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Large plastic items in the environment are degraded into tiny pieces known as microplastics (MPs). MP contamination in tropical lagoon ecosystems poses a significant pollution threat. The mud crab, Scylla serrata, is an important crustacean in the tropical lagoon, valued as a key source of edible seafood in Asia and Europe. The potential MPs of one hundred samples were examined using the stereomicroscope for characterisation, and further analysis was conducted using µ-FTIR. A total of 1157 MPs were found in the gills and gastrointestinal tract. The mean abundance (±SD) of MP in mud crabs was 11.57 ± 6.29 items/individual. MPs were detected in both tissues, displaying a variety of colours. Transparent MPs dominated the gills at 43.9%, while blue microplastics were prevalent in the gastrointestinal tract at 32.8%. The filament (fibre) was the most prominent MP type found in the gills and gastrointestinal tract. The collected MPs from both tissues were categorised into four size ranges: 0.05–0.25 mm and 1.00–5.00 mm were the common size ranges in the gills and gastrointestinal tract, respectively. The prominent polymer type was rayon. These findings provide considerable proof of MP contamination in the mud crab species Scylla serrata and its implications for food security. [ABSTRACT FROM AUTHOR]

Mud crabs are common edible crustaceans, which are fished along the coasts of India. Scylla tranquebarica (Fabricius 1798), commonly called green crab is one of the most economically important portunid crab in India. The study was carried out to determine the sex ratio, maturation and spawning, gonadosomatic index, fecundity and egg diameter. Sex ratio of 1 female to 1.3 male gave good results. Size at first maturity was observed at 11 cm carapace width (CW) in males and 10 cm (CW) in females. The highest GSI values in males (6.17) and females (5.12) were observed in the month of October. The maximum number of eggs produced by the females was up to 5 million. The egg diameter was recorded in the range of 0.69 to 0.76 mm. The incubation period was 11-13 days. The hatching success average percentage was recorded as 80%. For the incubation and larval rearing of mud crab, Scylla tranquibarica, the optimum requirement of water temperature and salinity were recorded as 28°C and 30 ppt, respectively. [ABSTRACT FROM AUTHOR]

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Effects of varied sediment and physico-chemical properties of water on allantoin content in tissues of Scylla serrata and its role in antioxidant homeostasis were investigated. Tissues of crabs were sampled from different coastal natural habitats of S. serrata of India during summer, winter, and rainy seasons and were analyzed to detect the variation in allantoin content and lipid peroxidation (LPx) and oxidative stress (OS) neutralizing antioxidant factors. High allantoin content in hepatopancreas over muscle tissue was observed in all seasons and sampling sites. The correlation coefficient values between allantoin and environmental factors, i.e., temperature, pH, salinity, organic carbon, Mg, and Ca, strongly support the stress-induced allantoin variation level in tissues. The level of allantoin had a negative correlation with levels of ROS, which was probably due to the upregulation of the activity of major antioxidant enzymes and assisting enzymes such as glutathione peroxidase (GPx), glutathione reductase (GR), and biotransforming enzyme glutathione -s- transferases (GST). A significant seasonal variation in the level of allantoin was correlated with the activity of including superoxide dismutase, catalase, GPx, GR, and GST, which was clearly noticed as a function of abiotic factors. Additionally, the level of allantoin did not correlate with small antioxidant molecules, such as ascorbic acid and reduced glutathione. Discriminant function analysis revealed that the level of allantoin and CAT and GR activities were the major contributing factors for the clear discrimination of groups. Therefore, allantoin can be considered as a significant factor for the seasonal modulation of OS physiology in mud crab Scylla serrata. [ABSTRACT FROM AUTHOR]

Bone tissue engineering offers a novel therapy for repairing bone defects or fractures. However, it is becoming increasingly challenging because an ideal scaffold should possess a similar porous structure, high biocompatibility, and mechanical properties that match those of natural bone. To fabricate such a scaffold, biodegradable polymers are often preferred due to their degradability and tailored structure. This study involved the isolation of chitosan from crab shells (Scylla serrata) waste to use as a biomaterial in combination with hydroxyapatite (HAP) and collagen I (COL I) to mimic the extracellular matrix (ECM) composition of bone. After being cast and freeze-dried, it resulted in an interconnected porous scaffold with a porosity of 51.44% ± 2.28% and a pore diameter of 109.88 μm ± 49.84 μm. The swelling ratio of the crab scaffold was measured at 358.31% ± 25.23%, 363.04% ± 1.56%, and 370.11% ± 3.7% at 1, 3, and 6 h, respectively. Consequently, the scaffold exhibited a degradation ratio of 8.17% ± 2.59%, 21.62% ± 5.43%, 22.59% ± 14.23%, and 23.12% ± 6.28% over the course of 1 to 4 weeks. It demonstrated excellent biocompatibility with MG-63 osteosarcoma cells. Although the compression strength was lower than 2-12 MPa, the crab scaffold can still be applied effectively for non-load-bearing bone defects. Crab shell waste emerges as a promising source of chitosan for tissue engineering applications. [ABSTRACT FROM AUTHOR]

Achieving global targets for ecosystem restoration necessitates the development of effective restoration approaches. Current restoration approaches focus primarily on mitigating abiotic stresses or supplementing propagules to restore foundation species that support associated species by 'engineering' local habitats. Although keystone predators can strongly affect foundation species in natural ecosystems via trophic cascades and are often diminished in degraded ecosystems, they are traditionally neglected in efforts to restore foundation species.Here, we investigated how a keystone predator (Scylla serrata) might affect the restoration of a foundational plant (Scirpus mariqueter) in a degraded salt marsh. In a series of restoration experiments, we examined the effects of proximity to existing Scylla burrows, as well reintroducing Scylla, on the establishment of planted Scirpus in restoration areas. Furthermore, we tested if Scylla affected Scirpus via non‐consumptive effects in experiments that controlled Scylla's consumption of grazers.We found that planted Scirpus suffered less grazing and achieved higher density in areas closer to existing Scylla burrows where Scylla predation on grazers was stronger. Consistently, reintroduction of Scylla reduced grazing on Scirpus and increased its density by 360%. These positive effects of Scylla on Scirpus were driven by consumptive effects that reduced the abundance of grazers and by non‐consumptive effects that inhibited the herbivory by grazers.Synthesis and applications. These results demonstrate that incorporation of keystone predators, including both their consumptive and non‐consumptive effects, into restoration designs can greatly enhance the restoration of foundation species. Our study thus highlights the value of co‐restoring keystone predators and foundation species. Given that predators are depleted in many ecosystems, this co‐restoration approach may be broadly applicable. [ABSTRACT FROM AUTHOR]

Chitosan is a marine polysaccharide commonly seen in the crustacean family, and the exoskeleton is covered by chitosan. In this study, shells of mud crabs were subjected to chitosan extraction which has been followed by demineralization, deproteination, and deacetylation. The chemical compositions of chitosans were characterized using Fourier transform infrared spectroscopy (FTIR). It exhibits antimicrobial activity against pathogens - E.coli, Staphylococcus, Klebsiella pneumonia, Bacillus cereus, and Salmonella typhi. It has therefore received attention as a potential food preservative. Transform Infrared Spectroscopy (FTIR) also spots out chemical bonds in a molecule by creating rather an infrared absorption spectrum. FTIR is an effective instrument for analysis and for also detecting the functional groups as well as characterizing covalent bonding information. FTIR spectroscopy finds out the functional molecules involved in the synthesis of nanoparticles and also, provides accuracy and reproducibility, which helps to detect small absorbance changes in the sample. The chemical compositions of chitosans were characterized further using FESEM.The FESEM pattern performs or indicates the silver nanoparticles to be embedded in a matrix of CS. The size of the particles is seen as with their uniformity. Not only this, but also the FESEM image of Ag nanoparticles shows somewhat the particles of spherical shape. Also, by Transmission Electron Microscopy (TEM) technique, the chemical compositions of chitosans were characterized. It exhibits that synthesized chitosan/silver nanocomposites have indeed a shape such as spherical with their uniformity as to their dispersion. Further, the chemical compositions of chitosans were characterized using Electron dispersive spectroscopy (EDS). The EDS histograms reveal rather successfully the percentage weight ratios of the elements found on the chitosan surface and the nanosilver concentrations in this study. In addition, by XRD analysis the chemical compositions of chitosans were characterized. It recognizes the multifarious crystalline phases present in the material so that the information touching the chemical compositions are revealed. In this study, mcf-7 cell line is chosen. Mcf-7 is a commonly used breast cancer cell line. For evaluation of anticancer study against mcf-7, the mcf-7 cell line is chosen for the study. In this study, anti-cancer study was very specially subjected to research and the chemical compositions of chitosans were characterized very seriously by FESEM, TEM, EDS, FTIR, and XRD for such anticancer study and therapy. [ABSTRACT FROM AUTHOR]

Objective: Mud crab culture/fattening is a lucrative business with high profit margins because they have high economic and export value. Compared with shrimp culture, crab fattening has many advantages such as a short production cycle, high tolerance to poor water quality, rapid growth rates in captivity, etc. Currently, cheap commercial feed for crabs is unavailable, so raw feeds such as low‐value fishes have been used for rearing mud crabs. The current study was conducted to determine the growth performance of mud crab Scylla serrata that were fed with different processed wet feeds. Methods: Crabs weighing 250–300 g were stocked in individual cages, and the experiment was conducted with three different feed treatments including processed chicken intestine, processed shrimp head waste, oyster meat, and the control feed was processed small‐sized low‐value fish. Result: Of all the feeds, mud crabs that were fed with chicken intestine showed better performance, followed by oyster meat, shrimp head waste, and low‐value fish. Conclusion: The present study concludes that fattening mud crabs with chicken intestine as feed showed better growth and economic performance. Impact statementIn India, low‐value fishes have been generally used as a wet feed for mud crab culture. Using chicken intestine as an alternative wet feed enhances the growth performance and economic performance in the mud crab culture. [ABSTRACT FROM AUTHOR]

Decapod crustaceans have tooth-like white denticles that are present only on the pinching side of the claws. In the mud crab, Scylla serrata, a huge denticle exists on the movable finger of the dominant claw. This is mainly used to crush the shells of the crab's staple food. The local mechanical properties, hardness (HIT) and elastic modulus (Er), of the peak and valley areas of the largest denticle were examined via a nanoindentation test. The microstructure and elemental composition were characterized using a scanning electron microscope and energy-dispersive X-ray spectroscopy. The striation patterns originating from a twisted plywood structure parallel to the surface were visible over the entire denticle. Most of the largest denticle was occupied by a hard area without phosphorus, and there was a soft layer corresponding to the endocuticle with phosphorus in the innermost part. The HIT of the denticle valley was about 40% lower than that of the denticle peak, and the thickness of the soft endocuticle of the denticle valley was five times thicker than that of the denticle peak. The HIT–Er map showed that the abrasion resistance of the denticle surface was vastly superior and was in the top class among organisms. The claw denticles were designed with the necessary characteristics in the necessary places, as related to the ecology of the mud crab. [ABSTRACT FROM AUTHOR]

Aim: Spatially explicit protections of coastal habitats determined on the current distribution of species and ecosystems risk becoming obsolete in 100 years if the movement of species ranges outpaces management action. Hence, a critical step of conservation is predicting the efficacy of management actions in future. We aimed to determine how foundational, habitat‐building species will respond to climate change in Fiji. Location: The Republic of Fiji. Methods: We develop species distribution models (SDMs) using MaxEnt, General Additive Models and Boosted Regression Trees and publicly available data from the Global Biodiversity Information Facility to predict changes in distribution of suitable habitat for mangrove forests, coral habitat, seagrass meadows and critical fisheries invertebrates under several IPCC climate change scenarios in 2070 or 2100. We then overlay predicted distribution models onto existing Fijian protected area network to assess whether today's conservation measures will afford protection to tomorrow's distributions. Results: We found that mangrove suitability is projected to decrease along the Coral Coast and increase northward towards the Yasawa Islands due to precipitation changes. The response of seagrass meadows was predicted to be inconsistent and dependent on the climate scenario. Meanwhile, suitability for coral reefs was not predicted to decline significantly overall. The mangrove crab Scylla serrata, an important resource for fisherwomen in Fiji, is projected to increase in habitat suitability while economically important sea cucumber species will have highly variable responses to climate change. Main conclusions: Species distribution models are a critical tool for conservation managers, as linking spatial distribution data with future climate change scenarios can aid in the creation and resiliency of protected area programmes. New protected area designations should consider the future distribution of species to maximize benefits to those taxa. [ABSTRACT FROM AUTHOR]

Decapod crustaceans have tooth-like denticles on their claw fingers, which come into direct contact with predators and prey. Since the denticles are subject to more frequent and intense stress than other parts of the exoskeleton, they must be especially resistant to wear and abrasion. We clarified the mechanical resistance and tissue structure of the denticles arranged in a line on the fixed finger of the mud crab, which has huge claws. The denticles of the mud crab are small at the fingertip and become larger closer to the palm. The denticles have a twisted-plywood-pattern structure stacked parallel to the surface regardless of size, but the abrasion resistance strongly depends on the size of the denticles. Due to the dense tissue structure and calcification, the abrasion resistance increases as the denticle size increases, reaching its maximum at the denticle surface. The denticles of the mud crab have a tissue structure that prevents them from breaking when pinched. The high abrasion resistance of the large denticle surface is an essential feature for the frequent crushing of shellfish, which is the mud crab's staple food. The characteristics and tissue structure of the claw denticles on the mud crab may provide ideas for developing stronger, tougher materials. [ABSTRACT FROM AUTHOR]

Infecting a wide range of hosts, members of Reovirales (formerly Reoviridae) consist of a genome with different numbers of segmented double stranded RNAs (dsRNA) encapsulated by a proteinaceous shell and carry out genome replication and transcription inside the virion. Several cryo-electron microscopy (cryo-EM) structures of reoviruses with 9, 10 or 11 segmented dsRNA genomes have revealed insights into genome arrangement and transcription. However, the structure and genome arrangement of 12-segmented Reovirales members remain poorly understood. Using cryo-EM, we determined the structure of mud crab reovirus (MCRV), a 12-segmented dsRNA virus that is a putative member of Reovirales in the non-turreted Sedoreoviridae family, to near-atomic resolutions with icosahedral symmetry (3.1 Å) and without imposing icosahedral symmetry (3.4 Å). These structures revealed the organization of the major capsid proteins in two layers: an outer T = 13 layer consisting of VP12 trimers and unique VP11 clamps, and an inner T = 1 layer consisting of VP3 dimers. Additionally, ten RNA dependent RNA polymerases (RdRp) were well resolved just below the VP3 layer but were offset from the 5-fold axes and arranged with D5 symmetry, which has not previously been seen in other members of Reovirales. The N-termini of VP3 were shown to adopt four unique conformations; two of which anchor the RdRps, while the other two conformations are likely involved in genome organization and capsid stability. Taken together, these structures provide a new level of understanding for capsid stabilization and genome organization of segmented dsRNA viruses. Author summary: Mud crab reovirus (MCRV), a putative member of the Sedoreoviridae family in Reovirales, infects an economically important crab, Scylla serrata, and has resulted in serious economic loss for the crab aquaculture. In this study, we report the structure of MCRV, which has allowed us to examine the detailed structural elements that might be responsible for capsid stability, as well as those involved in genome packaging and RdRp organization. The arrangement of viral polymerases inside the capsid differ from what has been seen in other viruses of the same order, as ten of the vertices are occupied by RdRp in a symmetrical organization not seen elsewhere. In addition, the VP11 protein is analogous to the "clamp" protein of turreted reovirads. [ABSTRACT FROM AUTHOR]

Herein, moribund mud crab (Scylla serrata) samples were collected from various farming systems, brooders from wild and hatchery quarantine section, located in Tamil Nadu, Andhra Pradesh, and Odisha. The infected crabs showed clinical signs of lethargic movement with the sleeping position in the culture ponds, tanks, and wild-caught. In the wet mount study, massive numbers of viral giant cells were observed in the infected crab hepatopancreas and connective tissue. Mud crab reovirus (MCRV) inclusion bodies were noticed in the connective tissue of hepatopancreas, gill lamellae, muscle and gonads in histopathology analysis. Also, viral particles proliferated into the cytoplasm of the cells, but they did not affect the host nuclei. The infected crab samples were confirmed in the PCR using specific primers (ReoF and ReoR) and rDNA sequence analysis showed 99% similarity with mud crab reovirus and Scylla serrata reovirus (OL466868 and OL466869). The ultrastructural study (TEM) revealed that MCRV viral particles ranged between 70 and 75 nm in diameter, icosahedral shape, and non-enveloped with two capsid layers located in the cytoplasm of the cells. The prevalence of mud crab reovirus infection was recorded between 80 and 100% in cultured farms within 25 days and 19–33% in the wild from the collected samples. In the pathogenicity study, intramuscular injection bioassay reached 100% mortality and a co-habitation assay was 70% mortality on 14 days of MCRV post-infection. Thus, our results suggest that MCRV is highly pathogenic to mud crab culture. [ABSTRACT FROM AUTHOR]

Global climate change–induced ocean warming and acidification have complex reverberations on the physiological functioning of marine ectotherms. The Sundarbans estuarine system has been under threat for the past few decades due to natural and anthropogenic disturbances. In recent years, petroleum products' transportation and their usage have increased manifold, which causes accidental oil spills. The mud crab (Scylla serrata) is one of the most commercially exploited species in the Sundarbans. The key objective of this study was to delineate whether rearing under global environmental drivers (ocean acidification and warming) exacerbates the effect of a local driver (oil pollution) on the physiological energetics of mud crab (Scylla serrata) from the Sundarbans estuarine system. Animals were reared separately for 30 days under (a) the current climatic scenario (pH 8.1, 28°C) and (b) the predicted climate change scenario (pH 7.7, 34°C). After rearing for 30 days, 50% of the animals from each treatment were exposed to 5 mg L−1 of marine diesel oil for the next 24 h. Physiological energetics (ingestion rate, absorption rate, respiration rate, excretion rate, and scope for growth), thermal performance, thermal critical maxima (CTmax), acclimation response ratio (ARR), Arrhenius activation energy (AAE), temperature coefficient (Q10), warming tolerance (WT), and thermal safety margin (TSM) were evaluated. Ingestion and absorption rates were significantly reduced, whereas respiration and ammonia excretion rates significantly increased in stressful treatments, resulting in a significantly lower scope for growth. A profound impact on thermal performance was also noticed, leading to a downward shift in CTmax value for stress-acclimated treatment. The present results clearly highlighted the detrimental combined effect of global climatic stressors and pollution on the physiological energetics of crabs that might potentially reduce their population and affect coastal aquaculture in forthcoming years. [ABSTRACT FROM AUTHOR]

The mud crab, Scylla serrata, has huge claws in comparison with its body size. The color of the claw top's finger surface changes from white to deep-mottled blue, and this discoloration was strongly associated with the change in hardness inside the finger cross section. With special attention to the discoloration points, the tissue structure of the exoskeleton was investigated via scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction (XRD), and the mechanical properties were examined using Vickers hardness and nanoindentation tests. The exocuticle in the deep blue surface exoskeleton was as thin as that in other crustaceans, and the exoskeleton was occupied by the endocuticle with a twisted plywood structure. On the other hand, in the white surface exoskeleton, the thickness of the hard and dense exocuticle accounted for 52–59% of the exoskeleton thickness. This percentage increased at the claw tip. The hardness of the exocuticle was 2.5 times that of the endocuticle, and the microstructures and mechanical properties gradually varied at the boundary between the exo- and endocuticle. The mechanical properties were almost constant in the exocuticle, but calcium (Ca) concentrations decreased from the outer surface toward the boundary in that region and magnesium (Mg) concentrations increased. The change in the unit cell volume obtained via XRD suggested that some of the Ca atoms in the calcite crystal structure in that region were replaced with Mg atoms. Changes in crustacean coloration may help us to understand the tissue structure and mechanical properties within the exoskeleton. [ABSTRACT FROM AUTHOR]

Swimming crabs of the genus Portunus are revised based on analysis of three genetic markers (COI , 16S and H3) and a morphological comparison. The analyses reveal the polyphyletic composition of Monomia , Portunus and Xiphonectes and the paraphyly of Achelous. Portunus , in our revised composition, is restricted to 13, Monomia to ten and Xiphonectes to 14 species. Other species are transferred to Achelous (28) and Cycloachelous (nine) or to newly established genera. Four new genera are separated from Xiphonectes and one new genus from Monomia. The systematic composition of the portunid subfamily Portuninae now comprises 11 genera: Arenaeus , Allomonomia gen. nov. , Cavoportunus , Callinectes , Cycloachelous , Eodemus gen. nov. , Incultus gen. nov. , Monomia , Portunus , Trionectes gen. nov. and Xiphonectes. The genus Lupella is synonymized with Achelous (Achelouinae). Xiphonectes pulchricristatus and Xiphonectes spinipes are placed in Alionectes gen. nov. , Portunus ponticus is transferred to Lupocycloporus (both Lupocyclinae), and Monomia euglypha is now placed in Cycloachelous (Portuninae). Portunus mokyevskyi is considered a junior synonym of Scylla tranquebarica (Necronectinae). Xiphonectes leptocheles is confirmed as a valid species. Cycloachelous granulatus unispinosus is also considered a valid species and is to be treated as Cycloachelous unispinosus. [ABSTRACT FROM AUTHOR]

Three isoenergetic diets differing in their fishmeal/soy protein concentrate (SPC) ratio were assessed on the tissue growth and energy budget of juvenile crabs Scylla serrata in postmolt stages (PMolt) and in intermolt stages (IMolt). The average growth rates on a dry matter basis were 2.064 ± 0.324% and 0.492 ± 0.08% initial BW.day−1 during PMolt and IMolt stages, respectively. The efficiencies of the feed conversion (FCE, %), protein retention (PRE, %) and energy retention (ERE, %) were similar for the three experimental diets. However, FCE, PRE and ERE in PMolt stages were four to five times higher than in IMolt stages. The feed intake, energy and protein required for growth in PMolt stages were obviously higher than in IMolt stages. The energy budgets (% total energy intake) were marginally affected by diet but were significantly affected by the molt stage. The maintenance energy was lower in PMolt stages (49.84 ± 4.9%) than in IMolt stages (83.33 ± 2.45%). The excess in maintenance energy in IMolt stages represents the portion set aside for the next molt: shell energy content (4.97 ± 0.31%) and energy for ecdysis (±28%). Conversely, recovery energy was significantly higher in PMolt stages (34.39 ± 0.99%) than in IMolt stages (8.33 ± 1.7%). In conclusion, SPC sustained good tissue growth and good feed utilization and can be used as a main source of dietary protein for crab juveniles in captivity. [ABSTRACT FROM AUTHOR]

The claws of the mud crab, Scylla serrata, are huge in comparison with its body size. Many bulges ranging from 5 to 23 μm in height and 90 to 146 µm in diameter were observed on the mottled, deep-blue exoskeleton surface of the mud crab's claw. These cuticle bulges were closely related to irregularly present exocuticles on the surface layer of the exoskeleton's cross section. The bulges exist between the exocuticles, and at the apex of these bulges was a tube that bundled many pore canals that penetrated the exoskeleton. This tube was thick (62–66 µm) near the inner side and narrowed (12–22 µm) toward the outer surface. On the other hand, the exocuticles had a heterogeneous tissue structure in a coarse region extending normally to the surface, with a diameter of 3 to 7 µm, and a dense region between them. Calcium concentrations were high in the dense region, and phosphorus and magnesium concentrations were high in the coarse region. As a result, the mechanical properties (hardness: H and modulus: Er) were distributed inside the exocuticle, and the mapping of H and Er using a nanoindentation test clarified the heterogeneity. [ABSTRACT FROM AUTHOR]

This paper examines the effectiveness of crab culture as an adaptation strategy against salinity intrusion in the south-west region of Bangladesh. The research uses descriptive statistics, such as mean, standard deviation, benefit-cost analysis, Cobb-Douglas production function, and total barrier index to show the socio-demographic information of the respondents and profitability, efficiency, and returns to scale along with barriers to crab culture. Simple random sampling has been used to select the sample from the study area. The result from benefit-cost analysis shows that crab production is economically viable and profitable. The estimated results from the Cobb-Douglas production function model indicate the positive influence of crab feed and crab seed on total yield of crab production. There are increasing returns to scale in crab production system where there is still scope to increase productivity of crab production. A few barriers to crab production have been identified. High feed cost and lack of credit are the top barriers to crab culture. [ABSTRACT FROM AUTHOR]

The influence of temperature on sex determination has been reported previously on many crustaceans. The interpretability of temperature capability to regulate the steroidogenic pathway, which in turn governs the offspring sex of mud crab, still remains unclear. Thus, the aim was to determine the effects of temperature on sex percentage and steroidal pathway in purple mud crab, Scylla tranquebarica. In sex percentage analysis, the eggs (28°C and 30°C), larvae (28°C, 30°C and 32°C) and juveniles (26°C, 28°C, 30°C) were exposed to different temperatures. The results revealed that exposure to a higher temperature during larvae (32°C) and juvenile (30°C) stages probably initiated the maleness (58.7%) and femaleness (60.8%) mechanism respectively. In steroid hormone analysis, the eggs (26°C, 28°C, 30°C and 32°C), larvae (29°C, 30°C, 31°C and 32°C) and juveniles (26°C, 28°C, 30°C and 32°C) were exposed to different temperatures. The steroidal assay corroborated the results of the sex percentages, which found higher dihydrotestosterone (172.4 pg/g) and testosterone (580.2 pg/g) levels when the larvae were incubated at a higher temperature (32°C) while higher estrone (136.9 pg/g) and estradiol (540.7 pg/g) levels when the juveniles were reared at high temperature (30°C). In brief, the temperature plays a significant role to redirect the mud crab sex during the larval and juvenile stages. [ABSTRACT FROM AUTHOR]

Background: Karkataka Taila (KT) is a virgin coconut oil (VCO) based Rasayana formulation that is enriched with the flesh of freshwater edible crab, Scylla serrata, used to treat Parkinson's Disease (PD) or Kampavata by local Ayurveda practitioners of Kerala state. There is no scientific study carried out on its toxicological effects so far. Objective: To understand the ayurvedic preparation method for KT and assessment of the toxicological effects of the KT and VCO on SH-SY5Y cell lines and Drosophila melanogaster embryos. Materials and methods: The SH-SY5Y cell lines treated with different concentrations of KT and VCO range from 6.25 µg/ml to 100 µg/ml and Drosophila melanogaster embryos fed with food containing different concentrations of KT and VCO, ranging from 0.005 % to 10 %. Results: KT and VCO did not show any significant cytotoxicity effect on SH-SY5Y cell lines up to a dose concentration of 25 µg. But, at 50 µg and 100 µg concentrations, KT has shown a cytotoxic effect and it was higher than the VCO. The toxicological analysis in Drosophila has shown that the survival rate of the KT treated group at concentration ranges from 0.005 % to 10 % is significantly decreased from 78.8 % to 27.7 %, compared to the control group, whereas in VCO treated group, at 0.005 % to 10 %, the survival rate has decreased from 76.2 % to 66 %, which is marginally higher than the KT treated group. Conclusion: Our findings revealed that as the concentration of Rasayana in the medium increases, there is a noticeable adverse effect on the percentage viability in SH-SY5Y cell lines and in the number of offspring in Drosophila. The effect of vehicle, VCO, at the same concentration has shown a protective effect on cell lines and flies. It can be concluded that the toxic effect has been observed only at higher concentrations of KT and at the lower concentration, the toxic effect has been minimal. [ABSTRACT FROM AUTHOR]

Mud crabs (Scylla spp.) are commercially important species in Buntal Mangroves, Kuching, Sarawak, harvested mainly to meet the demand from local seafood restaurants. Fishermen have claimed that the size of mud crabs has declined, but no scientific study has been carried out to verify the statement. Therefore, a study was carried out to determine mud crab species composition and current community structure. Between February 2019 and January 2020, a total of 244 mud crabs were caught in Buntal Mangroves using collapsible baited crab traps. Their carapace length (CL), carapace width (CW) and wet body weight (BW) were measured. Four species of mud crab were collected, namely Scylla serrata, S. paramamosain, S. tranquebarica and S.olivacea. The sex ratios of S. olivacea and S. paramamosain were male biased; however, no sexual dimorphism was observed across all species in this study. The largest but rarest species caught during this study was S. serrata. It is hoped that more research work could be done in future to support sustainable utilisation of the resource and benefit the local communities. [ABSTRACT FROM AUTHOR]

Research characterising the effects of future climate change on the marine environment remains heavily focussed on that of temperate regions and organisms. Furthermore, little is known of these effects on the early life stages of many marine species. Tropical regions are already experiencing an increase in sea surface temperature and decrease in sea surface salinity, conditions favoured by pathogenic bacteria such as Vibrio spp. The early life stages of crabs are known to be particularly vulnerable to both the direct physiological effects of climate change and exposure to harmful microorganisms, yet there are limited data on these effects on juveniles of many tropical crustacean species. This study assessed the metabolic responses of mud crab (Scylla serrata) juveniles to warming and/or freshening in the presence or absence of pathogenic bacteria in southwest India. Juvenile crabs were exposed to either ambient (28 °C/30 PSU) or one of three projected climate change regimes (28 °C/20 PSU (freshening), 32 °C/30 PSU (warming), 32 °C/20 PSU (warming + freshening)) for 10 days, in either the presence or absence of the pathogenic bacteria Vibrio parahaemolyticus. Results show that simulated climate change conditions, especially freshening, caused a significant increase in oxygen consumption rates (MO2), and that these were further increased when juveniles were exposed to V. parahaemolyticus. These results suggest that the effects of future climate change conditions could have significant implications for the conservation of wild stocks and commercial farming of this species in South Asia. [ABSTRACT FROM AUTHOR]

The present study was directed towards elucidation of immunological markers in WSSV‐infected mud crabs through a comparative study with whiteleg shrimp. Parameters analysed including serum protein levels, bacteriolytic activity, haemagglutination activity, phenoloxidase activity and total haemocyte count. Analyses of above said parameters revealed that during the course of WSSV infection, serum haemagglutinating and phenoloxidase activity in mud crabs did not show any significant change in contrast with the whiteleg shrimps. Possibly, such distinct immune response against WSSV may play an important role in pathogenicity caused by WSSV in the mud crab S. serrata and may contribute to the resistivity against WSSV by these crabs. [ABSTRACT FROM AUTHOR]

The giant mud crab, Scylla serrata (Forskål, 1775), is a targeted fishery along its geographic distribution, both for domestic and international markets. Population genetic data, evaluated with genetic markers such as microsatellites, can be used to identify management units (stocks) based on genetic dissimilarities between locations, informing localized management decisions for targeted fisheries. Additionally, microsatellite loci can be used to identify released individuals from stock enhancement programs, while simultaneously monitoring genetic impacts of hatchery-releases on wild populations. We isolated and characterized 16 novel microsatellite markers; fourteen of the markers were further evaluated for population structure among three localities in the US-Affiliated Pacific Islands: Palau, Pohnpei, and Kosrae. The significant genetic differentiation observed between Palau and Kosrae/Pohnpei suggests the newly described markers would be capable of elucidating structure across the broader scope of the geographic distribution of the species. Given the international trade for live mud crab, the evaluation of structure would highlight potential issues regarding the transport of live animals between locations with genetically differentiated stocks. Additionally, a multilocus exclusion probability of 0.999, with as few as three markers, suggests the novel microsatellite markers would be capable of identifying hatchery-sourced individuals as part of a stock enhancement program. [ABSTRACT FROM AUTHOR]

Interest in the production of crustacean aquaculture has focussed primarily on mud crab species; however, mud crab production still relies on wild‐caught juveniles due to the low production of viable seeds of mud crab. Thus, the aim of this study was to enhance mass propagation of purple mud crab seed by studying the relation of temperature on growth performance of the early life stage of purple mud crab. Several data such as survival, incubation duration and morphometric measurements were evaluated after temperature was exposed on the egg, larval and crablet stages. For the egg stage, high hatching success (78.95% and 75.00%) was noted within a limited temperature range (28°C and 30°C respectively). Also, significant increment of final egg diameter (0.33 ± 0.05 mm) after the berried crab incubated at 30℃. For larval stage, the highest survival rate was found when the larvae were reared at 30℃ and 31°C with 68.79 ± 2.69 and 66.98 ± 2.63% respectively. The largest morphometric measurements for megalopa (CW: 2.80 ± 0.15 mm) and C1 (CW: 2.86 ± 0.12 mm) were observed at 31℃. The yielded total juvenile at the end of the larval experiment indicated the highest production was obtained for temperature 31°C (1,095 ± 47.3 individuals) followed by 30°C (1,002 ± 84.7 individuals). For the crablet stage, the crablets were able to survive in a wide range of temperatures (26°C–32°C) with >95% survival; however, the temperature 26℃–29°C indicated larger morphometric measurements (CW: 6.24–6.39 mm). In brief, the optimal temperature for egg, larval and crablet stages was recommended within 28℃–30℃, 30℃–31℃ and 26℃–29℃ respectively. [ABSTRACT FROM AUTHOR]

Keywords: egg; juvenile; larva; mud crab; temperature EN egg juvenile larva mud crab temperature 707 713 7 01/07/22 20220201 NES 220201 INTRODUCTION A series of morphological variations started in early juvenile as an adaptability process to ensure the capability of mating and reproducing during adulthood (Parvizi et al., 2017). If sexual dimorphism occurred, the line between male and female is widening with the course of juvenile growth gl Copulatory organs, chelae, and abdomen can be used to differentiate between male and female juveniles. The traits of large chela in male crabs are considered to be evolved due to intra-sexual selection, in which the male crabs fight aggressively to access the female crabs (Yoshino et al., 2011). Most findings of brachyuran crabs applied the abdominal width as secondary characters to define the sexual maturity of female crabs (Waiho et al., 2016a; 2016b). [Extracted from the article]

This study focuses on the isolation, chemical and crystalline structures, and the kinetics of heterogeneous deacetylation of chitin from mud crab shells (Scylla serrata). The independent variables in this work are temperature, NaOH concentration, and reaction time. The degree of deacetylation (DD) of the resulting chitosan was determined for different reaction times. It was found that the DD increases nonlinearly with the reaction time. The deacetylation of the chitin followed pseudo first-order kinetics and it occurred in two stages, which are respectively attributed to the reaction of acetamide groups in the amorphous region on the external layer, and in the crystalline region inside the chitin particles. The rate constants for the latter stage of the deacetylation at 35°C, 75°C, and 105°C were 4.67×10−4 min−1, 3.00×10−3 min−1, and 4.61×10−3 min−1, respectively. Based on this temperature-dependent rate constant, the activation energy of the slow deacetylation stage was estimated to be 32.6 kJ mol−1. [ABSTRACT FROM AUTHOR]

The heavy metals namely Fe, As, Cu, Cd, and Pb were investigated in two marine fishes silver pomfret (Pampus argentus) and torpedo scad (Megalaspis cordyla), and three seafoods sibogae squid (Loligo sibogae), Indian white prawn (Fenneropenaeus indicus), and mud crab (Scylla serrata) by using inductively coupled plasma spectrophotometer (ICP-MS) from two renowned fish harvesting coastal area of Malaysia named as Kedah and Selangor. Among the target heavy metals, highest mean concentration of As and Fe were found in Scylla serrata (72.14±7.77 μg/g) in Kedah and Megalaspis cordyla (149.40±2.15 μg/g) in Selangor. Pearson's correlation results showed As-Fe-Cd-Cu originated from the same source. Maximum estimated daily intake (EDI) values of Scylla serrata were found 175.25 μg/g/day and 100.81 μg/g/day for child in both Kedah and Selangor areas respectively. Hazard quotient (HQ) and hazard index (HI) results revealed that local consumers of Kedah and Selangor will face high chronic risk if they consume Scylla serrata, Fenneropenaeus indicus, and Megalaspis cordyla on regular basis in their diet. Carcinogenic risk results suggested that all the studied species pose very high risk of cancer occurrences to the consumers in both areas. Therefore, it could be recommended that consumers should be aware when they are consuming these marine species since they can pose serious health risk associated with prolonged consumption. [ABSTRACT FROM AUTHOR]

We compiled known occurrence records of seven species of crabs identified in the literature and one documented in this report as having undergone range extensions in southern Africa. Of these eight species, six (Austruca occidentalis , Neosarmatium africanum , Ocypode ceratophthalmus , Portunus segnis , Tubuca urvillei , and Varuna litterata) have extended their ranges either across a major biogeographic boundary that separates the subtropical and warm temperate ecoregions of this coast, or into estuaries that historically lack mangrove forests. For the seventh and eighth species, Charybdis smithii and Scylla serrata , we were unable to find any distributional data that supported poleward range extension. In addition, we contribute the first record of the blue swimming crab, P. segnis , from the temperate south coast of South Africa. This early detection is likely to be part of an ongoing regional trend of tropical-adapted brachyuran crab species extending their ranges into temperate ecoregions. Résumé: Nous avons compilé les données d'occurrence connues de sept espèces de crabes identifiées dans la littérature et une documentée dans ce rapport comme ayant développé des extensions de répartition en Afrique du Sud. Sur ces huit espèces, six (Austruca occidentalis , Neosarmatium africanum , Ocypode ceratophthalmus , Portunus segnis , Tubuca urvillei , et Varuna litterata) ont étendu leur répartition soit à travers une limite biogéographique majeure qui sépare les écorégions subtropicale et tempérée chaude de cette côte, soit dans les estuaires qui historiquement n'ont pas de forêt de mangrove. Pour les septième et huitième espèces, Charybdis smithii et Scylla serrata , nous n'avons pas pu trouver de données de distribution qui supportent une extension vers le pôle. De plus, nous apportons le premier signalement du crabe bleu P. segnis , de la côte tempérée sud de l'Afrique du Sud. Cette première détection s'inscrit probablement dans une tendance régionale en cours des espèces de brachyures adaptées aux tropiques qui étendent leur aire de répartition vers des écorégions tempérées. [ABSTRACT FROM AUTHOR]

Background: The mangrove crab Ucides cordatus is considered a key species for the ecological balance of mangrove forests and a major source of employment and income for traditional crab collectors in Brazil. Several studies evidenced weak genetic variation among populations due to an efficient larval transport. However, gene flow patterns of the species is poorly understood, with no information about migration rates. The influence of the two main Brazilian currents in larval dispersion is also not clear. In order to provide baseline information for conservation, planning and management of this important fishery resource, the present study aimed to estimate and evaluate spatial distribution of genetic diversity, migration rates and gene flow directivity among populations of U. cordatus in Brazil. Methods: Nine microsatellites were used to resolve population structure of 319 crabs collected from six sites located along the Brazilian coast. The degree of geographical differentiation included estimates of genetic diversity, population structure and gene flow models, with spatial analysis of shared alleles (SASHA), isolation by distance tests, AMOVA, discriminant analysis of principal components (DAPC) and Bayesian clustering. We estimated the amount of ongoing gene flow between clusters using the coalescent-based method implemented in Migrate-N. Results: Loci were highly polymorphic (average of 12.4 alleles per locus) evidencing high genetic variability. There was significant differentiation among localities, despite of the low value of FST (= 0.019; P < 0.001). FST and Jost's D indexes were also estimated in pairwise comparisons and showed significant differences between most of the surveyed site pairs (P < 0.05). Structure evidenced a single genetic group among samples, however SASHA pointed to a non-panmictic condition (P = 0.011). AMOVA detected four statistical significant clusters with low level of differentiation (FCT = 0.037; P = 0.023). The gene flow model that best described the population connectivity was the island model, with ~24 crabs being exchanged among localities per generation. Discussion: The high migration rates found among localities seem to be the main force acting to sustain the distribution of the genetic diversity of U. cordatus. Despite the high gene flow and the weak population structure among samples, the significant genetic differences found suggest that gene flow alone does not bypass the effects of genetic drift, natural selection and/or human exploitation. These findings are vital for the establishment of a database to be used in the development of conservation programs. [ABSTRACT FROM AUTHOR]

Report cards are increasingly popular tools communicating the condition of coastal and riverine environments to environmental managers, stakeholders and the public, and synthesising complex data drawn from a range of indicators. Mud crabs have not previously been included in ecosystem health report cards in Australia or elsewhere but have been suggested as environmental indicators for tropical coastal marine environments in Australia. Mud crabs support commercial, recreational and Indigenous fisheries and their biology is relatively well known. For these reasons and due to their local relevance, mud crabs (Scylla serrata) were selected for long-term monitoring and inclusion in a report card for Gladstone Harbour, Australia. Three mud crab measures were identified to reflect the variety of pressures across Gladstone Harbour: abundance, prevalence of rust lesions and sex ratio. A standardised field monitoring program was developed to allow for ongoing scoring and reporting of the multi-metric indicator. An indicator scoring (distance from benchmark) and grading methodology was applied to the indicator and refined over the two years of monitoring. This article provides a novel framework for monitoring and scoring mud crabs for management purposes or for use in report cards, and outlines the process of developing an indicator for an iconic crustacean species. [ABSTRACT FROM AUTHOR]

Mud crab Scylla serrata of Kotania Bay and Pelita Jaya Bay of Western Seram District, has been harvested by local fishermen for more than 25 years. The mud crab has high economic value, and there is always a market for this fishery. The economic dependence of the fishermen forces them to harvest this resource extensively. No existing management strategy and extensive exploitation leads to unsustainable conditions of this fishery. With inadequate data condition, the Driver-Pressure-State-Impact-Response (DPSIR) model constructs an ecological, social-economy, and institutional conceptual model framework for sustainable management of this fishery. The driving force (D) in this fishery comes from the local fishers harvesting the mud crab. The two most sensitive attributes that affected mud crab sustainability from Rapfish analysis were used as state-level of DPSIR methodology. The result shows that the most sensitive variables from ecological, socio-economy, and institution were: caught before maturity, mud crab size, consumer attitude towards sustainability, just management, government quality, and monitoring and reporting, respectively. It was concluded that this conceptual model allows a better understanding of how the mud crab S. serrata system works and management actions taken at different system components. This conceptual model framework can be a useful tool to incorporate the participation of stakeholders, managers, and scientists in the process of a sustainable management plan. [ABSTRACT FROM AUTHOR]

We studied the patterns in production of three species of Brachyuran crabs, namely Scylla serrata, Scylla tranquebarica, and Portunus pelagicus inhabiting the famous Chilika lagoon. We collected data from 3–7 landing centers located in 2–3 different geographical sectors of the lagoon over a period of two consecutive years. Thereafter, we computed monthly averages of production using log-transformed data and performed Cosinor rhythmometry with a fixed time window (τ = 365.25 d) to obtain rhythm parameters, such as Mesor, amplitude, and the peak. The results revealed statistically significant circannual rhythms in the landing biomass of all three species. The circannual rhythm parameters varied across space and time. Of all the landing centers, the Satapada located in the outer channel sector registered the highest production, irrespective of species, although at different times of the year. The spatial and temporal differences observed in the production rhythms between Scylla species and P. pelagicus might be a reflection of optimization of coexistence in their shared niche. This spatiotemporal information on production of the three species of Brachyuran crabs are certainly valuable for building strategies and plans to be implemented during harvesting of those economically very important species that are considered as great Chilika delicacies. [ABSTRACT FROM AUTHOR]

Bio-waste materials from aquatic species are alternative sources of chitin and chitosan—high-value natural biodegradable and biocompatible polymers. More than 250,000 metric tons of shell, scale, and carapace waste are produced in the Philippines. An evaluation of the quality of raw chitin and chitosan yields from the bio-waste materials of Asian green mussel (Perna viridis), tropical oyster (Crassostrea iredalei), milkfish (Chanos chanos), tilapia (Oreochromis niloticus), and king mangrove crab (Scylla serrata) is needed for the sustainable sourcing. The mild extraction method done in this study showed significantly higher yields of chitin and chitosan for S. serrata and P. viridis (p = 0.001), with chemical structure confirmed through FTIR-ATR analysis. Elemental analysis showed pure extracts from S. serrata, P. viridis, and C. iredalei (N = 6.43–7.01%; DA = 98.7–104.1%). Extracts from the fish scales have high moisture content and glycoprotein contamination. Protein content, determined using UV-VIS spectrophotometry, was found to be significantly less in P. viridis and may be related to the fineness of particle size after grinding. It is recommended to improve the protocol to increase yield across all bio-waste materials, including additional tests to determine the quality of chitin and chitosan extracted, and to check water and oil holding capacities of the extracts to identify the best downstream applications of the varied chitin and chitosan qualities from each source. [ABSTRACT FROM AUTHOR]

Mud Crab fattening is a relatively new business idea in Kenya and is highly lucrative due to the reasonable prices offered at tourist hotels. This study was aimed at developing appropriate culture techniques for Mud Crabs to maximize harvestable biomass by the local communities and avoid recruitment overfishing. Growth and survival rates for mixed sex Mud Crabs was investigated for a period of 230 days in Mida Creek, Kenya, using bottom and floating cages, and two feed types in a crab fattening experiment. Crabs attained harvestable weight by the third month for both floating (466.2 ± 137 g) and bottom cages (542.2 ± 109.3 g). There was no significant difference in mean total weight of mixed-sex crabs in the two culture systems (t = 1.75, p>0.05), however males showed significantly higher total weight gain compared to females. A higher overall survival rate was found for crabs cultured in floating cages (63.8%), compared to bottom cages (44.9%). There was no significant difference in growth performance between crabs fed gastropod tissues and those fed fish offal. The long-term specific growth rate for floating cages (0.69 g d-1) was not significantly different from that of bottom cages (0.92 g d-1). An analysis of potential return on investment showed the floating cages to be more profitable per production cycle compared to the bottom ones. The floating cage system and mono-sex male crab culture are recommended to farmers within mangrove tidal flats in Kenya. [ABSTRACT FROM AUTHOR]

Horseshoe crabs, represented by only four extant species, have existed for around 500 million years. However, their existence is now under threat because of anthropogenic activities. The availability of genomic resources for these species will be valuable in planning appropriate conservation measures. Whole‐genome sequences are currently available for three species. In this study, we have generated a chromosome‐level genome assembly of the fourth species, the Asian coastal horseshoe crab (Tachypleus gigas; genome size 2.0 Gb). The genome assembly has a scaffold N50 value of 140 Mb with ~97% of the assembly mapped to 14 scaffolds representing 14 chromosomes of T. gigas. In addition, we have generated the complete mitochondrial genome sequence and deep‐coverage transcriptome assemblies for four tissues. A total of 26,159 protein‐coding genes were predicted in the genome. The T. gigas genome contains five Hox clusters similar to the mangrove horseshoe crab (Carcinoscorpius rotundicauda), suggesting that the common ancestor of horseshoe crabs already possessed five Hox clusters. Phylogenomic and divergence time analysis suggested that the American and Asian horseshoe crab lineages shared a common ancestor around the Silurian period (~436 Ma). Comparison of the T. gigas genome with those of other horseshoe crab species with chromosome‐level assemblies provided insights into the chromosomal rearrangement events that occurred during the emergence of these species. The genomic resources of T. gigas will be useful for understanding their genetic diversity and population structure and would help in designing strategies for managing and conserving their stocks across Asia. [ABSTRACT FROM AUTHOR]

Diversification of production systems has been identified as one of the major strategies for the long‐term sustainability of brackishwater aquaculture. On the context of diversification, a 180‐day culture experiment was carried out where four farming systems were tested: monoculture of mud crab, Scylla serrata (T1), polyculture of mud crab, with mullet Mugil cephalus and shrimp Penaeus indicus (T2), polyculture of mud crab with mullet, shrimp and oyster Crassostrea cuttackensis (T3), polyculture of mud crab with mullet, shrimp, oyster along with periphyton net (T4) covering 10% of the water spread area. There was no significant difference in the growth performances of mud crab, shrimp and oyster among the treatment but a significantly higher (p <.05) final average body weight (ABW) of M.cephalus was recorded in T4 (121.19 ± 2.09 g). Production considering only the fed animals (excluding oyster) was significantly (p <.05) higher in T4 (2,115 kg/ha) compared to other treatments. The overall water quality parameters do not vary significantly (p >.05) among the treatment ponds. Although there was no significant difference in total ammonia nitrogen (TAN) and nitrite‐N, highest value was recorded in T2 (56.23 ± 39.47 µg/L and 185.53 ± 110.71 µg/L) and T1 (55.78 ± 32.26 µg/L and 180.83 ± 103.65 µg/L). The results from the current experiment based on water quality and growth of animals showed that there is no negative interaction between the mud crab and other animals stocked in the polyculture pond which indicated that polyculture provides an efficient and sustainable utilization of resources. [ABSTRACT FROM AUTHOR]

Mud crabs, or mangrove crabs, are one of the most valuable groups of crab species in the world. Several studies have been conducted to describe the nutrient requirements of mud crabs. Only preliminary studies have been conducted to define the nutritional ingredients requirements for growing out diets. Results of the analysis revealed the major components of seaweeds (Ulva reticulate and Sargassum cinctum) poultry waste, earth worms and fish meal with carbohydrate 57.18% (Ulva reticulate) and 55.86% (Sargassum cinctum), 31.07%, 21.83% and 2.89%, followed by ash content of 21.3% (U. reticulate) and 14.1% (S. cinctum), 8.4%, 12.0% and 8.40%, respectively. The crude protein component of fishmeal, soyabean meal, earthworms and seaweeds were obtained in little amount with 61.20%, 48.3%, 36.2% and 13.41% (U. reticulate) and 10.67% (S. cinctum) and followed by crude lipid component of poultry waste 25.0%, seaweeds 13.41% (U. reticulate) and 10.67% (S. cinctum), earthworms 9.52% and fishmeal 9.20% respectively. These results of nutritional composition indicated that poultry waste, earthworms and seaweeds have potential as a source of feed supplement and human nutrition. [ABSTRACT FROM AUTHOR]

The evolutionary history of horseshoe crabs, spanning approximately 500 million years, is characterized by remarkable morphological stasis and a low species diversity with only four extant species. Here we report a chromosome-level genome assembly for the mangrove horseshoe crab (Carcinoscorpius rotundicauda) using PacBio reads and Hi-C data. The assembly spans 1.67 Gb with contig N50 of 7.8 Mb and 98% of the genome assigned to 16 chromosomes. The genome contains five Hox clusters with 34 Hox genes, the highest number reported in any invertebrate. Detailed analysis of the genome provides evidence that suggests three rounds of whole-genome duplication (WGD), raising questions about the relationship between WGD and species radiation. Several gene families, particularly those involved in innate immunity, have undergone extensive tandem duplication. These expanded gene families may be important components of the innate immune system of horseshoe crabs, whose amebocyte lysate is a sensitive agent for detecting endotoxin contamination. Horseshoe crabs have been morphologically stable across evolutionary time. Here, the authors generate a chromosome-level assembly for the mangrove horseshoe crab, with implications for innate immunity, and challenging assumptions about the role of genome duplication in adaptive radiation. [ABSTRACT FROM AUTHOR]

Mass mortality due to necrosis signs occurred in hatchery‐reared zoea stage larvae of the mud crab Scylla serrata in Okinawa, Japan, and a causative bacterium was isolated. In this study, we identified and characterized the bacterium by genome analysis, biochemical properties and pathogenicity. The bacterium was a Gram‐negative, non‐motile, long rod, forming yellow colonies on a marine agar plate. It grew at 20–33°C (not at 37°C) and degraded chitin and gelatin. Phylogenetic analysis of the 16S rRNA gene sequence identified the bacterium as Aquimarina hainanensis. Genome sequence data obtained from Illumina MiSeq generated 29 contigs with 3.56 Mbp in total length and a G + C content of 32.5%. The predicted 16 chitinase genes, as putative virulence factors, had certain homologies with those of genus Aquimarina. Experimental infection with the bacterium conducted on larvae of four crustacean species, brine shrimp Artemia franciscana, freshwater shrimp Caridina multidentata, swimming crab Portunus trituberculatus and mud crab S. serrata, revealed that this bacterium was highly virulent to these species. The present study suggests that the bacterium caused mass mortality in mud crab seed production was A. hainanensis and can be widely pathogenic to crustaceans. [ABSTRACT FROM AUTHOR]

Keywords: feeding behaviour; feeding enhancement; saponins; sugar EN feeding behaviour feeding enhancement saponins sugar 2164 2167 4 04/11/20 20200501 NES 200501 INTRODUCTION The highly valued mud crabs of the genus I Scylla i spp. (Decapoda, Portunidae) are widely distributed throughout the Indo-West-Pacific region, where they are closely associated with mangrove forests (Alberts-Hubatsch et al., [1]). This selective choice was often observed in the test feed treated with 50% or 100% SJ, and the turning from the test feed to the control feed was never observed. At these SJ concentrations, a crab took all five pieces of test feed in three trials, but this rigorous feed intake behaviour was never observed against the control feed. This feeding behaviour indicates that the crab preferred SJ treated feed and SJ supplementation enhanced feeding of I S. tranquebarica i . [Extracted from the article]

Crabs and shrimps (order Decapoda) use colours in various tasks such as foraging and mate choice. Colour vision requires at least two types of photoreceptors with different spectral sensitivities. Previous physiological studies revealed that most crabs including Scylla mud crabs have a single visual receptor system, i.e. they are colour blind. We determined colour vision by means of a behavioural experiment on hatchery-produced and wild-captured purple mud crab Scylla tranquebarica in a roofed hatchery. Adult crabs (8-10 cm carapace width) were subjected to classical conditioning to associate a food reward with a blue or a green stimulus placed among seven shades of grey. The hatchery-produced crabs learnt this task after 14 days of reward training, and thereafter distinguished blue in 27 non-reward trials, and green in 39 non-reward trials. The wild-captured crabs did so after 25 days of reward training, and distinguished green in 49 non-reward trials. These results indicated colour vision in S. tranquebarica. However, the crabs were unable to distinguish blue or green in dim light of 4.4 cd/m2 (which is slightly brighter than full moon light). The high colour vision threshold was attributed to the small optic parameters of the apposition compound eyes of S. tranquebarica. [ABSTRACT FROM AUTHOR]

Finding aquaculture development approaches to open up livelihood opportunities for the rural poor and in mainstreaming smallholder fish farmers to reduce poverty remain a challenge. This paper examines the community-based technology transfer mechanism of mudcrab nursery in ponds and its socioeconomic impacts on smallholder mudcrab growers in Northern Samar, Philippines. Results indicated that the technology is a viable enterprise done by a straight culture system method, which is the rearing of crablets from <1.0 to 4.0 cm for 42 days, or by-phases. However, technology adoption hinges on many factors like area ownership, farm distance from household, and market including the type of strategy needed to enhance technology uptake. Collaboration among research and development institutions and local partners is critical in training and empowering rural communities to adopt aquaculture technologies. [ABSTRACT FROM AUTHOR]

The taxonomic ambiguity of the Indian mud crab (genus Scylla de Hann 1833) is still a cause of concern as several papers have been published with misleading identification. This is the first attempt to resolve the taxonomic uncertainty of the mud crab commonly available in Indian coastal waters using molecular genetic markers ( ITS- 1 and sequencing of COI gene) combined with traditional morphometry. Additionally, we developed a PCR method by which Indian mud crab species can be identified rapidly and effectively. The results clearly indicate that the green morph of the Indian mud crab is Scylla serrata and the brown morph is S. olivacea. The S. serrata commonly mentioned in the literature from India is S. olivacea; the S. tranquebarica noted by many Indian researchers should belong to S. serrata. Caution should be taken when interpreting or implementing the biological, molecular, and aquaculture data in the literature. [ABSTRACT FROM AUTHOR]

The significant decrease in wild mud crab population highlights the need to manage the resources and domesticate crabs. This paper presents the initial results of the domestication of mud crab Scylla serrata aimed at producing good-quality captive broodstock. The analysis of the genetic structure of the base population was done as a prerequisite for domestication. Adult S. serrata from the northern to southern parts of the Philippines (Cagayan, Camarines, Samar, and Surigao) were obtained for genetic diversity analysis and domestication. Analysis of molecular variance showed that differences in the genetic variability between the four populations were not significant. Moreover, no significant deviation from Hardy-Weinberg Equilibrium was observed in each sample population and even in pooled populations. Body weight was positively correlated with the carapace width. Second spawning occurred 41-46 days after the first spawning and 34 days from second to third spawning. However, there was a decrease in the number of zoea in repeat spawnings. Twenty-four first-generation (F) families were produced from the four sites. The duration from spawning of the base population (P) to attainment of broodstock size F was 10-14 months. Four second-generation (F) families were produced after 11-12 months. Up to the F, crabs tested negative for six viruses: white spot syndrome virus, infectious hypodermal and hematopoietic necrosis virus, gill-associated virus, yellow head virus, Taura syndrome virus, and infectious myonecrosis virus. The reproductive performance of P was comparable to the succeeding generations. Several families were obtained from one population in a year. However, due to the cannibalistic behavior of crabs, more space is required for the nursery and grow-out phase. The domestication of S. serrata is the first study done on any mud crab species in the Indo-west Pacific region. The initial results would serve as guide to understand and eliminate the barriers to mud crab domestication. The breeding technology developed from this study will support the production of good-quality seedstock for farming. [ABSTRACT FROM AUTHOR]

Wild capture fisheries provide substantial input to the global economy through employment and revenue. The coastal zone is especially productive, accounting for just 7% of the total area of the ocean, but supporting an estimated 50% of the world's fisheries. Vegetated coastal ecosystems—seagrass meadows, tidal marshes and mangrove forests—are widely cited as providing nutritional input that underpin coastal fisheries production; however, quantitative evidence of this relationship is scarce. Using Australia as a case study, we synthesized fisheries stable isotope data to estimate nutritional input derived from coastal vegetated ecosystems and combined these "proportional contribution" estimates with total annual catch data from commercial fisheries to determine species‐specific dollar values for coastal vegetated ecosystems. Based on the data from 96 commercially important fish species across Australian states (total landings 14 × 106 tonnes pa), we provide a conservative estimate that Australia's coastal vegetated ecosystems contribute at least 78 million AUD per year to the fisheries economy. Two thirds of this contribution came from tidal marshes and seagrasses that were both equally valued at 31.5 million AUD per year (39.4%) followed by mangroves at 14.9 million AUD per year (18.6%). The highest dollar values of coastal ecosystems originated from eastern king prawn (Melicertus plebejus) and giant mud crab (Scylla serrata). This study demonstrates the substantial economic value supported by Australia's coastal vegetated ecosystems through commercial fisheries harvest. These estimates create further impetus to conserve and restore coastal wetlands and maintain their support of coastal fisheries into the future. https://drive.google.com/file/d/1ZoeGPFVOUHFqxY80UUz_vwij9-aZzzxl/view?usp=sharing [ABSTRACT FROM AUTHOR]

Measurements of either heartbeats or heart rate variability provide important information on metabolic changes and stress responses. In this study, we aimed to determine the suitable temperature conditions for maintaining product quality for post‐harvest processing of mud crab (Scylla serrata) through measuring cardiac performance. A bundle of implanted electrodes was used to record the electrocardiogram, from which the heart rate (HR) and heart rate variability (HRV) were derived to evaluate the physiological performances of the crabs under tying at different seawater temperatures. The lowest standard deviation of HR was detected at the seawater temperature of 18°C for the group of ascending temperatures and at 10°C for the group of descending temperatures. Lower HRV was detected at the range from 10 to 14°C. The results suggest that the temperature range of 14–18°C is suitable to reduce variability in heart rate and may decrease physiological stress. These conditions might help maintain the quality of live crabs during post‐harvest processing and transportation. [ABSTRACT FROM AUTHOR]