Soft-shell Crab Research Articles

Utilization Ecdysterone Hormone of Krokot (Portulaca oleracea) Extract on Molting Activity in Mud Crabs (Scylla serrate)

The Scylla serrate mangrove crab is one of the leading fisheries commodities in terms of exports, only behind shrimp, tuna and shellfish. Crabs have a fairly high price in foreign markets and most of the mud crabs obtained from wild catches are soft shell crabs. In terms of price, cultivating soft shell crabs is quite profitable, but most cultivators have several problems such as long maintenance periods and inconsistent molting times so that they do not experience business continuity. Applying herbal extracts via injection is an effective method because all the substances that trigger molting directly enter the body. Physiological engineering is needed to speed up the molting phase and get the same molting time. This research aims to identify the ecdysterone content in purslane leaves and determine the optimum dose of purslane leaf extract which can encourage skin molting in mud crabs. This research used a Randomized Block Design (RBD). The in silicons test results show that the compound that has the smallest binding affinity is ecdysone, namely -6.80 kcal/mol. Based on analysis of variance, the best molting percentage occurred in treatment B at 55.50%. The fastest molting period occurred in treatment C, namely on days 4 to 29 after injection. Treatments B and C had the highest survival rate, namely 100%, while in terms of increasing body weight and carapace width, the effect of all treatments was not significantly different. The water quality results for all groups were still within the optimum value, temperature 26.40 – 33.80ºC; pH 6.83 – 7.20; salinity 20.70 – 26.70 ppt and dissolved oxygen 4 – 4.52 ppm

Development of crab crispy product from soft shell crab, Scylla serrata

Development of crab crispy product from soft shell crab, Scylla serrata

Pendampingan Pembuatan Akun Lazada E-Commerce UMKM Garam Rebus di Desa Kaliwlingi

In Kaliwlingi Village there are various kinds of MSMEs, such as boiled salt, mangrove batik, soft shell crab, these are all the leading MSMEs in Kaliwlingi Village. Boiled salt is one of the products of Kaliwlingi MSMEs which is a leading MSME. However, Kaliwlingi boiled salt MSMEs also experience several obstacles in running their business, including product marketing which is still by word of mouth, limited human resources and minimal consumer capabilities. The aim of this KKN is to assist in marketing boiled salt products to further expand the boiled salt marketing network. This KKN includes marketing training using E-Commerce and assistance in using E-Commerce. The results of the KKN can be concluded that boiled salt MSMEs in Kaliwlingi Village can run their business professionally, and can increase production capacity due to the increase in the number of customers. The trend regarding the use of E-Commerce in Indonesia will continue to grow and now many people are starting to be selective about E-Commerce because there is intense competition between E-Commerce. What differentiates a company from its competitors lies in the strength of the market itself and UNCTAD (United Nations Conference Trade & Development) has issued a theory of 5 pillars of digital economic strength, namely market share, search engines, social media, video sharing and payment systems. LAZADA Group is a Southeast Asian E-Commerce company founded by rocket internet in 2012, and owned by Alibaba Group. Lazada in Indonesia itself was founded in 2012 and operates until now. Lazada's goal is to be a trusted online shopping place and provide the best quality in terms of quality and service.

Impact and accumulation of calcium on soft-shell mud crab Scylla paramamosain in recirculating aquaculture system

Soft-shell crabs are highly valued for their commercial significance and culinary appeal. To enhance production of soft-shell crabs, careful attention should be paid to the water calcium concentration in their culture. This study investigated the influences of different levels of calcium concentrations on the molting and growth of mud crab (Scylla paramamosain) within a meticulously controlled recirculating aquaculture system (RAS). We established three distinct water calcium concentration gradients (200, 300, and 450 mg/L) to comprehensively assess feeding habits, molting patterns, growth, and tissue calcium levels of mud crab. Initially, we observed a gradual reduction in water calcium concentrations with increments of crab molting events in RAS. Throughout one molting cycle, the feeding incidence of the crabs remained consistently high from 4 days to 37 days post-molt, irrespective of different calcium concentrations. Nonetheless, high water calcium levels (300 and 450 mg/L) significantly shortened molt intervals and accelerated exoskeletal calcification. Specifically, the molt intervals were 52.30 ± 2.72 d, 41.65 ± 5.24 d, and 37.70 ± 3.02 d, while the carapace hardening durations were 21.51 ± 4.33 h, 17.23 ± 3.38 h, and 13.46 ± 2.76 h at water calcium concentrations of 200, 300, and 450 mg/L, respectively. Moreover, elevated calcium concentrations also significantly enhanced weight gain of the mud crab during molting. Noteworthy, regardless of fluctuations in water calcium concentration, the condition factor of the molting crabs was approximately 63%, which could be an indicator of crab selection in soft-shell crab cultivation. Furthermore, the dynamic changes in calcium concentrations were disparate among different tissues in the post-molt stage. Gill and exoskeleton tissues exhibited an upward trend in calcium concentrations, while hemolymph and hepatopancreas tissues displayed distinct patterns of decrease followed by increase. Gill and exoskeleton tissues were identified as primary sites for calcium absorption and utilization, evidenced by a positive correlation between high calcium concentrations and increased calcium content in these tissues at 6 h and 3 d post-molt. Overall, our findings provide practical evidence for optimizing aquaculture management strategies through adjustments in water calcium concentration, thus to enhance production efficiency and profitability in soft-shell mud crab aquaculture.

Virus discovery in cultured portunid crabs: Genomic, phylogenetic, histopathological and microscopic characterization of a reovirus and a new bunyavirus

Portunid crabs are distributed worldwide and highly valued in aquaculture. Viral infections are the main limiting factor for the survival of these animals and, consequently, for the success of commercial-scale cultivation. However, there is still a lack of knowledge about the viruses that infect cultured portunid crabs worldwide. Herein, the genome sequence and phylogeny of Callinectes sapidus reovirus 2 (CsRV2) are described, and the discovery of a new bunyavirus in Callinectes danae cultured in southern Brazil is reported. The CsRV2 genome sequence consists of 12 dsRNA segments (20,909 nt) encode 13 proteins. The predicted RNA-dependent RNA polymerase (RdRp) shows a high level of similarity with that of Eriocheir sinensis reovirus 905, suggesting that CsRV2 belongs to the genus Cardoreovirus. The CsRV2 particles are icosahedral, measuring approximately 65 nm in diameter, and exhibit typical non-turreted reovirus morphology. High throughput sequencing data revealed the presence of an additional putative virus genome similar to bunyavirus, called Callinectes danae Portunibunyavirus 1 (CdPBV1). The CdPBV1 genome is tripartite, consisting of 6,654 nt, 3,120 nt and 1,656 nt single-stranded RNA segments that each encode a single protein. Each segment has a high identity with European shore crab virus 1, suggesting that CdPBV1 is a new representative of the family Cruliviridae. The putative spherical particles of CdPBV1 measure ∼120 nm in diameter and present a typical bunyavirus morphology. The results of the histopathological analysis suggest that these new viruses can affect the health and, consequently, the survival of C. danae in captivity. Therefore, the findings reported here should be used to improve prophylactic and pathogen control practices and contribute to the development and optimization of the production of soft-shell crabs on a commercial scale in Brazil.

Moulting Performances Evaluation of Female Orange Mud Crab, Scylla olivacea (Herbst, 1796) In-Captivity: Effects of Water Salinity and Limb Autotomy.

Female Scylla olivacea has become more popular in Malaysia as emerging species mainly for soft-shell crabs and crab fattening (to increase weight, size and ovary maturation so that they can be sold at a higher price). To harvest crabs in soft-shell conditions and fattening, both conditions depend mostly on moulting events. To accelerate the moulting process, the manipulation of water parameter (salinity) and autotomy of the limb is commonly used. In this study, the evaluation of the moulting performances of full limb autotomy (the removal of all the appendages except for the swimming legs) and non-ablated (control) using immature S. olivacea cultured in three different salinity treatments (10 ppt, 20 ppt and 30 ppt) were performed. Results indicate there were significant differences between mud crab's culture duration, BW increments, growth performances and feeding efficiency with salinity. However, CW increments and survival indicate no significant effect with salinity. Meanwhile, limb autotomy proved to affect the culture duration, BW increments, survival and feeding efficiency of S. olivacea. The study concludes that both salinity and limb autotomy play significant roles in moulting performances of S. olivacea, with 20 ppt being the best salinity to stimulate S. olivacea moulting and development compared with the other two treatments (10 ppt and 30 ppt). Limb autotomy also indicates promising results as this technique proved to accelerate the moulting duration of S. olivacea with a 100% moulting percentage within 30 days. Therefore, the outcome would certainly benefit in the aquaculture production of this species of commercial importance mainly on soft-shell crabs production and also emerge as crabs fattening technique.

Soft-shell crab detection model based on YOLOF

Soft-shell crab detection model based on YOLOF

Effects of Temperature and Diurnal Cycle in the Molting Schedule of Mangrove Crab, Scylla serrata (Forskål, 1775)

Soft-shell crab farming is gaining popularity since all crab parts can be eaten with almost no discards. However, its biggest challenge is the tedious monitoring every 4-hour interval to check for molting. A total of 90 mangrove crabs weighing 80-100 g were stocked in individual crab trays, recording 24-hour water temperature and incidence of hourly molting for 57 days to provide another basis for monitoring and cues in the molting schedule. Results showed that molting (82.24 %) happens at optimum temperature (Topt) levels, between 27–31°C, with a high incidence of molting (85.29 %) at nighttime when the water temperature is lower and within the Topt. Findings suggested that aside from 4-hour intervals, monitoring of molting for soft-shell crab farming is recommended at nighttime and early morning.

Investigating conspecific CsRV1 transmission in Callinectes sapidus

A reo-like virus, CsRV1, is found in blue crabs, Callinectes sapidus, from every North American location assessed, including Chesapeake Bay and the Atlantic and Gulf coasts, USA and associated with blue crabs in softshell production. CsRV1-associated crab mortality is prevalent in captive crabs, but it is still unknown how CsRV1 is transmitted. The purpose of this study was to examine the role that conspecific predation or scavenging may play in per os transmission in single exposure and repeated exposure experiments. For viruses without cell culture propagation, repeated exposure experiments have the challenge of presenting the virus consistently during the experiment and across time replicates. In a single-exposure experiment, none of the crabs fed muscle tissue of crabs carrying intense infections of CsRV1 developed CsRV1 infections. In a repeated-exposure trial, using infected muscle tissue prepared in alginate blocks, CsRV1 was detected in 11% of the crabs fed infected tissue but was not significantly different from the control group fed alginate lacking CsRV1. For repeated per os exposure experiments, the study demonstrated the utility of using alginate to present the same homogenous sample of virus, both injected and per os, over time for oral challenge experiments. Conspecific predation and scavenging could be a transmission route, but future work into this and other possible routes of transmission for CsRV1 is important to better understand the role this virus plays in wild crab populations and the soft-shell crab industry.

Erratum: Eyestalk Ablation to Increase Ovarian Maturation in Mud Crabs.

Erratum: Eyestalk Ablation to Increase Ovarian Maturation in Mud Crabs.

Evaluation of the Feasibility of Harvest Optimisation of Soft-Shell Mud Crab (Scylla paramamosain) from the Perspective of Nutritional Values.

Soft-shell crabs have attracted consumers' attention due to their unique taste and nutritional value. To evaluate the feasibility of harvest optimisation of soft-shell mud crabs, the proximate composition, mineral composition, and total carotenoid, amino acid, and fatty acid contents of edible parts of male and female soft-shell mud crabs at different moulting stages were determined and compared from a nutritional value perspective. The results showed that the sex and moulting stages could significantly affect the nutritional values of the edible portions of soft-shell crabs. The female or male soft-shell crabs in the postmoult Ⅰ stage had a much richer mineral element content than that in other moulting stages. The total carotenoid content in female soft-shell crabs was significantly higher than that in male crabs in all moulting stages, while male soft-shell crabs had better performance in amino acid nutrition than female soft-shell crabs. Moreover, it was found that soft-shell crabs in the postmoult Ⅱ stage had significantly higher contents of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), while significantly lower contents of saturated fatty acids (SFA) than those in other stages. The present study will provide a reference basis for the diversified cultivation of soft-shell crabs, and further promote the development of the mud crab industry.

Effects of Water Quality on the Growth, Molting and Mortality Of Mud Crab, Scylla Serrata Forskal (Decapoda: Portunidae) From Cox’s Bazar

The important decapod crustacean, the soft-shell crab, Scylla serrata is in great demand in different countries due to its taste next to shrimp and nutritional value, for which its farm is growing day by day as a source of income generation. This experiment was conducted for one year from January 2016 to December 2016 in Chaufaldandi, Cox’s Bazar, Bangladesh to study the growth, molting and mortality rates of the soft shell crab and water quality of the crab culture pond. During the three experiments in a year, matured male crab showed highest growth performance (28.00±7.02g to 32.15±3.87g). Mature female crab showed maximum molting (60%) during the 3rd experimental period (September to December), while immature crab depicted the highest rate of molting (75%) in the 2nd (May-August) and 3rd experimental periods (September- December). Mortality rate was found highest in mature male during the 1st experimental period (60%). The female crab showed maximum mortality rate (40%) during the 1st experimental period. The survival rate was best for female and immature S. serrata. The growth of S. serrata showed significant positive relationships with water temperature, salinity, water pH, soil pH, and alkalinity during the all three experimental periods. The 2nd and 3rd experimental periods were found to be the most favorable time to produce soft-shell crab due to suitable weather conditions. J. Biodivers. Conserv. Bioresour. Manag. 2022, 8(2): 25-36

The Origin of Soft-Shell Crabs

Soft-shell crabs are famous in seafood restaurants because they have a wonderful flavor, are easy to eat, and are highly nutritious! Soft-shell crabs are any regular edible crabs, but in their natural, soft-shell condition—because they have just shed their old shells, in an event called molting. Within a few hours after molting, while they are still in their soft-shell condition, these crabs are harvested and sold as soft-shell crabs. Crabs in the soft-shell condition have higher market value than crabs in the hard-shell condition. By understanding the origin of soft-shell crabs, we can improve the production of these crabs, as well as try to find ethical and sustainable ways to obtain them.

Characteristics of Nanochitosan from Soft Shell Crab Culture Waste in TarakanUsing The Ionic Gelation Method

Crab that is undergoing a molting process produces solid waste in the form of shells that can disturb the environment. One of the appropriate technologies that can be utilized in dealing with this waste is the manufacture of nanochitosan. The purpose of this study was to obtain nano-sized chitosan from soft shell crab culture waste by determining the quality of chitosan through analysis of water content, ash, nitrogen, Fourier Transform InfraRed (FTIR) and Particle Size Analyzer (PSA). The material used in this research is crab shells from soft shell crab culture waste. The method used in this research is descriptive quantitative. The results showed that the yield of chitosan produced was 4.67%. The quality of chitosan produced showed 8% water content, 1.5% ash and 4.83% nitrogen. In the FTIR spectra of nanochitosan powder, peaks appear which confirm the bond in chitosan, while in nanochitosan gel it is dominated by the absorption band of H-O which indicates the presence of water as a solvent. The value of the degree of deacetylation of the chitosan nanoparticles produced was 78.43%. The particle size of chitosan by ionic gelation method was 468.1±21.63 nm. The high speed of the magnetic stirrer is able to reduce the chitosan to a stable nano size and prevent agglomeration.

High prevalence of CsRV2 in cultured Callinectes danae: Potential impacts on soft-shell crab production in Brazil

Crabs can be infected by a variety of pathogenic micro-organisms but the most damaging are viruses. Naturally-occurring Callinectes sapidus reovirus 1 (CsRV1) is thought to contribute to mortality of Callinectes sapidus in soft crab culture in the USA. In Brazil, soft crabs are frequently produced using Callinectes danae, which suffers a similar rate of mortality in culture as C. sapidus. This study investigated whether CsRV1 could be detected in healthy or dead Callinectes danae from Paraná, Brazil and kept in captivity, we also evaluated the relationship between viral infection, and biochemical and behavioral parameters. C. danae from Paranaguá Bay were kept in a recirculation system for 14 days and subjected to weekly biochemical analyses and a reflex action mortality predictors (RAMP) test. RT-qPCR assays for CsRV1 were negative for all samples. However, electrophoretic analysis of extracted RNA from some crabs showed a pattern of 12 dsRNA bands that indicated intense infection by a reovirus with a genome organization different from CsRV1. The banding pattern was indistinguishable from a putative novel reovirus detected in C. sapidus in Rio Grande do Sul, Brazil, provisionally called CsRV2. The prevalence of dsRNA of CsRV2 showed no significant difference between crabs that died and survived. Interestingly, the presence of CsRV2 dsRNA was correlated with a significant reduction in glycogen concentration in hepatopancreas and a decrease in reflex action. The results obtained in this study are an early glimpse of the occurrence of reoviruses in C. danae and their potential effects in soft-shell crab systems in Brazil.

DETEKSI KEPITING MOLTING MENGGUNAKAN TEKNIK KLASIFIKASI MACHINE LEARNING

Soft crab is an export product where foreign demand is much higher than production. In the production of soft crabs, it is done by keeping the crabs individually in a crab box which is placed in the pond until they molt. Molting is a natural process of molting, i.e. removing the old tough skin for growth purposes. Shortly after molting, the new crab shells are still very soft and will harden again after water absorption occurs. Therefore it is important to monitor molting crabs to help farmers in the cultivation of soft shell crabs. The number of crab datasets is 1060 which consists of 1000 training data and 60 testing data. There are several popular image classification algorithms, namely K-Nearest Neighbors (KNN), Support Vector Machine (SVM), and Random Forest Classifier (RFC). KNN, SVM, and RFC are classification algorithms from Machine Learning. This study aims to compare the performance of the three algorithms so that the performance of the three algorithms is known. Several parameters are used to configure the KNN, SVM, and RFC algorithms. From the results of the trials conducted, KNN has the best performance with 98.33% accuracy, 98.33% precision, 98.38% recall, and 98.38% F1 Score.

Laju Pertumbuhan Dan Kecepatan Molting Kepiting Bakau (Scylla serrata) Dengan Pemberian Ekstrak Daun Pakis Hutan (Diplazium caudatum)

The cultivation of mud crabs is growing to get crabs in the soft shell condition. But most of the soft shell crab's farmers do not experience sustainable business. The main obstacle is the length of the maintenance period and moulting time does not unison thereby causing the feed and operating costs to be high. The research aimed to examine the effect of injection with forest fern leaf extract on growth rate and moulting speed of mangrove crabs (Scylla serrata) and determine the best dose in the process of injecting forest Fern Leaf extract for mangrove crab (Scylla serrata). Treatment of mangrove crab (Scylla serrata) weight ± 100 g with dose: P1 (NaCL 0.9%) P2 (50 mg.L-1) P3 (75 mg.L-1) P4 (100 mg.L-1) P5 (125 mg.L-1) 5 crabs each are cared for 30 days, The research was conducted using a single complete random draft (RAL), the results of various analyses showed the significant forest fern leaf extract against the growth of absolute weights, the rate of Specific growth, and relative growth, but no noticeable effect for molting speed and absolute length growth. The results of this research showed that a dose of 125 mg.L-1produces the highest value with result for moulting speed of 0.50 ± 0.57, length absolute growth of 0.37 ± 0.1 weighted absolute growth of 20 ± 5,74, specific growth rate of 0.54 ± 0.13, and relative growth of 0.64 ± 0.18.

Limb loss and feeding ability in the juvenile mud crab Scylla olivacea: Implications of limb autotomy for aquaculture practice

In Scylla mud crab farming, limb autotomy is commonly used in soft-shell crab production to expedite the moulting process and temporarily achieve high stocking density during crablet transportation. However, little is known about the effect of limb loss on the feeding ability of mud crabs. Therefore, we investigated the effect of various degrees of limb autotomy on the feeding ability of S. olivacea on either live blood cockles or cockle meat, and subsequently the effect of different live cockle size and days after limb removal. The removal of all appendages except for swimming legs compromised S. olivacea’s ability to feed on live cockles but not on cockle meat. When fed with live cockles, the total eaten cockle mass was similar among treatments, but the loss of limbs resulted in lower number of crabs engaged in feeding activity and longer feeding duration. When fed with cockle meat, crabs of all treatments engaged in feeding activity, and only full autotomised crabs showed prolonged feeding duration. Limb loss, but not cockle size nor day after limb removal, affected cockle consumption. Only crabs with one cheliped removed improved their feeding duration after Day 7, whereas crabs that lost both chelipeds did not show change in feeding duration. These results suggest that limb removal affect the feeding ability in mud crabs, and this serves as essential knowledge for future optimisation of the feeding practices of mud crab juveniles right after transportation or during soft-shell crab culture.

Automated molting detection system for commercial soft-shell crab (Portunus pelagicus) production

Automated molting detection system for commercial soft-shell crab (Portunus pelagicus) production

Is it Possible to Keep the Exoskeleton of the Crab Callinectes Ornatus Soft for Several Days?

Soft-shell crab is considered a gastronomic delicacy, reaching high values in the international market. Under normal conditions, the process of hardening of the crab's exoskeleton after moulting takes approximately two days to complete; however, the commercial consistency of soft-shell crab is lost in just 3 hours. The goal of this research was to evaluate the effects of chemical changes of water on the duration of postmoult, specifically at the stage in which they can be marketed as soft-shelled crab. In this research, Callinectes ornatus (n=241) underwent two experiments: One group was maintained in tanks with partial daily water renewal (Experiment 1), and other in tanks without water renewal (Experiment 2). In the experiment 1, the chemical characteristics of the water remained unchanged over time (p > 0.05), and the median time to hardening of the exoskeleton after moulting was 3 hours.