Search

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]

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]

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]

Copyright of Ege Journal of Fisheries & Aquatic Sciences (EgeJFAS) / Su Ürünleri Dergisi is the property of Ege Journal of Fisheries & Aquatic Sciences (EgeJFAS) / Su Urunleri Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Giant mud crab (Scylla serrata sp.) shell prepared through pyrolysis at various temperatures without any modification were characterized for physicochemical properties and methyl violet (MV) removal potential. Hence, this paper investigated the performance and mechanism of biochar derived from giant mud crab shell as adsorbent in the removal of methyl violet as well as the potential for regenerating adsorbents via hot water regeneration. The results show that CSB500 (produced through pyrolysis at 500 °C) exhibits a surface area of 59.73 m2/g and mesopore size of 31.3 nm, favorable for methyl violet removal at 3139 mg/g. The equilibrium adsorption data agreed well with Langmuir and Redlich-Peterson isotherm models, indicating a monolayer adsorption of MV. The kinetics data fitted better with both pseudo-first-order and pseudo-second-order models. The intraparticle diffusion and Boyd's models revealed that both film and pore diffusion may be involved in the adsorption process. In hot water regeneration studies, CSB500 shown superior regeneration performance when using water with temperature of 70 °C rather than 30 °C for 9th regeneration cycles, with retained to achieve >90 % MV removal for 6th regeneration cycles. Biochar derived from giant mud crab shell has shown significant promise as a low-cost, effective, and ecologically friendly with reasonably good adsorption capacity and reusability for dye removal, and it can be considered as an environmental sustainability strategy in wastewater treatment. [Display omitted] [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]

This is an initial paper in a series of overviews of biological research and aquaculture development of the mud crab, Scylla serrata, in China. Results of experimental ecological studies on mud crabs are reported here. As a result of these experimental studies, results that are important for mud crab culture were also discovered and these include, methods to condition and manage broodstock, determination of ecological conditions that are suitable for embryonic development, and the influence of temperature, salinity, diet and larval density on development and survival of larvae. Results of this work will be useful in establishing a good method for artificial mass culture of larvae. [ABSTRACT FROM AUTHOR]

Mud crabs, Scylla spp. , are commercially important in many Indo-Pacific countries. The larval development of mud crabs has been reported previously as five zoeal and one megalopal stages. This paper reports larval rearing experiments that revealed variability in larval developmental stages in the mud crab Scylla paramamosain, one of four mud crab species. In addition to normal five zoeal stages, an alternative pathway of developing through six zoeal stages was observed for the crab. There were evidences suggested that the appearance of the additional Zoea-VI larvae was associated with unfavourable dietary conditions, including poor quality of diet, inadequate quantity of dietary supply and a period of starvation for newly hatched larvae. Based on exuviae and larval specimens, the morphology of the additional Zoea-VI larvae was described. [ABSTRACT FROM AUTHOR]

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]

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]

Commercial marine fish farming in Singapore is mainly the culture of economically important foodfish species in floating cage nets. There are 84 licensed fish farms occupying 46.5 hectares (ha) of coastal waters. Production from these farms accounts for the bulk of aquaculture production in Singapore, being 3554 tonnes (‘metric tons’, t) in 1995, or 98% of total production of 36251. The commonly cultured species are the green mussels, Ferna viridis L., which form the bulk of production (70.4%). finfish like the groupers, Epinephelus tauvina Forsskal and B. malabaricus Schneider, Asian sea bass, Lates calcarifer Bloch, and snappers, Lutjanus johni Bloch and L. argentimaculatus Forsskal, and crustaceans like the mangrove crab. Scylla serrata Forsskal and spiny lobster, Panilunts polyphagus Herbst. The basic farm structure for fish and mussel culture is the floating wooden raft. In finfish farming, polyethylene cage nets are attached to the raft in which popular foodfishes are cultured. The mussel raft is a structure to which polyethylene ropes are attached to collect and grow out green mussels from natural spatfall. Fish seeds for farming are mostly wild-caught. Only the Asian sea bass and the banana shrimp (Penaeus merguiensis de Mann) are produced by commercial hatcheries in Singapore and the region. The fry of pompano (Trachinotus blochii Lacepede. and T. falcatus Klausewitz & Nielsen) are imported from Taiwan. Trash fish is still the main feed used for the farming of finfish and crustaceans like the mangrove crab and lobster because it is cheap and readily available. This paper also reviews the economics of commercial finfish and mussel farming in Singapore today. [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]

Hemocyanins are large extracellular respiratory proteins distributed within the hemolymph of arthropods, molluscs and larval stages of certain insects. In the present study, we characterized the humoral immune functions of cation specific antibacterial hemocyanin (Ab-Hcy) from mud crab, S. serrata . The bacteriolytic activity of Ab-Hcy was against pathogenic and non-pathogenic to crustaceans which includes, Bacillus sp. N1, B. flexus N3, E. coli , P. aeruginosa , V. harveyi , V. parahaemolyticus and V. vulnificus and also expressed bacteriostatic activity against E. coli , B. flexus N3 and V. harveyi . The agglutination activity of Ab-Hcy ranged from 4-16 against B. flexus N3, E. coli , V. harveyi and V. vulnificus and Ab-Hcy also agglutinated with rat and human O erythrocytes (HA titer: 2). The Ab-Hcy lysed the panel of mammalian erythrocytes and strong hemolytic activity of 1.40, 1.28 and 1.22 units·min − 1 ·mg protein − 1 against human A, B and O erythrocytes respectively. It was also found that the Ab-Hcy possess phenoloxidase (PO) activity by oxidizing L-DOPA. These results suggest that Ab-Hcy from the serum of mud crab, S. serrata , is capable of performing multiple humoral immune functions in addition to oxygen transportation. Statement of relevance This manuscript deals with the humoral immune functions, particularly antibacterial property of hemocyanin in crustacean. In this paper we report the different type of antibacterial activity and other humoral immune functions of a hemocyanin isolated from the serum of mud crab, Scylla serrata . This work will help to understand the role of respiratory molecule in immune system, also will be helpful improve disease free crustacean aquaculture industry. And we also state this research work is relevant and suitable to publish in the Journal “Aquaculture”. [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]

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]

Abstract: Competent larvae of most benthic marine invertebrates including brachyuran decapod crustaceans can delay their settlement and metamorphosis in the absence of suitable environmental cues. This however may carry significant costs for the post-larval performance and fitness of early benthic juveniles. In this paper, we examined in the laboratory whether delayed larval metamorphosis affects early juvenile performance of the mangrove crab Ucides cordatus, measured as survival and growth through the first five juvenile crab stages (JI–JV). We further investigated whether ‘carry-over’ effects of an extended larval period vary intraspecifically among juveniles from three different hatches (F1–F3). Ucides megalopae were cultivated in two treatments. In the first one, the control, megalopae were cultivated continuously in exposure to conspecific crab odours (adult-conditioned seawater=ACSW) until moulting to the first juvenile crab stage. In the second, the delay-treatment, settlement-competent megalopae were kept for 20days in pure filtered seawater without metamorphosis-triggering odours. From day 21 onwards, megalopae were transferred to ACSW to induce larval moult. The results showed that delayed metamorphosis affects early juvenile survival and growth of U. cordatus. In the delay-treatment, survival rates of juveniles (JI–JV) from F1–F3 were 11–31% lower and intermoult development periods 1.5–4.2days longer than in the control. Delayed juveniles (F1–F3) exhibited 9.2–14.1% smaller body sizes (carapace width) and 1.4–3.9% lower growth rates mostly in the first two moulting events compared to specimens derived from non-delayed megalopae. Most of the detrimental effects were observed in almost all five crab stages studied, indicating that the costs of delayed metamorphosis may persist throughout early juvenile development. Juvenile morphology, however, was not affected. Our study also showed that carry-over effects of delayed larval moult vary intraspecifically among offspring produced by different females. This plasticity in phenotypic effects could relate to differences in the nutritional state, health or age of the females, to stressful environments during embryogenesis or to genetic differences. The observed carry-over effects of delayed settlement on early juvenile performance may affect the overall recruitment success and population dynamics of U. cordatus. In the field, such a situation would appear when new mangrove areas void of conspecific crabs are colonized or when degraded sites are re-populated by larvae originating from elsewhere populations. [Copyright &y& Elsevier]

Abstract: In our previous studies, five serine proteases containing clip domain were characterized from the swimming crab Portunus trituberculatus. To further investigate the characterization and function of serine proteases, one serine protease (PtSP) and one serine protease homolog (PtSPH1) without clip domain were identified from haemocytes cDNA library in this paper. They both possessed an SP or SP-like domain at the C-terminal. In contrast to PtSP, absence of Ser catalytic residue resulted in the loss of serine protease activity of PtSPH1. Phylogenetic analysis suggested either SPs or SPHs might not have a single origin in gene evolution. Six introns presented in PtSP genomic DNA with one uncommon splice site (GG) was discovered at exon 1/intron 1 boundary region. Four introns with common splice sites were found in PtSPH1 genomic DNA. RT-PCR results showed that PtSP mRNA was mainly distributed in haemocytes, gill and eyestalk, whereas PtSPH1 transcript was mainly expressed in stomach. PtSP showed slight increase during the first 48 h compared to control groups except 8 h point after Micrococcus luteus challenge. However, significant up-regulation was observed in the expression level of PtSPH1 challenged by Gram-negative bacteria Vibrio alginolyticus, Gram-positive bacteria M. luteus and fungi Pichia pastoris during the first 48 h. It indicates that PtSPH1 might be more sensitive to microorganism challenges compared with PtSP. [Copyright &y& Elsevier]

Abstract: In this paper, we analyzed population genetic diversity of Scylla paramamosain in Hainan Island of China based on COI gene sequence. Totally 92 individuals were collected from six localities: Haikou, Wenchang, Wanning, Sanya, Dongfang and Danzhou. A 761 bp fragment was sequenced, defining 32 different haplotypes. H4 was the most frequent haplotype, existing in all six localities, while the majority of haplotypes were rare ones, existing in only one or two individuals. Haplotype diversity (h) and nucleotide diversity (π) ranged from 0.625 to 0.914 and from 0.001 to 0.003, with an average of 0.841 and 0.002, respectively. Genetic distance ranged from 0.001 to 0.003 within localities and from 0.002 to 0.003 between localities. The AMOVA analysis indicated a low level of genetic differentiation among six localities (F ST = 0.0176, P > 0.05). Neutrality tests and mismatch analysis implied a potential population expansion event for this crab species. [Copyright &y& Elsevier]

Abstract: Reliable estimates of growth and mortality parameters are crucial for understanding how populations of exploited species may respond to shifts in fishing pressure. Results of previous studies on growth of the ecologically and economically important mangrove crab Ucides cordatus in Brazil differ strongly and age estimates for minimum legal capture size (60mm carapace width) range between less than 1 and 6–10years. These discrepancies are probably due to inherent problems of the applied methods, namely laboratory based observations and cohort-analyses. The present paper takes a new approach by measuring individual growth increments of U. cordatus in situ. Crabs were measured, tagged, released into 100m² field enclosures and periodically recaptured. There was no indication of an enclosure effect and 209 growth increments were obtained from specimens measuring 20.5 to 89.5mm in carapace width (CW). For improving the size coverage of the von Bertalanffy growth curve, first instar juveniles were reared in the laboratory up to an age of six months. Their average percent size increase (PI) was 22.57±6.75% during biweekly measurements, resulting in a CW of 7.8 to 11.5mm after six months. Average PI of the enclosure crabs ranged between 10.87±1.17% (indiv.<40mm CW) and 1.43±0.87% (indiv.>80mm CW) per moult and two large females had moulted without growing. Growth analysis revealed a larger asymptotic size in males than in females (89mm versus 72mm) while the growth parameter K of the von Bertalanffy growth function (VBGF) was lower in males (0.17 versus 0.25), resulting in similar growth performance of the two sexes (males: 1.16; females: 1.10). Age at legal minimum capture size estimated by the inversed VBGF was 6.13years in males and 7.38years in females, corroborating the mid to upper range of earlier growth estimates. Mortality parameters (Z, M and F) were calculated using length converted catch curves. Z in males was higher than in females (0.69 versus 0.49), as expected from the male-biased fishery. M, F and the exploitation rate E were estimated for three different scenarios taking into account the uncertainty of the age/size of functional maturity. Our study provides key information for the sustainable management of the U. cordatus fishery and confirms that the species is relatively slow growing and long-lived (>10years), suggesting a high vulnerability to overfishing. [Copyright &y& Elsevier]

Abstract: Most marine organisms are characterized by at least one planktonic phase during their life history, potentially allowing interconnection of populations separated by several hundred kilometers. For many years, the idea that marine species are genetically homogenous throughout their range of distribution, due to passive larval transport, has been a paradigm. Nowadays, a growing number of studies underline the existence of boundaries in the marine realm and highlight how larval dispersal is a complex process depending on biotic as well as abiotic factors. Marine fragmented habitats, such as atolls, mangroves and estuaries, are optimal systems for investigating the marine dispersion process under a metapopulation approach, since populations can be geographically defined a priori as opposed to those occupying open marine environments. Within this frame, the present paper investigates the population genetic structure and the demographic history of the mangrove crab Neosarmatium meinerti within the western Indian Ocean by partial sequences of the mitochondrial DNA cytochrome oxidase subunit I. A total of 167 specimens were sampled from six mangrove sites distributed along the East African coast, from Kenya to South Africa, also including a mangrove forest located on Mahé Island, Seychelles. A sharp genetic break between the mainland and the Seychelles is recorded, revealing the existence of two historically distinct groups that can be defined as independent evolutionary units. Gene flow along the East African coast appears to be high enough to form a single metapopulation, probably by means of stepping stone populations. Otherwise, this mainland metapopulation is currently under expansion through a gradual moving front from the subtropical toward the equatorial populations. [Copyright &y& Elsevier]

Abstract: Brazilian legislation defines coastal zone as a national patrimony – the geographic space of interaction of air, sea and land formed by the counties directly influenced, but not necessarily by those located in the coastline; also included are those distant until 50km from the coastline, holding activities of great impact for the coastal zone or its ecosystems. The definition includes also the territorial sea of 12 nautical miles. Coastal management is conducted by a national plan legally enforced, complemented by states and counties plans, and a coastal ecologic-economic zoning limited to small portions of the coastal zone. A resolution of the “Environmental National Council” defines as “permanent preservation areas”, of very restricted use, coastal ecosystems as mangroves, sand dunes, and reproduction sites of wild fauna. One could expect that the Brazilian coast should be more protected and properly managed than other countries where a national management plan is lacking (Argentina) or where the guidelines exist but are not yet legally enforced (South Africa). Notwithstanding, we note today in Brazil an intensification of conflicts opposing small-scale vs. industrial fishermen; shrimp farming vs. mangrove crab harvesting; resorts installation vs. native communities; oil and gas activities vs. NGOs; and conflicts on environmental permit between federal and state governmental agencies. This paper evaluates the possible reasons for the failure of the complex legal suite available in Brazil and suggests that participatory management and concerted actions with relevant stakeholders are the key elements for the successful cases. [Copyright &y& Elsevier]

Abstract: Chemical pollution such as chromium and phenol in the sea water has been increasing in recent years in China sea. At the same time, marine shellfish such as prawn and crab are sensitive to this pollution. β-N-Acetyl-d-glucosaminidase (NAGase, EC.3.2.1.52) catalyzes the cleavage the oligomers of N-acetylglucosamine (NAG) into the monomer. In this paper, the effects of phenol on the enzyme activity from green crab (Scylla serrata) for the hydrolysis of p-nitrophenyl-N-acetyl-β-d-glucosaminide (pNP-NAG) have been studied. The results showed that appropriate concentrations of phenol could lead to reversible inhibition on the enzyme and the inhibitor concentration leading to 50% activity lost, IC50, was estimated to be 75.0±2.0mM. The inhibitory kinetics of phenol on the enzyme in the appropriate concentrations of phenol has been studied using the kinetic method of substrate reaction. The time course of the enzyme for the hydrolysis of pNP-NAG in the presence of different concentrations of phenol showed that at each phenol concentration, the rate decreased with increasing time until a straight line was approached. The results show that the inhibition of the enzyme by phenol is a slow, reversible reaction with fractional remaining activity. The microscopic rate constants are determined for the reaction on phenol with the enzyme. [Copyright &y& Elsevier]

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]

As an important step toward development of a formulated diet for hatchery culture of the mud crab, Scylla serrata, this paper reports on laboratory experiments to assess the potential of a microbound diet (MBD) as a replacement for Artemia nauplii fed to megalopal larvae of S. serrata. The effects of different proportions of dietary MBD and Artemia on survival and moulting success of megalopa to the crab stage were investigated. In the first experiment, megalopae were reared communally and fed either 100% MBD, 100% Artemia or different combinations of the two (75%:25%, 50%:50%, 25%:75%). The experiment was terminated when all larvae had either metamorphosed or died. Larvae fed a combination of 25% MBD and 75% Artemia consistently showed the highest survival among all treatments throughout the experiment. Survival of larvae fed 100% MBD was the lowest early in the experiment but improved to become the second highest toward the end of the culture period. Overall survival of larvae fed 100% MBD did not differ significantly from that of larvae fed 100% Artemia. Moulting to the crab stage began on day 7 for larvae in the treatment receiving a 50%:50% combination of MBD and Artemia. On day 8, all larvae in treatments receiving greater than 25% MBD had some first stage crabs. Larvae fed Artemia only were the last to moult to the juvenile crab stage, but moulting occurred simultaneously on day 10. Because of cannibalism observed in the first experiment, a second experiment was conducted where megalopae were reared individually and fed either 100% Artemia or 100% MBD. Ninety percent of larvae from both treatments successfully moulted to the crab stage. Again, megalopae fed MBD began moulting 1 day ahead of those fed Artemia. The results of these studies show that the MBD used contained all necessary nutrients to sustain successful moulting of S. serrata megalopae to the crab stage. The acceptability of MBD by S. serrata larvae suggests significant potential for using the MBD in future experiments to investigate larval nutritional requirements of this commercially important crab species. Indeed, the more rapid moulting of larvae fed MBD in both experiments suggests that the MBD may have contained certain beneficial nutrients that were not provided by Artemia alone. The fact that no significant differences in survival between megalopae fed 100% MBD and those fed 100% Artemia in both communal and individual rearing experiments suggests that total replacement of Artemia with MBD is possible for S. serrata megalopae. This could result in substantial savings in operating costs for S. serrata hatcheries. [Copyright &y& Elsevier]

This paper reports on experiments to determine particle size preference and optimal ration for the various larval stages of the mud crab, Scylla serrata, fed microbound diets (MBD). All experiments used 14C-labelled rotifers as components of MBD, and ingestion was determined by assessing the 14C content of S. serrata larvae after feeding on the MBD. Five size ranges of MBD (<150, 150–250, 250–400, 400–600 and 600–800 μm) were used to assess ingestion by Zoea I, Zoea III, Zoea V and Megalopa. All were fed a ration equivalent to twice the equivalent dry weight of live foods provided to each larval stage under standard rearing conditions (standard ration). MBD particle size preference increased with increasing larval development. Highest ingestion rates by Zoea I, Zoea III, Zoea V and Megalopa were found for particle size ranges of <150, 150–250, 250–400 and 400–600 μm, respectively. MBD within these particle size ranges were used in subsequent experiments to assessed optimum rations for each of the four larval stages. Larvae were fed rations based on multiples or fractions of the standard ration (100%): 12.5%, 25%, 50%, 100%, 200% and 300%. There were no significant increases in ingestion, for any of the four larval stages, when ration was increased above 100%. For Zoea I, Zoea III and Zoea V larvae, there was no significant difference in the rate of MBD ingestion when ration was reduced to 50%; however, a 25% ration brought about a significant decrease in ingestion. There was no significant decrease in the rate of ingestion by Megalopa when ration was reduced from 100% to either 50%, 25% or 12.5%. The results suggest that rations currently used for larval rearing of S. serrata may be excessive. Little is currently known of the feeding behaviour and nutritional requirements of S. serrata larvae, and the results of this study are a significant development in this field. [Copyright &y& Elsevier]

Apart from penaeid shrimp culture, crab farming and fattening and other several diversified aquaculture practices are now emerging as viable ventures in India. About 11 types of crab products are being exported from India with an average unit value realization of USS 3.73 kg-1, pinpointing its importance in the foreign exchange earnings. An economic evaluation of mud crab culture, fattening and fattening with composite culture of shrimp/finfish has been attempted in this paper. The major operating cost was that of seed and it was higher for crab fattening (87% of the total operating cost). Feed costs were very low compared to that of shrimp farming. Annual profit obtained was US$ 22812.5 ha-1 year-1 for culture and US$ 30820.8 ha-1 year-1 for fattening. Economic indicators such as net profit, rate of return, pay back period and breakeven price indicate that crab fattening/culture is much more profitable than any other coastal aquaculture operations currently in practice, provided hatchery production is established in the country to ensure adequate supply of mud crab seeds. [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]