Reproductive condition of the black-lip pearl oyster Pinctada margaritifera during the lunar phase.

This study analyzed the relationship between the lunar phase and the reproductive cycle of Pinctada margaritifera inhabiting Weno Island, Chuuk Lagoon, Micronesia. We measured indicators of maturity (gonadosomatic index [GSI] and sexual maturation-related genes) and investigated changes in the gonadal maturity stages (GMS) of P. margaritifera over lunar cycle. GSI was higher around the full moon. GMS of P. margaritifera were classified as the early gametogenesis stage, ripe and spawning stage, and spent and degenerating stage. A large percentage of oysters was observed in the ripe and spawning stage at the first quarter moon in female and the full moon in male as well as in the spent and degenerating stages at the third quarter moon in both sexes. In addition, the expression of doublesex- and mab-3-related transcription factor 2 (DMRT2) in the male P. margaritifera black-lip pearl oyster was the highest during the full and third quarter moon phases, whereas no difference in expression was observed with the lunar phase in females. In contrast, the expression of vitellogenin (VTG) was the highest in female P. margaritifera during the first and third quarters. No difference in expression was observed according to the lunar phase in males. The results suggest that the lunar phase directly affects the expression of sexually mature gonads in P. margaritifera black-lip pearl oyster.

Transcriptional and toxic responses to saxitoxin exposure in the marine copepod Tigriopus japonicus.

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.

A Scalable Haze-Free Antireflective Hierarchical Surface with Self-Cleaning Capability.

The lotus effect indicates that a superhydrophobic, self-cleaning surface can be obtained by roughening the topography of a hydrophobic surface. However, attaining high transmittance and clarity through a roughened surface remains challenging because of its strong scattering characteristics. Here, a haze-free, antireflective superhydrophobic surface that consists of hierarchically designed nanoparticles is demonstrated. Close-packed, deep-subwavelength-scale colloidal silica nanoparticles and their upper, chain-like fumed silica nanoparticles individually fulfill haze-free broadband antireflection and self-cleaning functions. These double-layered hierarchical surfaces are obtained via a scalable spraying process that permits precise control over the coating morphology to attain the desired optical and wetting properties. They provide a "specular" visible transmittance of >97% when double-side coated and a record-high self-cleaning capability with a near-zero sliding angle. Self-cleaning experiments on photovoltaic devices verify that the developed surfaces can significantly enhance power conversion efficiencies and aid in retaining pristine device performance in a dusty environment.

Effects of particulate matter (PM2.5) on life history traits, oxidative stress, and defensome system in the marine copepod Tigriopus japonicus.

Particulate matter (PM2.5) generated in large cities creates new problems in marine ecosystems and may adversely affect its inhabitants. However, the mechanisms underlying the same remain unclear; hence, we investigated the effects of PM2.5 on life history traits (e.g., mortality, development, and fecundity), cellular reactive oxygen species (ROS) levels, antioxidant enzyme (e.g., glutathione peroxidase [GPx], superoxide dismutase [SOD], and catalase [CAT]) activities, and the transcript levels of detoxification-related genes (cytochrome P450s [CYPs]) and antioxidant (glutathione S-transferases [GSTs]) in the copepod Tigriopus japonicus. Among the life history traits, developmental time was the only trait to significantly deviate (P < 0.05) in response to PM2.5 (compared to that in the controls). Significant changes in ROS levels and antioxidant enzymatic activities (P < 0.05) in response to PM2.5, suggested that PM2.5 can induce oxidative stress, leading to adverse effects on the T. japonicus life history. In addition, PM2.5 induced a differential regulation of various CYP and GST genes, particularly CYP307E1, GST-kappa, and GST-sigma were significantly upregulated (P < 0.05), suggesting that these genes likely play crucial roles in detoxification mechanisms and could be useful as reliable biomarkers for PM2.5 toxicity. Overall, the results of this study provide new insights into the potential toxicity of PM2.5.

Effects of dinoflagellate Gymnodinium catenatum on swimming behavior and expression of heat shock protein (hsp) genes in the brine shrimp Artemia franciscana.

To understand the effects of the toxic marine dinoflagellate, Gymnodinium catenatum, on the brine shrimp, Artemia franciscana, we examined the acute toxicity and swimming behavior parameters such as swimming speed, swimming distance, and swimming path trajectory with transcriptional regulation of heat shock protein (hsp) genes in response to G. catenatum exposure. Mortality was not observed in response to G. catenatum. In the case of swimming behavior parameters, swimming speed and swimming distance were significantly decreased (P < 0.05) for 5 min at three concentrations (240, 360, and 600 cells/mL) of G. catenatum, whereas no significant change in swimming path trajectory was observed, suggesting that G. catenatum has potential adverse effects on the swimming behavior of A. franciscana. Additionally, the four A. franciscana-hsp genes (hsp26, hsp40, hsp70, and hsp90) were upregulated in response to G. catenatum. In particular, A. franciscana-hsp40 was significantly upregulated in response to 600 cells/mL G. catenatum, suggesting that A. franciscana-hsp genes are highly associated with cellular defense mechanisms and that A. franciscana-hsp40 is a potential biomarker for G. catenatum exposure. Overall, this study improves our understanding of the effects of G. catenatum on the swimming behavior and cellular defense mechanisms of A. franciscana.

New records of two deep-sea eels collected from the Western Pacific Ocean based on COI and 16S rRNA genes.

BACKGROUND: Two deep-sea eels collected from the Western Pacific Ocean are described in this study. Based on their morphological characteristics, the two deep-sea eel specimens were assumed to belong to the cusk-eel family Ophidiidae and the cutthroat eel family Synaphobranchidae. METHODS AND RESULTS: To accurately identify the species of the deep-sea eel specimens, we sequenced the mitochondrial genes (cytochrome c oxidase subunit I [COI] and 16S ribosomal RNA [16S rRNA]). Through molecular phylogenetic analysis based on mtDNA COI and 16S rRNA gene sequences, these species clustered with the genera Bassozetus and Synaphobranchus, suggesting that the deep-sea eel specimens collected are two species from the genera Bassozetus and Synaphobranchus in the Western Pacific Ocean, respectively. CONCLUSIONS: This is the first study to report new records of the genera Bassozetus and Synaphobranchus from the Western Pacific Ocean based on COI and 16S rRNA genes.

iTRAQ-based proteomic profiling, pathway analyses, and apoptotic mechanism in the Antarctic copepod Tigriopus kingsejongensis in response to ultraviolet B radiation.

iTRAQ proteomic profiling was conducted to examine the proteomic responses of the Antarctic copepod Tigriopus kingsejongensis under ultraviolet B (UVB) exposure. Of the 5507 proteins identified, 3479 proteins were annotated and classified into 25 groups using clusters of orthologous genes analysis. After exposing the T. kingsejongensis to 12 kJ/m2 UVB radiation, 77 biological processes were modulated over different time periods (0, 6, 12, 24, and 48 h) compared with the control. A Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that UVB exposure in T. kingsejongensis downregulated ribosome and glyoxylate and dicarboxylate metabolism at all time points. Furthermore, antioxidant and chaperone proteins were highly downregulated in response to UVB exposure, causing protein damage and activating apoptotic processes in the 48 h UVB exposure group. These proteomic changes show the mechanisms that underlie the detrimental effects of UVB on the cellular defense systems of the Antarctic copepod T. kingsejongensis.

Identification and response of cytochrome P450 genes in the brackish water flea Diaphanosoma celebensis after exposure to benzo[α]pyrene and heavy metals.

The cytochrome P450 (CYP) enzyme family is extensive; these enzymes participate in phase I enzyme metabolism and are involved in xenobiotic detoxification in all living organisms. Despite their significance in xenobiotic detoxification, little is known about the species-specific comparison of CYPs and their molecular responses in aquatic invertebrates. We identified 31 CYPs in the brackish water flea Diaphanosoma celebensis via thorough exploration of transcriptomic databases and measured the transcript profiles of 9 CYPs (within full sequences) in response to benzo[α]pyrene (B[α]P) and two heavy metals (cadmium [Cd] and copper [Cu]). Through phylogenetic analysis, the CYPs were separated and clustered into four clans: mitochondrial, CYP2, CYP3, and CYP4. The expression of 9 CYPs were differentially modulated (up- and/or downregulated) in response to B[α]P, Cd, and Cu. In particular, CYP370A15 was significantly upregulated in response to B[α]P, Cd, and Cu, suggesting that the identified CYPs are involved in xenobiotic detoxification and are useful as biomarkers in response to B[α]P, Cd, and Cu. This study aimed to comprehensively annotate cladoceran CYPs; our results will add to the existing knowledge on the potential roles of CYPs in xenobiotic detoxification in cladocerans.

Effects of paralytic shellfish poisoning toxin-producing dinoflagellate Gymnodinium catenatum on the marine copepod Tigriopus japonicus.

To understand how the marine copepod Tigriopus japonicus responds to the toxic marine dinoflagellate Gymnodinium catenatum, we assessed acute toxicity and investigated swimming behavior parameters (e.g., swimming speed, swimming path trajectory, and swimming distance) in response to G. catenatum exposure. In addition, the mRNA expression levels of detoxification-related genes (e.g., phase I cytochrome P450 [CYP] and phase II glutathione-S transferase [GST]) were measured in G. catenatum-exposed copepods. No significant change in survival was observed in response to G. catenatum, but swimming speed was significantly decreased (P < 0.05) at a high concentration of G. catenatum (600 cells/mL). Furthermore, the swimming distance was significantly decreased (P < 0.05) compared to that of the control at 600 cells/mL G. catenatum, while no significant change in swimming path trajectory was observed, suggesting that G. catenatum potentially has adverse effects on the swimming behavior of T. japonicus. In addition, the transcriptional regulation of T. japonicus CYPs and -GSTs were significantly upregulated and downregulated (P < 0.05), respectively, in response to G. catenatum. In particular, certain genes (e.g., CYPs [CYP307E1, CYP3041A1, and CYP3024A2] and GSTs [GST-kappa, GST-mu5, and GST-omega]) were significantly induced (P < 0.05) by G. catenatum, suggesting that these genes likely play a critical role in detoxification mechanisms and might be useful as potential molecular biomarkers in response to G. catenatum exposure. Overall, these results elucidate the potential impacts of the dinoflagellate G. catenatum on the swimming behavior and detoxification system of the marine copepod T. japonicus.

Exosomal arrow (Arr)/lipoprotein receptor protein 6 (LRP6) in Drosophila melanogaster increases the extracellular level of Sol narae (Sona) in a Wnt-independent manner.

Wg/Wnt as a signaling protein binds to Frizzled (Fz) and Arrow (Arr), two Wg co-receptors essential for Wg signaling for cell proliferation, differentiation, and cell survival. Arr has a long extracellular region, a single transmembrane domain and an intracellular region. Here, we report that a new arrm7 mutant is identified in a genetic screen as a suppressor of lethality induced by overexpression of Sol narae (Sona), a secreted metalloprotease in ADAMTS family involved in Wg signaling. arrm7 allele has a premature stop codon, which encodes Arrm7 protein missing the intracellular region. arrm7 clones show cell death phenotype and overexpression of Arrm7 protein also induces cell death. Levels of extracellular Sona were decreased in both arrm7 and arr2 null clones, demonstrating that Arr increases the level of extracellular Sona. Indeed, Arr but not Arrm7, increased levels of Sona in cytoplasm and exosome fraction by inhibiting the lysosomal degradation pathway. Interestingly, Arr itself was identified in the exosome fraction, demonstrating that Arr is secreted to extracellular space. When Sona-expressing S2 cells were treated with exosomal Arr, the extracellular level of active Sona was increased. These results show that exosomal Arr dictates Sona-expressing cells to increase the level of extracellular Sona. This new function of Arr occurred in the absence of Wg because S2 cells do not express Wg. We propose that Arr plays two distinct roles, one as an exosomal protein to increase the level of extracellular Sona in a Wnt-independent manner and the other as a Wg co-receptor in a Wnt-dependent manner.

Influence of salinity on population growth, oxidative stress and antioxidant defense system in the marine monogonont rotifer Brachionus plicatilis.

Salinity stress influences energy balance, induction of stress proteins, and reproductive success, which are important to life parameters of aquatic organisms. However, physiological and molecular responses of salinity stress have not been studied in the rotifer. To understand the effects of salinity changes on the rotifer, we examined the marine monogonont rotifer Brachionus plicatilis (B. plicatilis) for salinity stress-induced changes in population growth, reactive oxygen species (ROS) levels, and antioxidant enzymatic activities (e.g., glutathione S-transferase [GST], superoxide dismutase [SOD] and catalase [CAT]). In addition, antioxidant-related transcripts (GSTs [GSTs-1-1 and GSTs-1-2], MnSOD1 and CAT2) were investigated in different salinity-exposed rotifers. A significant decrease (P < 0.05) in population growth was observed in response to high salinity (35 psu) in B. plicatilis. Moreover, the rotifers exposed to high salinity (35 psu) exhibited increased ROS levels with enhanced SOD and CAT enzymatic activities, compared to those in controls (15 psu). Additionally, significant change (P < 0.05) of antioxidant-related genes (GSTs [GSTs-1-1 and GSTs-1-2], MnSOD1 and CAT2) was observed in response to different salinities. Overall, these findings indicate that high salinity induce ROS-mediated oxidative stress, leading to growth retardation and modulation of the antioxidant defense system in B. plicatilis. These findings provide a better understanding on the adverse effects of salinity changes on lifecycle parameters and oxidative stress defense mechanism in rotifers.

Water penetration dynamics through a Janus mesh during drop impact.

Here, we study the water penetration dynamics through a Janus membrane with opposite wettability, i.e., (super-) hydrophobic on one side and (super-) hydrophilic on the other side, during drop impact. It is demonstrated that the penetration dynamics through the membrane consists of two temporally distinct events: dynamic pressure driven penetration dynamics on a shorter timescale and capillary pressure driven penetration dynamics on a longer timescale. For penetration under dynamic pressure, the threshold velocity for the penetration is dependent on the wettability of the impact side, such that a smaller impact velocity is required for water penetration when a water drop is impinged onto the superhydrophobic side over the superhydrophilic side. We demonstrate that this difference in the penetration dynamics upon drop impact can still be accounted for by the balance between the dynamic pressure and the capillarity pressure after adjusting the relative magnitude of the two contrasting pressures required for the penetration. Meanwhile, it is demonstrated that the penetration dynamics under capillary pressure is governed by the balance between the capillary pressure and the viscous pressure while the penetration mainly proceeds through the penetration area, which is formed during short-time penetration, showing the dynamic coupling between the two penetration dynamics. By elucidating the penetration dynamics on a Janus membrane, we believe that our results can help in designing Janus membranes for various fluidic applications such as oil-water separation, aeration, and water harvesting.

Contact time on curved superhydrophobic surfaces.

When a water drop impinges on a flat superhydrophobic surface, it bounces off the surface after a certain dwelling time, which is determined by the Rayleigh inertial-capillary timescale. Recent works have demonstrated that this dwelling time (i.e., contact time) is modified on curved superhydrophobic surfaces, as the drop asymmetrically spreads over the surface. However, the contact time on the curved surfaces still remains poorly understood, while no successful physical model for the contact time has been proposed. Here, we propose that the asymmetric spreading on the curved surface is driven by either the Coanda effect or inertia depending on the ratio of the drop diameter to the curvature diameter. Then, based on scaling analysis, we develop the contact time model that successfully predicts the contact time measured under a wide range of experiment conditions such as different impact velocities and curvature diameters. We believe that our results illuminate the underlying mechanism for the asymmetric spreading over the curved surface, while the proposed contact time model can be utilized for the design of superhydrophobic surfaces for various thermal applications, where the thermal exchange between the surface and the water drop occurs via a direct physical contact.

The reference genome of the selfing fish Kryptolebias hermaphroditus: Identification of phases I and II detoxification genes.

The selfing fish Kryptolebias hermaphroditus has unique reproductive system for self-fertilization, making genetically homozygous offsprings. Here, we report on high density genetic map-based genome assembly for the K. hermaphroditus Panama line (PanRS). The numbers of scaffolds were 5212 and the genome was 683,992,224 bp (N50 = 27.45 Mb). The length of anchored scaffold onto 24 linkage groups was 652,231,070 bp (95.3% of genome) with 0.01% of the gap and 39.33% of GC content and complete Benchmarking Universal Single-Copy Orthologs value was 96.6%. The numbers of annotated genes were 36,756 (average gene length 1368 bp) with the GC content of 54.1%. To examine the difference between the two sister species in the genus Kryptolebias, we compared the genomes of K. hermaphroditus PanRS and Kryptolebias marmoratus PAN line on the composition of transposable elements. To demonstrate applications of genome library, phase I and II detoxification related gene families have been analyzed, and compared the syntenies containing loci of CYP and GST genes on linkage groups. This K. hermaphroditus genome information will be helpful for a better understanding on genome-wide mechanistic view of detoxification and antioxidant-related genes over evolution in the view of fish environmental ecotoxicology.

Effects of temperature changes on life parameters, oxidative stress, and antioxidant defense system in the monogonont marine rotifer Brachionus plicatilis.

Global warming is a big concern for all organisms and many efforts have been made to reveal the potential effects of temperature elevation on aquatic organisms. However, limited studies on molecular mechanistic approaches on physiological effects due to temperature changes are available. Here, we investigated the effects of temperature changes on life parameters (e.g., population growth [total number of rotifers], and lifespan), oxidative stress levels and antioxidant activities (e.g., glutathione S-transferase [GST], catalase [CAT], superoxide dismutase [SOD]) with expression levels in the monogonont marine rotifer Brachionus plicatilis. The changes in temperatures led to significant reduction (P < 0.05) in lifespan, possibly due to significant decrease (P < 0.05) in antioxidant activities, reducing the potential to cope with significant elevation in the temperature-induced oxidative stress in B. plicatilis. To further assess the actual induction and clearance of reactive oxygen species (ROS), N-acetyl-L-cysteine was used to examine whether the temperature-induced oxidative stress could be successfully scavenged. Furthermore, expression patterns of the antioxidant-related genes (GSTs, SODs, and CATs) were down- or upregulated (P < 0.05) in response to different temperatures in B. plicatilis. Overall, these findings indicate that ROS-mediated oxidative stress led to cellular damage and antioxidant defense system, resulting in deleterious effects on life parameters in rotifer.

Sunscreens containing zinc oxide nanoparticles can trigger oxidative stress and toxicity to the marine copepod Tigriopus japonicus.

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.

In vivo toxicities of nine engineered nano metal oxides to the marine diatom Skeletonema costatum and rotifer Brachionus koreanus.

This study compared in vivo acute toxicities of nine engineered nano metal oxides to the marine diatom Skeletonema costatum and rotifer Brachionus koreanus. The sequence of their toxicities to S. costatum, based on growth inhibition, was: nano zinc oxide (nZnO) > nTiO2 (rutile) > nMgO > Annealed nMgO > nTiO2 (anatase) > Î³-nAl2O3 > nIn2O3 > α-nAl2O3 > nSnO2. Similarly, nZnO was also the most toxic to B. koreanus, but the other nano metal oxides were non-lethal. nMgO and nZnO were confirmed to trigger reactive oxygen species (ROS) mediated toxicity to the two marine organisms, while nTiO2 (both anatase and rutile forms) likely induced oxidative stress as shown by their acellular ROS production. nZnO may also cause damage in the endocrine system of B. koreanus, as indicated by the increased transcription of retinoid X receptor. Annealed nMgO reduces its toxicity via removal of O2- and impurities from its surface.

Two antidepressants fluoxetine and sertraline cause growth retardation and oxidative stress in the marine rotifer Brachionus koreanus.

To understand effects of two widely used antidepressant on the antioxidant defense mechanism in the marine rotifer Brachionus koreanus, we assessed acute toxicity and measured population growth, reactive oxygen species (ROS) levels, glutathione (GSH) levels, and antioxidant enzymatic activities (GST, GR, and SOD) in response to fluoxetine hydrochloride (FLX) and sertraline hydrochloride (SER). The no observed effect concentration-24 h of fluoxetine and sertraline were 1000 µg/L and 450 µg/L, respectively, whereas the median lethal concentration (LC50)-24 h of fluoxetine and sertraline were 1560 µg/L and 507 µg/L, respectively. Both fluoxetine and sertraline caused significant reduction (P < 0.05) in the population growth rate indicating that both antidepressants have a potential adverse effect on life cycle parameters of B. koreanus. The intracellular ROS level and GSH level were significantly modulated (P < 0.05) in response to fluoxetine and sertraline. In addition, antioxidant enzymatic activities have shown significant modulation (P < 0.05) in response to FLX and SER in B. koreanus. Furthermore, transcriptional profiles of antioxidant genes (GSTs, SODs, and GR) have shown modulation in response to FLX compared to SER-exposed B. koreanus. Our results indicate that fluoxetine and sertraline induce oxidative stress, leading to reduction in the population density and modulation of antioxidant defense mechanism in the marine rotifer B. koreanus.

Author Correction: An ADAMTS Sol narae is required for cell survival in Drosophila.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The genome of the marine monogonont rotifer Brachionus plicatilis: Genome-wide expression profiles of 28 cytochrome P450 genes in response to chlorpyrifos and 2-ethyl-phenanthrene.

Brachionus spp. (Rotifera: Monogononta) are globally distributed in aquatic environments and play important roles in the aquatic ecosystem. The marine monogonont rotifer Brachionus plicatilis is considered a suitable model organism for ecology, evolution, and ecotoxicology. In this study, we assembled and characterized the B. plicatilis genome. The total length of the assembled genome was 106.9 Mb and the number of final scaffolds was 716 with an N50 value of 1.15 Mb and a GC content of 26.75%. A total of 20,154 genes were annotated after manual curation. To demonstrate the use of whole genome data, we targeted one of the main detoxifying enzyme of phase I detoxification system and identified in a total of 28 cytochrome P450 s (CYPs). Based on the phylogenetic analysis using the maximum likelihood, 28 B. plicatilis-CYPs were apparently separated into five different clans, namely, 2, 3, 4, mitochondrial (MT), and 46 clans. To better understand the CYPs-mediated xenobiotic detoxification, we measured the mRNA expression levels of 28 B. plicatilis CYPs in response to chlorpyrifos and 2-ethyl-phenanthrene. Most B. plicatilis CYPs were significantly modulated (P < 0.05) in response to chlorpyrifos and 2-ethyl-phenanthrene. In addition, xenobiotic-sensing nuclear receptor (XNR) response element sequences were identified in the 5 kb upstream of promoter regions of 28 CYPs from the genome of B. plicatilis, indicating that these XNR can be associated with detoxification of xenobiotics. Overall, the assembled B. plicatilis genome presented here will be a useful resource for a better understanding the molecular ecotoxicology in the view of molecular mechanisms underlying toxicological responses, particularly on xenobiotic detoxification in this species.