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Agonistic behaviours and cannibalism are key factors that restrict increases in the production of crab aquaculture. To explore the effects of feeding strategies on the boldness, agonistic behaviour and physiological response of swimming crab (Portunus trituberculatus), three treatment groups were established (feeding once a day:S0, every 3 days: S3 and every 6 days:S6). The intensity and duration of fighting, and agonistic behaviours were compared. The hepatosomatic index and the concentration of glycogen, glucose and lactate were also measured. The main results were as follows: (1) With an increase in time between feeding, boldness, duration and intensity of fighting increased first, then decreased, reaching a maximum in the S3 group, and this was significantly higher than in the S6 group. (2) Agonistic behaviour increased first and then decreased. The 'move to', 'cheliped display' and 'contact behaviours' of crabs in the S3 group were significantly higher than the S6 group; (3) Before fighting, with the increase in feeding time, the hepatosomatic index, glycogen and glucose concentration of crabs decreased, and these indicators were significantly higher in the S0 group than in the S6 group. (4) After fighting, the glucose and lactate concentrations were significantly greater than those before fighting. These results suggest that both boldness and feeding strategy can affect the agonistic behaviour of crab. Short‐term reductions in food resources promoted inter‐individual fighting, and bold individuals were more likely to win battles. However, a long‐term decrease in food resources reduced fighting among individuals. [ABSTRACT FROM AUTHOR]

Chinese mitten crab is a unique aquatic product in China. As a highly nutritious, delicious, and intriguing food, it is deeply loved by consumers. Through field visits and household interviews in Chongming District of Shanghai and Suzhou of Jiangsu Province, the author collected relevant materials and made a detailed analysis of the strengths and weaknesses, opportunities and threats of the development and application of crab culture in the development of Chinese mitten crab industry in Shanghai by using SWOT model. The results show that the development and application of crab culture in the development of Chinese mitten crab industry in Shanghai can adopt growth‐oriented, transformation and upgrading, diversification and defensive development strategies. It is expected to promote the sustainable development of Chinese mitten crab industry in Shanghai through the development and application of crab culture. [ABSTRACT FROM AUTHOR]

From 2015 to 2016, the hepatopancreatic lesion syndrome had a higher mortality rate, which caused great economic losses to farmer. In order to study the high-efficiency disease-preventing crab pond intercropping mode, an experiment was successfully conducted to intercrop Chinese sucker (Myxocyprinus asiaticus) in a crab pond in 2017. We optimized the traditional stocking mode, and mainly cultured river crabs when intercropping Chinese suckers. Meanwhile, the cultivation environment was strengthened, and the test pond was not affected by disease throughout the year. The results showed that the production benefits were river crab 115 620 yuan/hm², Chinese sucker 44 280 yuan/hm², and silver carp and bighead carp) 5 418 yuan/hm², with a total output of 165 318 yuan/hm², and the output-input ratio was 11.72. The Chinese sucker-intercropping river crab culture mode promoted the improvement of pond culture environment, effectively controlled the occurrence of hepatopancreatic lesion syndrome, and significantly improved the economic benefits of crab pond culture. [ABSTRACT FROM AUTHOR]

Despite the exceptional palaeontological richness of the renowned Santana Group from the Early Cretaceous Araripe Basin of Brazil, only one specimen of true crabs (Brachyura) has been discovered to date. Here we present two new genera and species of brachyuran crabs from the upper Aptian-lower Albian Romualdo Formation of the Santana Group, represented by 30 specimens from several localities across the Araripe Basin in the state of Pernambuco, Brazil. One taxon, Exucarcinus gonzagai Prado and Luque gen. et sp. nov., is similar to several endemic stem raninoidans (Orithopsidae) from the late Aptian and early Albian of Colombia and the USA, respectively, while Romualdocarcinus salesi Prado and Luque gen. et sp. nov., seems to be closer to "higher" true crabs (Eubrachyura) from the Cenomanian of Spain. The presence of taxa similar to those from the mid-Cretaceous of northern South America, southern North America, and western Europe, reinforces the view of a Tethyan marine influence in Araripe during the breakup of South America and Africa, and adds to the growing data that suggest a generic and specific degree of endemism of true crabs in tropical South America during the mid-Cretaceous. [ABSTRACT FROM AUTHOR]

Inland aquaculture ponds in China collectively cover 2.57 million ha, so emissions of the greenhouse gases methane (CH 4 ) and nitrous oxide (N 2 O) from these ponds may constitute a significant contribution to global warming. During 2016 and 2017, CH 4 and N 2 O fluxes and a range of pond-water and sediment properties were measured in replicated ( n  = 4) “mixed-fish” and “crab” aquaculture ponds in southeast China. Annual CH 4 and N 2 O emissions were 64.4 kg C ha −1 and 2.99 kg N ha −1 , respectively, from the “mixed-fish” ponds, and 51.6 kg C ha −1 and 3.32 kg N ha −1 , respectively, from the “crab” ponds. Emission differences between pond types were significant ( p  < 0.05) for both gases. CH 4 fluxes from the “crab” ponds were significantly increased by the presence of aquatic vegetation, but N 2 O fluxes were not affected. Emissions of N 2 O were estimated to be 0.54% and 0.71% of the total nitrogen input (in the feed) for the “mixed-fish” and “crab” ponds, respectively. The net economic benefit-scaled sustained-flux global warming potential (NEB-scaled SGWP) of the “crab” ponds was 61.6% higher ( p  < 0.05) than that of the “mixed-fish” pond. Our CH 4 and N 2 O emissions results suggest that aquaculture ponds can be important contributors to regional and national GHG inventories, with aquaculture type an important factor in total GHG impact. Further CH 4 and N 2 O flux research is needed at aquaculture ponds across China to better establish the range of potential GHG impacts, and to confirm the importance of the influencing factors identified in this study. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: The plumpness of hepatopancreas and gonad tissues in live Chinese mitten crabs (Eriocheir sinensis) depends on the grading scale and its commercial value. In this work, a low‐field T1‐weighted 1H magnetic resonance imaging (LF‐1H MRI) technique was developed to nondestructively analyze the plumpness of hepatopancreas and gonad tissues in live E. sinensis. Both male and female E. sinensis were characterized by two‐dimensional (2D) LF‐1H MRI. Moreover, a three‐dimensional (3D) LF‐1H MRI model that quantitatively integrated the total volume of lipid tissues in live E. sinensis was used. RESULTS: The results showed 2D LF‐1H MRI could accurately discriminate the plumpness of hepatopancreas and gonad tissues in live E. sinensis. The results of the 3D LF‐1H MRI model displayed that the lipid volume of E. sinensis could be used to quantify lipid accumulation in lipid tissues. CONCLUSION: LF‐1H MRI technology was successfully developed to accurately discriminate the development of E. sinensis hepatopancreas and gonad tissues in a nondestructive manner, indicating its application potential in grading commercial live crabs or advising crab farmers on breeding and fattening processes. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the occurrence, distribution, potential sources, and ecological risk of antibiotics in aqueous phase of Lake Guchenghu, China. Target antibiotics in surface water of Lake Guchenghu, adjacent streams, and crab ponds were detected seasonally. The results showed that erythromycin-H2O (1.60-2450 ng/L), sulfadiazine (ND-654 ng/L), and florfenicol (ND-919 ng/L) were the predominant antibiotics in Lake Guchenghu. The concentrations of antibiotics in Lake Guchenghu Basin showed obvious seasonal variation, with the highest concentration in summer. In general, the concentrations of antibiotics in crab ponds and streams were higher than those in the lake and spatial distributions of antibiotics were affected by pollution sources. The types and origins of antibiotics indicated that wastewater from ponds was the main source of antibiotics in the lake. Risk assessment suggested that as individual compound, erythromycin-H2O and clarithromycin posed a high risk to algae while other compounds might pose low or no risk. The mixture of antibiotics may pose a high risk to aquatic organisms in Lake Guchenghu. Overall, our study revealed the occurrence and spatiotemporal variation of antibiotics in Lake Guchenghu, which was related with crab culturing. [ABSTRACT FROM AUTHOR]

In order to address the issues of nonuniform feeding and high labor cost plaguing the process of farming Chinese river crabs, the present study proposes a multifunctional automatic river crabs feeding boat based on Advanced RISC Machine (ARM) and Global Positioning System / Inertial Navigation System (GPS/INS) integrated navigation. This paper proposes a new calculation method based on real time point insertion. This method calculates the current target position of the boat in the real time according to the position of the boat and the turning points of the current route. A new turning and route-switching strategy is also presented in this paper to improve the ship's operational efficiency and prevent the ship from veering off the target route due to its high speed. Considering the boat's unique movement characteristics including non-linearity, large delay and underdamped nature, a route-speed dual-loop control algorithm is designed based on fuzzy Proportion Integration Differentiation (PID) method. Through analyzing the bait distribution associated with the feeding machine, the present study proposes an inner-spiral-based full coverage traversal method and a travel distance optimization model so as to improve the uniformity of the automatic feeding. Results show that the speed overshoot is no more than 5% and the steady-state error can be kept within 3%. Compared with the finite point method, the real time point insertion method decreases the peak route deviation errors by 82.82% and 84.14% while turning and going straight. [ABSTRACT FROM AUTHOR]

River crab is a unique aquatic product in China. As a kind of food with high nutrition, delicious and intriguing, it is deeply loved by the majority of consumers. At present, the research on river crab mainly focuses on the breeding techniques, neglecting the important role of crab culture in the development of industry. Taking crab culture as the breakthrough point, the author analyzes the connotation of crab culture and the current situation of the development of Shanghai river crab industry through literature review and field investigation, and then analyzes the strengths, weaknesses, opportunities and threats of the application of crab culture in the development of Shanghai river crab industry by using SWOT model. Based on this analysis, the author puts forward some ideas about the application of crab culture in the development of Shanghai river crab industry. It is expected to promote the sustainable development of river crab industry in Shanghai through the application of crab culture. [ABSTRACT FROM AUTHOR]

Swimming crab ( Portunus trituberculatus ) as an economic-potential aquatic animal is widely cultivated in China. However, there have been few studies examining the effects of different structures for production of this species of crab. Here we select two types of materials (polyethylene net and plastic basket) as potential shelters to evaluate their effects on the molting, growth and culture performance of swimming crab. Shelter 1 (S1) was made into Z-like shape by polyethylene nets while shelter 2 (S2) was made by a half plastic basket. We find that most of crabs preferred to harbor in these two types of shelters to complete the molting period. Compared with S1, crabs in S2 showed a significantly higher hiding rate and molting rate ( P < 0.05). The shelters, shelter 2 in particular, can effectively shorten the molting period and improve both the weight growth rate and the specific growth rate of crabs after molting. Moreover, S2 can well prevent the cannibalism because crabs in this group performed a significantly higher survival rate and lower disabled rate than those both in the S1 group and in the control group ( P < 0.05). To further test the efficiencies of these two shelters, they were employed in outdoor ponds where crabs showed final survival rates of 45% (1.8 times of the control) in the S2 group and 30.3% (1.2 times of the control) in the S1 group, respectively. More importantly, crabs in the S2 group led to a net profit of 263.7 × 10 3 RMB/ha far higher than the control (99.9 × 10 3 RMB/ha). Altogether, S2 is worthy of widely being promoted in the aquaculture of swimming crab because of its advantages of low cost, easy operation and high efficiency in the practical application. [ABSTRACT FROM AUTHOR]

A new pearl white freshwater crab was collected in sympatry with Potamonautes sidneyi (Rathbun, 1904) in the Indian Ocean coastal belt forest at Mbotyi on the Wild Coast of the Eastern Cape Province, South Africa. Specimens of the two sympatric congeneric species were subjected to DNA sequencing of three partial mitochondrial loci (COI, 12S rRNA and 16S rRNA) together with morphological examination. Phylogenetic analyses of the new species were undertaken to determine its evolutionary relationship with the other east and southern African species of freshwater crabs. Results revealed that, Potamonautes mhlophe sp. nov. is sister to P. dentatus (Stewart & Cook, 1995) and distantly related to the sympatric P. sidneyi. The two congeneric sympatric species were characterised by the absence of shared COI haplotypes and marked sequence divergence value for the latter locus. Furthermore, Potamonautes mhlophe sp. nov. is morphologically distinct from P. sidneyi based on the structure of the first and second gonopods. Considering the congruence between the mtDNA and morphology, the new species is herein described. [ABSTRACT FROM AUTHOR]

Megalopae and early juveniles of Portunus trituberculatus (Miers, 1876), a commercially important species, are known to utilize drifting seaweeds before transition to benthic habitats, but little is understood about this settlement behavior. Clinging and burying behavior of P. trituberculatus was investigated during nighttime and daylight by culturing megalopae and first to fifth crab stages in tanks with different bottom substrates (polyethylene, gravel, or sand) and an attachment substrate (artificial seaweed) in the water column. Clinging behavior on the artificial seaweed was observed for all growth stages. The proportions of individuals that exhibited clinging behavior increased from megalopae to the first crab stage, peaked in second and third crab stages, and declined through the fourth and fifth crab stages in all treatment groups. The proportion of crab stages that buried in the substrate was much higher in daytime than in nighttime (P < 0.001). For daytime observations, the burying rates linearly increased from first or second to fifth crab stages and were higher in tanks provided with sand as opposed to gravel. Our results suggest that early juvenile crabs utilize drifting seaweeds as a vehicle, and they voluntarily shift to benthos after the fourth crab stage when the risk of predation is reduced, as first to third crab stages are known to be vulnerable to predation by benthic fishes. The juveniles of P. trituberculatus thus appear to "hitchhike" drifting seaweeds before final settlement on the bottom. The present study supports the idea that hitchhiking behavior could be an important transport mechanism leading to settlement by larval and juvenile stages in decapod crustaceans. [ABSTRACT FROM AUTHOR]

The Mekong Delta is the most important rice- and shrimp-producing region for food and economic security in Vietnam. Rice-shrimp farming is practised where salinity fluctuates substantially between wet and dry seasons. Research points to several potential risk factors for rotational systems, but how these link directly to both rice and shrimp production remains poorly quantified for systems that stock and harvest animals year-round. We examined water and soil quality of 18 rice-shrimp-crab ponds, in which shrimp and crab are grown in both wet and dry seasons, in the Cà Mau Province of Vietnam. Multiple lines of evidence indicated that environmental conditions experienced by both rice and shrimp were suboptimal and contributed to low yields and survival. Year-round cropping of shrimp and crab was associated with sustained suboptimal salinity, intensified by drought, for the wet-season cultivation of rice. Although rice seedlings were sown in all 18 ponds, only three had a harvestable crop. Low shrimp production and survival was associated with sustained suboptimal water temperatures (too high), salinity (too high in the dry season and too low in the wet season) and dissolved oxygen concentrations (too low). Food availability and quality may also have affected shrimp production. Improving productivity of rice-shrimp-crab ponds in the study region may require (1) separation of rice and shrimp crops and improving efficiency of soil washing practices such that salinity conditions are more suitable for each when grown, and (2) management intervention to increase oxygenation of water, and the availability and quality of food for shrimp. [ABSTRACT FROM AUTHOR]

Cases of co-occurrence among freshwater decapods are few. In their European range, the crab Potamon fluviatile and the white-clawed crayfish Austropotamobius pallipes complex do not usually share the same stream section or pond even if they live in sympatry, suggesting a strong segregation of the two species. The coexistence was hypothesized during the Pleistocene era, but without evidence of recent contact between them. The co-occurrence of these two species (i.e., occupying a common area) is reported in a stream of the Central Italy, being the first case in Italy and in Europe. To assess this co-occurrence, in 2015 we investigated three transects (only crabs, only crayfish and both species), collecting biotic and abiotic data. The three transects were similar for canopy cover, substrate composition and density of potential shelters (but not for the abiotic parameters), and characterized by a good water quality and abundance of preys, being suitable for the two species. No agonistic behavioural patterns have been observed, leading to hypothesize that co-occurrence may be favoured by the slightly smaller size of crayfish and crabs in the shared area than the size of animals in the other transects or by the different microhabitats chosen by crayfish and crabs when sharing the same stream section. Other possible explanations are discussed here, but further studies are necessary to better understand the co-occurrence of these two native crustaceans. Moreover, urgent measures are demanded to guarantee the survival of these protected species hampered by several threats. [ABSTRACT FROM AUTHOR]

Mud crab ( Scylla paramamosain ) is an economically important marine cultured species in China's coastal area. Mud crab reovirus (MCRV) is the most important pathogen of mud crab, resulting in large economic losses in crab farming. In this paper, next-generation sequencing technology and bioinformatics analysis are used to study transcriptome differences between MCRV-infected mud crab and normal control. A total of 104.3 million clean reads were obtained, including 52.7 million and 51.6 million clean reads from MCRV-infected (CA) and controlled (HA) mud crabs respectively. 81,901, 70,059 and 67,279 unigenes were gained respectively from HA reads, CA reads and HA&CA reads. A total of 32,547 unigenes from HA&CA reads called All-Unigenes were matched to at least one database among Nr, Nt, Swiss-prot, COG, GO and KEGG databases. Among these, 13,039, 20,260 and 11,866 unigenes belonged to the 3, 258 and 25 categories of GO, KEGG pathway, and COG databases, respectively. Solexa/Illumina's DGE platform was also used, and about 13,856 differentially expressed genes (DEGs), including 4444 significantly upregulated and 9412 downregulated DEGs were detected in diseased crabs compared with the control. KEGG pathway analysis revealed that DEGs were obviously enriched in the pathways related to different diseases or infections. This transcriptome analysis provided valuable information on gene functions associated with the response to MCRV in mud crab, as well as detail information for identifying novel genes in the absence of the mud crab genome database. [ABSTRACT FROM AUTHOR]

The immunostimulatory role of dietary saponins on swimming crabs was investigated under field conditions. Portunus trituberculatus were fed diets enriched with Quillaja saponin (QS) at 150, 300 and 450 mg kg −1 . They had an enhanced growth rate and increased resistance against Vibrio alginolyticus compared to crabs not fed with QS. Significant effects were observed on the average body weight, percentage weight gain and specific growth rate ( p < 0.05). Total hemocyte and hyaline cell counts of P. trituberculatus fed with 300 and 450 mg kg −1 saponin in their diets significantly increased ( p < 0.05) compared to the control. Phenoloxidase, superoxide dismutase, catalase and glutathione peroxidase activities significantly increased in response to the incorporation of QS in the diet. However, the respiratory burst activity did not increase significantly. The phagocytic activity was significantly enhanced at 300 and 450 mg kg −1 of saponin. QS diets can enhance growth of P. trituberculatus and its immune resistance against V. alginolyticus . Dietary administration of saponin may help to control diseases and improve production in the crab aquaculture industry. [ABSTRACT FROM AUTHOR]

Improvement of feed quality for mangrove crab larvae rearing is one of the important factors to increase of crablet production. The aim of the research was to know the influenzing of enriched Artemia nauplii using Nannochloropsis sp fed to the different stages of larvae Scylla olivacea on crablet production. Twelve units of tanks volume 250 L filled with saline water salinity 30 ppt, aerated, then stocked with new hatched mud crab larvae zoea-1 at the density 100 ind./L. The larvae zoea-1 were fed rotifer, Brachionus sp. and after zoea-3, beside fed by rotifer, the larvae were also fed by Artemia naupli. Four treatments were tested, namely: A). Artemia nauplii enriched using Nannochloropsis sp. was given to the larvae zoea-3 until develop to megalop stage. B). Artemia nauplii enriched using Nannochloropsis sp was given to the larvae zoea-4 until develop to megalop stage. C). Artemia nauplii enriched using Nannochloropsis sp was given to the larvae zoea-5 stage until develop to megalop stage. D). Artemia nauplii without enriched using Nannochloropsis sp. was given to the larvae zoea-3 until develop to megalop stage. Result of the research showed that the highest of Larvae Development Indexes and Megalop Occurence Indexes was obtained in treatment A and resulted the highest of crablet production, then followed by treatment C and B and those were significantly different (P<0.05) with the crablet production in treatment D. The use of Artemia nauplii enriched by Nannochloropsis sp. to feed larvae, S. olivacea stage zoea-3 to zoea-5 until develop to the megalop stage is one of the key factor to enhance the crablet production. By this finding, the crablet production in hatchery will be increased and the mud crab culture in brackishwater pond able to developed. [ABSTRACT FROM AUTHOR]

We examined the food preference of Chinese mitten crabs, Eriocheir sinensis (H. Milne Edwards, 1853), under food shortage, habitat choice in the presence of predators, and cannibalistic behavior by comparing their response to the popular culture plant Elodea nuttallii and the structurally more complex Myriophyllum verticillatum L. in a series of mesocosm experiments. Mitten crabs were found to consume and thus reduce the biomass of Elodea, whereas no negative impact on Myriophyllum biomass was recorded. In the absence of adult crabs, juveniles preferred to settle in Elodea habitats (appearance frequency among the plants: 64.2 ± 5.9%) but selected for Myriophyllum instead when adult crabs were present (appearance frequency among the plants: 59.5 ± 4.9%). The mortality rate of mitten crabs in the absence of plant shelter was higher under food shortage, primarily due to cannibalism. The proportion of molting crabs dying in the structurally more complex Myriophyllum habitats was significantly lower than in the less complex Elodea habitats, indicating that Myriophyllum provides better protection from cannibalistic behavior, likely due to its structurally more complex canopy. Stable isotope analyses of crab samples revealed a trophic shift in both δ13C and δ15N (Δδ13C: 2.2⁻4.0‰; Δδ15N: 1.5⁻2.8‰) during the experimental period. Significant positive correlations between body mass and δ13C and δ15N were recorded, suggesting that cannibalistic feeding might further increase crab growth and lead to ontogenetic increases in trophic position with increasing size. Our study overall demonstrates that a combination of submerged aquatic vegetation functioning as a highly suitable food with other less palatable plant species acting as efficient refuges against predators may be the optimal method of plant stocking in mitten crab aquacultures to ensure both high crab growth and a high survival rate.

The novel Eriocheir sinensis reovirus (Es RV) is a pathogen that causes severe disease and high mortality rates in cultivated crabs. Here, we established a highly sensitive and specific rapid reverse transcription loop-mediated isothermal amplification ( RT- LAMP) assay that was cheaper and more suitable for field applications in crab aquaculture than those of traditional reverse transcription-polymerase chain reaction ( RT- PCR) analysis. The amplification was completed within 45 min under isothermal conditions at 65°C. The RT- LAMP test for Es RV had a detection limit of 15 pg, and sensitivity was 100 times greater than that of conventional RT- PCR. The LAMP primers for Es RV were not amplified by other pathogen strains, indicating good specificity. In addition to detection by electrophoresis, RT- LAMP results were detectable by visual observations of reaction tube turbidity, and calcein was added to visually detect the amplification products. These results indicate that this highly convenient, rapid and sensitive RT- LAMP assay can be used to detect Es RV-infected aquatic organisms. Significance and Impact of the Study Tremor disease ( TD) is one of the most serious diseases of Eriocheir sinensis. A novel E. sinensis reovirus (Es RV) was identified from E. sinensis afflicted with TD and caused high mortality. We developed a reverse transcription loop-mediated isothermal amplification assay with high specificity, sensitivity and rapidity to detect Es RV, which can be used to diagnose aquatic animal diseases, particularly where expensive diagnostic instruments are not available. [ABSTRACT FROM AUTHOR]

The occurrence of morphologically immature megalopae, which retain zoeal features such as dorsal spines and furcae of telson, is closely correlated with larval mass mortality during seed production of the swimming crab Portunus trituberculatus in Japanese hatcheries. To determine the cause of immature megalopal morphology, zoeae were reared with various supplementary schedules and density of diets (rotifer, Artemia and phytoplanktons including Chlorella vulgaris and Nannochloropsis oculata). In addition, to assess the relationship between immature morphology and endocrine control, the effect of causative dietary factor was compared with the effect of eyestalk ablation at various timing during zoeal development. Megalopal immature morphology was more distinct in Chlorella-supplemented groups than in Nannochloropsis-supplemented groups. High density Chlorella supplementation was associated with the highest incidence of immaturity and resulted in larval mass mortality. The premoult of the third zoeal stage was identified as a critical period at which Chlorella supplementation led to the highest incidence of immaturity. This critical period coincided with the critical period at which larval metamorphosis was regulated by the eyestalk neurosecretory system. Our results suggested that the occurrence of immature megalopal morphology under culture conditions is most likely caused by phytoplankton (especially, Chlorella) supplementation, which disrupts the endocrine regulation. On the basis of our results, we successfully prevented the occurrence of immature megalopal morphology in 500 L tanks by excluding the influence of phytoplankton before the critical period (i.e. discontinuing phytoplankton supplementation and supplying rotifer cultured with non-phytoplankton materials). [ABSTRACT FROM AUTHOR]

The present research, undertaken in a mangrove swamp in northeastern Brazil (Mamanguape River Estuary), examined the factors that led to the overwhelming acceptance of the tangle-netting technique by crab harvesters in detriment to the now illegal tamping technique. Both techniques are the only ones currently used at our study site and in many other areas in Brazil, despite being prohibited by law. Data were collected through direct observations to determine capture efficiency, productivity, daily production, selectivity, and harvesting effort, and through interviews with crab harvesters, focusing on their perceptions of the capture techniques, the conditions of crab stocks and the sales price of a dozen crabs. Our results indicated that the two capture techniques did not significantly differ in terms of their efficiency or productivity, but daily production rates differed significantly, being greater using tangle-netting. The tangle-netting permits a greater harvesting effort (6 h and 34 min) compared to tamping (4 h and 19 min). Tangle-netting is also less selective than tamping indicated by the larger number of captured smaller specimens, including females. This results in a lower average sales price for a dozen crabs caught by tangle-netting (US$ 0.95) compared to tamping (US$ 1.02). The greater daily production of crab harvesters using the tangle-netting technique nevertheless increased their net gain, explaining their preference for this method, Given that tangle-netting results in greater harvesting pressure but lower selectivity compared to tamping, it may potentially be less sustainable. All of the crab harvesters interviewed having more than 20 years of experience (n = 34) stated they perceived that stocks of U. cordatus had become reduced over the last 20 years, together with average crab sizes. It is now important to examine the structure of the local U. cordatus population and to assess its fishery to allow evaluating whether the illegal, but prominent tangle-netting and tamping mangrove crab capture techniques are sustainable or not. We further suggest improving the dialogue between decision makers and fishermen, which barely exists to date, to initiate a discussion about possible ways of resolving the current situation of illegality of the fishermen. This will be key to achieving effective sustainable co-management of this important natural mangrove forest resource. [ABSTRACT FROM AUTHOR]

Vibrio alginolyticus is a virulent pathogen that affects crab aquacultures. In the present study, the immune responses and antioxidant status of big and small (based on body weight and size) 80-, 100- and 120-day-old specimens of Portunus trituberculatus , challenged for 72 h with Vibrio alginolyticus , were studied. The total hemocyte count (THC), and phagocytic, prophenoloxidase and phenoloxidase activities, of the big individuals (BIs) were higher than those of the small individuals (SIs) ( P < 0.05). The antioxidant status of the organisms showed a similar pattern: superoxide dismutase (SOD) activity and glutathione/oxidized glutathione (GSH/GSSG) in the cell-free hemolymph and hepatopancreases of the BIs were higher than in the SIs ( P < 0.05). There were no significant differences in α 2 -macroglobulin (α 2 -M), antibacterial and bacteriolytic activities in the cell-free hemolymph, or glutathione peroxidase activity in the cell-free hemolymph or hepatopancreas between the BIs and SIs. The α 2 -M and crustin gene expression levels in the hemocytes, and SOD expression in the hemocytes and hepatopancreas, were also significantly higher in the BIs. The results suggest that, compared with the SIs, the BIs possessed a higher resistance to V. alginolyticus infection. [ABSTRACT FROM AUTHOR]

We examined the effects of population density on body size and burrow characteristics of Uca bengali Crane, 1975. We predicted that (1) males in high-density areas (HD) should be larger in size and build higher quality burrows than males in low-density areas (LD), and (2) HD females should be larger in size, but build lower quality burrows than LD females, as HD females can find higher numbers of good quality male burrows around them for breeding and egg incubation. Our results showed that males and females in HD were larger in size than those in LD. Since HD males were larger in size, they built higher quality burrows than males in LD. On the other hand, even though LD females were smaller in size than HD ones, they built higher quality burrows than HD females. Our results thus indicate that density effects both body size and burrow characteristics. [ABSTRACT FROM AUTHOR]

The food consumption pattern in megalopae of the snow crab Chionoecetes opilio (Fabricius, 1788) was investigated in the laboratory. Ten megalopae were individually cultured and given an excess of Artemia nauplii each day. All megalopae moulted into first-instar crabs 28-34 days after metamorphosis. The mean total number and total weight of Artemia consumed during the megalopal stage were 1920 individuals and 5.2 mg, respectively. Hence, the food requirement of snow crab megalopae was estimated as ~190% of the dry body weight of the first-instar crab. Initially, the number of Artemia consumed was nearly constant or decreased only slightly but, later, Artemia consumption decreased with development days. Two-segmented regressions provided good fits to the relationship between the number of days after metamorphosis and the cumulative number of Artemia consumed by individual megalopae. The mean value of the time after metamorphosis of the breakpoint in the rate of food consumption was estimated as 69% of the stage duration, which corresponds to the intermediate of late premoult. Crab sizes (carapace width, wet and dry body weight) were not significantly dependent on the number of Artemia consumed during the entire megalopal period although a positive correlation between these variables was observed. These results provide useful information on the appropriate feeding schedule and management practice for culturing snow crab megalopae and contribute to the understanding of megalopal growth efficiency to the first-instar crab in their natural habitat. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) may pose risks to freshwater organisms, including crabs that live at the interface of sediments and water column all year round. One of the major changes that occur during oocyte maturation of crabs is the production of vitellin. In the present study, the authors investigated the effects of Cd on oocyte size, vitellin level, and vitellogenin (Vtg) messenger RNA (mRNA) expression in the ovary of the freshwater crab Sinopotamon henanense. The authors studied the impacts of Cd on carbohydrate as well as on the protein metabolism, metallothionein, glutathione (GSH) synthesis, energy-related parameters, and mRNA expression of genes involved in energy metabolism. After Cd treatment, vitellin concentration, Vtg mRNA expression, and oocyte diameter decreased. Less carbohydrate and enhanced protein catabolism were found in the ovary. Adenosine triphosphate to adenosine diphosphate (ATP:ADP) ratios, reduced nicotinamide adenine dinucleotide (NADH) to oxidized nicotinamide adenine dinucleotide (NAD+) ratios, mitochondrial membrane potential, and energy production-related mRNA expressions increased in the ovary after 10 d Cd treatment and decreased after 20 d. Metallothionein and GSH synthesis were up-regulated after 10 d on Cd exposure. Moreover, Cd caused a time-dependent up-regulation of malondialdehyde. The authors' findings show significant effects of Cd on vitellogenesis, which suggests that Cd slows down vitellogenesis in S. henanense because of excessive energy consumption and an activated defense system. Environ Toxicol Chem 2015;34:1609-1616. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Chinese mitten crab (CMC, Eriocheir sinensis) is an economically valuable species in South-East Asia that has been widely farmed in China. Characterization of the intestinal bacterial diversity of CMC will provide insights into the aquaculturing of CMCs. Based on the analysis of cloned 16S rRNA genes from culture-independent CMC gut bacteria, 124 out of 128 different clones reveal ＞95% nucleotide similarity to the species belonging to the four phyla of Tenericutes, Bacteroidetes, Firmicutes and Proteobacteria; one clone shows 91% sequence similarity to the member of TM7 (a candidate phylum without cultured representatives). Fluorescent in situ hybridization also reveals the abundance of Bacteroidetes in crab intestine. Electron micrographs show that spherical and filamentous bacteria are closely associated with the microvillus brush border of the midgut epithelium and are often inserted into the space between the microvilli using a stalk-like cell appendage. In contrast, the predominant rod-shaped bacteria in the hindgut are tightly attached to the epithelium surface by an unusual pili-like structure. Both 16S rRNA gene denaturing gel gradient electrophoresis and metagenome library indicate that the CMC Mollicutes group 2 appears to be present in both the midgut and hindgut with no significant difference in abundance. The CMC Mollicutes group 1, however, was found mostly in the midgut of CMCs. The CMC gut Mollicutes phylotypes appear to be most closely related to Mollicutes symbionts detected in the gut of isopods (Crustacea: Isopoda). Overall, the results suggest that CMCs harbor diverse, novel and specific gut bacteria, which are likely to live in close relationships with the CMC host. [ABSTRACT FROM AUTHOR]

An epidemic of 'milky disease' in the mud crab ( Scylla paramamosain) generally breaks out in the fall when the crab is near maturity, resulting in large economic losses in crab farming. Vibrio parahaemolyticus has been proven to be one of the major pathogens. In this study, the mud crabs were challenged with V. parahaemolyticus, and their innate immune responses were investigated in terms of total haemocyte counts ( THCs), haemocytic enzyme activities and gene expression levels during a 114-h period. The THCs of the mud crabs decreased significantly after 42 h of exposure. The activities of the haemocytic enzymes, including acid phosphatase-alkaline phosphatase, phenoloxidase, superoxide dismutase (SOD), peroxidase and nitric oxidase synthethase, were significantly enhanced during the challenge course. The gene expression levels also significantly increased for all tested genes (pro PO, Cu/Zn- SOD, Prx, LYS, CRU and ALF) with the exception of CAT down-regulated expression. The results may imply that the immune responses of the mud crab could be activated by the pathogens, and the data here will provide many clues for further systematic investigation of 'milky disease' caused by V. parahaemolyticus and the disease prevention in mud crab S. paramamosain. [ABSTRACT FROM AUTHOR]

In order to study fishery stocks and the effect of the male-biased fishery on multiple paternity, new genetic resources were developed forMetacarcinus edwardsii, the most important crab of artisanal fishery in Chile. A total of eight microsatellite loci were isolated and characterized in this crab, using an enriched library. Six to 27 alleles per locus were observed in two samples of 24 crab individuals. The observed heterozygosity ranged from 0.58 to 1.00 and all loci showed no deviation from Hardy–Weinberg equilibrium for either. Two sampling sites separated by 300 km showed no differences in allele frequencies, indicating that both sites are a part of the same population. Further, the genotypes of five ovigerous females and their newly hatched larvae showed that only one male was involved in the fertilization of each clutch. The variation detected in these markers is currently being used both for the study of populations ofMetacarcinus edwardsiiin a highly exploited geographic area and in order to elucidate the mating system of this species. [ABSTRACT FROM PUBLISHER]

Populations of the coconut crab, Birgus latro (Linnaeus, 1767), have been depleted by primarily overharvest. The aim of this study was to develop artificial propagation technologies for the restocking and conservation of this species: it is a terrestrial hermit crab with aquatic larvae. Megalopae (post-larvae stage) were group cultured for six months with access to both "land" and "sea" areas (trial 1). In addition, shell-carrying juveniles aged one month were group cultured on land until the age of 13 or 24 months (trial 2). Furthermore, juveniles that had abandoned their gastropod shells were cultured individually and their moult and growth was monitored. The survival rates of animals ranged from 26-55% in trial I, and they grew to a mean thoracic length (TL) of approx. 1 mm. In trial 2, the juveniles grew to a mean TL of approx. 4 mm at age 24 months. The juveniles changed their gastropod shells for larger ones according to their growth based on their body width. The juveniles found soon after abandoning their gastropod shells varied in size (2.5-8.6 mm TL), age (15-26 months old), and the degree of the formation of pleonal tergal plates. The juveniles without shells moulted 5-6 times during the culture period of 9-20 months. Two survivors grew to 6.8 mm TL and 11.9 mm TL at an age of 24 and 37 months, respectively. The body colour pattern of the juveniles was retained through successive moults. Our results demonstrated the feasibility of artificial production of the coconut crab juveniles and the utility of using natural marks to monitor their growth and migration after being released in the wild. [ABSTRACT FROM AUTHOR]

Abstract: To increase prediction accuracy, reduce aquaculture risks and optimize water quality management in intensive aquaculture ponds, this paper proposes a hybrid dissolved oxygen content forecasting model based on wavelet analysis (WA) and least squares support vector regression (LSSVR) with an optimal improved Cauchy particle swarm optimization (CPSO) algorithm. In the modeling process, the original dissolved oxygen sequences were de-noised and decomposed into several resolution frequency signal subsets using the wavelet analysis method. Independent prediction models were developed using decomposed signals with wavelet analysis and least squares support vector regression. The independent prediction values were reconstructed to obtain the ultimate prediction results. In addition, because the kernel parameter δ and the regularization parameter γ in the LSSVR training procedure significantly influence forecasting accuracy, the Cauchy particle swarm optimization (CPSO) algorithm was used to select optimum parameter combinations for LSSVR. The proposed hybrid model was applied to predict dissolved oxygen in river crab culture ponds. Compared with traditional models, the test results of the hybrid WA–CPSO-LSSVR model demonstrate that de-noising and capturing non-stationary characteristics of dissolved oxygen signals after WA comprise a very powerful and reliable method for predicting dissolved oxygen content in intensive aquaculture accurately and quickly. [Copyright &y& Elsevier]

The effects of crab aquaculture on the water and sediment quality and the pelagic and macrobenthic community of the adjacent reclamation area of Guchenghu Lake, Jiangsu Province were evaluated over two consecutive crop cycles from April 2010 to November 2011. The results indicated that most of the nutrient concentrations in both the water column and the sediment varied temporally and showed significant spatial differences. The peak values of most of the physico-chemical parameters measured were obtained during the summer or autumn, whereas the opposite result was observed for suspended solids. A higher zooplankton density and lower phytoplankton biomass were observed in ponds than in other sampling sites, whereas Cyanophyta (80 %), with Planktothrix rubescens as the dominant taxon, was predominant in the canal closest to the ponds. The benthic community was dominated by Bellamya aeruginosa in the ponds. Limnodrilus hoffmeisteri was the predominant species in the canal. Comparative analysis of the impact of crab culture showed that it produced a relatively low level of disturbance but introduced large quantities of nutrients and organic matter into the canal around the farming ponds. The introduction of these substances increased the risk that Guchenghu Lake would be affected by pollution. [ABSTRACT FROM AUTHOR]

Samples of intestine and hepatopancreas from 65 blue land crabs (Cardisoma guanhumi), a crustacean commonly consumed as a food item in Grenada, were collected from six geographic sites in Grenada and tested for Salmonella by enrichment and selective culture. The individual animal prevalence of Salmonella based on isolation was 17% (11 of 65), and all infected crabs were from three of the six sampled locations. Isolates were identified by serotyping as Salmonella enterica serovars Saintpaul (n = 6), Montevideo (n = 4), and Newport (n = 1). The intestines of all 11 infected crabs were positive for Salmonella, but only 7 of 11 hepatopancreas samples were positive for Salmonella, and these isolates were the same serovar as isolated from the matching intestine. These three Salmonella serovars are known to cause human illness in many countries, and in the Caribbean Salmonella Saintpaul has been frequently isolated from humans. In a disc diffusion assay, all isolates were susceptible to all 11 drugs tested: amoxicillin-clavulanic acid, ampicillin, cephalothin, chloramphenicol, ciprofloxacin, gentamicin, imipenem, neomycin, streptomycin, tetracycline, and trimethoprim-sulfamethoxazole. To our knowledge, this report is the first concerning isolation and antimicrobial susceptibilities of Salmonella serotypes from the blue land crab. [ABSTRACT FROM AUTHOR]

Highlights: [•] This paper presents a dissolved oxygen content prediction model based on IPSO-LSSVR. [•] IPSO as a global optimizer is employed to optimize the hyper-parameters of LSSVR model. [•] IPSO-LSSVR has a better performance for prediction of dissolved oxygen content. [•] IPSO-LSSVR yields better prediction results than standard LSSVR and BP neural network. [•] IPSO-LSSVR is an effective prediction model tool for water quality in the aquaculture. [Copyright &y& Elsevier]

Since the last decade, the South West (SW) region of Bangladesh has been found to be already engaged in practicing floating garden, cage culture, crab culture, etc., as the adaptation strategies to overcome the adverse effects of climate change (CC). Considering both, without CC (1961-1990) and with CC (1981-2010), this paper analyzes the trends of spatial, temporal, and extreme event indices for both temperature and rainfall based on fifty years (1961-2010) of data. Data have been collected from five Bangladesh Meteorological Departments distributed over the SW region and Rclimdex software is used for quality control and calculation of indices of rainfall as well as of temperature. During the monsoon, rainfall has been found with higher variability in magnitude as well as in spatial distribution. Over the last decade, both the highest monthly maximum 1-day rainfall and the highest monthly maximum consecutive 5-day rainfall were observed at Jessor, where water logging is a severe problem. Year to year variation of maximum summer temperature is increasing whereas minimum winter temperature is found to be decreasing. Additionally, the decreasing trends of consecutive wet days indicate that duration of the extreme rainfalls have become shorter. In the case of daily temperature, the winter trend has been drastically changed from increasing to decreasing. But in the case of other seasons, increasing temperature trends are found to be increasing at a faster rate. This study identifies the locations that are already vulnerable to changing condition and will be further exacerbated in the upcoming decades. [ABSTRACT FROM AUTHOR]

The results of bioeconomic analysis informed by a survey of 80 small-scale mud crab farmers in Vietnam are presented in this paper. Mud crab farming in Vietnam is profitable, with net revenue being approximately 135 and 41 million VND/year (USD 7000-USD 2100 per year) in the central and southern regions, respectively. Profitability was significantly higher in the centre compared with the north, as almost three times the biomass is harvested in the centre compared with the south (in turn, due to higher aquaculture area and survival rates). The benefit-cost ratio (the ratio between total revenue and total costs) is 3.55 in the centre and 1.97 in the south. The crabs are fed almost exclusively on low-value finfish in the centre and the south. Feeding rates were found to be low, with 95% of biomass gain coming from natural feed in the environment rather than supplementary feeding by the farmer. If pellets are to be adopted widely by mud crab farmers, negative perceptions regarding the poor adaptability of mud crab to pellets (northern farmers only), relatively slow growth rates compared with low-value finfish and lack of availability of pellets need to be overcome. [ABSTRACT FROM AUTHOR]

Abstract: This study aims to determine the effects of low temperature acclimation on the antioxidant defenses and ATPase activities in mud crab (Scylla paramamosain). The activities of ATPases and antioxidative enzymes, as well as malondialdehyde (MDA) content, were measured in the muscle of S. paramamosain acclimated at 5, 10, 15, and 27°C (control group). The activities of superoxide dismutase, catalase, and glutathione peroxidase gradually declined with decreasing temperatures and then significantly lowered at 5 and 10°C compared with those at 27°C (P <0.01 or P <0.05). Significant accumulation of MDA, a lipid peroxidation indicator, was observed at 5 and 10°C (P <0.01). Compared with the control, the activities of four different ATPases significantly increased at 10°C (P <0.01 or P <0.05). However, Na+/K+-ATPase and Mg2+-ATPase activities in the 5°C group showed no significance compared with those in the control (P >0.05). Ca2+-ATPase and Ca2+/Mg2+-ATPase activities at 5°C were remarkably lower compared with those at 27°C (P <0.01). At low temperatures, antioxidant defense ability decreases with decreasing antioxidant enzyme activities, and MDA was accumulated in cell. The higher levels of ATPase activities at 10°C, compared with the control, suggest compensation to maintain the physiological homeostasis of cytosol ion levels. However, ability to compensate for ATPase activity decreases beyond the critical value of low temperature (i.e., at 5°C). Therefore, juvenile mud crabs should be cultivated in water at temperatures above 5°C. This is an important guideline for farmers culturing mud crab in cold water. In addition, antioxidant parameters and ATPase activities can be used as biomarkers to assess the effects of low temperature acclimation on S. paramamosain. [Copyright &y& Elsevier]

Studies were carried out on the annual breeding period, lunar reproductive rhythm and daily activities rhythm of the western Atlantic fiddler crab Uca (Leptuca) leptodactyla Rathbun, 1898 from Guaratuba Bay, southern Brazil. This species reproduces from September to March, when ovigerous females are present and males construct their hoods. The monthly average air temperature fluctuates from 19.2 to 24.8°C in this period. Hoods were constructed in accordance with the semilunar cycle of the breeding period; it lasted eight days, with the maximum frequency exactly on syzygy days (full or new moon). On a sunny full moon day in midsummer, males began to construct hoods 1.5 h after the substrate became exposed to the air, as the tide went out; the maximum density of hoods occurred after 3.5 h. The breeding patterns of most fiddler crabs of the world including U. leptodactyla are not determined by species-specific rules but by environmental conditions of the habitat, while other species respond in different manner to the same climatic conditions. Construction of hoods by males is a secure indication of the reproductive period of the fiddler crab U. leptodactyla from southern Brazil. The timing of hood construction within a day is similar to that in its consubgeneric species in spite of differences in local climatic conditions. [ABSTRACT FROM AUTHOR]

The effect of five constant temperatures (20°C, 23°C, 26°C, 29°C and 32°C) on the growth of juvenile arched swimming crabs, Callinectes arcuatus, was evaluated over a 360-day experimental period. The crabs were reared in a recirculating system. The growth rate was significantly greater (p < 0.05) at 29°C, which was close to the species-preferred temperature of 26°C. The lowest growth rate occurred at 20°C. Blue crabs grown for 360 days at 29°C were twice as large as those grown at 23°C. The findings of this study could be applied to optimise the culture conditions for this tropical crab. [ABSTRACT FROM AUTHOR]

Threats to wild horseshoe crab populations and growing interest in their use for research, education and biomedical applications have prompted demand for improved techniques to rear and maintain crabs in captivity. Although numerous laboratory studies have been conducted to determine growth and survival of horseshoe crabs under various conditions, these data have not been compiled and summarized to inform culture practices. We surveyed the literature and analysed the range of available techniques to identify and define a consistent set of conditions for maximum growth and survival of horseshoe crabs in culture. We considered three age classes; embryo, juvenile and adult, and included all extant species ( Limulus polyphemus, Carcinoscorpius rotundicauda, Tachypleus gigas and Tachypleus tridentatus). We discovered relatively few published studies that clearly related husbandry conditions to growth and survival. Comparison among studies was complicated by inconsistent data collection and reporting techniques. Most published sources reported data for younger age classes, and more studies considered L. polyphemus than Asian species. The most commonly reported variables (temperature, salinity, enclosure maintenance and diet composition) showed size dependent and in some cases species-specific effects on growth and survival that will be important in guiding culture efforts. We suggest that future studies give additional consideration to substrate type, water flow, dissolved oxygen concentrations, diet quality and the quantity and frequency of feeding. If laboratory-reared stocks are to be used for propagation and restoration activities, future studies will benefit from closing these data gaps and promoting international data sharing. [ABSTRACT FROM AUTHOR]

The distribution of the alien crab Percnon gibbesi in the Mediterranean Sea was assessed, based on new data from four independent surveys in Albania-Montenegro, Tunisia, Libya, and Crete (Greece), personal observations of the authors and a thorough compilation of existing information. The species is reported herein for the first time from Albania, Algeria, Cyprus, Israel, and Lebanon. Percnon gibbesi rapidly increased its spatial distribution in the Mediterranean Sea after its first report in 1999. At present, twelve years after its introduction, P. gibbesi is established in most Mediterranean coasts, especially in middle latitudes. It is absent from the Adriatic Sea (except from its southern limit in the Albanian part of Otranto Strait), the Ligurian Sea, the Corsica Island, and the northern Aegean Sea, possibly because of the low winter temperatures prevailing in these areas. In the North African coasts, P. gibbesi has not yet been observed in Morocco. After its initial introduction, its further spreading in the Mediterranean basin seems to be governed primarily by natural dispersal via larval transport by currents. The invasion rate of P. gibbesi was assessed in the Kaş -- Kekova Marine Protected Area in southern Turkey, based on a time series of monitoring data from 2002 to 2010. The species was first observed in 2006 in two sites and rapidly increased its occupancy and abundance the following years. Its occupancy (probability of presence in 500 m length of coastline) reached 23% within four years from its first sighting. Its abundance increased exponentially with an intrinsic rate of increase r=0.79, corresponding to more than doubling of the population per year. [ABSTRACT FROM AUTHOR]