Japanese Mitten Crab Research Articles

Functional roles and localization of hydrolases in the Japanese mitten crab Eriocheir japonica

The Japanese mitten crab Eriocheir japonica inhabits rivers throughout Japan and is being cultivated for food. To conduct aquaculture efficiently, it is crucial to comprehend the physiological functions of the target organisms. However, there is a lack of fundamental information on Japanese mitten crabs. In this study, hydrolases were extracted from the midgut glands of Japanese mitten crabs and their metabolic activities were analyzed. An enzyme with hydrolytic activity was discovered within the cytosol of the midgut gland. Western blot analysis also revealed that the Japanese mitten crab contains a hydrolase with cross-reactivity to human carboxylesterase 1 (hCES1) antibodies. The substrate specificity of the S9 fraction of the midgut gland was investigated and, interestingly, it was revealed that it reacts well with indomethacin phenyl ester and fluorescein diacetate, which are substrates of hCES2, not substrates of hCES1. Furthermore, this enzyme was observed to metabolize the ester derivative of astaxanthin, which is a red pigment inherent to the Japanese mitten crab. These findings underscore the significance the midgut gland in the Japanese mitten crab as an important organ for metabolizing both endogenous and exogenous ester–type compounds.

Crabs Eriocheir japonica and Paralithodes camtschaticus Are a Rich Source of Lipid Molecular Species with High Nutritional Value.

Due to their valuable meat and hepatopancreas, the world's most famous delicacies, crabs, have become target species of commercial fisheries and aquaculture. By methods of supercritical fluid and high-performance liquid chromatography, coupled with high resolution mass spectrometry, we analyzed triacylglycerols (TG) and phospholipids (PL)-glycerophosphoethanolamines (PE), glycerophosphocholines (PC), glycerophosphoserines (PS), and glycerophosphoinositols (PI)-in the hepatopancreas and muscles of the Japanese mitten crab Eriocheir japonica and the red king crab Paralithodes camtschaticus inhabiting the Sea of Japan. TGs were the main class of lipids in the crab hepatopancreas, while they were found in trace amounts in muscle. TGs of E. japonica differed from those of P. camtschaticus by a higher content of 16:0, 16:1, 18:2, and 20:4 FA and a lower content of eicosapentaenoic and docosahexaenoic acids. The Japanese mitten crab differed from the red king crab by a lower content of molecular species with eicosapentaenoic acid in PC and PI; an increased content of arachidonic acid in PE, PS, and PI; and a lower content of molecular species with docosahexaenoic acid in PE in the hepatopancreas and muscles. The high nutritional value of the crabs E. japonica and P. camtschaticus was confirmed by a high content of molecular species of lipids with n-3 polyunsaturated fatty acids. The data of the lipid molecular species profile provide new background information for future studies on biochemistry and aquaculture of crabs.

Genetic and morphological evidence indicates the persistence of Japanese mitten crab mitochondrial DNA in Europe for over 20 years and its introgression into Chinese mitten crabs

Cryptic biological invasions are largely unrecognised, leading to an underestimation of the number of invading taxa and their potential impacts. The Chinese mitten crab, Eriocheir sinensis, is a highly invasive species with serious economic and ecological impacts in Europe. Recently, mitochondrial DNA (mtDNA) of the Japanese mitten crab, E. japonica, has been discovered in populations from The Netherlands, Poland and Germany, but the taxonomic status and time of introduction of specimens carrying this mtDNA are uncertain. To this end, we investigated the morphology and variation of the mitochondrial cytochrome c oxidase subunit I (COI) gene of mitten crabs collected in central-western Europe between 1998 and 2020. Mitten crabs from Belgium harboured a Japanese mitten crab COI haplotype in 33% to 65% of individuals, even in our earliest samples from 1998. All other studied populations carried only Chinese mitten crab COI haplotypes. Morphologically, many of the juvenile Belgian mitten crabs showed intermediate traits between the two species, while all investigated adult mitten crabs, regardless of their mitochondrial haplotype or country of origin, were morphologically assigned to E. sinensis. This intermediate morphology of the juveniles and genetic-morphological discrepancy of adults suggests that Japanese mitten crabs introgressed with Chinese mitten crabs, which could have happened both before and after the introduction of mitten crabs to Europe. A specific Chinese mitten crab COI haplotype, found in Belgium, was previously only known from Vladivostok (Russia), where Chinese and Japanese mitten crab hybrids naturally occur. This Far East region is, therefore, a plausible source for at least part of the mitten crab mitochondrial diversity in Belgium.

Crayfish co-introduced symbiotic ostracod found on native crab in Japan: The first record of epibiont ostracod found a new host.

Ankylocythere sinuosa (Rioja, 1942), a symbiotic ostracod native to North America, was found from the Japanese mitten crab Eriocheir japonica (De Haan, 1835), a species native to Japan, collected from a pond in Shizuoka City, Shizuoka Prefecture, central Japan. Introduced North American crayfish Procambarus clarkii (Girard, 1852), which is a host of A. sinuosa in their native range, inhabits ponds sympatrically with Japanese mitten crabs, and it is thought that the ostracods transferred from the exotic crayfish to the native crabs. In recent years, along with the artificial transportation of crayfish around the world, their symbiotic ostracods also have been found on the body surfaces of exotic crayfish in Europe and Japan. However, no studies have confirmed the infestation of exotic ostracods on native crustaceans in the field. A wide range of developmental stages of A. sinuosa from juveniles to adults were found in Japanese mitten crabs, and mating individuals were also found. This strongly suggests that they can reproduce on the body surface of Japanese mitten crabs. In the future, it will be necessary to strengthen measures against alien species to prevent these exotic symbionts from infestating native ecosystems, and we also need to investigate the exact impact of this symbiont on Japanese mitten crabs.

Burrow utilization by the Japanese mitten crab <i>Eriocheir japonica</i> in the clay sediment of a freshwater river of Kyushu, Japan

This is the first record of the burrows of the Japanese mitten crab Eriocheir japonica. Morphologies of the burrows found in the clay sediment used by this crab were recorded by excavating them in a small freshwater river in Japan. Only E. japonica was found inside 2 of the 10 burrows examined (15 crabs and one crab, respectively), and the other 8 were empty. Crabs of various sizes (6.1–47.0 mm in carapace width) were collected from inside the occupied burrows. Burrow morphology ranged from single tunnels to complex burrows with multiple openings and tunnels. Openings (2–10 cm in diameter) were mostly located underwater. The single tunnels were 14–65 cm long. Considering the different digging habits of other burrowing animals found in this area, it can be concluded that E. japonica constructed these burrows. Burrows resembled those of the Chinese mitten crab E. sinensis, but were different in their location (freshwater vs. tidal), sediment type (clay vs. sand and silt), opening placement (mainly underwater vs. intertidal) and occupation rate (low vs. high). The low occupation rate suggests that E. japonica do not always rest in their burrows and rather prefer to hide beneath the riverbed’s large rocks. These results reflect the adaptation of E. japonica to the unstable environment of Japanese rivers.

Radiocaesium accumulation and fluctuating asymmetry in the Japanese mitten crab, Eriocheir japonica, along a gradient of radionuclide contamination at Fukushima

The 2011 Tohoku earthquake-tsunami and the subsequent nuclear accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS) led to large-scale radionuclide contamination of the marine and freshwater environment. Monitoring studies of marine food products in the Fukushima region have generally demonstrated a declining trend in radiocaesium concentrations. However, the accumulation and elimination of radiocaesium and potential biological effects remain poorly understood for freshwater biota inhabiting highly contaminated areas at Fukushima. Consequently, the present study aimed to assess radiocaesium accumulation and developmental effects on the commercially important catadromous Japanese mitten crab, Eriocheir japonica. E. japonica were collected from four sites along a gradient of radionuclide contamination 4–44 km in distance from the FDNPS in 2017. To determine potential developmental effects, fluctuating asymmetry (FA) was used as a measure of developmental stability. Combined 134Cs and 137Cs values for whole E. japonica from highly contaminated sites 4 and 16 km in distance from the FDNPS were 3040 ± 521 and 2250 ± 908 Bq kg−1 wet weight respectively, 30 and 22 times greater than the Japanese standard limit of 100 Bq kg−1. Estimated total dose rates based on radiocaesium concentrations in whole crabs and sediment ranged from 0.016 to 37.7 μGy h−1. No significant relationship between radiocaesium accumulation and FA was recorded, suggesting that chronic radiation exposure at Fukushima is not inducing developmental effects in E. japonica as measured using fluctuating asymmetry. Furthermore, estimated dose rates were below proposed regulatory limits where significant deleterious effects are expected. The present study will aid in the understanding of the long-term consequences of radiation exposure for non-human biota and the management of radioactively contaminated environments.

Habitat preference and locomotive traits of the Japanese mitten crab Eriocheir japonica within the stream unit of the freshwater river environment

Preferences by the Japanese mitten crab Eriocheir japonica of three mesoscale environments within a river unit (pools, riffles and runs) were investigated in a freshwater river by pot fishing and hand-net collecting during the fall. In addition, E. japonica’s life modes during each growth stage were elucidated by comparing data obtained by hand-net collecting into three size groups (20 mm < CW, 20 mm ≤ CW < 40 mm, and 40 mm ≤ CW). Both the number of crabs caught per pot and per 10 m stretch sampled along the river by hand-net collecting indicated that mean catch values varied in the following manner runs < pools < riffles, and that this variation was large in riffles and small in pools and runs. Only large crabs of 40 mm ≤ CW could be collected by pot fishing; in contrast, small juveniles were only caught by hand-net collecting. Results of the hand-net collecting indicated that small juveniles (CW < 20 mm) preferred to be in riffles, while the mid-size class crabs (20 – 40 mm CW) presence in the riffles decreased and once they became adults (40 mm ≤ CW) they chose to be in pools. In all size classes, runs were not a preferred choice. These results suggest that the small juveniles are oriented by their positive rheotaxis. Their movement is probably affected by flow regimes, creating large variations in their density in the riffles. In contrast, adults can freely move within a stream unit and use pools as their resting site, thus they are steadily captured in large numbers with a small variation in the pools by pot fishing. However, the adults can actively wander around riffles and runs, searching for animal food, and are attracted to the riffles by bait odors depending on the water flow. Therefore, the most effective catching method is to set the pots in riffles when the river is swollen.

An outbreak of Paragonimus westermani infection among Cambodian technical intern trainees in Japan, exhibiting various extrapulmonary lesions.

We encountered an outbreak of paragonimiasis among Cambodian technical intern trainees (TITs) at a food-processing factory in Fukuoka, Japan. The patients were 20-28years old, seven females and two males, who had been in Japan for one to four years. All of them had consumed raw or undercooked Japanese mitten crab they purchased at a local grocery store near their training place. CT images showed multiple lesions not only in the lungs but in the extrapulmonary organs as well, such as subcutaneous tissues, abdominal muscles, and mesentery, in most of the patients. Their medical records indicated that all of them acquired infection in Japan, not in Cambodia. Diagnosis was made serologically and the patients were treated with praziquantel successfully. Foreign workers and TITs are increasing in Japan so rapidly, that food borne-infections, including paragonimiasis, should be considered in people from developing countries who have exotic dietary habits.

First indication of Japanese mitten crabs in Europe and cryptic genetic diversity of invasive Chinese mitten crabs

The Chinese mitten crab (Eriocheir sinensis) is a prominent aquatic invader with substantial negative economic and environmental impacts. The aim of the present study was to re-evaluate the genetic diversity of mitten crabs throughout their native and invaded ranges based on publicly available sequence data, and assess if multiple introductions or rapid adaptation could be responsible for biologically divergent mitten crabs in Northern Europe. We assembled available genetic data of a fragment of the mitochondrial cytochrome c oxidase subunit one gene (COI) for all species of the genusEriocheir. We applied phylogenetic and population genetic analyses to compare native and invasive populations, and to identify possible source populations. The phylogenetic reconstruction revealed that five COI sequences from Europe, morphologically identified as Chinese mitten crab, actually belong to the Japanese mitten crab (Eriocheir japonica), representing the first indication of its presence in European waters. All other COI sequences from Europe could unambiguously be assigned to the Chinese mitten crab. In some Northern German populations of Chinese mitten crabs, genetic diversity was surprisingly high, due to seven unique haplotypes encoding several amino acid substitutions. This diversity may reflect a cryptic introduction from an unsampled native location, or rapid adaptation in the invaded range. Based on the genetic diversity shared between native and introduced range, Feiyunjiang, a tributary of the Yangtze River, emerges as a plausible source population for the original introduction of Chinese mitten crabs to Europe. This study highlights the complex and dynamic invasion processes of mitten crabs in Europe. We urge to further monitor mitten crab invasions using genetic tools.

Potential competitive impacts of the invasive Chinese mitten crab Eriocheir sinensis on native Japanese mitten crab Eriocheir japonica

The Chinese mitten crab Eriocheir sinensis is an invasive species outside native range and represents a substantial threat to recipient ecosystems. It is regarded as an invasive species in Japan and has recently been found in Tokyo Bay, but little is known about its possible impacts on native species, especially on the congener Japanese mitten crab Eriocheir japonica. This study examined shelter competition between E. sinensis and E. japonica under laboratory conditions. Shelter competition trials were conducted in pairs of native and invasive males in different size combinations. Our results indicated that competition between two species was size-dependent: E. japonica always successfully defended shelter when competing with size-matched or slightly larger E. sinensis; E. sinensis always won shelter when its carapace or chela were at least 10 or 7% larger, respectively, than those of E. japonica. The two species exhibited different behavioural patterns: compared with E. sinensis, E. japonica frequently displayed positive behaviour (approach, walking leg contact, chela contact) and seldomly displayed negative behaviour (retreat). Our results highlight the important role of strong native competitors in controlling invasion success and suggest E. sinensis may be unlikely to exclude native E. japonica from its habitat by direct competition for shelter.

Cerebral Paragonimiasis With Hemorrhagic Stroke in a Developed Country

Paragonimiasis is a food-borne parasitic disease caused by Paragonimus lung flukes, which are epidemic in Asia. Cerebral paragonimiasis accounts for <1% of symptomatic paragonimiasis but is the most common extrapulmonary infection. Cerebral paragonimiasis often mimics stroke and sometimes causes severe neurological sequelae.A 61-year-old woman was admitted to the hospital for severe headache. A head computed tomography scan revealed intracerebral hemorrhage with subarachnoid hemorrhage. The patient also had lesions in the lungs. She frequently ate Japanese mitten crab. Peripheral blood examination results of increased eosinophilia and immunological testing results confirmed the diagnosis of Paragonimus westermani infection. The patient was successfully treated with praziquantel as the first-line agent. Cerebral paragonimiasis is currently rare in developed countries; however, it is an important disease to consider.

Cannibalism in the Japanese mitten crab, Eriocheir japonica

Cannibalism is ubiquitous in crustaceans but relatively little is known about the degree of cannibalism in the Japanese mitten crab, Eriocheir japonica (De Haan, 1835). In this study, we examined the possibility of cannibalism in intermolt Japanese mitten crab in relation to predator–prey size difference, predator sex, prey density, and presence of alternative food and shelter under laboratory conditions. Predator crabs were starved for 48 h and then exposed to smaller conspecifics as prey for 24 h, after which the number of dead/injured prey was recorded. Our results indicated that E. japonica cannibalizes conspecifics when the relative size difference between cannibal and victim becomes large. Males were more cannibalistic than females and predated on conspecifics following a type II functional response. The presence of alternative food and shelter effectively mitigated cannibalism. The extent of cannibalism in the field remains unknown but we hypothesize that the segregated distribution pattern of E. japonica along river courses may be an evolutionary adaptation to reduce intraspecific predation.

Genetic admixture of mitten crabs in the Northeast Asia hybrid zones

Hybridization and genetic admixture in hybrid zones promote phenotypic and genotypic adaptive changes in organisms. Hybrids between Chinese mitten crab (Eriocheir sinensis) and Japanese mitten crab (Eriocheir japonica) have been reported in the Vladivostok region of Russia. However, the direction and extent of hybridization remains unknown in Northeast Asia. In this paper, genetic variation and admixture were investigated by examining a mitochondrial NADH dehydrogenase subunit II gene (ND2) and 10 microsatellite DNA loci in mitten crabs from the Tumen River in China and Vladivostok in Russia. In addition, the adjacent distributions of E. sinensis in China and E. japonica in Japan were analyzed. The Tumen River and Vladivostok were both identified as hybrid zones of E. sinensis and E. japonica. As indicated by ND2 sequences analysis, the mitten crabs in the Tumen River and Vladivostok displayed 5–10 times higher nucleotide diversity and more mixed haplotypes than pure E. sinensis and E. japonica. Meanwhile, approximately 31.25% of the mitten crabs in Vladivostok and 30.00% in the Tumen River were identified as potential hybrids, indicating strong genetic admixture between the two mitten crabs in these hybrid zones. Our results provide quantitative evidence of genetic admixture of E. sinensis and E. japonica in Northeast Asia.

Integral biochemical index of the state of aquatic organisms under polluted conditions

The state of marine and estuary organisms living in the polluted coastal zone of Peter the Great Bay in the Sea of Japan has been estimated using molecular biomarkers of oxidative stress and biotransformation that characterize changes in animal metabolism under the effect of pollutants. The integral biochemical indices were calculated and graphically represented for mussels Crenomytilus grayanus collected at marine stations with different degrees of pollution and for the Japanese mitten crab Eriocheir japonica from the estuaries of rivers flowing into Peter the Great Bay, based on statistical processing of the results. It has been noted that the values of the indices correspond to the degree of pollution of animal sampling areas.

Selectivity of Two Methods for Surveying the Japanese Mitten Crab, Eriocheir Japonica (De Haan, 1835), in a Riverine Environment

Differences between the results of pot fishing and hand-net collecting of the Japanese mitten crab, Eriocheir japonica (De Haan, 1835), were examined to increase the accuracy of sampling natural population in freshwater and tidal areas of a small river. Large adult crabs were caught in pots; small juveniles mostly collected with the hand nets. The difference in size composition in the freshwater river is probably caused by changes in the dietary preferences and behaviors that occur as crabs grow larger. The sex ratio was strongly male-biased in pot fishing in the tidal river in contrast to hand-net collecting (no bias), and males captured in the pots were slightly larger than those caught by hand-nets. The sex ratio bias observed in pot fishing in the tidal river can be explained by mating behavior, whereas the differences in the size of males between the two methods can be explained by the dimorphism and alternative mating strategy of male E. japonica . The proportions of ovigerous females in the tidal river in early winter were larger in pot than in hand-net samples. Differences in the proportion of ovigerous females between the two gears in the tidal river may have resulted from the presence of two groups differing in reproductive season and the wandering activities of ovigerous and non-ovigerous females. Although pot fishing is useful for studying reproductive ecology, the resulting data is sometimes strongly biased. In contrast, hand-net collecting is essential for gathering a complete range of crabs from all size classes and the data generated by this method is more representative of their distribution pattern. It is necessary to make up for the shortcoming of each sampling method.

Fertility and embryonic mortality level of the Japanese mitten crab Eriocheir japonica (Crustacea: Decapoda: Varunidae) in Primorye

Reproductive biology of the Japanese mitten crab Eriocheir japonica (de Haan, 1835) was studied in the northern part of its habitat. It was revealed that E. japonica from the water bodies of Primorye, in contrast to crabs in the central part of the habitat on the Japanese Islands, lays fewer eggs in the first clutch, does not have direct dependence between the size-weight characteristics of females and the number of eggs in the third clutch, and shows higher level of embryonic mortality. The loss of eggs during the embryonic period in each of three sequentially laid clutches was 16, 34, and 52%, respectively (28% in total during the period of reproduction). Fecundity was approximately 43%. It was registered that the specifics of reproductive biology of E. japonica (monocyclicity, prolonged period of reproduction, portion spawning, indirect embryonic development, high fertility, relatively small and yolk enriched eggs, pelagic planktotrophic larva, high level of energy costs on reproduction, egg bearing on the pleopods, high level of embryonic mortality), an intermediate strategist, is in a good agreement with its life strategy, thereby enabling this species to realize its reproductive potential in the northern part of the habitat.

Migration Process of Megalopae of the Japanese Mitten Crab Eriocheir japonica (De Haan) from Open Sea to Tidal River

The migration process of megalopae from the sea to a tidal river is an important subject for catadromous Brachyura. The process of invasion and settlement of the megalopae of the Japanese mitten crab Eriocheir japonica was investigated in a small river in temperate Japan. First, to elucidate the relationship between settlement and lunar rhythm, megalopae were collected using artificial grass mats (900 cm2) in the upper tidal river area every 3–4 days from November to December. An evident semi-lunar rhythm was detected, and the settlement was concentrated in the spring tide around the days of full moon and new moon. All the megalopae completed metamorphosis within 5 days before the next spring tide. Second, the relationship between settlement and tidal cycles within a day was investigated in the upper tidal river by collecting megalopae using artificial grass mats every 2 h during 1 day in November. Megalopae exhibited in their settlement an evident nocturnal behavior and synchronization with the tidal cycles. A mass of megalopae suddenly began settling on the mat during the night when the tide came in and high salinity water (ca. >10‰) reached the sampling site. In contrast, after the sunrise, very few megalopae were collected even during the flood tide. Third, the upstream migration process of megalopae in the tidal river was surveyed by hand-net sweeping at five stations during the night every hour for 7 h in May. No larvae were collected during the ebb tide before sunset, but swimming megalopae suddenly gathered at the rivermouth just after sunset. Aggregated megalopae shifted upstream with the flow of the highly saline water mass until the latter reached a weir in the uppermost tidal area. In the subsequent ebb tide, the megalopae remained in the uppermost area. Therefore, they utilized a selective tidal transport mechanism; megalopae migrated upstream from the sea preferably during the night around the spring tide and reached the uppermost tidal river during a single flood tide. Combined with previous data showing the distribution pattern of parent crabs and the settled megalopae, it was estimated that all megalopae were supplied from the sea’s offshore area, and river population dynamics depend on the supply of megalopae from the sea. This also suggests the larval exchange and gene flow between local river populations of E. japonica within a metapopulation structure.

Effects of dams and weirs to the distribution of Japanese mitten crab in Imizu plain, Toyama

Effects of dams and weirs to the distribution of Japanese mitten crab in Imizu plain, Toyama

Effect of natural disturbance on migrations and population dynamics of a catadromous species, Eriocheir japonicus, along the Lo-Mei stream in northern Taiwan

Japanese mitten crab, Eriocheir japonicus (de Haan), migrates between stream and sea and breeds in shallow coastal areas, exhibiting a catadromous life cycle. This study investigated how the crabs adjust reproductive strategy and migratory behavior to climate fluctuation and what kind of life history strategy individual crabs adopt in a disturbed environment. We conducted a 14-year monitoring study from 1998 to 2011 in Lo-Mei Stream in northern Taiwan. Streamflow and flood timing are controlled by precipitation and typhoons. Abundance of crabs was lower after disturbances by several typhoons and by lower temperatures associated with cold winters in 2006 and 2007. Samples from 2003 showed a reversal in reproductive trends, with increasing size in the same pattern of oocytes, compared to reproductive biology from 1999 to 2005. The life history of E. japonicus can be divided into three stages: spawning migration, growth period, and upstream migration of juveniles to compensate for downstream migration of mature crabs. Reproductively, in E. japonicus the combination of semelparity and synchronous breeding can increase reproductive potential and increase survival in a less disturbed environment at the optimum time. Environmental cues play an important role as major triggers in the persistence of populations.

Molting growth patterns of the Japanese mitten crab Eriocheir japonica (de Haan) under laboratory-reared conditions

ABSTRACT The molting growth pattern of the Japanese mitten crab Eriocheir japonica (de Haan, 1835) was investigated under laboratoryreared conditions. Crabs were individually reared in freshwater for 5 years in a constant temperature room at 23–25°C. The age after metamorphosis and instar number were recorded for each molt, and the intermolt period was calculated for each crab. Carapace width (CW) was measured and the percentage molt increment was calculated. Eleven crabs reached a CW > 10 mm. Each growth curve (ageCW relationship) had two phases in the juvenile stage. Growth rate gradually decreased in the younger phase before changing to nearly constant in the older phase. During the younger phase, the percentage molt increment decreased from 25.0%–38.1% to 6.0%–26.2% (ca. 2–10 mm CW, 1st to 11th instars), and the intermolt period increased from 4–9 days to 40–300 days (ca. 2–20 mm CW, first to thirteenth instars). During the older phase, both parameters became broadly flat but showed marked fluctuation...