Macrophthalmus Japonicus Research Articles

Characterization and Transcriptional Response of Ecdysone Receptor Gene in the Mud Crab Macrophthalmus japonicus: Effects of Osmotic Stress and Endocrine Disrupting Chemicals

The ecdysone receptor (EcR) induces hormonal pathways by binding ecdysteroids to other nuclear receptors for development, reproduction, and molting processes. To further understand the role of EcR in polluted environments, we characterized EcR and assessed the transcriptional responses of the EcR gene to osmotic stress, and to endocrine disrupting chemicals (EDCs) such as bisphenol A (BPA) and di-(2-ethylhexyl) phthalate (DEHP) in the intertidal mud crab Macrophthalmus japonicus. Phylogenetic analysis showed that the ligand binding domain of M. japonicus EcR formed two different clusters among crab species. Osmotic stress prompted different expression patterns of EcR mRNA in M. japonicus crabs under low and high salinities. BPA exposure induced significant up-regulation of EcR as early as day 1 in M. japonicus gills and hepatopancreas. However, the expression levels of EcR returned to similar, or lower, levels as controls, by days 4 and 7. In contrast, EcR mRNA expression was significantly induced in M. japonicus gills and hepatopancreas exposed to most of the DEHP concentrations over all exposure times. Hepatopancreatic tissue is more sensitive than gill tissue in terms of EcR gene responses to EDCs. Taken together, these results suggest that the role of EcR in endocrine protection may involve different processes according to the type of EDCs and up-regulatory responses of the EcR transcript could be used as an indicator for detecting changes in hormonal systems caused by environmental stressors.

Salinity and bisphenol A alter cellular homeostasis and immune defense by heat shock proteins in the intertidal crab Macrophthalmus japonicus

Heat shock proteins (HSPs) play crucial roles in cellular metabolic processes, as well as in protective immune responses. In this study, we determined the cellular and immune-related functions of HSPs in the intertidal mud crab Macrophthalmus japonicus under osmotic and bisphenol A (BPA) exposure stress. We performed transcriptional profiling of six HSP genes (HSP70, HSP60, HSP90, HSP83, HSP40, and HSP21) in M. japonicus gills and hepatopancreas. Tissue-specific responses were observed as differentially expressed HSP transcripts in M. japonicus. Under osmotic stress, expression levels of HSP70, HSP90 and HSP40 mRNA increased at high salinity (40 psμ), and decreased at low salinity (10 psμ) in M. japonicus gills. In contrast, HSP60 expression was significantly diminished under high salinity, and increased under low salinity. HSP21 was down-regulated under all salinity changes over 1, 4, and 7 days. In the hepatopancreas, under osmotic stress, most HSP transcripts were up-regulated at an early exposure time point (day 1) with subsequent down-regulation (day 7). On day 4, HSP70, HSP60, HSP90 and HSP40 transcript levels increased in M. japonicus, whereas HSP83 and HSP21 transcript levels decreased in the hepatopancreas following most salinity changes. In addition, BPA exposure generally induced HSP responses in the gills. In particular, HSP70 and HSP83 were significantly up-regulated at all concentrations of BPA on days 1 and 4. However, induced responses of HSP transcripts diminished by day 7, except for HSP83 and HSP40. In the hepatopancreas, HSP70 and HSP90 mRNA expression showed significant up-regulation, whereas transcription of HSP60, HSP83, and HSP21 was down-regulated on days 1 and 4. These results suggested that HSPs are differently involved in the molecular adaptation and defense responses of crabs to BPA and osmotic stress.

Feeding behavior of the ocypodid crab Macrophthalmus japonicus and its effects on oxygen-penetration depth and organic-matter removal in intertidal sediments

This study examined the poorly understood feeding behavior of the ocypodid crab Macrophthalmus japonicus in the field to explore its effects on oxygen-penetration depth (OPD) and organic-matter removal from intertidal sediments. An in situ investigation was conducted on an upper mud flat in the mouth of the Han River estuary, on the western coast of Korea. The behavior of M. japonicus and variation in the OPD within its habitat were surveyed and contents of organic materials such as organic carbon (OC), organic nitrogen (ON) and δ15N in its feeding pellets were compared as contrasted with non-feeding sediments during the daytime ebb in summer. We continuously recorded the surface activity of the crab during two main feeding periods and during a resting period, when the crabs remain immobile on the surface. Feeding periods exceeded 1 h; crabs fed on sediments more actively during the first feeding period (45 pseudo-pellets individual−1 h−1) than during the second feeding period (19 pseudo-pellets individual−1 h−1). The feeding period duration increased as body size decreased. Adult crabs devoted more of their time to basking in sunlight to dry their bodies, whereas young crabs spent most of their time feeding. Crab feeding activity on the surface generally enhanced the OPD. Conversely, OPD decreased during basking, when most crabs were immobile. Crab feeding greatly altered sediment geochemistry in the intertidal flat. In feeding pellets, OC and ON concentrations decreased to 55% and 60%, respectively, of those in non-feeding sediments. OC and ON were removed at rates of 1.89 mmol C m−2 h−1 and 0.24 mmol N m−2 h−1, respectively. The removal rate of OC by crab feeding was three-fold higher than that of OC mineralization by diffusive oxygen uptake (average: 0.56 mmol C m−2 d−1) and was comparable with the rate of anaerobic carbon mineralization (1.74–3.83 mmol m−2 h−1) in this region. The increase in the C/N ratio (10.6%–12.5%) and decrease in δ15N (7.21‰–5.99‰) in feeding pellets compared with non-feeding sediments indicate that M. japonicus removed N more selectively to meet requirements. These results imply that in situ crab activity significantly influenced OC and ON cycles; therefore, it is necessary to consider processes such as macroinvertebrate production and consumption when evaluating the purification function of intertidal sediments.

Assessment of CH4 oxidation in macroinvertebrate burrows of tidal flats

In tidal flats that lack plants, methane (CH4) fluxes are both positive (gas emission) and negative (gas “sinking”) in nature. The levels of methanotroph populations significantly affect the extent of CH4 sinking. This preliminary study examined CH4 flux in tidal flats using a circular closed-chamber method to understand the effects of macroinvertebrate burrowing activity. The chamber was deployed over decapods (mud shrimp, Laomedia astacina and crab, Macrophthalmus japonicus) burrows for ~ 2 h, and the CH4 and CO2 concentrations were continuously monitored using a closed, diffuse CH4/CO2 flux meter. We found that Laomedia astacina burrow (which is relatively long) site afforded higher-level CH4 production, likely due to diffusive emission of CH4 in deep-layer sediments. In addition, the large methanotrophic bacteria population found in the burrow wall sediments has CH4 oxidation (consumption) potential. Especially, nitrite-driven anaerobic oxidation of methane (AOM) may occur within burrows. The proposed CH4-oxidation process was supported by the decrease in the δ13C of headspace CO2 during the chamber experiment. Therefore, macroinvertebrate burrows appear to be an important ecosystem environment for controlling atmospheric CH4 over tidal flats.

Tomographic reconstructions of crab burrows from deltaic tidal flat: Contribution to palaeoecology of decapod trace fossils in coastal settings

Trace fossils play an important role in reconstructing palaeoecology and depositional environment. Their palaeoecological implications can be better understood when the trace makers are correctly identified. Neoichnology studies the burrow morphologies, behavioral ecology of modern organisms and their interaction with the environment. Neoichnology is of great significance in linking burrowing behaviors of extant organisms with interpretation of trace fossil palaeoecology. This paper reports a study on burrows produced by the ocypodid crab (Macrophthalmus japonicus De Haan) in the tidal region of the Yellow River Delta using CT scanning techniques. Our results show that M. japonicus produces abundant I-, U-, and Y-shaped burrows in a mudflat of the delta. These domicile structures are similar in morphological characteristics to the trace fossil Psilonichnus, suggesting M. japonicus as its possible additional trace maker. Our study supports the usage of Psilonichnus as a significant palaeoenvironmental indicator for coastal and shelf environments. Furthermore, this study highlights the great potential of applying CT techniques in future ichnological-related studies.

Environmental Pollutants Impair Transcriptional Regulation of the Vitellogenin Gene in the Burrowing Mud Crab (Macrophthalmus Japonicus)

Vitellogenesis is a pivotal reproductive process of the yolk formation in crustaceans. Vitellogenin (VTG) is the precursor of main yolk proteins and synthesized by endogenous estrogens. The intertidal mud crab (Macrophthalmus japonicus) inhabits sediment and is a good indicator for assessing polluted benthic environments. The purpose of this study was to identify potential responses of M. japonicus VTG under environmental stresses caused by chemical pollutants, such as 1, 10, and 30 µg L−1 concentrations in di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA) and irgarol. We characterized the M. japonicus VTG gene and analyzed the transcriptional expression of VTG mRNA in M. japonicus exposed to various chemicals and exposure periods. A phylogenetic analysis revealed that the M. japonicus VTG clustered closely with Eriocheir sinensis (Chinese mitten crab) VTG, in contrast with another clade that included the VTG ortholog of other crabs. The basal level of VTG expression was the highest in the hepatopancreas and ovaries, and tissues. VTG expression significantly increased in the ovaries and hepatopancreas after 24 h exposure to DEHP. Increased responses of VTG transcripts were found in M. japonicus exposed to DEHP and BPA for 96 h; however, VTG expression decreased in both tissues after irgarol exposure. After an exposure of 7 d, VTG expression significantly increased in the ovaries and hepatopancreas for all concentrations of all chemicals. These results suggest that the crustacean embryogenesis and endocrine processes are impaired by the environmental chemical pollutants DEHP, BPA, and irgarol.

Endocrine-disrupting chemicals impair the innate immune prophenoloxidase system in the intertidal mud crab, Macrophthalmus japonicus

Endocrine-disrupting chemicals (EDCs), xenobiotics that interfere with endogenous hormone function, have been studied for their impacts in aquatic environments. However, there is limited information about the potentially hazardous impact of bisphenol A (BPA) and di-(2-ethylhexyl) phthalate (DEHP) on the marine environment. The aim of this study was to investigate the effects of BPA and DEHP on the immune response of the intertidal mud crab, Macrophthalmus japonicus. In order to examine immunological responses involving the prophenoloxidase (proPO) system, mRNA transcript and activity levels of six immune-related genes, including lipopolysaccharide and β-1,3-glucan-binding protein (LGBP), proPO, phenoloxidase (PO), peroxinectin (PE), serine protease inhibitor (Serpin), and trypsin (Tryp), were assessed in M. japonicus hepatopancreas and gills exposed to BPA or DEHP. Expression of immune genes generally decreased in M. japonicus hepatopancreas and gills exposed to all concentrations of BPA by days 4 and 7. However, at day 1, expression of Serpin and Tryp genes was significantly increased in M. japonicus hepatopancreas and gills exposed to BPA. For DEHP exposure, all genes, with the exception of Serpin, were significantly downregulated in M. japonicus gills. In the hepatopancreas, gene expression of PO, proPO, and LGBP increased at day 1, and then decreased by day 7, while mRNA expression of Serpin and Tryp exhibited up-regulation over all exposure periods. In addition, PE gene expression was upregulated in hepatopancreas at day 7 in a dose-dependent manner. Taken together, these results indicated that the crab immune responses were perturbed by exposure to BPA, and, in particular, DEHP.

Copper, zinc, manganese, cadmium and chromium in crabs from the mangrove wetlands in Qi'ao Island, South China: Levels, bioaccumulation and dietary exposure

Abstract Mangrove wetlands are under increasing pollution pressure from human activities due to rapid industrialization and urbanization of coastal regions. Many pollutants such as heavy metals may be accumulated via food chains to hazardous levels which will thus bring potential health issues to humans. In the present study, three species of crabs (Sesarma dehaani, Sesarma plicata, Macrophthalmus japonicus) and associated sediments from three mangrove habitats with different vegetation were collected from the mangrove wetlands in Qi'ao Island, South China to investigate the levels, bioaccumulation and dietary exposure of heavy metals including copper (Cu), zinc (Zn), manganese (Mn), cadmium (Cd) and chromium (Cr). Metal concentrations in sediment samples were 65–91, 212–247, 506–1256, 0.6–1.3, and 8.8–14 mg/kg dry weight for Cu, Zn, Mn, Cd and Cr, respectively. The spatial heterogeneity of these metals in mangrove sediments was observed with a descendant order of metal concentrations as Mn > Zn > Cu > Cr > Cd at each site. Species-specific and tissue-specific accumulation of metals was also found in mangrove crabs, both in the degree of accumulation of particulate metals and the tissues in which they were most abundant. All biota-sediment accumulation factors (BSAF) values >1 for Cd in each crab species suggested that the native mangrove crabs tended to be good tools for the monitoring of Cd pollution in mangrove forests. Results of the estimated daily intake (EDI) and target hazard quotient (THQ) suggested that consumption of the mangrove crabs in Qi'ao Island might subject local residents to potential health risks as far as the metals are concerned.

The first complete mitochondrial genome sequence of the mud crab Macrophthalmus japonicus (arthropoda, decapoda, macrophthalmidae)

Macrophthalmus japonicus is located in the Macrophthalmidae family, but genetic research about the whole mitochondrial genome in Macrophthalmidae family doesn’t exist. Here, we report the first complete mitochondrial genome from M. japonicus, which is composed of 16,170 base pair (bp) containing 13 protein coding genes, 22 transfer RNAs, 2 ribosomal RNAs, and A + T rich region. The overall nucleotide composition of M. japonicus was G + C: 33.6%, A + T: 66.4% with a strong AT bias. The phylogenetic relationship using whole mitochondrial genome showed that M. japonicus was closest with Eriocheir japonica although their respective families are different.

Changes in exoskeleton surface roughness and expression of chitinase genes in mud crab Macrophthalmus japonicus following heavy metal differences of estuary

Risk assessment of heavy metals is important for the health evaluation of inhabiting species in aquatic ecosystem. This study investigated whether chitin exoskeleton of mud crab Macrophthalmus japonicus is affected by heavy metals in estuary sediments in Korea. We compared heavy metal concentrations and analyzed the expression of M. japonicus chitinase genes, which play the crucial role in the formation of chitin exoskeleton. Concentrations of heavy metals were highly observed in crab body inhabiting Hampyeong among estuarine sites. High expressions of chitinase 1 were observed in crab gill and hepatopancreas from Myodo, which is the site with the lowest concentration of heavy metal in crab body. The surface roughness of the exoskeleton decreased with the increased concentration of heavy metals accumulated in the crab body. These results suggest that the total bioconcentration of heavy metals in crabs affected the expression of chitinase genes and changes in the exoskeleton surface roughness.

Insights into Macroinvertebrate burrowing Activity and Methane Flux in Tidal Flats

Kang, J.; Koo, B.J.; Jeong, K.-S.; Woo, H.J.; Seo, J.; Seo, H.-S.; Kim, M.-S., and Kwon, K., 2018. Insights into macroinvertebrate burrowing activity and methane flux in tidal flats. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 681–685. Coconut Creek (Florida), ISSN 0749-0208.The CH4 flux was examined preliminarily in tidal flats using a circular closed-chamber method to understand the effects of macroinvertebrate burrowing activity. The chamber was deployed over decapods (mud shrimp, Laomedia astacina and crab, Macrophthalmus japonicus) burrows for ~ 2 h, and the CH4 and CO2 concentrations were continuously monitored using a closed, diffuse CH4/CO2 flux meter. It founds that Laomedia astacina burrow (which is relatively long) site afforded higher-level CH4 production, likely due to diffusive emission of CH4 in deep-layer sediments. In addition, the proposed CH4-oxidation process (i.e., reverse methanogenesis) was supported by the decrease in the δ13C of headspace CO2 during the chamber experiment. Therefore, macroinvertebrate burrows appear to be an important ecosystem environment for controlling atmospheric CH4 over tidal flats.

The method of habitat assessment for crab-feeding birds on tidal flat by Habitat Suitability Index models for the burrowing crab Macrophthalmus japonicus

The method of habitat assessment for crab-feeding birds on tidal flat by Habitat Suitability Index models for the burrowing crab <i>Macrophthalmus japonicus</i>

Effects of the bioturbating crab &lt;i&gt;Macrophthalmus&lt;/i&gt; &lt;i&gt;japonicus&lt;/i&gt; on abiotic and biotic tidal mudflat characteristics in the Tama River, Tokyo Bay, Japan

Effects of the bioturbating crab &lt;i&gt;Macrophthalmus&lt;/i&gt; &lt;i&gt;japonicus&lt;/i&gt; on abiotic and biotic tidal mudflat characteristics in the Tama River, Tokyo Bay, Japan

Changes of exoskeleton surface roughness and expression of crucial participation genes for chitin formation and digestion in the mud crab (Macrophthalmus japonicus) following the antifouling biocide irgarol

Irgarol is a common antifoulant present in coastal sediment. The mud crab Macrophthalmus japonicus is one of the most abundant of the macrobenthos in the costal environment, and its exoskeleton has a protective function against various environmental threats. We evaluated the effects of irgarol toxicity on the exoskeleton of M. japonicus, which is the outer layer facing the environment. We analyzed transcriptional expression of exoskeleton, molting, and proteolysis-related genes in the gill and hepatopancreas of these exposed M. japonicus. In addition, changes in survival and exoskeleton surface characteristics were investigated. In the hepatopancreas, mRNA expression of chitinase 1 (Mj-chi1), chitinase 4 (Mj-chi4), and chitinase 5 (Mj-chi5) increased in M. japonicus exposed to all concentrations of irgarol. Mj-chi1 and Mj-chi4 expressions from 1 to 10μgL−1 were dose- and time-dependent. Ecdysteroid receptor (Mj-EcR), trypsin (Mj-Tryp), and serine proteinase (Mj-SP) in the hepatopancreas were upregulated in response to different exposure levels of irgarol at day 1, 4, or 7. In contrast, gill Mj-chi5, Mj-Tryp, and Mj-SP exhibited late upregulated responses to 10μgL−1 irgarol compared to the control at day 7. Mj-chi1 showed early upregulation upon exposure to 10μgL−1 irgarol and Mj-chi4 showed no changes in transcription in the gill. Gill Mj-EcR presented generally downregulated expression patterns. In addition, decreased survival and change of exoskeleton surface roughness were observed in M. japonicus exposed to the three concentrations of irgarol. These results suggest that exposure to irgarol induces changes in the exoskeleton, molting, and proteolysis metabolism of M. japonicus.

Identification and expression of proteolysis-response genes forMacrophthalmus japonicusexposure to irgarol toxicity

Macrophthalmus japonicus is one of the most abundant macrobenthic animals in estuarine zone, which are transition areas between freshwater and marine environments. The crabs are potential bio-indicators reflecting aquatic sediment toxicity. So far, limited genetic research has focused on this group of animals largely due to the limited genomic information. In this study, we performed de novo transcriptome sequencing to produce the most comprehensive expressed sequence tag resource for M. japonicus , and identified stress response genes in M. japonicus exposed to antifouling biocides irgarol. Using 454 pyrosequencing, a total of 887 690 reads were obtained, which were assembled into 24 217 high-quality expressed sequence tags. These contigs were then clustered into 17 289 isotigs and further grouped into 12 923 isogroups. About 48% of the isogroups showed significant matches to known proteins based on sequence similarity. Moreover, irgarol toxicity induced up-regulation of stress response genes, associated with proteolysis and oxidation–reduction in biological process by Gene ontology analyses. Our data provide the most comprehensive transcriptome resource available for M. japonicus . This resource allowed us to identify genes associated with proteolysis processes, which facilitated the quantitative analysis of differential gene expression respond to irgarol toxicity. These data would provide foundation for future genetic and genomic studies of crustacean species and monitoring to freshwater as well as marine ecosystems.

Antioxidative-related genes expression following perfluorooctane sulfonate (PFOS) exposure in the intertidal mud crab, Macrophthalmus japonicus

Perfluorooctane sulfonate (PFOS) is a persistent environmental contaminant that is used as a surfactant in various industries and consumer products. The intertidal mud crab, Macrophthalmus japonicus, is one of the most abundant macrobenthic creatures. In this study, we have investigated the effect of PFOS on the molecular transcription of antioxidant and detoxification signaling in M. japonicus crab. The selected stress response genes were superoxide dismutases (CuZnSOD and MnSOD), catalase (CAT), glutathione peroxidase (GPx), phospholipid hydroperoxide glutathione peroxidase (PHGPx), peroxiredoxin (Prx), and thioredoxin reductase (TrxR). Significant up-regulation of SODs and CAT was observed after 24 and 96 h exposure to PFOS at different concentrations. The gene expression levels of GPx, PHGPx, and TrXR were significantly up-regulated after exposure to PFOS for 96 h. The transcript levels of CAT and PHGPx were induced in dose- and time-dependent manners after PFOS treatments. However, Prx gene expression was significantly up-regulated in M. japonicus crabs exposed to 10 and 30 μg L-1 PFOS for 96 h. Additionally, PFOS toxicity in M. japonicus induced reduced survival rates at relatively high concentrations of PFOS exposure. Our findings support the contention that exposures to PFOS induced the response of genes related to oxidative stress and detoxification in M. japonicus crabs.

Chitinase gene responses and tissue sensitivity in an intertidal mud crab (Macrophthalmus japonicus) following low or high salinity stress

Changes in salinity affect the physiological status of the marine habitat including that of the intertidal mud crab Macrophthalmus japonicus. Chitinases play significant biological roles in crustaceans such as morphogenesis, nutrient digestion, and pathogen defense. In this study, the osmoregulatory function of three chitinase gene transcripts was determined compared to seawater (SW, 31 ± 1psu) in M. japonicus gills and hepatopancreas under different salinities (10, 25, and 40psu) for 1, 4, and 7days. In SW-exposed crab, quantitative real-time PCR analysis showed chitinase 1 (Mj-chi1) and chitinase 4 (Mj-chi4) transcripts constitutively expressed in all the tested tissues with strong expression in hepatopancreas, but chitinase 5 (Mj-chi5) showed highest expression in stomach. When exposed to different salinities, Mj-chi1 showed significant up-regulation at day 4 whereas Mj-chi4 showed late up-regulation (day 7) at all the salinities in hepatopancreas. In the gills, early up-regulation (day 1) in Mj-chi1 and time-dependent late up-regulation (day 7) in Mj-chi4 at high salinity were observed. These results indicate the possibility of using Mj-chi4 as a marker against salinity changes. Moreover, our results further suggest that Mj-chi1 and Mj-chi4 transcriptions were significantly affected by changes in salinity; however, Mj-chi5 in gills was less affected by salinity and showed no effect in hepatopancreas. Thus, chitinase transcription modulations in the gills are more sensitive than hepatopancreas to salinity stress. Further, present data indicate the possible existence of different physiological roles among chitinase gene families, which need to be clarified in more detail by future biochemical and physiological functional studies.

PFOS (perfluorooctane sulfonate) 노출에 따른 조간대 칠게(Macrophthalmus japonicus)의 생태독성학적 판정점 제시

PFOS (perfluorooctane sulfonate) 노출에 따른 조간대 칠게(Macrophthalmus japonicus)의 생태독성학적 판정점 제시

Modeling Intertidal Crab Distribution Patterns Using Photographic Mapping Among Tropical Australian Estuaries

Intertidal crabs are abundant in tropical estuaries and have bio-indicator potential. However, the use of intertidal crabs in guiding management actions is limited because high-replication, cost-effective tools to analyze their distribution patterns at large scales are lacking. This study used assemblage modeling and photography to rapidly build formal understanding of the spatial organization of crab communities in the low intertidal zone, between mean sea level at low spring tide and the edge of the mangrove forest, within and among estuaries. A classification and regression tree model revealed seven distinct habitats based on relative occurrence of five species (Uca coarctata, Uca seismella, Macrophthalmus japonicus, Metopograpsus frontalis, and Metopograpsus latifrons) among eight estuaries along 160 km of coast in North Queensland, Australia (18° 28′–19° 25′ S, 146° 12′–147° 14′ E), across four sampling trips between April 2009 and October 2010. Photography provided high-replication sampling across a large area relative to the aim of the study but did not represent the whole intertidal crab community. Complementary hand collections within one estuary allowed the occurrences of three other species (Perisesarma longicristatum, Australoplax tridentata, and Metopograpsus thukuhar) to be fitted into the model. Species occurred across habitats, yet a high occurrence of different species characterized each habitat. The presence of some species not usually found on low intertidal banks suggested connectivity across the intertidal landscape. The model provided a formal basis to add previous small “site or transect specific” scale spatial distribution knowledge as well as other ecological information. Areas with outlying values can be identified as research and management priorities in the absence of other information, although this prioritization should be done with care. The approach may be transferable to other organisms and systems to provide rapid, cost-effective information on the distribution of key fauna where background understanding and resources are limited.

Identification of potential markers and sensitive tissues for low or high salinity stress in an intertidal mud crab (Macrophthalmus japonicus)

Macrophthalmus japonicus is an intertidal mud crab is an ecologically important species in Korea, can tolerate a wide range of natural and anthropogenic stressors. Environmental changes especially salinity cause physiological stress to the marine habitats. Differential gene transcription of M. japonicus tissues provided information about tissue specific responses against salinity. Five potential genes were identified and their transcription levels were determined quantitatively comparison to seawater (SW: 31 ± 1 psu) in M. japonicus gills and hepatopancreas after exposed them to different salinities. Ecdysteroid receptor (Mj-EcR), trypsin (Mj-Tryp), arginine kinase (Mj-AK), lipopolysaccharide and β-1,3-glucan binding protein (Mj-LGBP) and peroxinectin (Mj-Prx) in hepatopancreas up-regulated against different salinities. In contrast, the gills, Mj-EcR, Mj-Tryp and Mj-AK showed late up-regulated responses to 40 psu compared to SW. All genes except Mj-LGBP showed up regulation in the gills as time dependent manner. These genes can be considered as potential markers to assess responses in salinity changes. This study suggests hepatopancreas is a suitable tissue for transcriptional, biochemical and physiological responses analysis on M. japonicus in low and high salinity stress.