Harpacticoid Copepod Tigriopus Japonicus Research Articles

Acute and Chronic Effects of the Antifouling Booster Biocide Diuron on the Harpacticoid Copepod Tigriopus japonicus Revealed through Multi-Biomarker Determination

Diuron, an additive biocide in antifouling paints, is widely employed to curtail the attachment of organisms on submerged surfaces in aquatic structures. Despite the detection of diuron in aquatic ecosystems, information regarding its acute and chronic impacts on aquatic invertebrates, particularly planktonic crustaceans, remains limited. In this study, we analyzed the acute (24 h) and chronic (12 days exposure across three generations) effects of different concentrations of diuron (1/10 of the no observed effect concentration (NOEC), the NOEC, and 1/10 of the lethal concentration 50% (LC50), derived from the 24 h acute toxicity value of 1152 μg L−1) on the harpacticoid copepod Tigriopus japonicus. The acute exposure experiment indicated that the 1/10 LC50 value of diuron significantly reduced the copepod’s feeding rate and acetylcholinesterase activity. In response to the 1/10 LC50 value, the intracellular reactive oxygen species were elevated alongside increased malondialdehyde levels, while the glutathione content was depleted. The enzymatic activities of glutathione S-transferase, catalase, and superoxide dismutase were significantly enhanced by the 1/10 LC50 value, suggesting a proactive role of the antioxidant defense system against oxidative stress. Conversely, the activities of glutathione peroxidase and glutathione reductase enzymes were increased at the NOEC value, while their values were reduced by the 1/10 LC50 value. Chronic exposure to 1/10 NOEC and NOEC values revealed the adverse multigenerational effects of diuron. The second generation exhibited the most sensitivity to diuron, with the NOEC value notably reducing survival rate, body length, nauplius-to-adult development, neonates per brood count, and extending the reproduction period. Taken together, our findings underscore that even sublethal diuron levels can adversely impact copepod populations across generations through intergenerational toxicity.

Suppression of cannibalism in the intertidal copepod Tigriopus japonicus (Mori, 1932) and improvements in population density using artificial substrates

AbstractThe present study investigated population growth, egg production and cannibalism in the intertidal harpacticoid copepod Tigriopus japonicus (Mori, 1932). Copepods were cultured on artificial substrates with different surface areas, from 13.5 × 103 to 10.6 × 104 mm2, to clarify the effect of surface area in a culture vessel on population density. The cannibalism rate at a surface area of 10.6 × 104 mm2 was significantly lower (by a sixth) than that at 13.5 × 103 mm2. These results suggest that artificial substrates play a role in preventing cannibalism by providing shelter and can increase the stocking population density of T. japonicus in a vessel.

The genome of the harpacticoid copepod Tigriopus japonicus: Potential for its use in marine molecular ecotoxicology

The copepod Tigriopus japonicus has been widely used as an experimental species in the field of ecotoxicology. We have sequenced and assembled the whole genome of T. japonicus with comparative analysis of gene families that represent detoxification phases in two additional public genomes of Tigriopus spp., namely, T. californicus and T. kingsejongensis. The total length of the T. japonicus assembled genome was 196.6 Mb with an N50 value of 10.65 Mb and consisted of 339 scaffolds and 25,143 annotated genes. The detoxification gene families encoding cytochrome P450s (CYP450s), glutathione S-transferases (GSTs), and ATP-binding cassette (ABC) proteins in Tigriopus spp. have shown species-dependent diversity in several gene sets, suggesting that these genes have undergone a species-specific expansion to increase their fitness to different marine habitats and environmental pressures. Our study will provide a better understanding of the detoxification system in Tigriopus spp. and will contribute to various areas of research, including ecotoxicology.

Phototactic behavior of the marine harpacticoid copepod Tigriopus japonicus related to developmental stages under various light conditions

Marine harpacticoid copepod Tigriopus japonicus is commonly distributed in the tide-pools and shows benthic behavior. To determine its phototactic behavior, the movement pattern was investigated with different light wavelengths (white, peaks at 460 and 570 nm; blue at 470 nm; green at 525 nm; and red at 660 nm) and intensities (0.5, 2.0, 3.5, 5.0, 15.0 W/m2) related to developmental stages i.e., nauplius and adult. The eyespot of the two developmental groups efficiently absorbed the light wavelength from 400 to 550 nm, while the level of absorbance was different. For the horizontal phototactic behavior, nauplii showed negative phototaxis with the all tested light wavelengths and intensities ranging 0.5–5.0 W/m2, while they lost phototactic movement at 15 W/m2 of all conducted light wavelengths except with the red light shown negative phototaxis. The adults showed negative phototaxis at 0.5 and 3.5 W/m2, while positive phototaxis at 2.0 W/m2 regardless of light wavelengths. The vertical phototactic movement was only monitored with adults. At 2.0 and 3.0 W/m2, >40% of adults showed planktonic behavior with the blue light. The results elucidate that T. japonicus has different patterns of phototaxis related to developmental stages which can be used to manipulate its distribution for dispersal.

Effect of increased pCO2 in seawater on survival rate of different developmental stages of the harpacticoid copepod Tigriopus japonicus

ABSTRACTThe rapid increase in carbon dioxide levels in seawater is causing ocean acidification and is expected to have significant effects on marine life. To explore the ability of the harpacticoid copepod Tigriopus japonicus to adapt to an increased concentration of dissolved carbon dioxide (CO2) in seawater, we compared the survival rates of adult and nauplius stages at 400, 1000, and 1550 ppm pCO2 over a 14-day period. The survival rate of T. japonicus dramatically decreased over time with increase in pCO2 concentration. At 1550 ppm, the survival rate showed a decrease of more than 20% at the end of the experimental period over that at 400 ppm. Furthermore, the survival rate decreased by a greater amount at all concentrations in nauplii than in adults, with a greater effect in wild-collected specimens than in culture-derived individuals. The results suggest that future ocean acidification may negatively influence the sustainability of T. japonicus and thus may eventually influence benthic ecosystems.

過酸化水素の植物プランクトン，ワカメ配偶体，シオダマリミジンコ，タテジマフジツボ幼生に対する影響

Seawater is used as a readily available heat exchange medium in steam condensers and LNG regasifiers in coastal power plants and factories. Hydrogen peroxide is often used as an antifoulant in such systems or as a veterinary product for aquaculture. However, ecotoxicological studies of hydrogen peroxide on a variety of marine organisms, especially for common coastal marine species are insufficient unlike those of chlorine which is another antifoulant. Therefore, we studied the biological effect of hydrogen peroxide on five phytoplanktons (Heterocapsa triquetra, Rhodomonas salina, Tetraselmis sp., Skeletonema marinoi-dohrnii complex and Chaetoceros didymus), seaweed gametophytes (Undaria pinnatifida), and crustacean zooplanktons (marine harpacticoid copepod Tigriopus japonicus and larvae of the barnacle Amphibalanus amphitrite), and compared with that of residual chlorine. Test results indicated that the lowest no observed effect concentrations (NOEC) of hydrogen peroxide and residual chlorine were estimated to be 1.05 mg/L and less than 0.1 mg/L for all the organisms used in this study, respectively. The difference between the NOECs of hydrogen peroxide and residual chlorine was considered to be due to their different action mechanisms.

Production and use of two marine zooplanktons, Tigriopus japonicus and Diaphanosoma celebensis, as live food for red sea bream Pagrus major larvae

We evaluated the effectiveness of two representative marine zooplankton, the harpacticoid copepod Tigriopus japonicus and the euryhaline cladoceran Diaphanosoma celebensis, as live food for red sea bream Pagrus major larvae. Chicken-dropping extract (CDE) was applied to both zooplankton cultures to improve population growth. Population growth of both zooplankton was significantly enhanced by CDE supplementation (at 1 or 2 ml/l). The highest amount of docosahexaenoic acid (DHA) and higher DHA/eicosapentaenoic acid ratio were detected in T. japonicus, whereas D. celebensis showed similar values to that of Artemia. Effectiveness of both animals as live food was tested by rearing red sea bream larvae on them for 28 days and comparing the results with those for Artemia. There were no significant differences in total length (8.6 ± 1.1–8.7 ± 0.7 mm) or wet weight (8.2 ± 0.3–9.4 ± 0.1 mg) among fish larvae feeding on the three different zooplankton. Survival rate was significantly higher with T. japonicus (39.4 ± 3.1 %) than with D. celebensis (20.8 ± 3.8 %) and Artemia (16.7 ± 9.8 %). Viability was significantly higher in fish fed with T. japonicus (60.0 ± 27.8 %) and D. celebensis (60.0 ± 32.2 %) than in those fed with Artemia (44.4 ± 12.3 %). Fish fed with T. japonicus contained higher n-3 highly unsaturated fatty acids than those fed with D. celebensis and Artemia. It is concluded that T. japonicus and D. celebensis have high potential as live food in marine fish larviculture.

BDE-47 causes developmental retardation with down-regulated expression profiles of ecdysteroid signaling pathway-involved nuclear receptor (NR) genes in the copepod Tigriopus japonicus

2,2′,4,4′-Tetrabromodiphenyl ether (BDE-47) is a persistent organic pollutant (POP) in marine environments. Despite its adverse effects (e.g. developmental retardation) in ecdysozoa, the effects of BDE-47 on transcription of ecdysteroid signaling pathway-involved-nuclear receptor (NR) genes and metamorphosis-related genes have not been examined in copepods. To examine the deleterious effect of BDE-47 on copepod molting and metamorphosis, BDE-47 was exposed to the harpacticoid copepod Tigriopus japonicus, followed by monitoring developmental retardation and transcriptional alteration of NR genes. The developmental rate was significantly inhibited (P<0.05) in response to BDE-47 and the agricultural insecticide gamma-hexachlorocyclohexane. Conversely, the ecdysteroid agonist ponasterone A (PoA) led to decreased molting and metamorphosis time (P<0.05) from the nauplius stage to the adult stage. In particular, expression profiles of all NR genes were the highest at naupliar stages 5–6 except for SVP, FTZ-F1, and HR96 genes. Nuclear receptor USP, HR96, and FTZ-F1 genes also showed significant sex differences (P<0.05) in gene expression levels over different developmental stages, indicating that these genes may be involved in vitellogenesis. NR gene expression patterns showed significant decreases (P<0.05) in response to BDE-47 exposure, implying that molting and metamorphosis retardation is likely associated with NR gene expression. In summary, BDE-47 leads to molting and metamorphosis retardation and suppresses transcription of NR genes. This information will be helpful in understanding the molting and metamorphosis delay mechanism in response to BDE-47 exposure.

Pelagic microalgae as suitable diets for the benthic harpacticoid copepod Tigriopus japonicus

It has been reported that certain microal- gae have the ability to cause various negative effects on pelagic calanoid copepods. However, whether such pelagic microalgae have similar negative effects on benthic copepods has had little attention. The results of the present study indicated that both benthic naupliar and copepodite stages of the harpacticoid copepod Tigriopus japonicus could effectively utilize five species of pelagic microalgae to complete their development. The effects of different concentrations of various microalgae species on naupliar survival were significant; however, no significant effects on copepodite survival were detected. When fed with two diatoms Chaetoceros muelleri and Skeletonema costa- tum as well as the dinoflagellate Prorocentrum micans and the chrysophyte Isochrysis galbana at high concentrations (C8.50 lgC ml -1 ), the survival of both naupliar and copepodite stages of T. japonicus was more than 90%. However, when the diatom Nitzschia closteriumf. minutissima was fed at the high concentrations of 8.50 lgC ml -1 , the naupliar sur- vival was 76.3 ± 3.2 %. Interestingly, the negative effects of N. closterium f. minutissima as a diet in the naupliar stage did not affect the survival of the copepodites, which may be explained by increased mobility of copepodites.

Acute and chronic toxicity of polychlorinated biphenyl 126 to Tigriopus japonicus: Effects on survival, growth, reproduction, and intrinsic rate of population growth

The harpacticoid copepod Tigriopus japonicus has a wide geographical distribution and is considered as a suitable model species for the assessment of toxicity of marine pollutants. The aim of the present study was to test the impacts of polychlorinated biphenyl (PCB) 126 (3,3',4,4',5-pentachlorobiphenyl) on the growth, development, and reproduction of T. japonicus in two successive generations. We first quantified the 96-h 50% lethal concentration (2.83 mg/L; all reported concentrations are nominal values), the no-observed-effect concentration (0.6 mg/L), and the lowest-observed-effect concentration (LOEC; 1.2 mg/L) of PCB126 in the nauplii. Nauplii were more sensitive than the adults, which still survived at the highest tested PCB126 concentration (8 mg/L). In the chronic toxicity testing, 10 life history traits were quantified for T. japonicus. No obvious effect on any of these traits was observed in the first generation (F0) at tested concentrations (<100 µg/L) lower than the LOEC. During the second generational life-cycle exposure (F1), however, PCB126 had an obvious toxic effect on the reproduction (>1 µg/L) and growth (>0.1 µg/L). Thus, copepods became more sensitive to PCB126 exposure as generations developed. Among the different traits tested, body size was the most sensitive parameter. Reproduction (fecundity, number of clutches, nauplii/clutch) and intrinsic population growth were also significantly impacted by PCB exposure. The survivorship, sex ratio, hatching time, and development were not affected. Environmental risk assessment of contaminants must therefore be based on a long-term multigenerational exposure to provide a realistic measurement of the influences of pollutants on aquatic life.

Ecotoxicological effects of brine discharge on marine community by seawater desalination

To determine ecotoxicological effects of brine discharge from the desalination plant and the potential tolerance impact associated with various marine communities, marine ecotoxicological assessment was carried out using four phytoplankton species (Skeletonema coastatum, Chlorella vulgaris, Tetraselmis suecica and Isochrysis galbana) and macroalgae (Ulva pertusa) as primary producer, and two zooplankton species (neonate for rotifer Brachinonus plicatilis, adult of harpacticoid copepod Tigriopus japonicus) and one demersal fish (olive flounder, Paralichthys olivaceus) as consumers. Values of 72 h EC50 of population growth inhibition (PGI) for S. costatum, C. vulgaris, T. suecica and I. galbana were estimated as 55.1, 61.7, 56.9 and 42.2 ppt, respectively, and I. galbana was the most sensitive to brine. No significant differences in brine sensitivity were found in the ranges of 30.0–45.0 ppt for S. costatum and T. suecica, and less than 40.0 ppt for I. galbana. Mortality rates of B. plicatilis neonate and a...

Acute toxicities of trace metals and common xenobiotics to the marine copepod Tigriopus japonicus: Evaluation of its use as a benchmark species for routine ecotoxicity tests in Western Pacific coastal regions

Marine copepods have recently been recognized as important organisms in ecotoxicity testing for regulatory purposes. The harpacticoid copepod Tigriopus japonicus has a wide geographical distribution along the coast in the Western Pacific including Japan, South Korea, Taiwan, and Hong Kong. This study evaluated the acute toxicity sensitivity profile of Tigriopus japonicus against 12 common toxic substances including six endocrine disrupting chemicals (EDCs), three biocides and three trace metals. Through standard acute toxicity test procedures, toxicity endpoints LC(50), LC(10), and no observed effect concentration (NOEC) of each chemical were obtained. Although T. japonicus depicted different sensitivities towards different chemicals, a dose-response relationship was consistent in all cases. T. japonicus was particularly sensitive to most of the EDCs, but relatively less sensitive to molinate (a thiocarbate herbicide). Across all tested chemicals, tributyltin (TBT) was the most toxic to the copepod with the LC(50), LC(10), and NOEC of 0.05, 0.03, and 0.02 mg/L, respectively. A comparison made with available data on acute toxicities of these chemicals to other marine copepod species revealed that T. japonicus is generally more sensitive to EDCs and in particular to TBT. We, therefore, strongly advocate that T. japonicus shall be adopted as a benchmark marine species for routine ecotoxicity testing and ecotoxicological studies in Western Pacific coasts.

Analysis of 686 expressed sequence tags (ESTs) from the intertidal harpacticoid copepod Tigriopus japonicus (Crustacea, Copepoda)

The intertidal harpacticoid copepod Tigriopus japonicus is an important species in the study of marine pollution. To facilitate molecular biomonitoring using T. japonicus, we constructed a T. japonicus unidirectional cDNA library using λZAP expression vector, excised to pBluescript vector with the aid of helper phage, and analyzed 686 randomly picked expressed sequence tags (ESTs) from this species. From the 686 ESTs sequenced, we found several functional genes such as vitellin, kinases and potential detoxification-related genes. We are now preparing a T. japonicus cDNA chip for molecular ecotoxicological studies. In this paper, we discuss the potential use of T. japonicus ESTs and their importance in ecotoxicology.

Estrogenic compounds affect development of harpacticoid copepod Tigriopus japonicus

The aim of this investigation was to evaluate the impact of estrogenic compounds on the harpacticoid copepod Tigriopus japonicus after continuous exposure to environmentally relevant concentrations. Natural estrogen (17beta-estradiol), three known estrogenic compounds in vertebrates (bisphenol A, 4-nonylphenol, p-t-octylphenol), and an invertebrate molting hormone (20-hydroxyecdysone) were tested for their effects on development and reproductive characters in two successive generations of T. japonicus. Less than 24-h-old nauplii (parentals) were exposed to four sublethal concentrations of these compounds for 21 d at 25 degrees C. The first brood of nauplii (F1) produced was monitored further under the same culture conditions and exposures to test compounds. Results showed that all estrogenic compounds affected development (both in number of days to reach copepodid stage and sexual maturity) in the parental generation. Similar effects were apparent in the F1; however, fecundity, sex ratio, and survival were not significantly affected, even at concentrations as high as 10 microg/L (nominal concentration). The invertebrate molting hormone 20-hyroxyecdysone had no detectable effect on any of the endpoints tested but gave the lowest 48-h 50% lethal concentration (LC50) value. The results suggest that endocrine disruption could occur in copepods following exposure to environmentally relevant concentrations of estrogenic compounds, especially if they are exposed starting from embryonic development.

Acute toxicity of Bunker A and C refined oils to the marine harpacticoid copepod Tigriopus japonicus mori.

Acute toxicity of Bunker A and C refined oils to the marine harpacticoid copepod Tigriopus japonicus mori.

Identification of sex, age and species-specific proteins on the surface of the harpacticoid copepod Tigriopus japonicus

Behavioral experiments have shown that male copepods of the species Tigriopus japonicus (Nori) can distinguish species, sex, and developmental stage of potential mates using contact chemoreception. Lectin-binding patterns on the body surface of females have indicated that surface-bound glycoproteins may be important signals in mate choice. In the present study, the proteolytic enzyme trypsin was used to cleave surface proteins from females, reducing their attractiveness to males. The protein fragments released were used to make monoclonal antibodies. Three levels of screening were used to identify monoclonal antibodies that recognized proteins involved in mate recognition. One monoclonal antibody bound to the terminal urosome and lateral prosome of CV females, and its binding significantly decreased female attractiveness to males. Western blotting showed that this antibody bound the trypsin-cleaved fragment and proteins of homogenized CV females and virgin adult females, but did not bind proteins of homogenized males, CIII females, or females of T. californicus or T. fulvus. This antibody recognized proteins on the surface of females that may enable males to discriminate conspecifics, sex, and age. It is likely that this molecule has a central role in the evolution of reproductive isolation in this group.