Macrophthalmus Japonicus Research Articles

Expressions of Immune Prophenoloxidase (proPO) System-Related Genes Under Oxidative Stress in the Gonads and Stomach of the Mud Crab (Macrophthalmus japonicus) Exposed to Endocrine-Disrupting Chemicals

Expressions of Immune Prophenoloxidase (proPO) System-Related Genes Under Oxidative Stress in the Gonads and Stomach of the Mud Crab (Macrophthalmus japonicus) Exposed to Endocrine-Disrupting Chemicals

Effect of endocrine-disrupting chemicals on the expression of a calcium ion channel receptor (ryanodine receptor) in the mud crab (Macrophthalmus japonicus)

Endocrine-disrupting chemicals (EDCs) are toxic pollutants generated by artificial activities. Moreover, their hormone-like structure induces disturbances, such as mimicking or blocking metabolic activity. Previous studies on EDCs have focused on the adverse effect of the endocrine system in vertebrates, with limited investigations conducted on ion channels in invertebrates. Thus, in this study, we investigated the potential adverse effects of exposure to bisphenol-A (BPA) and di-(2-ethylhexyl) phthalate (DEHP) at the molecular level on the ryanodine receptor (RyR), a calcium ion channel receptor in Macrophthalmus japonicus. In the phylogenetic analysis, the RyR amino acid sequences in M. japonicus clustered with those in the Crustacean and formed separated branches for RyR in insects and mammals. When exposed to 1 μg L−1 BPA, a significant increase in RyR mRNA expression was observed in the gills on day 1, although a similar level to the control group was observed from day 4 to day 7. However, the RyR expression due to DEHP exposure decreased on days 1 and 4, although it increased on day 7 following exposure to 10 μg L−1. The RyR expression pattern in the hepatopancreas increased for up to 4 days, depending on the BPA concentration. However, there was a tendency for the expression to decrease gradually after the statistical significance increased during the early stage of DEHP exposure (D1). Hence, the transcriptional alterations in the M. japonicus RyR gene observed in the study suggest that exposure toxicities to EDCs, such as BPA and DEHP, have the potential to disrupt calcium ion channel signaling in the gills and hepatopancreas of M. japonicus crabs.

Modulating responses of indicator genes in cellular homeostasis, immune defense and apoptotic process in the Macrophthalmus japonicus exposed to di(2-ethylhexyl) phthalate as a plastic additive

Di(2-ethylhexyl) phthalate (DEHP), have been increasingly used as plasticizers to manufacture soft and flexible materials and ubiquitously found in water and sediments in the aquatic ecosystem. The aim of the present study was to evaluate the effect of DEHP exposure on cellular homeostasis (HSF1 and seven HSPs), immune responses (ILF), and apoptotic responses (p53, BAX, Bcl-2). DEHP exposure upregulated the expression of HSF1 and ILF. Moreover, it altered the expression levels of HSPs (upregulation of HSP70, HSP90, HSP40, HSP83, and HSP67B2 and downregulation of HSP60 and HSP21) in conjunction with HSF1 and ILF in the gills and hepatopancreas of M. japonicus exposed to DEHP. At the protein level, DEHP exposure changed apoptotic signals in both tissues of M. japonicus. These findings indicate that chronic exposures to several DEHP concentrations could disturb cellular balance, damage the inflammatory and immune systems, and induce apoptotic cell death, thereby affecting the survival of M. japonicus.

Growth characteristics and population dynamics of Macrophthalmus japonicus with decreasing microphytobenthos biomass in muddy estuarine tidal flat

The present study evaluated the population dynamics, growth, and biomass production of the ocypodid crab Macrophthalmus japonicus in muddy estuarine tidal flat through monthly surveys over a 10-year period. The mean annual biomass was 4.71–11.51 (7.9±2.5) g dry·m−2, and secondary production was 2.1–19.3 g dry·m−2·year−1 (11.3±5.3 g dry·m−2·year−1) and 1.59–6.16 (3.71±1.55) g C·m−2·year−1. Two to three cohorts of M. japonicus were observed in each year, with the population density of 10–61 individuals·m−2. New recruitment was noted around August in the summer of each year, with an estimated lifespan of 2–3 years. The production/biomass ratio was 0.46–2.02 (1.38±0.44). The population density of M. japonicus showed stable seasonal variations, while annual growth, production, and biomass decreased over the years. M. japonicus growth was associated with microphytobenthos biomass. In particular, long-term field investigations revealed the association between M. japonicus and microphytobenthos, suggesting that the feeding pressure of M. japonicus affected microphytobenthos biomass. Our findings will contribute to the better understanding of the growth characteristics and population dynamics of M. japonicus as well as the interactions between prey and predators in benthic tidal flat ecosystems, providing fundamental information for estimating material cycles.

The crab Macrophthalmus japonicus burrows on a tidal flat of the Yellow River Delta in China: Their 3D morphological variability in relation to physicochemical conditions and palaeoichnological perspective

Several environmental parameters, sediment grain size and its total organic carbon (TOC) content, turbidity and salinity of water, have been measured, and burrows of the crab Macrophthalmus japonicus were studied by high-resolution CT imaging of sediment cores sampled at 32 stations along transects from supratidal to subtidal settings of the Yellow River Delta in China. The burrows are present only at some stations in muddy and sandy-silty sediments. They are concentrated in some patchy areas affected by low hydrodynamic conditions and high food abundance near a muddy tidal creek, exposed to slightly higher energy close to creeks, or far from tidal creeks. However, they are absent in other places with similar organic matter content and/or distance from tidal creeks, irrelevant to salinity, turbidity, and substrate consistency. The distribution and morphology of the burrows cannot be correlated with simple environmental parameters. Possibly, the crabs created their own environment the best suitable for their life. The burrows are unlined and show I-, J-, L-, U- and Y-shape resembling the small version of the trace fossil Psilonichnus, the Y-shaped Polykladichus, the U-shaped Arenicolites, whereas the complex, shallow M. japonicus burrows are similar to Pholeus bifurcatus, and the multi-branched, mostly inclined galleries superficially to Thalassinoides paradoxicus. These analogical trace fossils, although in the sediment record ascribed to occur in different ichnofacies and to have been probably produced by various animals, may occur together in the studied deposits wherein they have been produced by the same animal in the same habitat.

Sediment temperature characteristics and their relation to distribution patterns of two sentinel crab species in intertidal flats in western Japan

In the context of global climate change, monitoring focused on temperature and benthic animals in intertidal flats and the development of metrics to assess climate change and ecosystem responses are essential for a sustainable society. However, few studies have assessed the relationship between intertidal sediment temperature and the distribution of benthic animals. To address this gap, in the present study, intertidal sediment temperatures were observed in 12 intertidal flats in 11 survey areas over 335 days, from October 2, 2019, to August 31, 2020, using water temperature data loggers. The characteristics of intertidal sediment temperatures were variable among the survey areas, and a correlation analysis suggested that such characteristics are possibly influenced by various spatial-scale factors, such as geographical, basin, and habitat scales. Furthermore, two sentinel crab species, Macrophthalmus japonicus and Macrophthalmus banzai were collected, and the number of wintering individuals of each species was estimated based on their carapace width to analyze the changes in abundances of the two species in each survey area. The results show that the number of days with daily minimum temperature ≥ 19 °C was the factor that influenced the abundance rate, suggesting that M. japonicus and M. banzai populations may decrease and increase, respectively, according to future climate change in Japan. Our findings emphasize the importance of long-term monitoring of sediment temperatures and benthic animals in intertidal flats to evaluate the influence of future climate change.

Responses of multifunctional immune complement component 1q (C1q) and apoptosis-related genes in Macrophthalmus japonicus tissues and human cells following exposure to environmental pollutants.

Apoptosis is a key defense process for multiple immune system functions, playing a central role in maintaining homeostasis and cell development. The purpose of this study was to evaluate the effects of environmental pollutant exposure on immune-related apoptotic pathways in crab tissues and human cells. To do this, we characterized the multifunctional immune complement component 1q (C1q) gene and analyzed C1q expression in Macrophthalmus japonicus crabs after exposure to di(2-ethylhexyl) phthalate (DEHP) or hexabromocyclododecanes (HBCDs). Moreover, the responses of apoptotic signal-related genes were observed in M. japonicus tissues and human cell lines (HEK293T and HCT116). C1q gene expression was downregulated in the gills and hepatopancreas of M. japonicus after exposure to DEHP or HBCD. Pollutant exposure also increased antioxidant enzyme activities and altered transcription of 15 apoptotic signaling genes in M. japonicus. However, patterns in apoptotic signaling in response to these pollutants differed in human cells. HBCD exposure generated an apoptotic signal (cleaved caspase-3) and inhibited cell growth in both cell lines, whereas DEHP exposure did not produce such a response. These results suggest that exposure to environmental pollutants induced different levels of immune-related apoptosis depending on the cell or tissue type and that this induction of apoptotic signaling may trigger an initiation of carcinogenesis in M. japonicus and in humans as consumers.

Estimating the amount of food ingested by the ocypodid crab Macrophthalmus japonicus via feeding pellets

This study aimed to estimate the amount of food ingested by the ocypodid crab Macrophthalmus japonicus using the number of feeding pellets produced. The amount of food ingested by the ocypodid crab has not been confirmed because of its characteristic of producing pseudofeces, such as feeding pellets. We measured the gut content turnover rate, rate of feeding pellets, actual number of feeding pellets produced, and crab behavior using a video recorder during emersion at the Katsuura River muddy tidal flat, Japan. The pellet production rate increased with increasing soil temperatures. M. japonicus did not constantly feed during emersion, and the feeding percentage did not increase, even during longer emergence times. The number of feeding pellets had a significant positive correlation with emergence time and soil temperature. Neither the production rate nor the number of feeding pellets produced was influenced by crab size. The amount of food ingested by M. japonicus was estimated based on soil temperature, carapace width, and emersion time. The amount of food ingested by M.japonicus could be estimated using three simple on-field parameters. This study contributes to a better understanding of the material cycle in tidal flat ecosystems and provides important parameters for estimating the amount of food ingested by ocypodid crabs in tidal flats.

Genetically isolated population of the coastal species with high dispersal potential: the case of the sentinel crab <i>Macrophthalmus japonicus</i> (Brachyura: Macrophthalmidae) in Japan

Genetic homogeneity among populations of marine organisms with high dispersal potential is maintained by high gene flow whereas genetic differentiation is often formed under the presence of dispersal barriers. One of the possible dispersal barriers for intertidal species in Japan is the Sea of Japan because several tidal-flat species are absent in the region due to the small tidal range. In this study, we aimed to validate this possibility by examining the population genetic structure of the intertidal crab Macrophthalmus japonicus, which possesses a long planktonic larval period indicating high dispersal potential but is absent on the Sea of Japan side in Honshu Island. In total, 83 haplotypes of the mitochondrial cytochrome c oxidase subunit I were recovered from 154 specimens collected from 10 Japanese sampling sites and three GenBank sequences from China and Korea. All populations showed high genetic diversity except for the northernmost population at Asadokoro site in Mutsu Bay. The ΦST values among populations were low, even between populations with great distances such as the Pacific side of northeastern Honshu and Kyushu Islands (ca. 1500 km). On the other hand, the ΦST values between Asadokoro site and the other Japan sites were high. The isolation of the northernmost population despite the high dispersal potential of M. japonicus is probably because of the absence of neighboring populations that can supply larvae to the northernmost population and the invasion of larvae from the Pacific side is blocked by ocean currents.

First record of <i>Macrophthalmus japonicus</i> (De Haan, 1835) (Brachyura: Macrophthalmidae) population from the Pacific coast of Iwate Prefecture, northern Japan

The tidal flats at Otomo-ura (Iwate Prefecture), which had been converted to farmland through a reclamation project from 1959 to 1969, have been partially restored after the tsunami caused by the Great East Japan Earthquake in 2011. In the course of monitoring the benthic fauna of the tidal flats for 11 years after the tsunami, we found some adult sentinel crabs of the genus Macrophthalmus at a muddy area for the first time on July 28, 2022. During subsequent observations of the mud flat, we noted that the adult male crabs exhibited waving display of vertical non-forward-pointing type. Allocleaning, performed by both sexes, was also observed. Morphological characters include: the carpus and propodus of the ambulatory leg 3 of the adult male are not associated with tuft of setae on their ventral surfaces, and the subdistal tooth of leg 3 is not distinct. Based on these behavioral and morphological characteristics, the macrophthalmid crab was identified as Macrophthalmus japonicus. This is the first record of this species along the coast of Iwate Prefecture. In addition, five of six females captured on July 28 and August 14, 2022, were ovigerous (range in carapace width: 19.1–25.0 mm), which indicates that the crabs are reproducing on the tidal flat.

Quantitative comparison of clamworm (Perinereis aibuhitensis) and crab (Macrophthalmus japonicus) burrowing effects on nitrogen and phosphorus dynamics at the sediment–water interface

Exploring nitrogen and phosphorus dynamics in estuarine ecosystems is of great significance for understanding the nutrient cycle in terrestrial and marine ecosystems. However, the ecological functions of common species remain unclear because there is a dearth of observational data. To quantitatively compare the bioturbation effects of the clamworm Perinereis aibuhitensis and crab Macrophthalmus japonicus on the migration of nitrogen and phosphorus in the sediment–pore water–overlying water interfaces, an indoor experiment was carried out using microcosms containing substrate, water, and living specimens collected from the Dagu Estuary, China. The physical structure of the sediments was greatly altered by both clamworms and crabs, and the amount of suspended particulate matter in the overlying water was in the order: crab > clamworm > control groups. Sediments, especially the 0–2 cm layer, were continuously mineralized under bioturbation, releasing NH3-N, NO2−-N, NO3−-N, and dissolved total phosphorus. During the experiment, the release rate of NH3-N (2.45 mg L−1 to 10.23 mg L−1), NO2−-N (0.25 mg L−1 to 7.34 mg L−1), NO3−-N (0.02 mg L−1 to 6.03 mg L−1), and dissolved total phosphorus (0.07 mg L−1 to 0.16 mg L−1) in the crab group was higher than that in the clamworm group (NH3-N, 0.93 mg L−1 to 6.11 mg L−1; NO2−-N, 0.51 mg L−1 to 6.18 mg L−1; NO3−-N, 0.01 mg L−1 to 5.24 mg L−1, and dissolved total P, 0.04 mg L−1 to 0.08 mg L−1). Our findings indicate that crabs might play a more important role in promoting nitrogen and phosphorus migration than clamworms because of their stronger bioturbation strategies in sediments. Bioturbation by both clamworms and crabs reduced nitrogen and phosphorus accumulation in surface sediments and accelerated organic matter mineralization in the sediments, which may promote nutrient recycling in estuarine ecosystems.

Comparison of the sensitivities of crustacean species to recombinant Photorhabdus insect-related (Pir) toxins of acute hepatopancreatic necrosis disease-causing Vibrio parahaemolyticus

Abstract Photorhabdus insect-related PirAvp (where vp stands for Vibrio parahaemolyticus) and PirBvp of Vibrio parahaemolyticus were expressed in Escherichia coli, designated rPirAvp and rPirBvp, respectively, then tested on 4 crustaceans via immersion tests. PirBvp toxin was detected from 2 h after incubation and accumulated with bacterial growth. The culture filtrate of 15 nM PirBvp toxin caused 100% mortality of Litopenaeus vannamei within 4 days after immersion. Litopenaeus vannamei showed 100% mortality at 7 days after immersion in purified 4 nM rPirAvp, rPirBvp, or rPirAvp + rPirBvp mixture. The cumulative mortalities in the rPirAvp, rPirBvp or rPirAvp + rPirBvp mixture were 50, 83 and 100% in Macrobrachium rosenbergii after 12 days of immersion, 11, 77 and 100% in Palaemon paucidens after 10 days of immersion, and 36, 96 and 100% in Macrophthalmus japonicus after 6 days of immersion, respectively.

Apoptotic p53 Gene Expression in the Regulation of Persistent Organic Pollutant (POP)-Induced Oxidative Stress in the Intertidal Crab Macrophthalmusjaponicus.

Persistent organic pollutants (POPs), some of the most dangerous chemicals released into the aquatic environment, are distributed worldwide due to their environmental persistence and bioaccumulation. In the study, we investigated p53-related apoptotic responses to POPs such as hexabromocyclododecanes (HBCDs) or 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in the mud crab Macrophthalmus japonicus. To do so, we characterized M. japonicus p53 and evaluated basal levels of p53 expression in different tissues. M. japonicus p53 has conserved amino acid residues involving sites for protein dimerization and DNA and zinc binding. In phylogenetic analysis, the homology of the deduced p53 amino acid sequence was not high (67–70%) among crabs, although M. japonicus p53 formed a cluster with one clade with p53 homologs from other crabs. Tissue distribution patterns revealed that the highest expression of p53 mRNA transcripts was in the hepatopancreas of M. japonicus crabs. Exposure to POPs induced antioxidant defenses to modulate oxidative stress through the upregulation of catalase expression. Furthermore, p53 expression was generally upregulated in the hepatopancreas and gills of M. japonicus after exposure to most concentrations of HBCD or BDE-47 for all exposure periods. In hepatopancreas tissue, significant increases in p53 transcript levels were observed as long-lasting apoptotic responses involving cellular defenses until day 7 of relative long-term exposure. The findings in this study suggest that exposure to POPs such as HBCD or BDE-47 may trigger the induction of cellular defense processes against oxidative stress, including DNA repair, cell cycle arrest, and apoptosis through the transcriptional upregulation of p53 expression in M. japonicus.

Integrated analysis of exoskeletal surface profile and chitin-related gene expression on Macrophthalmus japonicus mud crabs exposed to hexabromocyclododecane

Hexabromocyclododecanes (HBCDs), widely used brominated flame retardants, easily accumulate in aquatic organisms such as Macrophthalmus japonicus crabs, which inhabit tidal flat sediments. To analyze the effects of HBCD exposure in chitin-formed exoskeleton, we investigated molecular responses of chitin-related genes as well as physical changes of the exoskeletal surface form as a new biological end-point on M. japonicus. The expression patterns of chitin biosynthesis-, modification-, and degradation-related genes in the gills and hepatopancreases of M. japonicus were also analyzed. Additionally, the survivability and exoskeleton surface profiles of M. japonicus crabs were evaluated. M. japonicus chitin synthase expression was significantly downregulated, whereas that of the chitinase transcript was significantly upregulated upon exposure to all HBCD concentrations on day 7. Contrastingly, the gene expression of chitin deacetylase 1 significantly increased upon exposure to all HBCD concentrations on day 1, and this increase was significantly elevated on day 4. The expression of chitin deacetylase 1 was dose-dependent. Additionally, decreased survival and exoskeleton surface profile changes were observed in M. japonicus crabs exposed to all HBCD concentrations. These results suggest that exposure to HBCD induces changes in the synthesis, modification, and degradation of chitin, a pivotal component of the cuticular exoskeleton, and may disrupt the exoskeletal surface structure in M. japonicus crabs.

EDCs trigger immune-neurotransmitter related gene expression, and cause histological damage in sensitive mud crab Macrophthalmus japonicus gills and hepatopancreas

Endocrine-disrupting chemicals (EDCs), distributed at various concentrations in freshwater and marine ecosystems, affect the survival, reproduction, and behavior of wide ranges organisms. Most toxicology studies on EDCs have focused on the endocrine system of invertebrates, and research on invertebrate neurotransmitters is limited. In the present study, we investigated the expression of Macrophthalmus japonicus genes encoding γ-aminobutyric acid transporter subtype 2 (GAT-2) and glutamine synthetase (GS), which play important roles as neurotransmitters at synapses. We observed differences in the mRNA expression levels of GAT-2 and GS as well as histological changes in various tissues after exposure to bisphenol-A (BPA) and di-(2-ethylhexyl) phthalate (DEHP). The amino acid sequences of M. japonicus GAT-2 and GS formed separate branches in crustaceans, fish, insects, and mammals. M. japonicus GAT-2 and GS expression levels were highest in the gills, hepatopancreas, and stomach, and showed different between DEHP or BPA treatments. In particular, hepatopancreas GS expression on Day 1, the first step in the presynaptic process, was upregulated after BPA and DEHP exposure, while GAT-2, sequential step in the presynaptic process, was significantly elevated only in DEHP. After BPA treatments, gill GS expression was increased at all concentrations, whereas GAT-2 expression was overall down regulations. In contrast, in DEHP treatment groups hepatopancreatic GS and GAT-2 expression at Day 1 was only significantly higher and all groups including gill GS and GAT-2 expression were downregulation. Histological changes in the gills and hepatopancreas were observed in a concentration-dependent manner. Accordingly, BPA and DEHP exposure in crabs could be stimulate neurotransmitter gene expression and alter the morphological structure of gill and hepatopancreas.

Dynamics of organic carbon under bioturbation by mud crabs (Macrophthalmus japonicus) and clamworms (Perinereis aibuhitensis) in an estuary ecosystem

Understanding of the dynamic characteristics of organic carbon in estuary ecosystem is of great significance for the carbon cycle in terrestrial and marine ecosystems. In order to quantify effects of the clamworm (Perinereis aibuhitensis) and mud crab (Macrophthalmus japonicus) on the migration of organic carbon, an indoor experiment was carried out by using a microcosm system with in-situ substrate, water and living specimen from Dagu estuary, China. The results showed that macrobenthos accelerated the release of organic carbon from sediment into water body, which increased the concentration of dissolved organic carbon (DOC) in pore water and the DOC fluxes across the sediment-water interface. Crab promoted more DOC efflux in the early experiment while the contribution of the clamworm was greater in the later experiment. In addition, macrobenthos stimulated the release of colored dissolved organic matter (CDOM) into overlying water, especially humic-like substance. The content of CDOM of the clamworm and crab groups was always higher than that of the control group, and the humic-like peak A fluorescence intensity continued to increase and red shift occurred. In conclusion, the clamworm and crab accelerated the mineralization of organic matter in sediment and promoted the release of organic carbon, which may affect the carbon cycle in the estuary and change the income and expenditure characteristics of the organic carbon.

Hemolymph composition, gene expressions in the gills, and thus the survival of euryhaline crabs are controlled by ambient minor cations according to osmotic condition-dependent manner.

Na+ and Cl− are the most abundant dissolved ions in seawater, constituting ~ 85% of total ions. They significantly affect the osmolality of body fluids of marine invertebrates. Seawater also contains minor ions such as Mg2+, Ca2+, K+, and SO4 2‐ , but their effects on marine organisms are unclear. This study analyzed the effects of Mg2+, Ca2+, and K+ (ambient minor cations) on survival, hemolymph ionic composition, and gene expression in the gills of three euryhaline crabs: Helice tridens, Macrophthalmus japonicus, and Chiromantes dehaani. Ambient minor cations were required for survival of H. tridens and M. japonicus under isosmotic conditions with seawater. The ambient minor cations also affected the osmolality and ionic composition of hemolymph by regulating expressions of specific genes in the gills required for Na+ uptake, such as Na+/K+ ATPase, cytoplasmic carbonic anhydrase, and Na+/H+ exchanger. Administration of carbonic anhydrase and Na+/H+ exchanger inhibitors increased the survival rate even if ambient minor cations did not exist. In contrast, under hypo‐osmotic conditions, ambient minor cations had different effects on crabs, a lethal effect on M. japonicus, and an increase of the hemolymph K+ concentration in H. tridens and M. japonicus. It is thus concluded that the effects of ambient minor cations are osmolality‐dependent. In contrast, in C. dehaani, the hemolymph ionic composition and survival rate were hardly affected by ambient minor cations, probably reflecting the habitat of this species. These results strongly indicated that C. dehaani is less susceptive to ambient minor cations compared to H. tridens and M. japonicus.

Expression Levels of the Immune-Related p38 Mitogen-Activated Protein Kinase Transcript in Response to Environmental Pollutants on Macrophthalmus japonicus Crab.

Environmental pollution in the aquatic environment poses a threat to the immune system of benthic organisms. The Macrophthalmus japonicus crab, which inhabits tidal flat sediments, is a marine invertebrate that provides nutrient and organic matter cycling as a means of purification. Here, we characterized the M. japonicus p38 mitogen-activated protein kinase (MAPK) gene, which plays key roles in the regulation of cellular immune and apoptosis responses. M. japonicus p38 MAPK displayed the characteristics of the conserved MAPK family with Thr-Gly-Tyr (TGY) motif and substrate-binding site Ala-Thr-Arg-Trp (ATRW). The amino acid sequence of the M. japonicus p38 MAPK showed a close phylogenetic relationship to Eriocheir sinensis MAPK14 and Scylla paramamosain p38 MAPK. The phylogenetic tree displayed two origins of p38 MAPK: crustacean and insect. The tissue distribution patterns showed the highest expression in the gills and hepatopancreas of M. japonicus crab. In addition, p38 MAPK expression in M. japonicus gills and hepatopancreas was evaluated after exposure to environmental pollutants such as perfluorooctane sulfonate (PFOS), irgarol, di(2-ethylhexyl) phthalate (DEHP), and bisphenol A (BPA). In the gills, p38 MAPK expression significantly increased after exposure to all concentrations of the chemicals on day 7. However, on day 1, there were increased p38 MAPK responses observed after PFOS and irgarol exposure, whereas decreased p38 MAPK responses were observed after DEHP and BPA exposure. The upregulation of p38 MAPK gene also significantly led to M. japonicus hepatopancreas being undertested in all environmental pollutants. The findings in this study supported that anti-stress responses against exposure to environmental pollutants were reflected in changes in expression levels in M. japonicus p38 MAPK signaling regulation as a cellular defense mechanism.

Effects of di-(2-ethylhexyl) phthalate on Transcriptional Expression of Cellular Protection-Related HSP60 and HSP67B2 Genes in the Mud Crab Macrophthalmus japonicus

Di-2-ethylhexyl phthalate (DEHP) has attracted attention as an emerging dominant phthalate contaminant in marine sediments. Macrophthalmus japonicus, an intertidal mud crab, is capable of tolerating variations in water temperature and sudden exposure to toxic substances. To evaluate the potential effects of DEHP toxicity on cellular protection, we characterized the partial open reading frames of the stress-related heat shock protein 60 (HSP60) and small heat shock protein 67B2 (HSP67B2) genes of M. japonicus and further investigated the molecular effects on their expression levels after exposure to DEHP. Putative HSP60 and small HSP67B2 proteins had conserved HSP-family protein sequences with different C-terminus motifs. Phylogenetic analysis indicated that M. japonicus HSP60 (Mj-HSP60) and M. Japonicus HSP67B2 (Mj-HSP67B2) clustered closely with Eriocheir sinensis HSP60 and Penaeus vannamei HSP67B2, respectively. The tissue distribution of Heat shock proteins (HSPs) was the highest in the gonad for Mj-HSP60 and in the hepatopancreas for Mj-HSP67B2. The expression of Mj-HSP60 Messenger Ribonucleic Acid (mRNA) increased significantly at day 1 after exposure to all doses of DEHP, and then decreased in a dose-dependent and exposure time-dependent manner in the gills and hepatopancreas. Mj-HSP67B2 transcripts were significantly upregulated in both tissues at all doses of DEHP and at all exposure times. These results suggest that cellular immune protection could be disrupted by DEHP toxicity through transcriptional changes to HSPs in crustaceans. Small and large HSPs might be differentially involved in responses against environmental stressors and in detoxification in M. japonicus crabs.

Pemanfaatan dan pusim penangkapan kepiting jangkang (Macrophthalmus japonicus de Haan 1835) di perairan pesisir timur Kota Surabaya

Aktivitas perikanan tangkap di pesisir timur Kota Surabaya menggunakan beragam alat tangkap yang sederhana. Salah satu diantaranya adalah perikanan tangkap dengan cara memungut kepiting jangkang sebagai target tangkapan. Nelayan menggunakan papan untuk meluncur di atas hamparan lumpur guna menangkap target tangkapan berupa kepiting jangkang (Macrophthalmus japonicus) yang kondisi karapasnya masih lunak. Nelayan tidak menangkap kepiting yang kondisi karapasnya keras. Penelitian bertujuan menentukan jenis spesies sumber daya kepiting jangkang target tangkapan, lokasi penangkapan kepiting jangkang serta pola musim penangkapannya. Penelitian menggunakan metode deskriptif yang bersifat survei. Penelitian dilaksanakan pada bulan Februari sampai dengan Juli 2018. Lokasi penelitian di perairan pesisir Kota Surabaya. Responden adalah nelayan penangkap kepiting jangkang dengan lokasi tangkapan di pantai timur Kota Surabaya. Untuk penentuan jenis spesies, dilakukan sepuluh kali sampling terhadap hasil tangkapan, masing-masing sebanyak 25 ekor kepiting dalam kondisi karapas lunak. Lokasi penangkapan ditentukan oleh nelayan, pembuatan peta lokasi dengan menggunakan program Arcview 3.3. Pola musim penangkapan dilakukan dengan penentuan nilai Indeks Musim Penangkapan (IMP). Hasil penelitian sebagai berikut: 1). Jenis kepiting yang menjadi target tangkapan nelayan adalah jenis Macrophthalmus japonicus; 2). Daerah penangkapan kepiting adalah pada hamparan pasut dengan dasar berlumpur di wilayah pesisir timur Kota Surabaya pada koordinat 7014’24”–7015’05” LS dan 112048’09”–112049’04” BT; 3). Pola musim penangkapan kepiting berdasarkan IMP adalah, musim puncak secara berturut berlangsung pada bulan: April (612,96%), dan Mei (164,68%). Musim sedang pada bulan: Juli (77,76%), Maret (68,61%), Februari (64,04%), dan Januari (59,47%). Musim paceklik pada bulan: Juni (42,69%), November (36,59%), Agustus (32,02%), Oktober (18,30%), Desember (18,30%), dan September (4,57%).