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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]

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]

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]

An "abnormal" female Scylla paramamosain, named "Butter crab" (B_♀) is more popular than wild‐type mud crab (CK) with people. Histologically, "butter crab" ovaries are partially degraded, with full of yellow oily substances in body. Composition of the essential nutritional components is quite similar in "butter crab" and CK. In a comparison of fatty acids, B_♀ is richer. A comparison of flavour amino acids and nucleotide in muscle showed that sweet amino acids and bitter amino acids in B_♀ is lower than CK_♀, but umami amino acids are significantly higher in B_♀. However, the umami amino acid content in the gonads is significantly less in B_♀ than CK_♀. Moreover, umami nucleotides in B_♀ muscle is significantly higher. From the perspective of EUC evaluation, the umami taste of CK_ ♀ gonads is strongest, followed by B_ ♀ gonads. In the hepatopancreas, the umami taste ranks CK_♀> B_♀ >CK_♂, and there are no significant differences among muscles in the three groups. In conclusion, the characteristics of "butter crab" are more fragrant and nutritious, with sweet and umami taste. The article systematically scientifically analysed the nutritional composition and flavour characteristics of "butter crab", providing a novel insight for development of S. paramamosain industry. [ABSTRACT FROM AUTHOR]

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Management practices and environmental quality of the crab (Scylla serrata) farming ponds in Gosaba and Basanti blocks, 24 Parganas (South), West Bengal has been investigated. Split bamboo fenced rectangular culture units are preferred by over 70% of the farmers with highly variable stocking density. Total inorganic nitrogen and BOD increased with the increasing biomass of the crabs in both the sites. Salinity, total alkalinity and hardness played direct roles in body weight gain and survival rate. Water salinity of 17.50 to 20.0 ppt and hardness upto 1000 mg l-1 were found to be optimal for body weight gain of the cultured crabs. [ABSTRACT FROM AUTHOR]

The academic interest in the production of soft‐shell swimming crabs has increased in direct proportion to the increasing demand worldwide for this gastronomic delicacy. The techniques of obtaining this product are essentially based on the maintenance of swimming crabs at premoult stage in open, semi‐closed or closed farming systems, until the moment of moulting. These different types of systems reflect the biological e environmental control method evolution. To achieve industrial scale production of soft swimming crabs, the option of using closed systems has increased in recent years. This type of system offers several advantages, such as greater control over environmental variables, greater ease of installation, higher storage densities, greater ease of monitoring ecdysis occurrence and, especially, the possibility of incorporating several forms of automation. In this review, the main production systems currently used, as well as the main techniques for obtaining the animals, their management under controlled conditions, harvesting and slaughter, are presented and discussed, focusing on future perspectives for the world production of soft‐shell swimming crabs. [ABSTRACT FROM AUTHOR]

Abstract: A female swimming crab (Portunus trituberculatus) with fully developed ovaries is considered one of the most nutritious types of seafood. The fishing yield of P. trituberculatus in China has always been high; however, its economic value has been low and unreliable due to poor ovarian development and low nutritional value. Artificial fattening is an effective way to improve the value of wild‐caught crabs, and this study focused on analysing the ovarian development and nutritional quality of the female P. trituberculatus during an artificial fattening period. Therefore, this study provides scientific evidence on the effects of artificial fattening on female P. trituberculatus and can guide the development of nutritional quality regulations for wild‐caught female crabs during the fattening process. The results showed that the ovaries of the wild female P. trituberculatus developed gradually. The ovarian morphology became bulkier, while the gonadosomatic index (GSI) and total edible yield (TEY) were significantly improved after artificial fattening. Significant changes in the nutritional components of the edible tissues were observed, and the moisture content in the ovaries and hepatopancreas decreased continually, while both the protein and fat content in the ovaries significantly increased. Moreover, the fat content in the hepatopancreas significantly increased. The saturated fatty acids(ΣSFA) in the ovaries and hepatopancreas had an increasing trend after fattening, while ΣPUFA and Σn‐3PUFA first decreased and then increased. In contrast, the ratio of Σn‐3PUFA to Σn‐6PUFA decreased steadily. However, the fatty acid composition of the muscles did not change significantly. The levels of all the amino acids increased continuously during the fattening process, and EAA increased significantly in the early stages of the fattening period. Consequently, all amino acids became nonlimiting amino acids after fattening. Furthermore, the ratio of EAA/NEAA in the ovaries increased continually until the end of the fattening period. On the other hand, the fatness and TEY increased significantly after artificial fattening. In addition, the nutritional value significantly improved with the exception of the high‐quality fatty acids in the ovaries and hepatopancreas, which were slightly lower in both. [ABSTRACT FROM AUTHOR]

Starvation and exposure to formalin were investigated as possible stress tests for evaluating the quality of mud crab, Scylla serrata, larvae. For the starvation stress test, newly hatched zoeae stocked in 150-ml containers were either starved or fed rotifers. Similarly, newly hatched zoeae were stocked in containers with seawater of 0 (control), 20, 30 and 40 mg/L formalin for the formalin stress test. The zoeae from the same batches were used for seed production to monitor their performance and validate the results of stress tests. Starvation was found to be unsuitable for larval quality evaluation. However, the impact of initial food deprivation on the newly hatched larvae indicates that feeding immediately after hatching is necessary for mud crab larvae. Exposure of larvae to 40 mg/L formalin for 3 hr appeared to be a reliable and practical method for larval quality assessment as the survival of larvae in the mass production tanks validated the classification of good and poor quality batches in the stress tests. On this basis, a hatchery operator can decide which batch should be cultured further. Finally, there appears to be a link between the quality of larvae and the performance at the megalopa and early juvenile crabs. [ABSTRACT FROM AUTHOR]

Signalling behaviour is integral to animal contests. However, post-contest signals, such as victory displays, have received relatively little attention. One hypothesised function of victory displays is to ensure a more lasting dominance by reducing the risk of losers re-initiating a new contest with winners. Despite several theoretical studies using game theory that support this hypothesis, empirical support for the understanding of when and why victory displays are used with respect to browbeating is lacking. We use a common South-East Asian mangrove crab, Perisesarma eumolpe, to examine whether the performance of victory displays by winners, among other factors, affects the time of fight re-initiation by losers, if at all re-initiated. Using mixed-effects survival analysis models, we analysed 77 fights from 27 staged contest trials between randomly paired males. We found losers that experienced victory display performed by winners, presented a decreased instantaneous hazard rate of re-initiating a new fight than losers that did not. These results corroborate previous game theoretical models indicating that victory displays may function to reduce the chances of losers re-initiating another fight. In discouraging losers from restarting a fight, winners reduce the potential costs of a future contest. [ABSTRACT FROM AUTHOR]

The giant mud crab Scylla serrata provides an important source of income and food to coastal communities in East Africa. However, increasing demand and exploitation due to the growing coastal population, export trade, and tourism industry are threatening the sustainability of the wild stock of this species. Because effective management requires a clear understanding of the connectivity among populations, this study was conducted to assess the genetic diversity and connectivity in the East African mangrove crab S. serrata. A section of 535 base pairs of the cytochrome oxidase subunit I (COI) gene and eight microsatellite loci were analysed from 230 tissue samples of giant mud crabs collected from Kenya, Tanzania, Mozambique, Madagascar, and South Africa. Microsatellite genetic diversity (He) ranged between 0.56 and 0.6. The COI sequences showed 57 different haplotypes associated with low nucleotide diversity (current nucleotide diversity = 0.29%). In addition, the current nucleotide diversity was lower than the historical nucleotide diversity, indicating overexploitation or historical bottlenecks in the recent history of the studied population. Considering that the coastal population is growing rapidly, East African countries should promote sustainable fishing practices and sustainable use of mangrove resources to protect mud crabs and other marine fauna from the increasing pressure of exploitation. While microsatellite loci did not show significant genetic differentiation (p > 0.05), COI sequences revealed significant genetic divergence between sites on the East coast of Madagascar (ECM) and sites on the West coast of Madagascar, mainland East Africa, as well as the Seychelles. Since East African countries agreed to achieve the Convention on Biological Diversity (CBD) target to protect over 10% of their marine areas by 2020, the observed pattern of connectivity and the measured genetic diversity can serve to provide useful information for designing networks of marine protected areas. [ABSTRACT FROM AUTHOR]

The taxonomy of Polyonyx pedalis Nobili, 1906, is revised on the basis of the syntypes and additional material from various areas of the Indo-West Pacific. Examination of a large series of specimens revealed that P. pedalis s. str. is restricted to the waters of the Red Sea and the western Indian Ocean. Specimens from the western Pacific are here referred to three new species. The four species are superficially similar but can be distinguished by the shape and structure of the carapace, and comparative lengths of the meri of the ambulatory legs. There are indications that their preferred habitats also differ. Polyonyx pedalis, P. heok, new species, and P. kumejima, new species, live symbiotically with tube-dwelling polychaetes; the first two species are associated with species of the genus Chaetopterus (family Chaetopteridae), while P. kumejima is found with a species of Sabellidae. Polyonyx planus, new species, was obtained by brushing coral rubble or from the underside of rocks, and no symbiotic host was recorded. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the present status of the Mud Crab (Scylla serrataForskal) population in Koggala Lagoon, including details on size at maturity, sex ratio and carapace width - body weight relationship. This Crab is the most common edible Crab species found in the lagoon, comprising 93.10% of total catch from crab pots and 89.86% of total catch from crab nets. Sex ratios (male:female) were 1:0.86 and 1:0.82 in crab pots and nets, respectively. Female crabs of various sizes were randomly sampled to determine size at maturity. The results indicate that size at maturity of females was 12.17 cm carapace width. Size at maturity of males could not be determined using external characteristics. Population parameters were estimated from length-frequency data collected in 2009 and 2011. Asymptotic carapace length (L∞) and growth constant (K) were estimated to be 20.12 cm, 0.91 yr−1in 2009 and 19.27 cm, 3.2 yr−1in 2011, respectively. Exploitation rates were 0.32 in 2009 and 0.44 in 2011. There was a significant difference in Crab size between harvests by the crab nets versus traditional crab pots. Results indicate thatS. serratapopulation is declining due to over-fishing as of increased fishing gear efficiency from traditional crab pots to modern crab nets. Commercial catches of crab net and crab pots comprised 85.7% and 72.0% of immature females, respectively, based on the size at first maturity revealed by this study. In order to maintain natural health of the Mud Crab population, immediate management action is needed to regulate fishing in Koggala Lagoon. [ABSTRACT FROM AUTHOR]

The effect of dose-dependent gamma irradiation and subsequent cold storage on bacteriological profile of tissues derived from Scylla serrata was evaluated. Irradiation at 0.5, 1.0 and 2.0 kGy significantly reduced the (P = 0.0001) total plate count (TPC) by 1.0, 2.0 and 2.5 log units, respectively. Treatments of 1.0 and 2.0 kGy irradiation reduced total coliform (TC) count below 1 most probable number (MPN)/g in the muscle and hepatopancreas and below 50 MPN/g in the gills of S. serrata. Irradiated tissues stored at -20C showed significant reduction in TPC and TC. Bacillus spp. was predominant in the tissues before and after gamma irradiation. While live crab tissues harbored both gram-positive and gram-negative bacteria in equal proportion, more than 90% of them from irradiated tissues were gram-positive. Biochemical and 16S rRNA gene-based study on generic composition of heterotrophic bacteria revealed fairly good diversity in nonirradiated tissues and the dose-dependent gamma irradiation significantly reduced their diversity concomitantly. [ABSTRACT FROM AUTHOR]

The present study evaluates the combined effect of dose-dependent gamma irradiation and cold storage on sensory characteristics of mud crab, Scylla serrata. The samples were irradiated at 0.5, 1.0 and 2.0 kGy and stored at 4°C and -20°C along with non-irradiated control. The sensory properties of the both irradiated and cold stored samples were assessed at weekly intervals up to maximum of 28 days. Though extended storage at 4°C (up to 14 days) resulted reduction in sensory quality of both irradiated and non-irradiated control samples, irradiated samples scored significantly higher value which was concomitant with the irradiation doses applied. Gamma irradiation at any applied dosage (0.5, 1.0 and 2.0 kGy) has no significant advantage on sensory characteristics of crab during their storage at -20°C until 14 days compared to control; further extended storage (up to 28 days), however, enhanced the degree of sensory quality in the samples received 1.0 and 2.0 kGy gamma irradiation compared to the samples irradiated with the low dose (0.5 kGy) and control. The overall experimental results indicated that gamma irradiation at the dose range of 1.0-2.0 kGy and the subsequent cold (4°C) and frozen storage (-20°C) would be helpful to extend the shelf life of Scylla serrata by maintaining fairly good sensory quality for maximum duration of 14 and 28 days respectively. [ABSTRACT FROM AUTHOR]

Crab meat is a valuable source of proteins and functional lipids and it is widely consumed worldwide. However, the prevalence of crab allergy has increased over the past few years. In order to understand crab allergy better, it is necessary to identify crab allergens. The aim of the present study was to compare the IgE-binding proteins of raw and cooked extracts of mud crab (Scylla serrata). Raw and cooked extracts of the mud crab were prepared. Protein profiles and IgE reactivity patterns were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) followed by immunoblotting using sera from 21 skin prick test (SPT) positive patients. In SDS-PAGE, 20 protein bands (12 to 250 kDa) were observed in the raw extract while the cooked extract demonstrated fewer bands. Protein bands between 40 to 250 kDa were sensitive to heat denaturation and no longer observed in the cooked extract. In immunoblotting experiments, raw and cooked extracts demonstrated 11 and 4 IgE-binding proteins, respectively, with molecular weights of between 23 and 250 kDa. A heat-resistant 36 kDa protein, corresponding to crab tropomyosin was identified as the major allergen of both extracts. In addition, a 41 kDa heat-sensitive protein believed to be arginine kinase was shown to be a major allergen of the raw extract. Other minor allergens were also observed at various molecular weights. [ABSTRACT FROM AUTHOR]

We aimed to evaluate the practicability of probiotics in controlling larval necrosis symptoms and mass mortality occurred during seed production of the mud crab Scylla serrata. We targeted a bacterium in the family Flavobacteriaceae that causes necrosis symptoms of mud crab larvae. Five candidate probiotic bacterial strains, which showed inhibitory effects against the causative bacterium but were innocuous to larvae, were screened from the seed production environment. Sterile culture medium supernatants of the candidate strains inhibited the causative bacterium through the secretion of extracellular factors. These inhibitory effects were largely reduced when the strains were inoculated into sea water, suggesting medium-dependent production of inhibitory factors. The strain that exhibited the highest inhibitory effect on larval necrosis in 7-day larval rearing experiments was selected as a probiotic strain. In large-scale larval rearing experiments, the probiotic treatment significantly suppressed larval necrosis symptoms and improved larval survival in the early rearing period until the fourth zoeal stage. However, the effect disappeared after the fifth (last) zoeal stage, corresponding to a decrease in inoculated probiotic bacterial counts in the larval rearing water. Almost all larvae had died by the first crab stage. The effectiveness of probiotics developed in vitro has not yet proved practical in commercial-scale seed production. The continuous proliferation of probiotic bacteria and extracellular production as inhibitory factors in larval rearing water are the key factors in developing probiotics for commercial-scale seed production. [ABSTRACT FROM AUTHOR]

The mud crab Scylla serrata (Forskal, 1775) (Portunidae) is a commercial species in the Indo-West-Pacific. Despite its high fishery value, the microhabitat of its early juvenile stages remains unknown. We studied microhabitat use by the 'early benthic stage' (EBS, between 3 and 30 mm carapace width, CW) at two sites in eastern Australia by two types of artificial benthic collectors and baited traps. 92% of EBS mud crabs were captured in muddy areas, compared to 8% on sandy habitats. The majority of the EBS mud crabs (87%) was found in intertidal areas within the mangrove fringe, only few individuals (13%) were found on unvegetated mud flats seawards to the mangroves. EBS from the mudflat (including first instars of 3-4 mm CW) were significantly smaller (p < 0.001) than those from the mangrove habitat. This indicates an active migration from the mud flat towards the mangrove fringe as the crabs grow. The recapture of mud crabs in close proximity to their tagging site at the mangrove fringe suggest that EBS-crabs have a small home range. Cannibalism is considered a major driver in the distribution patterns of EBS mud crabs, which may explain, why EBS-crabs stay at the more sheltered site near the mangrove fringe. By identifying the microhabitat of the critical early benthic stages of S. serrata in eastern Australia, our findings may contribute to the development of appropriate management and conservation strategies for this commercially important species. [ABSTRACT FROM AUTHOR]

Estuarine edible crab, Scylla serrata (Crustacea: Decapoda) occupy diverse habitats and their strategy of survival is correlated to multidimensional immune responses and its inhabiting in bio-unsafe environment is under constant threat of physiological stress caused by diverse xenobiotics including arsenic. Experimental crabs, exposed to 1-3 ppm of sodium arsenite for a maximum period of 30 days in controlled laboratory condition indicated that arsenic as cytotoxicant as well as immunotoxicant causes damage and an alteration in cytotoxic status and antioxidant status in hemocytes. In this study, we investigated the intrahemocytic production of phenoloxidase, super oxide anion, nitric oxide, and its subsequent scavenging under the exposure of sodium arsenite. Arsenic induced variations in generation of cytotoxic molecules as well as antioxidant enzymes activity in intrahemocyte is indicative to possible immune-alteration of the animal distributed in bio-unsafe environment. Arsenic induced impairment of immune response may initiate an opportunistic growth of microbes in crab. Chronic exposure of S. serrata to arsenic may lead to decline of this economically important endemic species in Sundarbans Biosphere Reserve of West Bengal. [ABSTRACT FROM AUTHOR]

In response to concerns over excessive discarding from Australian recreational round traps (with four funnel entrances) used to target giant mud crabs, Scylla serrata, an experiment was done to assess the independent and cumulative utility of paired, bottom-located horizontal escape gaps (46×120 mm) and increasing mesh size (from 51 to 101 mm). Compared to conventional traps comprising 51-mm mesh throughout, those with the same mesh size and escape gaps caught significantly fewer (by 95%) undersize (<85 mm carapace length – CL) crabs while maintaining legal catches. Traps made from 101-mm mesh (but with the same funnel entrances as conventional designs) and with and without escape gaps similarly retained fewer undersize crabs and also yellowfin bream Acanthopagrus australis (the key bycatch species) by up to 94%, but there were concomitant reductions in fishing power for legal sizes of S. serrata. Although there were no immediate mortalities among any discarded crabs, there was a greater bias towards wounding among post molts than late inter-molts and less damage to individuals in the 101-mm conventional than 51-mm conventional traps (without escape gaps). The results support retrospectively fitting escape gaps in conventional S. serrata traps as a means for reducing discarding, but additional work is required to determine appropriate mesh sizes/configurations that maximize species and size selectivity. [ABSTRACT FROM AUTHOR]

Aquatic animals can often undergo substantial physiological responses to salinity; however, associated lipid/fatty acid alterations to their various tissues have received little attention. To investigate this, we measured the growth of mud crab,Scylla serrata, juveniles over two moults (duration of 23–60 days) at salinities of 4, 12, 20, 28, 36 and 44‰ (30 replicates/treatment). After the second moult, 6-day post moult crabs were sampled for hepatosomatic index (HSI), haemolymph osmolality, Na+, K+and Ca2+levels, anterior/posterior gill Na+/K+-ATPase activity as well as the lipid/fatty acid composition of the anterior and posterior gills, hepatopancreas and muscle. High salinities of 36 and 44‰ significantly lowered crab growth and HSI (p<0.01).S. serratastrongly hyper-regulated haemolymph osmolality and ions likely due to significantly enhanced posterior gill Na+/K+-ATPase activity. At decreasing salinities, eicosapentaenoic acid, arachidonic acid,n-3 and long chain polyunsaturated fatty acid (PUFA) significantly increased (p<0.05), likely to maintain Na+/K+-ATPase activity via increased membrane fluidity. Muscle and hepatopancreasn-3/n-6 PUFA ratios significantly decreased (p<0.05) at increasing salinities indicating possible fatty acid metabolic modifications. Results indicate thatS. serratajuveniles are well adapted to low salinities, with higher salinities likely reducing their metabolism, reflected by lower growth, HSI and higher posterior gill and hepatopancreatic triacylglycerol. [ABSTRACT FROM AUTHOR]

The giant mud crab (Scylla serrata) is an important fisheries species throughout southeast Asia and the South Pacific. In Australia, marine protected areas (MPAs) and fish habitats have been declared specifically to protect the local populations of S. serrata. The cannibalistic behaviour of S. serrata coupled with the potential attraction of increased predators may counteract the effect of excluding fishing from these areas as a means of increasing the local crab population. The population dynamics of S. serrata could also be confounded by the spatio-temporal variability in environmental conditions (e.g. run-off and temperature). Here, we used a spatially explicit individual-based model (IBM) to explore the population dynamics of S. serrata in an MPA located in southern Moreton Bay, Queensland, Australia. This IBM simulated the life cycle dynamics of individual S. serrata and integrated the key processes affecting its population dynamics. These processes include physical transport of the planktonic life stages, movement, growth, metamorphosis, setting, reproduction, spawning, harvesting, and predation. Individual variability was built into the model to account for demographic variation. The modelled scenarios indicated that the effect of the different harvest strategies trialled on the population dynamics after 30 months and the MPA influenced the number of individuals in the creek system resulting in a partial 35% population increase. Further development and application of this model has implications for MPAs and catch limits under multiple stressors including climate change. [ABSTRACT FROM PUBLISHER]

The biochemical composition (proteins, lipid, ash and moisture) of different parts of the body (gill, meat, egg) of fattened and natural mud crab Scylla serrata was determined. Twenty four samples of S. serrata (12 from wild & 12 from fattening farm) of different sizes and sexes (half of the sample is male) were used in this study. The mean protein and lipid contents are significantly (p<0.05) higher in fattened crabs than natural in natural crabs regardless of size and sexes. Moisture and ash were higher in natural crab than in fattened ones. The highest and lowest moisture content was noticed in gills and eggs in both natural and fattened crabs. Protein and lipid contents were comparatively higher in eggs than in other body parts. Female crabs contained high protein and lipid than males in both natural and fattened crabs. From the results of this study it may considered that fattened crab might be comparatively superior to natural crabs as they appear to provide higher levels of protein and fat for human nutrition. [ABSTRACT FROM AUTHOR]

In Neotropical mangroves the crabs Ucides cordatus and Goniopsis cruentata have been considered the most significant propagule consumers, but their relative importance has not been investigated. The aim of this study was to compare the magnitude of predation by these crabs on three mangrove species propagules: Avicennia schaueriana, Laguncularia racemosa and Rhizophora mangle. We found that G. cruentata is a more important predator than U. cordatus in both natural and restored areas. We also tested the hypothesis that Ucides and Goniopsis have antagonistic effects on propagules predation using a cage experiment where the presence/absence of these species was manipulated in a 2 × 2 factorial design. The effects of Goniopsis were stronger in the absence of Ucides due to negative interactions between these predator species. Moreover, we found that Goniopsis preference for A. schaueriana and L. racemosa can favor the dominance of R. mangle in Neotropical mangroves. This study suggests that propagule predation by Goniopsis should be controlled in mangrove restoration programs at abandoned shrimp farms and destroyed areas, if dominance by R. mangle is undesirable relative to mixed species communities. [ABSTRACT FROM AUTHOR]

The feeding choices of the mangrove crab Ucides cordatus for various mangrove plant leaves ( Avicennia schaueriana, Laguncularia racemosa, and Rhizophora mangle) at different ages (mature, senescent pre-abscission, and decomposing leaves) were examined. In a controlled experiment set in a mangrove area, we evaluated crab selection for different plant leaves by analyzing foraging rate (number of leaves with predation marks) and leaf consumption. Crabs were housed individually in plastic containers and after a 3-day fast supplied with leaf fragments every 24 h for 72 h. Uneaten leaves were removed before each new food offering. No food selection was observed in the first day, but after this period, senescent leaves, which have a high polyphenol content, were rejected. On the third day, an interactive effect between plant species and leaf age was shown to affect leaf selection, with mature leaves of A. schaueriana and L. racemosa being more selected than the other treatments. This observation was consistent across crab sexes and ages. Our results show that food selection by this mangrove crab changes through time in fasted animals, suggesting that this variable must be controlled in food preference studies. [ABSTRACT FROM AUTHOR]

The black mud crab, Scylla serrata (Forskål 1775), is the most economically important edible crab in South-East Asia. In the present study, the complete mitochondrial genome of black mud crab, S. serrata, was determined with the sequential polymerase chain reaction and primer walking sequencing. The complete mitochondrial genome was 15,721 bp in length with an A+T content of 69.2 % and contained 37 mitochondrial genes (13 protein coding genes (PCGs), 2 ribosomal RNA genes and 22 transfer RNA genes) and a control region (CR). The analysis of the CR sequence shows that it contains a multitude of repetitive fragments which can fold into hairpin-like or secondary structures and conserved elements as in other arthropods. The gene order of S. serrata mainly retains as the pancrustacean ground pattern, except for a single translocation of trnH. The gene arrangement of S. serrata appears to be a typical feature of portunid crabs. Phylogenetic analyses with concatenated amino acid sequences of 12 PCGs establishes that S. serrata in a well-supported monophyletic Portunidae and is consistent with previous morphological classification. Moreover, the phylogenomic results strongly support monophyletic Pancrustacea (Hexapoda plus 'Crustaceans'). Within Pancrustacea, this study identifies Malacostraca + Entomostraca and Branchiopoda as the sister group to Hexapoda, which confirms that 'Crustacea' is not monophyletic. Cirripedia + Remipedia appear to be a basal lineage of Pancrustacea. The present study also provides considerable data for the application of both population and phylogenetic studies of other crab species. [ABSTRACT FROM AUTHOR]

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Morphological changes in the embryos, egg size and development, incubation period and morphological structures of newly hatched zoea of three mud crab Scylla species were determined. The three species exhibited similar embryonic development composed of 10 stages. The mean egg diameter of Scylla serrata was significantly larger ( P<0.05) at the prehatch stage. The mean egg diameters of Scylla tranquebarica and Scylla olivacea were similar ( P>0.05). The incubation period was the longest in S. serrata and the shortest in S. olivacea. There was a positive relationship between egg size and larval size, as S. serrata exhibited the largest egg size and first zoea. However, no correlation was detected between egg size at prehatch and lengths of the morphological structures of the newly hatched zoea. The three species exhibited similar lengths of cephalic structures, but S. olivacea had significantly shorter ( P<0.05) abdominal structures. The duration of spawning from ablation was the shortest in S. tranquebarica and the longest in S. olivacea. The study is relevant to aquaculture and fisheries management of Scylla species. [ABSTRACT FROM AUTHOR]