibitor (PBO) elevated mortality, confirming the involvement of CYP genes in UV-B induced toxicity. Low-dose UV-B (1.5 kJ/m 2 ) induced developmental delays, and higher doses (6–18 kJ/m 2 ) caused reproductive impairments in ovigerous females. The significant up-regulation of CYP genes belonging to clans 2/3/MT/4/20 in T. japonicus exposed to UV-B (12 kJ/m 2 ) confirmed molecular interaction between UV-B and CYP genes. Moreover, orphan CYPs, such as CYP20A1 , provide good insight on the deorphanization of invertebrate CYPs . Overall, these results demonstrate the involvement of UV-B radiation in the expression of all the CYP genes in T. japonicus and their susceptibility to UV-B radiation. This will provide a better understanding of the mechanistic effects of UV-B in copepods through the predicted AhR-mediated up-regulation of CYP genes. [ABSTRACT FROM AUTHOR]

Aquatic invertebrates contribute significantly to environmental impact assessment of contaminants in aquatic ecosystems. Much effort has been made to identify viable and ecologically relevant invertebrate test organisms to meet rigorous regulatory requirements. Copepods, which are ecologically important and widely distributed in aquatic organisms, offer a huge opportunity as test organisms for aquatic toxicity testing. They have a major role not only in the transfer of energy in aquatic food chains, but also as a medium of transfer of aquatic pollutants across the tropic levels. In this regard, a supratidal and benthic harpacticoid copepod Tigriopus japonicus Mori (order Harpacticoida) has shown promising characteristics as a test organism in the field of ecotoxicology. Because there is a need to standardize a battery of test organisms from species in different phylogenetic and critical ecosystem positions, it is important to identify another unrelated planktonic species for wider application and comparison. In this regard, the cyclopoid copepod Paracyclopina nana Smirnov (order Cyclopoida) has emerged as a potential test organism to meet such requirements. Like T. japonicus , it has a number of features that make it a candidate worth consideration in such efforts. Recently, the genomics of P. nana has been unraveled. Data on biochemical and molecular responses of P. nana against exposure to environmental chemicals and other stressors have been collected. Recently, sequences and expression profiles of a number of genes in P. nana encoding for heat shock proteins, xenobiotic-metabolizing enzymes, and antioxidants have been reported. These genes serve as potential biomarkers in biomonitoring of environmental pollutants. Moreover, the application of gene expression techniques and the use of its whole transcriptome have allowed evaluation of transcriptional changes in P. nana with the ultimate aim of understanding the mechanisms of action of environmental stressors. Whole-animal bioassays and gene expression studies indicate that P. nana may serve as an excellent tool to evaluate the impact of diverse disturbances in the marine environment. With a better understanding of toxicological mechanisms, ecotoxicologists will be able to understand defense mechanisms against toxicants in copepods. In this review, we illustrate the potential of P. nana as an alternative as well as a complementary invertebrate model organism for risk assessment of aquatic pollutants. [ABSTRACT FROM AUTHOR]

Saxitoxin (STX) is a highly toxic marine neurotoxin produced by phytoplankton and a growing threat to ecosystems worldwide due to the spread of toxic algae. Although STX is an established sodium channel blocker, the overall profile of transcriptional levels in STX-exposed organisms has yet to be described. Here, we describe a toxicity assay and transcriptome analysis of the copepod Tigriopus japonicus exposed to STX. The half-maximal lethal concentration of STX was 12.35 μM, and a rapid mortality slope was evident at concentrations between 12 and 13 μM. STX induced changes in swimming behavior among the copepods after 10 min of exposure. In transcriptome analysis, gene ontology revealed that the genes involved in nervous system and gene expression were highly enriched. In addition, the congenital neurological disorder and nuclear factor erythroid 2-related factor 2–mediated oxidative stress pathways were identified to be the most significant in network analysis and toxicity pathway analysis, respectively. This study provides valuable information about the effects of STX and related transcriptional responses in T. japonicus. [Display omitted] • Saxitoxin exposure induced mortality and behavioral changes in Tigriopus japonicus. • Genes involved in neuron system-related pathways were deregulated. • NRF2-mediated oxidative stress response was predicted as the main toxicity pathway. [ABSTRACT FROM AUTHOR]

Engineered multi-walled carbon nanotubes (MWCNTs) have received widespread applications in a broad variety of commercial products due to low production cost. Despite their significant commercial applications, CNTs are being discharged to aquatic ecosystem, leading a threat to aquatic life. Thus, we investigated the adverse effect of CNTs on the marine copepod Paracyclopina nana . Additional to the study on the uptake of CNTs and acute toxicity, adverse effects on life parameters ( e.g . growth, fecundity, and size) were analyzed in response to various concentrations of CNTs. Also, as a measurement of cellular damage, oxidative stress-related markers were examined in a time-dependent manner. Moreover, activation of redox-sensitive mitogen-activated protein kinase (MAPK) signaling pathways along with the phosphorylation pattern of extracellular signal-regulated kinase (ERK), p38, and c-Jun-N-terminal kinases (JNK) were analyzed to obtain a better understanding of molecular mechanism of oxidative stress-induced toxicity in the copepod P. nana . As a result, significant inhibition on life parameters and evoked antioxidant systems were observed without ROS induction. In addition, CNTs activated MAPK signaling pathway via ERK, suggesting that phosphorylated ERK ( p -ERK)-mediated adverse effects are the primary cause of in vitro and in vivo endpoints in response to CNTs exposure. Moreover, ROS-independent activation of MAPK signaling pathway was observed. These findings will provide a better understanding of the mode of action of CNTs on the copepod P. nana at cellular and molecular level and insight on possible ecotoxicological implications in the marine environment. [ABSTRACT FROM AUTHOR]

Abstract: Ecdysteroids are steroid hormones that play an important role in development, growth, molting of larva, and reproduction in the Arthropoda. The effect of ecdysteroids is mediated by its binding to ecdysteroid receptor (EcR). To investigate the role of EcR during development and the effect to environmental stressors on EcR expression in a copepod, we isolated and characterized cDNA and 5′-promoter region of the Tigriopus japonicus EcR (TJ-EcR), and studied mRNA expression pattern. The full-length TJ-EcR cDNA sequence was 1962bp in length and the open reading frame encoded 546 amino acids. The deduced TJ-EcR protein contained well-conserved DNA-binding domain and ligand-binding domain. Phylogenetic analysis revealed that TJ-EcR was clustered with the EcR of other crustaceans. TJ-EcR mRNA was expressed in a developmental stage-specific manner: high in early developmental stages and low in the adult stage. Significantly elevated expression of the TJ-EcR gene in adults was detected at hypersalinity (42ppt) and high temperature (35°C) condition. The 5′-flanking region of TJ-EcR gene contains heat shock protein 70 response elements, implying that the environmental stressors may affect its expression via the stress-sensor. In addition, bisphenol A (100µg/L) repressed TJ-EcR expression. Our results suggest that TJ-EcR could be a biomarker for the monitoring of the impact of environmental stressors in copepods. [Copyright &y& Elsevier]

• In T. japonicus , no mortality was shown in response to atrazine up to 20 mg/L in acute toxicity assessment. • In nauplii, retardation in the growth and prolonged molting and metamorphosis resulted under chronic exposure of atrazine at 20 mg/L. • Body sizes were significantly decreased in 20 mg/L atrazine-exposed T. japonicus nauplii with the generation of ROS. • Ecdysteroid biosynthetic pathway-involved genes were significantly downregulated (P < 0.05) in response to atrazine. Atrazine is a widely used pesticide which acts as an endocrine disruptor in various organisms. The aim of this study was to investigate adverse effects of atrazine on life parameters, oxidative stress, and ecdysteroid biosynthetic pathway in the marine copepod Tigriopus japonicus. In T. japonicus , no mortality was shown in response to atrazine up to 20 mg/L in acute toxicity assessment. In nauplii, retardation in the growth and prolonged molting and metamorphosis resulted under chronic exposure of atrazine at 20 mg/L. In addition, body sizes of T. japonicus nauplii were significantly decreased (P < 0.01 in length and P < 0.001 in width) in response to 20 mg/L of atrazine. Furthermore, atrazine induced oxidative stress by the generation of reactive oxygen species at all concentrations compared to the control in the nauplii. Also, significant increase in glutathione- S transferase activity was observed in adult T. japonicus at low concentration of atrazine. To understand effects of atrazine on ecdysteroid biosynthetic pathway-involved genes (e.g., neverland , CYP307E1 , CYP306A1 , CYP302A1 , CYP3022A1 [ CYP315A1 ], CYP314A1 , and CYP18D1) were examined with mRNA expressions of ecdysone receptor (EcR) and ultraspiracle (USP) in response to 20 mg/L atrazine in nauplii and adults. In the nauplii, these genes were significantly downregulated (P < 0.05) in response to atrazine, compared to the control but not in the adult T. japonicus. These results suggest that atrazine can interfere in vivo life parameters by oxidative stress-induced retrogression and ecdysteroid biosynthetic pathway in this species. [ABSTRACT FROM AUTHOR]

Abstract: The copepod, Tigriopus japonicus has been recognized as an excellent marine model species for ecotoxicological studies. The present study cloned and characterized the p53 gene of this copepod and studied its expression pattern. We discovered that p53 expression patterns varied among different developmental stages of the copepod, having the highest expression in the adult. Such variation was possibly associated with the molting cycle. By using real-time RT-PCR, we further investigated the modulatory pattern of the p53 gene in the copepod after exposure to three alkylphenols (i.e. nonylphenol, octylphenol, and bisphenol A) which are known as endocrine disruption chemicals (EDCs). The results showed that the three alkylphenols significantly induced p53 gene expression in the copepod, indicating the involvement of p53 in such stress-responses. Thus, the copepod p53 gene provides one of the stress-response biomarkers for exposure to EDC-like compounds. [ABSTRACT FROM AUTHOR]

Abstract: The intertidal copepod, Tigriopus japonicus, has been recognized as a promising model species for marine environmental genomics. To obtain extensive genomic DNA sequences from this species, we sequenced genomic DNA from adult copepods using genomic sequencers GS-FLX and GS-FLX-Titanium and attained 1,914,995 reads (average read length 299.8bp) including 574.2Mb of genomic DNA information. After subjecting them to assembly, we acquired 193,642 contigs (total contigs length 129.7Mb), and finally were able to obtain 10,894 unigenes (E-value>0.1; length>200bp) containing 33,081,455bp after a nonredundant (NR) blast search. In this paper, we summarize the genomic DNA sequences of T. japonicus and discuss its potential use in environmental genomics and ecotoxicological studies for uncovering mechanisms of environmental stresses and chemical toxicities to marine crustaceans. [ABSTRACT FROM AUTHOR]