Wild Mud Research Articles (Page 1)

ABSTRACTMud crab (Scylla paramamosain) is an economically important aquaculture crustacean species in China and Southeast Asia countries. However, the catches of wild mud crabs declined sharply due to overfishing and environmental pollution. Therefore, it is necessary to understand the current genetic resources and population history of mud crab (S. paramamosain), which would provide appropriate guidelines for genetic resource management and breeding programs. To achieve this goal, a total of 146 mud crabs from four geographic populations in the southeast coast of China were collected for whole genome resequencing to investigate the genetic diversity, population genetic structure, and runs of homozygosity (ROHs). Results showed that the nucleotide diversity (π) ranged from 0.00157 to 0.00160, with observed heterozygosity (0.248–0.257) approximately equal to expected heterozygosity (0.260–0.265), indicating that these populations were near Hardy–Weinberg equilibrium, albeit with relatively low polymorphism. The results of PCA, population structure, phylogenetic tree, and linkage disequilibrium (LD) analysis consistently indicated weak genetic differentiation among different geographic populations. ROHs detection revealed 47,142 ROHs in mud crabs, with over 60% shorter than 0.1 Mb. Moreover, the average genomic inbreeding coefficient estimated by ROHs (FROH = 0.0293) and homozygous sites (FHOM = 0.0389) suggested relatively low inbreeding in mud crab populations. Notably, 29 candidate genes were identified in potential ROH islands, including growth and development‐related genes (IARS and UNC79), which may play an important role in the adaptive evolution of mud crabs. Overall, our results would provide valuable insights for conserving, managing, and improving the genetic resources of mud crabs (S. paramamosain).

Evaluation of lead and cadmium bioaccumulations related to oxidative responses in the tissues of two wild mud crabs, Scylla olivacea and Scylla paramamosain, from Pattani Bay, Thailand

Comparative analysis of the microbiota in wild mud crab (Scylla serrata) intestine, sediment, and water in Koggala Lagoon, Sri Lanka

Scylla olivacea, or the mud crab, is a crucial economic contributor in Southeast Asia, notably in the coastal region of the Ganges-Brahmaputra delta. This study compared the nutritional and heavy metals of fattened and wild-captured mud crabs from the southwest coastal areas of the Ganges-Brahmaputra delta, focusing on proximate composition, fatty acids, amino acids, and heavy metals. Fattened mud crabs showed higher crude protein levels (13.2%–14.4%), particularly in males, and higher crude fat and ash contents than their wild counterparts. Among fatty acids, fattened crabs had the highest palmitic acid levels (34.0%–41.2%), whereas wild crabs were rich in linoleic and linolenic acids. Amino acid analysis revealed that histidine and arginine were the most prevalent essential amino acids in fattened and wild crabs, respectively. Elemental analysis indicated that calcium levels were high in both groups. However, zinc, copper, iron, and manganese concentrations exceeded recommended dietary allowances. Furthermore, the wild mud crabs contained heavy metals lower than that of the fattened mud crabs. Notably, nickel, lead, and cadmium levels surpassed maximum permissible limits, suggesting potential health risks in fattened and wild mud crabs. The concentration of Omega-3 fatty acids was higher in wild crabs than in cultured ones. These findings emphasize the need for cautious consumption and strict monitoring in mud crab aquaculture to ensure food safety and sustainability.

Ecotoxicological impact of heavy metals on wild mud crabs (Scylla olivacea) in Malaysia: An integrative approach of omics, molecular docking and human risk assessment

Changes of nutrient composition in the ovaries and hepatopancreas of mud crab Scylla paramamosain broodstock and their offspring performance at different salinities

Scylla mud crabs are economically important portunid species for aquaculture in many countries. However, mass production of mud crabs as a supply of seafood is still difficult up-to-date. This review aimed to provide an overview of the major constraints faced in the grow-out farming of mud crabs, and the potential solutions were discussed. The major constraints in the Scylla mud crabs' grow-out culture are (1) inadequate seed supply, (2) cannibalism, (3) disease outbreaks, and (4) no commercial formulated feed that is specifically designed for mud crabs. The inadequate wild mud crabs seed supply can be solved through artificial seed production seed in the hatcheries, but the knowledge of mud crab requirements at early life stages is needed to improve the rearing techniques and production. Cannibalism in the grow-out culture of mud crabs is manageable, provided that the farmers are knowledgeable about the basic prevention methods (shelter provision, size grading, monosex culture) and they are practicing it. On the disease outbreaks, research into discovering new alternatives to antibiotics and prevention methods should be prioritized. Finally, the commercial formulated grow-out diet that is specific for the Scylla mud crabs should be developed to replace the use of natural products for feeding.

This study was conducted to investigate the reproductive cycle and size at maturity of wild mud crab, Scylla tranquebarica, in the mangrove forest of Marudu Bay. The sampling was conducted for 12-month consecutively with the assistance of local fishermen. Each sampling was carried out for 2 days, and baited crab traps were deployed in the river. During the sampling period, a total of 1459 crab specimens were caught. The different maturation stages of crab can be found throughout the year. The percentage of mature female crabs (Stage III to V) was relatively higher in February (38.5%) and May (50.5%), and lower in March (17.6%) and June (17.4%). A similar trend was observed in the male crab. Recruitment of crabs into the mangrove forest was observed after the breeding season. It was observed through histological observations that when 50% of the crabs were sexually mature, the size at maturity was in the range of 94.0 to 96.1 mm and 97.0 to 99.5 mm carapace width for female and male, respectively. This study suggests that S. tranquebarica breeds throughout the year and shows two peak breeding seasons and recruitment in Marudu Bay. This information can be used as baseline for mud crab fisheries management in Sabah.

The selected study area in Fisheries Management Area (FMA) 713 in Kartanegara District, East Kalimantan Province, Indonesia has extensive mangrove forests with suitable habitat for mud crabs (Scylla sp.), a valuable fisheries resource. Concerns have been raised regarding reported declines in the abundance of mud crabs and in the condition of their mangrove habitat. To evaluate the management status of the mud crab fishery in this area, an assessment was carried out using the Indonesian Ecosystem Approach to Fisheries Management (EAFM) methodology. The 25 indicators assessed represent 6 domains: Fisheries Resources, Habitat and Ecosystems, Fishing Technology, Social, Economic, and Institutional. The flag model technique was applied using multi-criteria analysis through an expansion of the composite index. The results indicate that the overall management status of mud crab fisheries in Kutai Kartanegara District was in the Moderate class (on a scale of Poor, Insufficient, Moderate, Good, Excellent). Indicators in the Habitat and Ecosystems, Fishing Technology, and Institutional Domains highlighted areas of concern where improvements are needed. The Fisheries Resources Domain aggregate status (moderate) indicated that wild mud crab stocks were still reasonably abundant and reliable, supporting the moderate status in the Social and Economic Domains, which relate to the welfare of fishing communities. The Institutional Domain status was in the poor category. Good governance measures to improve the Institutional Domain indicators have the potential to strengthen the other domains, in particular the Habitat and Ecosystem Domain and the Fishing Technology Domain, and to improve the overall EAFM status of the mud crab fishery in the future.

BackgroundMud crab, Scylla paramamosain, a euryhaline crustacean species, mainly inhabits the Indo-Western Pacific region. Wild mud crab spawn in high-salt condition and the salinity reduced with the growth of the hatching larvae. When the larvae grow up to megalopa, they migrate back to estuaries and coasts in virtue of the flood tide, settle and recruit adult habitats and metamorphose into the crablet stage. Adult crab can even survive in a wide salinity of 0–35 ppt. To investigate the mRNA profile after salinity stress, S. paramamosain megalopa were exposed to different salinity seawater (low, 14 ppt; control, 25 ppt; high, 39 ppt).ResultsFirstly, from the expression profiles of Na+/K+/2Cl- cotransporter, chloride channel protein 2, and ABC transporter, it turned out that the 24 h might be the most influenced duration in the short-term stress. We collected megalopa under different salinity for 24 h and then submitted to mRNA profiling. Totally, 57.87 Gb Clean Data were obtained. The comparative genomic analysis detected 342 differentially expressed genes (DEGs). The most significantly DEGs include gamma-butyrobetaine dioxygenase-like, facilitated trehalose transporter Tret1, sodium/potassium-transporting ATPase subunit alpha, rhodanese 1-like protein, etc. And the significantly enriched pathways were lysine degradation, choline metabolism in cancer, phospholipase D signaling pathway, Fc gamma R-mediated phagocytosis, and sphingolipid signaling pathway. The results indicate that in the short-term salinity stress, the megalopa might regulate some mechanism such as metabolism, immunity responses, osmoregulation to adapt to the alteration of the environment.ConclusionsThis study represents the first genome-wide transcriptome analysis of S. paramamosain megalopa for studying its stress adaption mechanisms under different salinity. The results reveal numbers of genes modified by salinity stress and some important pathways, which will provide valuable resources for discovering the molecular basis of salinity stress adaptation of S. paramamosain larvae and further boost the understanding of the potential molecular mechanisms of salinity stress adaptation for crustacean species.

First detection of white spot syndrome virus (WSSV) in wild mud crab Scylla spp. (de Haan, 1883) from Setiu Wetlands, Malaysia

Investigation of Parasites and Ecto-Symbiont in Wild Mud Crab, Genus Scylla from Terengganu Coastal Water, Malaysia: Prevalence and Mean Intensity

Most Asian country have been success for the culturing of the mud crab i.e. Thailand, Vietnam and Philippines but no action were taken to solve the barnacle infestation problem of mud crab. Previous study did not mention about significant of the attachment of pedunculate barnacle to the mud crab. But somehow, this pedunculate barnacle may be able to give effect to the mud crab respiratory system especially for adult mud crab. This preliminary study are to observe the effect of the pedunculate barnacle attachment to their host using histopathological and Scanning Electron Microscopy (Tabletop SEM 1000, Hitachi) observation. Histological sectioning of gill wild mud crab with the Hematoxylene and Eosin staining (H&E Stain) were done to study about their effect. The results show the attachment of the pedunculate barnacle is temporary and will be left the host-gill during molting period.

Morphological Distribution of Pedunculate Barnacle Octolasmis cor (Aurivillius, 1892) found on Gill of Wild Mud Crab (Genus: Scylla) from Terengganu Coastal Waters, Malaysia

Morphological Description of Pedunculate Barnacle Octolasmis angulata (Aurivillius, 1894) on Wild Mud Crab Genus Scylla from Setiu Wetland, Terengganu Coastal Water, Malaysia

Pedunculate, Goose or Stalked barnacles are commonly found in the hard substrate of marine or brackish area and it also recorded found attached on the living organisms as their host. Thirty seven wild mud crabs (Scylla olivacea) were sampled from Setiu Wetland (5°40’47.93”N, 102°42’45.04”E), Terengganu, Malaysia. The 625 sample of barnacles were collected and the samples were preserved in 70% alcohol and observed by using Table Top Scanning Electron Microscope (Hitachi TM1000). The morphology and characteristic of the barnacle were recorded based on the observation of their peduncle, capitulum, calcareous plates, carina, tergum and branched scutum. To our knowledge, there is no morphological study about the species of pedunculate barnacle that attached on gill of S. olivacea in Malaysia. Thus, this study provides the first report of pedunculate barnacle attached on S. olivacea in the east coast of peninsular Malaysia.

Biomarker responses and genotoxicity in the mud snail (Bullacta exarata) as indicators of coastal contamination

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 (F1) families were produced from the four sites. The duration from spawning of the base population (P0) to attainment of broodstock size F1 was 10–14 months. Four second-generation (F2) families were produced after 11–12 months. Up to the F2, 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 P0 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.

Hatchery-reared animals for stock enhancement should be competent to survive and grow at rates equivalent to those of wild conspecifics. However, morphological differences are often observed, and pre-conditioning steps may be required to improve the fitness of hatchery-reared juveniles prior to release. In the present study, hatchery-reared Scylla serrata juveniles were reared either individually (HR-solitary) or groups in tanks (HR-communal), the latter group being exposed to intraspecific competition and foraging for food. After 21 days, both groups were compared to similar size wild-caught juveniles in terms of morphometric measurements of carapace spination, abnormalities and carapace colouration. There were some limited significant differences between HR-communal crabs and HR-solitary crabs in terms of length of 8th and 9th lateral spines and in body-weight-carapace width ratio, but both treatments differed from wild crabs, which were heavier and had longer carapace spines for their size. In contrast, both HR treatments exhibited common abnormalities including deformities in the shape of the abdomen, in particular occurrence of an asymmetrical telson or a deeply folded telson. In all cases, abnormalities persisted through moulting. Initially, carapace colour differed in all measures of colour between HR and wild crabs. However, these differences reduced after a period of 4–8 days of conditioning on coloured tank backgrounds or dark sand or mud backgrounds, without moulting. Similarly, hatchery-reared crabs exhibited very limited burying behaviour on first exposure to sediment, but this increased to levels observed in wild crabs within 2–4 days. Thus, short-term conditioning of hatchery-reared crabs on dark sediments may be effective in increasing predator avoidance and survivorship in released animals, and present results suggest that this can be achieved after relatively short periods of 1 week or less.

A study was carried out to investigate the presence of bacteria flora in wild mud crab (Scylla serrata) from Setiu Wetland as well as their antibiotic resistances. A total of 91 bacterial isolates consisting of 12 bacterial species were successfully isolated from mud crab. Oxolinic acid was found to be effective against all the bacterial isolates whilst the highest percentage of antibiotic resistance was shown by lincomycin (94.5%) followed by ampicillin (90.1%), amoxicillin (86.8%) and oleandomycin (78.0%). The study is very useful to evaluate the safety of mud crab for human consumption based on wild mud crab-associated bacteria as well as their antibiotic resistances.