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Recirculating Aquaculture System (RAS) is introduced in aquaculture farming industry to reduce water resource utilization, efficient the energy and land uses, and also help minimalize the water exchange. This system enables utilization of unsuitable land and promotes a sustainable environment in aquaculture industry. Furthermore, this technology has been established and proved efficient in monitoring the aquatic animal condition subsequently helps in maintaining the water quality and help remove solid particle wastes from the aquaculture treatment. As today, RAS has been developed with more effective technologies such as the use of UV irradiation, solid capture, protein skimmer and also provided with highly techno bio-filtration set. Basically, this system was applied for broodstock maturation, nursery phase, and grow-out production. In this review article, we provide an overview of RAS between the clear water, probiotic, and biofloc technology, and the advantages of its combination. Even though RAS and biofloc is two different parallel system, the application of the probiotic and biofloc in the semi-RAS application system is intense to be investigated. The synergistic effect of RAS using this combination towards high yield aquaculture production will be highlighted in this review paper. Expectantly this review paper will generate awareness and useful information on the RAS application in the aquaculture system operation with help in maximize the impact to the aquaculture yield production.

Abstract Vibrio parahaemolyticus is a gram-negative facultative anaerobic bacterium implicated as the causative agent of several shrimp diseases. As part of the effort to provide biocontrol and cost-effective treatments, this research was designed to elucidate the effect of Morinda citrifolia fruit extract on the immunity of Penaeus vannamei postlarvae (PL) to V. parahaemolyticus. The methanol extract of M. citrifolia was vacuum evaporated, and the bioactive compounds were detected using gas chromatography‒mass spectrometry (GC‒MS). Thereafter, P. vannamei PL diets were supplemented with M. citrifolia at different concentrations (0, 10, 20, 30, 40, and 50 mg/g) and administered for 30 days before 24 h of exposure to the bacterium V. parahaemolyticus. A total of 45 bioactive compounds were detected in the methanol extract of M. citrifolia, with cyclononasiloxane and octadecamethyl being the most abundant. The survival of P. vannamei PLs fed the extract supplement was better than that of the control group (7.1–26.7% survival greater than that of the control group) following V. parahaemolyticus infection. Shrimp fed 50 mg/g M. citrifolia had the highest recorded survival. The activities of digestive and antioxidant enzymes as well as hepatopancreatic cells were significantly reduced, except for those of lipase and hepatopancreatic E-cells, which increased following challenge with V. parahaemolyticus. Histological assessment of the hepatopancreas cells revealed reduced cell degeneration following the administration of the plant extracts (expecially those fed 50 mg/g M. citrifolia) compared to that in the control group. Therefore, the enhanced immunity against V. parahaemolyticus infection in P. vannamei could be associated with the improved hepatopancreas health associated with M. citrifolia fruit extract supplementation.

Although the widely cultured Litopenaeus vannamei is highly tolerant to varying salinity levels, the rapid fluctuation of abiotic and biotic factors due to climatic changes may become stressors to the shrimp's physiology, resulting in impaired immunity and increased disease susceptibility. This study aimed to investigate the combined effects of both factors towards L. vannamei at transcriptomic level. L. vannamei were cultured at three different salinity levels (5 ppt, 20 ppt and 30 ppt) for 60 days and were challenged with Vibrio harveyi. RNA-seq analysis was conducted on the hepatopancreas to assess the differential expressed genes (DEGs) in both control and V. harveyi infected groups. Our results revealed 5,725 DEGs was observed in shrimp reared at 5 ppt, 3,643 DEGs at 20 ppt and 1,560 DEGs at 30 ppt. Most DEGs were identified to be associated with osmoregulation and transport activities, immune and stress regulation, nutrient metabolism, growth, chitin binding, gonadal development, and metal ion binding and toxicity. We identified that shrimp cultured at intermediate salinity of 20 ppt exhibits the greatest immunity level after infection by V. harveyi, given that low salinity (5 ppt) may augment the free ion metal toxicity, resulting in higher disease susceptibility. Both V. harveyi and salinity stress function together or separately to activate a wide range of immune and stress regulatory genes, which could be potential candidate markers for future RNAi and knockdown research in developing efficient prophylactic management strategies for L. vannamei.

Mud crab (Scylla olivacea) is a valuable crustacean that has been consumed as nutritious foods for human body maintenance, delicacy tasting and for medicinal purposes. This study aimed to develop a novel mud crab extract processed through lactic acid fermentation. The objective is to compare the nutritional value, antioxidant properties and lipid profiling of mud crab muscles and hepatopancreas extract. Protein content in mud crab muscles extract (MCME) was significantly (p .05) different to HE. The DPPH-radical scavenging activity of both extracts was similar (p > .05). However, the ferric reducing antioxidant power in MCME was higher (p

Live foods such as phytoplankton and zooplankton are essential food sources in aquaculture. Due to their small size, they are suitable for newly hatched larvae. Artemia and rotifer are commonly used live feeds in aquaculture; each feed has a limited dietary value, which is unsuitable for all cultured species. Whereas, copepod and cladocerans species exhibit favorable characteristics that make them viable candidates as sources of essential nutrients for hatchery operations. Due to their jerking movements, it stimulates the feeding response of fish larvae, and their various sizes make them suitable for any fish and crustacean. Even though Artemia is the best live feed due to its proficient nutritional quality, the cost is very expensive, which is about half of the production cost. A recent study suggests the use of amphipods and mysids as alternative live feeds in aquaculture. High nutritional value is present in amphipods and mysids, especially proteins, lipids, and essential fatty acids that are required by fish larvae during early development. Amphipods and mysids are considered abundant in the aquatic ecosystem and have been used by researchers in water toxicity studies. However, the culture of amphipods and mysids has been poorly studied. There is only a small-scale culture under laboratory conditions for scientific research that has been performed. Thus, further research is required to find a way to improve the mass culture of amphipods and mysids that can benefit the aquaculture industry. This review article is intended to provide the available information on amphipods and mysids, including reproductive biology, culture method, nutritional value, feed enhancement, and the importance of them as potential live feed in aquaculture. This article is useful as a guideline for researchers, hatchery operators, and farmers.

The mud crab Scylla paramamosain is a key species in China due to its high nutritional value and great economic worth and has grown in popularity. Myo-inositol can modulate versatile physiological functions in aquatic animals. In the present study, S. paramamosain megalopa were given graded concentrations of myo-inositol (0, 1, 2, 4, and 8 ppm) by water immersion to explore how their metamorphosis would be affected. The results showed that supplementing with myo-inositol remarkably increased transformation and survival rate from megalopa to crablet by at least 1.16 and 1.26 times, respectively. To decipher the molecular mechanism of how myo-inositol increases metamorphosis and survival rate, we further performed transcriptome-based gene expression profiling of both megalopa and crablet treated with myo-inositol. The integrative transcriptome analyses predicted that the differentially expressed genes (DEGs) were significantly enriched in chitinase activity, structural constituent of cuticle, and chitin binding, which are associated with the decomposition and reconstruction of cuticle. qPCR results confirmed that myo-inositol mediated gene expression levels of the above cuticle-related pathways. Considering the importance of the cuticle in exoskeleton formation and molting, it can be concluded that myo-inositol-induced changes in the cuticle decomposition and reconstruction might have accelerated the transformation from megalopa to crablet of S. paramamosain. Besides, numerous DEGs were significantly enriched in protein digestion and absorption, amino sugar and nucleotide sugar metabolism. It implies that myo-inositol may improve survival by regulating energy or nutrient absorption. Additionally, the accelerated metamorphosis by myo-inositol may improve survival from megalopa to crablet of S. paramamosain. Overall, this study will provide the first insights into the underlying molecular mechanisms by which myo-inositol increases metamorphosis and survival.

To enhance comprehension of the destiny of the spermatozoon throughout the reproductive process of mud crab (Scylla paramamosain) is important for achieving large-scale artificial breeding of Scylla. The reproductive systems of sexually mature male and female mud crabs were studied, utilizing the histomorphological method. The spermatozoon traveled from testicular lobules through the seminiferous duct, into the anterior vas deferens (AVD) via the collecting duct. The spermatophore wall formed at the end of the AVD. During copulation, spermatophores stored in the median vas deferens (MVD) were transferred to the seminal receptacle through the posterior vas deferens (PVD), ejaculatory duct, and gonopod, with seminal plasma secreted by both MVD and PVD together. After mating, the sperm plug was formed within the seminal receptacle's ventral zone. At ovary stage Ⅲ, the spermatophore wall ruptured, and the sperm plug disappeared. Bundled sperm packets congregated into a dense mass, while a few spermatozoa dispersed along the intermediate chamber to the dorsal zone. At ovary stage Ⅳ, the dorsal zone also exhibited a dense sperm mass due to increased dispersal. At ovary stage Ⅴ, merely a modest portion of the dense sperm mass remained in the ventral zone, and the rest dissociated and dispersed within the seminal receptacle. Following ovulation, sperm mass remained in the ventral zone, re-dissociating and re-dispersing once ovarian development reached stage Ⅲ again. The phased dispersion supply mode of spermatozoa behind multiple ovipositions was unveiled. Furthermore, we observed the ultrastructural changes in the spermatozoon during the process of the capacitation, including operculum widening, actin-containing substance accumulation, and the density of chromatin in the nucleus decreased. As presented herein, the elucidation of the dynamic changes of the spermatozoon, as well as the pattern of spermatozoa supply, contributes significantly to our enhanced comprehension of the reproductive biology of Scylla.

IntroductionCrustacean predators exhibit diverse trophic interactions across various habitats in aquatic ecosystems. To assess their ecological roles, it is essential to understand their complete dietary spectrum. Recently, DNA-based techniques such as DNA metabarcoding and high-throughput sequencing have provided insights into trophic networks and their response to environmental drivers.MethodsIn this study, we used these methods to investigate the impact of salinity gradients on the trophic networks of mud crabs (Scylla paramamosain) in marine ecosystems.ResultsOur results revealed that mud crabs prey on a wide range of taxa, including crabs (other than the host species), fish, shrimps, and other prey factions. Salinity gradients had a significant influence on the specific prey items, such as high predation on Metapenaeus, and Trigonopterus species in high salinity sites. Notably, crabs exhibited a greater infestation of Portunion parasites in environments with high salinity levels, in contrast to environments with lower salinity levels. Ordination analysis showed that mud crabs adapt their diet according to environmental constraints.DiscussionFurthermore, the results indicate that mud crabs showed opportunistic predation behavior as they were observed preying on other Portunidae species sharing the same trophic guild. Overall, these findings demonstrate the dietary plasticity and associated parasite infestation of an important crustacean predator, and provide evidence that environmental changes may affect incidences of the associated parasites as well as the specific predator-prey interactions indirectly through fluctuations in marine ecosystems.

Biofloc technology improves water quality and promote the growth of beneficial bacteria community in shrimp culture. However, little is known about the bacteria community structure in both water and gut of cultured organisms. To address this, the current study characterised the metagenomes derived from water and shrimp intestine samples of novel Rapid BFTTM with probiotic and clearwater treatments using 16S V4 region and full length 16S sequencing. Bacteria diversity of water and intestine samples of Rapid BFTTM and probiotic treatments were similar. Based on the 16S V4 region, water samples of >20 μm biofloc had the highest abundance of amplicon sequence variant (ASV). However, based on full length 16S, no clear distinction in microbial diversity was observed between water samples and intestine samples. Proteobacteria was the most abundant taxon in all samples based on both 16S V4 and full length 16S sequences. Vibrio was among the highest genus based on 16S V4 region but only full length 16S was able to discern up to species level, with three Vibrios identified—V. harveyi, V. parahaemolyticus and V. vulnificus. Vibrio harveyi being the most abundant species in all treatments. Among water samples, biofloc water samples had the lowest abundance of all three Vibrios, with V. vulnificus was present only in bioflocs of

Aquaculture produces nearly half of the seafood consumed by the ever-growing world population. There have been attempts to adopt novel technologies into the industry to increase profitability, particularly the Internet of Things (IoT). In aquaculture, it is therefore important to evaluate and address the challenges related to IoT. The purpose of this review is to categorize the challenges associated with implementing IoT systems in aquaculture according to the literature. This work reviewed prototyped IoT systems reported in the literature in the last five years. Moreover, some potential solutions to the reported challenges were discussed with the help of literature that can be used by researchers in the future. Among IoT systems used in aquaculture, some challenges are common, while others are specific to particular species or farms. Due to direct contact with water, maintenance of sensor probes is a common challenge. The literature addressed this problem through different designs that led to self-cleaning mechanisms. There were three categories of specific challenges: infrastructure-related, data-related, and perception-related. Infrastructural challenges primarily relate to electricity availability and internet connectivity. For electricity, energy harvesting technologies are suggested, and for internet connectivity, satellite internet or offline systems are suggested. The data related category covers challenges related to data loss due to device or network errors. Studies have shown that incorporating soft methods can help resolve most of these issues. Perception-related challenges examine barriers that prevent aquaculture farmers from implementing IoT systems. As one potential remedy for this barrier, literature suggests policy makers intervene in promoting the benefits of IoT systems and providing incentives.

Salinity changes have profound effects on the development, physiology, and molecular activity, as well as the associated microbiome of organisms living in marine and estuarine ecosystems. The associated microbiomes of aquatic organisms are reported to support key physiological functions such as nutrition, reproduction, behavior, and health. The mud crabs, a euryhaline crustacean species, has extra-ordinary ability to survive in a wide range of salinities. Although mud crabs are exposed to diverse salinity conditions, little is known about how these variations affect the symbiotic bacteria they harbor in each environment. This study aimed to deciphering the associated microbiome assembly of mud crabs as well elucidating the potential implications of different salinity conditions in this process. Here, we used high-throughput sequencing to examine how the assemblages of bacteria in the gut of mud crabs are shaped by different salinity gradients. A total of 57 bacterial phyla were detected with Firmicutes and Proteobacteria dominant. A greater difference of microbiome in the gut than stomach of mud crabs indicating guts were more sensitive to different salinity environments. Specific bacterial taxa were enriched in the guts of mud crabs sampled from different salinity settings. Furthermore, functional enrichment analyses also showed that only gut bacteria had significant differences of functions in different salinity levels (high salinity versus low salinity), playing critical roles of signal transduction, and cell growth and death pathways. These results suggested that the microbiota in guts of crabs are more prone to variations in the salinity. These findings provide a comprehensive understanding of the composition and plasticity of mud crabs microbiota, which could lead to innovative strategies development for boosting the aquaculture industry of mud crabs.

Asymmetric body traits in bilateral organisms are common and serve a range of different functions. In crustaceans, specifically among brachyuran crabs, heterochely and handedness in some species are known to aid in behavioural responses such as food acquisition, and sexual and territorial displays. However, the heterochely of the intertidal mud crab genus Scylla is still poorly understood. This study investigated the cheliped morphometric characteristics of orange mud crab Scylla olivacea and the relation of heterochely and handedness to sex. Scylla olivacea is heterochelous, with predominant right-handed (70.2%). Three morphometric variables, i.e., propodus length (PL), propodus depth (PD), and propodus width (PW) were significantly larger in the right cheliped and the estimated handedness based on these three variables were consistent with the presence of molariform teeth. The effect of sex had no influence on the occurrence of heterochely or handedness. The frequency of left-handedness increased with size, especially in males. We postulate that handedness reversal, a phenomenon seen in other crab species when the dominant hand is lost, also occurs in S. olivacea, thereby resulting in a change in left-handedness frequency. The use of chelipeds by males in mate and territorial defenses might provide an explanation for the higher risk of losing a dominant cheliped and thus, higher left-handedness frequency compared to females. Future behavioural research could shed light on the selective forces that affect the handedness distribution in mud crabs. Knowledge on heterochely and handedness of mud crabs could be useful for future development of less aggressive crab populations by claw reversal and the optimisation of limb autotomy techniques.

Gynogenesis is an established technique to generate all female type offspring and this technique has been successfully induced diploid gynogens progeny in aquatic animals of fishes and crustaceans. Monosex culture of all female shrimp and fishes were selected attribute to all female type offspring which have better size than male and help increase the market size and profitable. This article discusses on the protocol applied to produce gynogens progeny and the successful rate of gynogenesis production in fishes, molluscs and aquatic crustaceans of shrimps in general. Overall most of the UV length applied for irradiated the sperm were around 254–365 nm for (20–40 s), (20–80 s) and (5–8 s) for shrimps, 254 nm, 30 s for molluscs species and for fishes were around 254 nm for (1.5min) and (2–12 min) time of exposure respectively. For gynogenesis induction, the fertilized eggs were treated with cold shock, heat shock or cytochalasin- B for both shrimp and fishes gynogens technique. Fertilization rate was identified around 4.33%–19.67% in shrimp. Successful hatching rate was identified around 3.0%, 14.9%–37.2% of gynogens offspring in shrimp and various percentages of hatching rates were identified from each species of fish gynogens. Overall, there is still low survival rate of gynogens produced using gynogenesis technique and further study should be carried out to improve the gynogens production. The discussed protocols serve as a guide lines for the gynogenesis technique application of all female monosex culture in the future.

Increasing evidence have revealed a positive correlation between gut microbiota and shrimp health, in which a healthy shrimp gut consists of a complex and stable microbial community. Given that both abiotic and biotic factors constantly regulate shrimp gut microbiota, any changes affecting the levels of these factors could cause modification to the gut microbiota assemblage. The goal of this study was to explore the effects of salinity levels and pathogenic Vibrio harveyi infection on the diversity, structure, composition, interspecies interaction, and functional pathways of Litopenaeus vannamei gut microbiota. Juvenile shrimp were cultured at 5 ppt, 20 ppt, and 30 ppt for two months prior to Vibrio harveyi infection. After pathogenic V. harveyi challenge test, genomic DNA was isolated from the shrimp gut, and subjected to the 16S rRNA metagenomic sequencing analysis. We observed that gut microbiota diversity of shrimp cultured at 5 ppt and 30 ppt were lower than those cultured at 20 ppt after exposure to V. harveyi infection, suggesting that shrimp cultured at the two former salinity levels were more susceptible to V. harveyi infection. Network analysis also showed that shrimp cultured at 20 ppt exhibit a more stable bacterial network with complex interspecies interaction, even after induced by V. harveyi. Moreover, the presence of a high number of beneficial bacteria such as Pseudoruegeria, Rhodovulum, Ruegeria, Shimia and Lactobacillus in shrimp cultured at 20 ppt might have played a role in inhibiting the growth of V. harveyi and other potentially pathogenic bacteria. Besides, bacterial functional pathway prediction has also shown that metabolic pathways such as phenylalanine metabolism, glycine, serine and threonine metabolism, starch and sucrose metabolism, glyoxylate and dicarboxylate metabolism, carbon metabolism and biofilm formation process were significantly higher in shrimp cultured at 20 ppt. Collectively, our results suggested that 20 ppt is an optimal salinity that suppresses the growth of V. harveyi and potential pathogenic bacteria in the shrimp gut, which could possibly minimize the risk of pathogenic infection for sustainable production of healthy shrimp.

The aim of the present study was to determine the movement patterns of mud crabs, genus Scylla, within the mangrove area of the Setiu Wetland in Terengganu, Malaysia. Mark-release-recapture technique were conducted during 24 sampling trips. A fluorescent visible implant elastomer (VIE) tag was inserted within the crab’s shell and they were released at the same capture stations over an interval of two weeks before the next sampling. A total of 288 crabs of various sizes, sex and species were identified, measured, tagged and recorded. The numbers of male crabs were higher than females. Three species were present, dominated by S. olivacea at 54.2% and S.tranquebarica at 26.4%, with S. paramamosain in third place at 19.4%. Among the 288 crabs that were tagged and released, 26.38% were recaptured. The tagged crabs did not move very far from the release station based on the recapture data. The greatest mean chance of being recaptured within 24 h was 44.5%, and there were no tagged crabs recaptured after 48 h even on sampling trips at several points from the release site. Knowledge of movement patterns is essential to understand migration and population dynamics and the relationship between reproduction and local distribution.

Mud crabs (genus Scylla) are gaining attention as potential aquaculture species due to their lucrative market price and high demand. One of the essential components of mud crab culture is broodstock quality. The optimisation of mud crab broodstock culture currently focused on its nutritional aspects and common rearing parameters, including stocking density and temperature. The use of sandy substrate to induce egg extrusion in female Scylla broodstock is common; however, its optimisation has never been conducted. This study investigated (1) the substrate association of two Scylla species (S. olivacea, S. paramamosain) during broodstock conditioning until egg extrusion when the choices of fine (66.99 ± 14.48 μm) and coarse (656.17 ± 38.13 μm) sands were given; (2) the female reproductive output when S. olivacea females were individually exposed to either fine sand, coarse sand, or no sand treatments. Females, spawners and non-spawners, of S. olivacea and S. paramamosain were associated with fine sand and none was observed to bury in the coarse sand tray. The occurrence of egg extrusion was not significantly different between species but moderately associated with the duration of visits (stayed in sand for 1 d, 2 d, ≥3 d). The final incubation period in the sand tray was more than 2 days in all cases, except for one female S. paramamosain (buried in the sand for 1 day prior to egg extrusion). When no choice was available, the highest percentage (58.3%) of females extruded eggs in fine sand treatment, followed by coarse sand treatment (33.3%), and no sand treatment (8.3%). Sand type influenced the weight of egg clutch, total egg number, fecundity, and clutch size. These results suggest that fine sand (

Aquaculture is the aquatic equivalent of agriculture. While agriculture is predominantly based on the use of freshwater to grow crops, aquaculture utilizes freshwater (i.e. inland waters) and brackish water/seawater (i.e. coastal waters) to culture fish, plants, shellfish (bivalve, abalone, sea urchins and sea cucumbers), macro and microalgae. The increasing scarcity of captive aquatic fisheries resources has led to the regenerative farming practices of aquaculture. Aquaculture is the fastest-growing food sector in the world and about the most important means of providing sustainable food production currently. Among the several aquaculture techniques used, breeding technology has been exploited to improve food production. Beyond captive production, breeding technology has also been exploited for restocking programs of many aquatic ecosystems (i.e. rivers, lakes, sea, estuaries, etc.), hence, contributing positively to their management and ecosystem services. This comment, therefore, highlights some breeding technology as regards to their ability to improve sustainable captive production and aquatic ecosystem services.

Environmental factors affect the biological functions of aquaculture species both in the wild and in captivity. Therefore, optimization of the husbandry conditions under captivity can improve the production performance of an aquaculture species. In this study, the effect of water velocity on the glucose concentration, energy level of different body parts (i.e., hepatopancreas, gonad, muscle, and feces), and gonadal maturation of the Mud crab Scylla olivacea was evaluated. Immature crab samples of both sexes were collected from the Setiu Wetland and reared for 60 days in different water velocities (0, 20, 40, and 60 cm/s). The results of this study suggested that rearing the mud crab in 20 cm/s and 0 cm/s elicited the least stress as revealed by the glucose concentration of male and female crabs respectively when compared to other flow velocities. The trend of energy reserved in the hepatopancreas, and feces of both sexes however showed a significant decrease with the increasing flow velocity. A similar trend was also observed in the muscles of male S. olivacea. The energy in the muscle and gonad of the female mud crab on the other hand was higher in 20 cm/s and declining thereafter (with least recorded in 0 cm/s). This study also noticed that the 20 cm/s flow velocity advanced the stages of gonadal development (i.e., stages 3 and 4 for males and females respectively) of the crabs better than other flow velocities. It was therefore concluded that the 20 cm/s flow velocity is optimum to induce gonadal maturation and lessen the stress encountered by S. olivacea in captivity.

Texture is an important sensory attribute for overall quality and consumer acceptance of prawns. However, texture is affected during cold storage due to the proteolytic activity of endogenous proteases, resulting in poor quality and a short shelf life. The objective of this study is to determine the inhibitory effects of Annona muricata leaves extract (AMLE) (0, 3, 10 and 20%) on the trypsin, cathepsin B and collagenase activities extracted from the cephalothorax of Macrobrachium rosenbergii. In addition, the textural changes in M. rosenbergii during 20 days of cold storage (4 °C) were also determined. M. rosenbergii were soaked in four different treatments: 0, 3, 10 and 20% AMLE and 1.25% sodium metabisulphate for 10 min at 4 °C. Protease activity was significantly (p < 0.05) reduced at 10 and 20% AMLE. Similarly, cathepsin B showed a significant (p < 0.05) low after treatment at 20% AMLE. The maximum inhibitory activity of trypsin was achieved at 20% AMLE and the standard inhibitor (Tosyl-L-lysyl-chloromethane hydrochloride (TLCK)) compared to the control. Whereas, the lowest collagenase activity was obtained at 20% AMLE compared to the control. These inhibitory effects further maintain the firmness of M. rosenbergii coated with 20% AMLE up to the eighth day of storage when compared to the control. Meanwhile, the highest penetration work was found in the M. rosenbergii coated with 20% AMLE at the twentieth day of storage. In conclusion, treatment at 20% AMLE could be used as a natural preservative to inhibit protease, trypsin and collagenase activity of M. rosenbergii and thus can maintain firmness for up to 8 days of storage.

The present study aims to investigate the effects of exposure of the seminal plasma and spermatozoa of the giant grouper Epinephelus lanceolatus to dry ice (−79 °C) during transport on their quality. In all, 15 amino acid compounds were determined. The quantification of total proteins were measured using the Bradford method, and amino acid concentration were measured using the HPLC method. The cryopreserved seminal plasma was transferred from a liquid nitrogen tank to a styrofoam box filled with dry ice. Total protein and amino acids were measured after 24, 48, and 72 h. For comparative purposes, total protein and fifteen compound of amino acid were also measured. Both parameters were also measured after the cryopreserved seminal plasma were immersed in liquid nitrogen after 24 and 48 h exposed to dry ice. The results showed that the exposure of seminal plasma to dry ice for 24, 48 and 72 h during transportation or immersion back into the liquid nitrogen after 24 and 48 h does not change the total protein levels either in seminal plasma or spermatozoa. However, the level of each amino acid compound in the seminal plasma had significantly decreased.

Abstract Background Mud 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). Results Firstly, 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. Conclusions This 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.

The objective of the present study was to examine the effect of different rearing temperatures on growth, survival, instar development, and fatty acid (FA) composition of orange mud crab instars, Scylla olivacea. The experiment was conducted at four different water temperatures of 24 °C, 28 °C, 32 °C and 36 °C using instar stage 1 (C1) in temperature-controlled recirculating rearing systems and lasted for 30 days. The study findings revealed that higher temperatures (≥32 °C) significantly reduced intermolt duration, whereby most crabs reached instar stages C6-C7, although 10.3% were still in the C2−C3 developmental stage. In addition, at temperature 36 °C all crabs were dead after three days of culture. Surprisingly, at constant temperature of 28 °C, total Polyunsaturated Fatty Acid were lower (0.52) compared to those at lower, 24 °C (0.71) and higher temperature of 32 °C (0.74). However, the direct effects of temperature on total fatty acids composition in crabs could not be distinguished from indirect effects of variable crab size and molt number. In conclusion, high temperature of 32 °C negatively affects instars growth and may induce molting, especially in S. olivacea. Keywords: Aquaculture, Crustacean, Fatty acids, Molt, Scylla olivacea, Temperature

The cryopreservation is an important technology for the preservation of spermatozoa in the marine finfish culture industry. However, the high cost of producing appropriate sperm because of broodstocks maintenance and point-to-point transportation can be a major financial burden. The present study was conducted to determine the temperature changes during transferring the cryopreserved spermatozoa of giant grouper Epinephelus lanceolatus from liquid nitrogen to dry ice and their effect on the viability and the motility rate of the spermatozoa. The cryopreserved spermatozoa were transferred from the liquid nitrogen tank into the closed styrofoam box containing dry ice for shipping. The temperature exchange was recorded and the viability and motility rate of spermatozoa were measured. Within 56 h, the temperature of the cryopreserved spermatozoa was recorded at −43.5 ± 4.8 °C, nearly 30 °C warmer than the beginning of the experiment, −70.15 ± 2.90 °C. The present study revealed a high percentage of viability and motility rate of cryopreserved spermatozoa of E. lanceolatus, which were transported inside the styrofoam box using dry ice (−79 °C) as a cooling medium for 48 h and immersed back into the liquid nitrogen after 24 h and 48 h. Keywords: Dry ice, Cryopreservation, Shipping, Spermatozoa

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.

Genetic diversity is the determinant of the allocation of germplasm resources in the genetic improvement of aquaculture species. In this study, three F1 families, including a hybrid Scylla family (S. paramamosain ♂ × S. serrata ♀), a paternal family of S. paramamosain, a maternal family of S. serrata, and two wild populations, including a paternal population of S. paramamosain and a maternal population of S. serrata, were used to investigate the genetic diversity and genetic difference. The results indicated that 98 alleles of nine microsatellites loci were observed in five Scylla populations. The highest average value of Ho (observed heterozygosity), He (expected heterozygosity), and PIC (polymorphic information content) of the wild S. paramamosain population were 0.790, 0.799, and 0.771, respectively, suggesting the wild paternal population has high genetic diversity. The comparative analysis of PIC, Fst (fixation index), and HWE (Hardy–Weinberg equilibrium) indicated that the paternal S. paramamosain may be more suitable for artificial breeding than the maternal S. serrata from the perspective of allele frequency. Analysis of molecular variance analysis (AMOVA) showed that the total genetic variation mainly occurred within populations (73.28%), demonstrating that artificial breeding may induce genetic differentiation of the family groups of Scylla. The results of the analysis of Fst value, UPGMA (unweighted pair-group mean analysis) dendrogram, and genetic diversity indicated that the F1 hybrid offspring had a close genetic distance and high genetic identity with the paternal S. paramamosain populations. It indicated that the F1 hybrid offspring showed potential paternal genetic affinities and a similar potential for artificial breeding with S. paramamosain. The study will provide valuable information to evaluate the difference in the genetic diversity and population structure between hybrid offspring and distinct parental populations of Scylla.

Spiny lobsters of the genus Panulirus are economically important and support local fishing communities. However, mud spiny lobster Panulirus polyphagus is among the least known species within this genus in terms of their biological information. This study relates to the size distribution, length-weight relationship, and size at morphometric maturity of P. polyphagus in the Johor Strait. Within the year 2010, 300 specimens were collected off the coast of Johor Strait, Malaysia. There was no significant difference in body size (cephalothorax length, CL) and body weight (BW) between sexes. CL and BW were highly correlated and males of P. polyphagus displayed positive growth allometry, whereas the opposite was observed in females. Based on the merus (ML) and carpus length (CPL) of the third right walking leg, the piecewise linear regression analysis estimated that the size at maturity for male was 6.58 cm CL (based on ML) and 7.58 cm CL (based on CPL), whereas it was 8.18 cm CL (based on ML) and 6.75 cm (based on CPL) for females. Two discriminant functions of high classification and revalidation rates (> 98.6% in males and > 98.7% in females) that can discern maturation status in males and females of P. polyphagus were derived using the discriminant function analysis. Biological information derived from this study serves as an essential baseline for future fishery management and conservation of P. polyphagus.

This study focused on the effect of Noni, Morinda citrifolia fruit extract supplementation on the growth and the hepatopancreas function of Whiteleg shrimp, Penaeus vannamei Post Larvae (PL). The crude extract of M. citrifolia fruit was obtained through drying and methanol extraction followed by concentration through rotary evaporation. The extracts were incorporated into commercial shrimp pellet at the concentrations of 0%, 1%, 2%, 3%, 4% and 5%. Feeding trial was done for 30 days and shrimp samples were collected at 5 days interval for growth performance determination and physiology analysis on the hepatopancreas. Despite the inconsistency in growth performances during the early feeding period, the extract supplementation did improved the growth of P. vannamei PL. Significant differences in the digestive enzymes and antioxidant enzymes activities between treatments were observed. The correlation results showed only amylase were correlated with M. citrifolia fruit extract supplementation. In terms of the relationship with growth, amylase and lipase showed correlation with the BW changes of P. vannamei PL while trypsin otherwise. Antioxidant enzymes were strongly correlated with the concentration of M. citrifolia fruit extract supplemented and growth of P. vannamei PL. This indicates that the growth of shrimp was improved with increased antioxidant enzyme activities. The number of hepatopancreatic cells (B, R & E cells) also increased significantly with the increasing concentration of M. citrifolia supplementation during the 30-day feeding trial. Similarly, strong correlation was observed between the hepatopancreatic cells and the growth of P. vannamei PL. The appearance of cell atrophies and haemocytic infiltration in the hepatopancreas might indicate the stimulation of innate defense mechanism in the hepatopancreas by the extract supplementation.

Understanding factors affecting the reproductive performance of mud crab (Scylla paramamosain) is important for the optimization of the culture conditions. There are some indications that complete darkness could enhance and accelerate the spawning in female decapods, but sometimes it may lead to low larval quality. Therefore, the present study was carried out to clarify the effect of different light conditions on female S. paramamosain during the post-mating period. To accomplish this, proximate compositions, total carotenoid content, amino acid and fatty acid profiles were investigated in female S. paramamosain cultured under two different light conditions: complete darkness (0 ± 0 lx; 0 h light: 24 h dark) and normal light condition (7.00 ± 1.50 lx; 12 h light: 12 h dark; this light condition is regular in S. paramamosain hatcheries). Further, weight gain ratio (WGR), specific growth rate (SGR), gonado-somatic index (GSI), and hepatosomatic index (HSI) were also investigated. Different light conditions affected carotenoid, protein, amino acid, and fatty acid contents, but not growth parameters. Female S. paramamosain cultured under complete darkness had lower amino acids and protein contents in the muscle in comparison with those under the normal light condition. Moreover, complete darkness decreased the ovarian protein and carotenoid. The changes in fatty acids profiles were variable under the two light conditions. These results indicated that the lowering of carotenoid and protein contents in the ovary under complete darkness could be the potential limiting factors affecting the reproductive performance of post-mating female S. paramamosain.

Identification and exploring the role of novel sex-related genes is a crucial step for understanding the regulation mechanism of sexual development. In the present study, we identified a novel sex-related gene (designated as Sp-Pol) upstream of a sex-specific single nucleotide polymorphism (SNP). SNP1888 together with Sp-Pol were mapped on LG32 (which is a sex-related linkage group) of a high-density genetic map. The full-length cDNA of Sp-Pol consists of 1703 bp with an open reading frame (ORF) encoding 204 amino acids, a 344 bp 5′-UTR and a 744 bp 3′-UTR. Phylogenetic analysis showed that Sp-Pol may need to be classified as a new gene family due to the very low sequence identity with other known genes (less than 25% identity). The sex-biased expression pattern of Sp-Pol starts from crablet stage V (C5) with approximately three- to four-fold higher in males than in females. Sp-Pol was expressed at a higher level in gonads compared to other tissues, with the highest expression level in the testis. In testis, a downward trend was observed in the expression level of Sp-Pol from the testis stage I (T1) to testis stage III (T3). After unilateral eyestalk ablation, the expression level of Sp-Pol significantly increased in testis and hepatopancreas in males, while it was downregulated in the hepatopancreas of females. Fluorescence in situ hybridization (FISH) assay revealed that Sp-Pol transcripts were strongly localized in the epithelia of seminiferous tubules of the testis, and in the ovary, it was detected in the oogonium cells. These findings showed that Sp-Pol may play crucial roles in the gonad development of S. paramamosain.

Sexual dimorphism is generally obvious in brachyurans, and sexual dimorphism between species is of a higher degree to allow separation of trophic niches compared to the lower intraspecific variations between sexes. Mud crab genus Scylla are distributed along the Indo-West Pacific region, and species within this genus often exhibit overlapping niches and similar external morphologies. This study compared the intra- and interspecific sexual dimorphism patterns of three sympatric Scylla species from four distinct geographical locations along the equatorial region based on 24 morphometric characters. The consistency of sexual dimorphism patterns between locations was higher than between species. However, reproduction-related characters such as cheliped dimensions and abdomen width (AW) exhibited similar sexual dimorphism patterns across species. Discriminant function analysis based on the 23 morphometric ratios revealed the morphometric intraspecific divergence in all three Scylla species from the Asajaya mangrove forest. The cause for this regional intraspecific differentiation of mud crabs from the Asajaya mangrove forest remains unknown.

In order to uncover the sexual difference in morphology and how early they appear during the development stage of mud crab Scylla paramamosain, we measured, observed, and biostatistically analyzed morphological traits related to sex. For unveiling the morphological differences between sexes, morphological traits involving abdomen width (AW), carapace length (CL), and carapace width (CW) were first measured during the crablet development stage of S. paramamosain in the present study. The correlation analyses and path analyses exhibited that sexual dimorphism in the third abdomen width (AW3) and fourth abdomen width (AW4) could be used for sex identification from stage C VI (stage VI of crablet). Based on the stepwise discriminant analysis and standardized traits, a sex discriminant equation was constructed, which is capable for sex identification in crablets from stage C VI. Observations for secondary sexual traits and abdomen morphology (shape and pleopods) using a dissecting microscope or scanning electron microscope indicated that sexes are easily identified at stage C VIII according to the abdomen shape; meanwhile, at stage C II based on pleopod difference, and at stage C I by the presence or absence of gonopores. The findings in this study contribute greatly to the accuracy of sex identification of S. paramamosain during the early development stage, which promotes the understanding of the morphological differentiation mechanism of sex.

Biofloc formation is affected by the addition of carbon sources and the adequate aeration supply with a proper arrangement of aeration units. Apart from molasses was commonly used as carbon sources, the effect of different nitrogen types was also critically important in the biofloc formation. This study aimed to evaluate the effect of different aeration units and nitrogen types on the biofloc formation using bioflocculant-producing bacteria as inoculum. Experimental set-up was prepared with two types of aeration units (i.e.: air stone and aerotube) and three nitrogen types (i.e.: fish meal, grounded pellet and pellet). Water quality parameters, water physical appearance, biofloc volume and shrimp biomass were observed within 30 days of the study period. There were no significant difference (P ≤ 0.05) between the water quality parameters, however, biofloc volume and shrimp biomass showed a significant difference with the aeration units. Nitrogen types using pellet showed positive results with the formation of biofloc, while there was no formation of biofloc in the other treatments. Consequently, injection of bioflocculant-producing bacteria for the rapid formation of biofloc was recommended with a proper installation of aerotube units and pellet as a nitrogen type. Keywords: Aeration units, Nitrogen types, Inoculum, Litopenaeus vannamei, Biofloc

Many crustacean species including mud crab, genus Scylla are incapable of natural maturation under captivity, thus putting high pressure on the wild catch. Therefore, to increase the availability of mature broodstocks in captivity, this study determined the effect of Eyestalk Ablation (EA) and Methyl Farnesoate (MF) administration on ovarian maturation stages of the orange mud crab, Scylla olivacea. The study was conducted using a control group (T1) consisting of 95% alcohol (widely used as a chemical solvent), and three treatment groups consisting of: 5 µl/g oral administrated MF in the diet (T2), EA (T3) and a combination of both treatments of MF and EA (T4). The highest percentage of ovarian maturation Stage 4 was found in the T4 treatment (20.8%) compared to the other treatments which were T1 (0%), T2 (8.33%) and T3 (12.5%). Ovarian development of the treated groups (T2, T3, and T4) was significantly different compared to the control group (T1) (p 0.05), but it was significantly different when compared to the combination group of MF and EA (T4) (p

The lack of high-quality juvenile crabs is the greatest impediment to the growth of the mud crab (Scylla paramamosain) industry. To obtain high-quality hybrid offspring, a novel hybrid mud crab (S. serrata ♀ × S. paramamosain ♂) was successfully produced in our previous study. Meanwhile, an interesting phenomenon was discovered, that some first-generation (F1) hybrid offspring’s eyestalks were displaced during the crablet stage I. To uncover the genetic mechanism underlying eyestalk displacement and its potential implications, both single-molecule real-time (SMRT) and Illumina RNA sequencing were implemented. Using a two-step collapsing strategy, three high-quality reconstructed transcriptomes were obtained from purebred mud crabs (S. paramamosain) with normal eyestalks (SPA), hybrid crabs with normal eyestalks (NH), and hybrid crabs with displaced eyestalks (DH). In total, 37 significantly differential alternative splicing (DAS) events (17 up-regulated and 20 down-regulated) and 1475 significantly differential expressed transcripts (DETs) (492 up-regulated and 983 down-regulated) were detected in DH. The most significant DAS events and DETs were annotated as being endoplasmic reticulum chaperone BiP and leucine-rich repeat protein lrrA-like isoform X2. In addition, the top ten significant GO terms were related to the cuticle or chitin. Overall, high-quality reconstructed transcriptomes were obtained for the novel interspecific hybrid crab and provided valuable insights into the genetic mechanisms of eyestalk displacement in mud crab (Scylla spp.) crossbreeding.

Abstract Background Mud crabs, Scylla spp., are commercially important large-size marine crustaceans in the Indo-West Pacific region. As females have the higher growth rate and economic value, the production of all female stocks is extremely essential in aquaculture. However, the sex determination mechanism is still unclear. Development of sex-specific genetic markers based on next-generation sequencing proved to be an effective tool for discovering sex determination system in various animals. Results Restriction-site associated DNA sequencing (RAD-seq) was employed to isolate sex-specific SNP markers for S. paramamosain. A total of 335.6 million raw reads were obtained from 20 individuals, of which 204.7 million were from 10 females and 130.9 million from 10 males. After sequence assembly and female-male comparison, 20 SNP markers were identified to be sex-specific. Furthermore, ten SNPs in a short sequence (285 bp) were confirmed heterozygous in females and homozygous in males in a large population by PCR amplification and sequencing. Subsequently, a female-specific primer was successfully designed according to the female-specific nucleotide which could amplify an expected band from females but not from males. Thus, a rapid and effective method for molecular sexing in S. paramamosain was developed, meanwhile, this method could successfully identify the sex of S. tranquebarica and S. serrata. Finally, nine and four female-specific SNP markers were detected in S. tranquebarica and S. serrata, respectively. Conclusions Sex-specific SNP markers were firstly identified in crab species and showed female heterogamety and male homogamety, which provided strong genetic evidence for a WZ/ZZ sex determination system in mud crabs S. paramamosain, S. tranquebarica and S. serrata. These findings will lay a solid foundation for the study of sex determination mechanism, sex chromosome evolution, and the development of mono-sex population in crustaceans.

The United Nation’s 2030 development agenda adopted in 2015 outlines 17 Sustainable Development Goals (SDGs), and the organization has continued to put food security in the center of its vocalization. Aquaculture is currently the fastest-growing food production sector globally and a sustainable option for attaining food security. Food as a basic necessity for man’s survival is always a timely issue. Hence, owing to aquaculture’s unique role, it is expected that the demand for aquatic products (especially seafood) will continue to increase due to geometric population growth. Many seafood products are among the critical protein sources in the world. This is partly because they have micronutrients and essential fatty acids that are not present in land-based protein sources. According to the Food and Agriculture Organization, shellfish is one of the main cultured aquaculture groups in the world. Hence, the development of shellfish aquaculture has an important role in sustainable food supply and food security. In this article, an overview of the current and projected contributions of shellfish aquaculture to global food security is presented. Apparently, shellfish aquaculture in the next few decades will have to be intensified to bridge the gap between demand and supply in a cost-effective manner. Also, food waste would have to be reduced and natural resources should be used more efficiently to minimize the negative impacts on aquaculture on the environment.

Sexual dimorphism is a common phenomenon in the animal kingdom. To test the consistency of sexual dimorphism patterns among sympatric species of the same genus, ten morphometric characteristics of mud crabs Scylla olivacea, S. tranquebarica and S. paramamosain were measured and compared using Discriminant Function Analysis (DFA). The descriptive analysis revealed that in all three species, body size dimensions and cheliped dimensions were significantly larger in males whereas the abdomen width was female-biased. Also, we described a morphological variation (carapace width, CW ≤ CW at spine 8, 8CW) that is unique to S. olivacea. Discriminant function analysis revealed that all nine morphometric characteristics were sexually dimorphic in S. olivacea, S. tranquebarica (except right cheliped’s merus length, ML) and S. paramamosain (except 8CW). The obtained discriminant functions based on the morphometric ratios (with CW as divisor) correctly classified 100% of adults of known sex of all three species. Further, based on the selected body traits, DFA was able to almost completely distinguish males (94%), but not females (74%), among the three Scylla species. This study highlights that congeneric species of portunids (e.g., Scylla spp.) show similar sexually dimorphic characteristics (body size and secondary sexual characteristics).

Crustacean culture has been developing rapidly in various parts of the world. Therefore, it is important to understand their reproductive biology. Insulin-like androgenic gland hormone (IAG) secreted from the androgenic gland (AG) is widely accepted as a key regulator of sexual differentiation in male crustaceans. However, recently several sex-related genes (i.e., CFSH, DEAD-box family, Tra-2, Sxl, Dsx, Fem-1, Sox gene family, Foxl2, and Dmrt gene family) have been identified via transcriptomic analysis in crustaceans, indicating that sexual differentiation in crustaceans is more complicated than previously expected. It has been found that several non-coding RNAs (i.e., miRNAs, lncRNAs, and piRNAs) and IAG receptors may be involved in the sexual development of decapods. Identification and study of the regulation mechanism of sex-related genes, non-coding RNAs, and IAG receptors will provide valuable information regarding sexual development in decapods. In this review, the roles of hormonal and genetic factors in both males and females are discussed. In males, crustacean female sex hormone (CFSH), Sxl, Dmrt gene family, Dsx, Sox gene family, GEM, Fem-1, l-GnRH-III, and corazonin play important roles in IAG regulation in the “eyestalk-IAG-testis” endocrine axis. Unlike males, the regulation mechanism and interaction of sexual genes are relatively unknown in females. However, CFSH, IAG, Fem-1, FAMeT, Slo, UCHLs, Erk2, Cdc2, EGFR, Vg, VgR, and VIH seem to play crucial roles during ovarian development. This study summarizes the available information in the field, highlights gaps, and lays the foundations for further studies and a better understanding of the regulatory mechanism of sexual development in decapods.

Malaysian aquaculture sector consists of 391,000 t of cultivated organisms produced per year with an economic value for over USD 700 million as estimated in 2019. The COVID-19 pandemic caused a large global human pandemic and it is currently ongoing, affecting profoundly Malaysian aquaculture, which is vital for seafood provision and security assurance. Thus, to increase our understanding about how the pandemic affects aquaculture sectors is crucial to design possible management measures both at local and national level. To do it, we designed a survey, starting in May 2020, consisting of 25 online questions to collect information about the impact of COVID-19 on the aquaculture sectors in Malaysia. A total of 105 respondents (2625 answered questions) was captured within the Movement Control Order (MCO) period and later extended to the Conditional MCO (CMCO). Almost 90 % of respondents was unanimous in answering that, and COVID-19 had a heavy effect on aquaculture-related activities in Malaysia; 80 % of them indicated the market demand and logistic bottlenecks (72 %) as major constraints on their aquaculture activities. While the major option to solve aquaculture COVID-19 related issues was the use of online market or digital platforms (76 %), a large fraction of respondents requested for specific assistance to support aquaculture activities (e.g. financial support). Most respondents (93 %) was aware about the necessity of the Standard Operation Procedure (SOP) provided by the relevant agencies during the MCO / CMCO. Present data are crucial to develop policy measures both at national and international level to support seafood sectors under pandemic.

The mud crab Scylla paramamosain is a species with significant sexual dimorphism in growth rate and body size, of which the females are of higher economic and nutritional values than the males. Accordingly, there is an urgent need to explore the molecular mechanism underlying sex determination and gonadal differentiation. The single-molecule long-read technology combining with RNA sequencing was employed to construct a full-length transcriptome for gonads of S. paramamosain. In total, 1,562,819 FLNC reads were obtained from 1,813,758 reads of inserts (ROIs). Among them, the 10,739 fusion isoforms corresponded to 23,634 reads and were involved in 5,369 genes in the reference annotation. According to the criteria for new transcripts, a total of 213,809 isoforms were recognized as novel transcripts and then matched against Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), NR, Swissprot, and KOG databases. We also identified 22,313 SSRs, 169,559 lncRNAs, and 25,451 SNPs. Additionally, 349,854 alternative splicing (AS) events from 8,430 gene models were detected, and 5,129 polyadenylation sites were profiled from 3,090 genes. GO and KEGG annotation indicated that AS and APA probably play important roles in the gonadal development and maturation. Besides, the DEGs associated with gonadal development and maturation were identified and analyzed based on the RNA-Seq data.

Infestation of Sacculina beauforti on an aquaculture species, mud crab Scylla olivacea is alarming due to its high prevalence and the extreme morphological changes in hosts. To further understand its pathological effect on growth and reproduction of S. olivacea, gonadal and hepatopancreatic histological changes of infected individuals were compared with healthy individuals. Also, the histological characteristics of S. beauforti's mature externa was described. Hepatopancreases of infected individuals were loosely packed and rootlets were observed in the intertubular spaces. Although hepatopancreatic tubule count was significantly lower, tubule diameters were unaffected. Gonads, however, were severely affected. No germ cells were found in the infected testes (except for remnants of spermatozoa), indicating the arrest of spermatogenesis. Rootlets were also present in testes of infected individuals. Ovarian tissues of infected females were severely damaged with no rigid cell structures. Gonadosomatic index (GSI) of infected males and females were lower, but the hepatosomatic index (HSI) were higher than their healthy counterparts. No significant differences in GSI and HSI values were observed among infected males and females. Multiple regression analysis revealed that carapace width, GSI and HSI are statistically important for the prediction of infection status. Given the high prevalence of S. beauforti infection and its disruptive effects on the morphology and internal physiology of S. olivacea, this study, albeit fundamental and incomprehensive, highlights to farmers and researchers the emergence of a castrating parasite and the urgency for the development of preventive measures and treatments for this disease in an economically important aquaculture species.

The present study aims to isolate, identify, and evaluate potential probiotic, Lactic Acid Bacteria (LAB) from the gut and hepatopancreas of 10 healthy wild giant freshwater prawn, Macrobrachium rosenbergii. The samples were cultivated using a modified De Man, Rogosa and Sharpe (MRS) agar supplemented with 2% of CaCO3 (w/v). Bacterial colonies with strong clear zone were selected for further tests. From these, 17 isolates of LAB showed non-spore forming, homofermentative characteristics, Gram-positive, rod-shaped, non-motile bacteria and absences of catalase enzymes. The LAB was further identified using API 50 CH kit and 16S rRNA. The isolates LAB also showed tolerance to a variety of environmental conditions like pH, temperature, salt, bile and hemolysis activity in in vitro condition. Based on the results, two isolates LAB were identified as Lactobacillus plantarum and Entercoccus faecalis were suggested as potential probiotic candidates from giant freshwater prawn for Aquaculture industries.

The year 2020 was being ushered in by a global pandemic. Within months, COronaVIrus Disease (COVID-19) has spread to almost every country. With its long incubation period and highly contagious characteristics, most countries have initiated lockdown and social distancing is the new norm in most societies. Malaysia implemented the Movement Control Order (MCO) on 18 March 2020 when the cumulative COVID-19 cases were still below 800. Since then, MCO was extended several times and the latest phase of Recovery MCO (RMCO) will last until 31 August 2020. As seafood represents an important protein source, the aquaculture sector supports the livelihood of coastal communities in Malaysia, particularly those involved in micro- and small-scale fish farming activities. The emergence and spread of this pandemic severely disrupt market demand and supply chains of seafood industries. Therefore, this case report looks into the potential impacts of COVID-19 on the aquaculture sector of Malaysia. Then, the coping strategies implemented by Malaysia are highlighted and their potential effectiveness is discussed. Also, some useful recommendations are suggested to ensure the continuity and growth of the aquaculture sector. We believe that insights in this report are applicable to other sectors and countries with similar economic characteristics.

Molt stages in Giant freshwater prawn, Macrobrachium rosenbergii is among one of the most important factor affecting feed intake and their biochemical compositions. The present study was conducted to determine the effects of various molting stage on the feed intake and biochemical composition of glucose level, lipid and protein in M. rosenbergii during molting cycles. Molt stages were classified based on their epidermis structure and seta development. Results showed that M. rosenbergii fed with the higher percentage during C-stage, 98.40 ± 0.29 % compared to ecdysis (molting) with no feed intake (0 %) recorded. The biochemical compositions, glucose, lipid and protein level were higher during pre-molt stage and lower at post-molt stage. We found that all stages of molting affects the feeding behavior of M. rosenbergii. Additional studies are clearly needed to understand the mechanisms of abdominal muscles development during molt in prawns.

Discrimination of different fishes can be done through different means which includes morphological appearance. When two fishes are successfully hybridized, they produce progenies that have shared morphology between their pure parent, hence, making morphometric characterization an important aspect of hybrid discrimination. However, erythrocyte characterization is also a simpler method for characterization. The dataset presented in this article represents the traditional morphological data, truss network data and erythrocyte data of pure and novel hybrids from reciprocal crosses of African catfish Clarias gariepinus and Asian catfish Pangasianodon hypophthalmus. Breeding of the broodstocks was done to produce pure and hybrid progenies which were maintained for a period of four to six months. Based on the cross combinations and morphotypes, traditional measurement of twenty-five morphological characters and five meristic counts were recorded. Thereafter pictures of the different fish groups were used to determine values of thirty-six distances between ten landmark points. The morphological abnormality of the hybrids at market size is also presented in this data article for the very first time. Blood was then collected from the caudal peduncle of ten fish per group and smeared on a slide for observation under a compound microscope (at 100 × magnification). Data gotten included erythrocytes parameters such as cell major axis, cell minor axis, nucleus major axis, nucleus minor axis cell area, nucleus area, cell volume, and nucleus volume. Data recording was through the Microsoft excel spreadsheet; which was also used to process the data to get the exclusive ranges of values for paired progenies. The data as presented is associated with the research article “Morphological characterization of the progenies of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)” [1]. The dataset presented in this article can be used for easy identification of the novel hybrid progenies of the African Catfish and Asian Catfish.

Understanding the thermal tolerance of both candidate and potential aquaculture species is important for determining their temperature limit at certain stages of culture. The aim of the present work was to determine the effect of acclimation at different temperatures on the Critical Thermal Maxima (CTMax) and escaping temperature (Tesc) and Acclimation Response Ratio (ARR) of the mud crab, Scylla olivacea, and the crenate swimming crab, Thalamita crenata. Immature crabs (N = 135) were acclimatized at three temperatures of 24 °C, 28 °C and 32 °C and CTMax was measured after an acclimation period of one week and re-acclimation of at least three weeks. An increase in CTMax increased the mean escaping temperature (Tesc) for both crabs, and was within the range of their CTMax value. Only a few crabs tried to escape during the CTMax test in which the Tesc were 39.85 °C to 40.25 °C and 37.52 °C–38.21 °C for S. olivacea (n = 12) and T. crenata (n = 22), respectively. The CTMax of S. olivacea ranged from 40.03 °C to 43.39 °C, while the CTMax for T. crenata ranged from 37.11 °C to 42.42 °C, and both increased directly with temperature. Results obtained in the present study indicated that S. olivacea crabs were more tolerant to increased temperature than T. crenata, suggesting that S. olivacea is better adapted to high environmental temperature conditions.

The present datasets were conducted to investigate glucose concentration in hemolymph, energy levels at selected body parts (hepatopancreas, muscle, gonad), and feces among different sexes of crabs cultured at four different water velocities (0, 20, 40, and 60 cm/s) during a 60-day culture period. A total of 102 immature crabs (51 males, and 51 females) were sampled from Kuala Muda, Kedah coastal water, Peninsular Malaysia (5°39′N 100°19′E) from April to November of 2018. Results indicated that glucose concentration was the highest at water velocity of 60 cm/s for both male and female crabs (♂: 3.76 ± 0.08 mmol/L; ♀: 3.63 ± 0.06 mmol/L), whereas at 0 cm/s, the lowest levels of glucose concentration (♂: 0.13 ± 0.08 mmol/L; ♀: 0.19 ± 0.06 mmol/L) were recorded. As for energy analysis in hepatopancreas, results showed that both male and female crabs recorded the highest levels at 0 cm/s (no flow) with 37.919 ± 0.07 KJ/g and 34.636 ± 0.50 KJ/g, respectively. Energy for locomotion (muscle) of male crabs recorded the highest at 0 cm/s (♂: 26.823 ± 0.06 KJ/g), meanwhile for females, the highest was recorded at 20 cm/s (26.607 ± 0.34 KJ/g). Energy for reproduction of males could not be compared due to an insufficient available amount of testes/vas deferens, whereas female crabs recorded the highest energy usage at 20 cm/s water velocity (♀: 37.895 ± 0.08 KJ/g). For feces, both male and female crabs recorded the lowest energy at 60 cm/s (♂: 5.841 ± 0.03 KJ/g; ♀: 5.393 ± 0.01 KJ/g). Glucose assessment showed a direct relationship between increased velocity and glucose secretion in hemolymph at high velocity of 60 cm/s (stress condition) compared to other treatments. Regarding energy analysis, this research improved the mechanism of hepatopancreas, gonad, muscle and feces functions in development and reproduction, while it shed light on the influence of velocity on energy metabolism of S. olivacea. Keywords: Aquaculture, Crustacean, Hemolymph, Hydrodynamic, Environmental stressor, Energy distribution, Water turbulence

Acute Hepatopancreatic Necrosis Disease (AHPND), a disease caused by Vibrio parahaemolyticus (VpAHPND), kills Penaeid shrimps worldwide, resulting in severe economic losses during aquaculture. To further understand how Penaeus monodon post-larvae (PL) respond towards infection of this pathogenic bacterium, the expression of several important immune and bacterial toxin genes in three stages of P. monodon PL (PL15, PL30 and PL45) upon VpAHPND challenge, were determined. A 20-hrs challenge test with 2.7 × 107 cfu ml−1 of VpAHPND resulted 81, 65 and 1.7% mortality respectively for PL30, PL15 and PL45, indicating that PL30 was most vulnerable to VpAHPND. The immune response of shrimp PL at this stage was robust, with Toll-like receptor (TLR), prophenoloxidase (proPO), lysozyme (lyso) and penaeidin (PEN) augmented approximately 10.7, 4.7, 6.5 and 3.2-fold, respectively. The expression initiated at one hour post-infection (h.p.i), peaked at 16 h.p.i and 20 h.p.i, and decreased at 18 h.p.i, indicating the crucial involvement of these immune related genes in the defence and recovery of the first-line defence mechanisms during VpAHPND infection. This work also revealed that toxR gene represents a good indicator gene for Vibrio detection whereas PIR A, for VpAHPND pathogenicity determination of P. monodon. Overall, these findings provided novel insights into the immune response and VpAHPND susceptibility of different P. monodon PL stages during infection, with outcomes potentially useful in enhancing the application of health therapy and biosecured aquaculture practices to minimize the damaging risk of AHPND towards sustainable production of P. monodon. Keywords: Penaeus monodon, AHPND, PIR a, Immunity genes, Bacterial toxin gene

As water temperatures rise due to the effects of climate change, the effects of temperature on the physiological processes of aquaculture species must be studied. This study evaluates the effects of different water temperatures on the fatty acid (FA) composition and histological development of the gills in the blue swimmer crab, Portunus pelagicus. Three levels of water temperature (24 °C, 28 °C, and 32 °C) were used to determine their effects on the first 119 days of the crabs’ development after C8 stage in a recirculating aquaculture system. The study showed that the FA analysis in crabs in water with a temperature of 28 °C showed greater FA composition in their whole body compositions than in crabs kept at 32 °C. The results of the histological gill analysis showed that the number of hemocytes in the anterior gills of the crabs increased proportionately with the increases in temperature. In summary, temperature affects the Omega-3 and omega-6 concentrations and the histological conditions of the structure of the gills of the P. pelagicus. Keywords: Aquaculture, Climate change, Crustacean, Fatty acids, Portunid crabs

There are four species of mud crabs within the genus Scylla, and most of them live sympatrically in the equatorial region. Apart from a report in Japan about the finding of a natural Scylla hybrid more than a decade ago after the division of genus Scylla into four species by Keenan, Davie & Mann (1998), no subsequent sighting was found. Thus, this study investigates the possible natural occurrence of potential hybridization among Scylla species in the wild. A total of 76,211 individuals from mud crab landing sites around the Malacca Straits, South China Sea and Sulu Sea were screened. In addition to the four-purebred species, four groups (SH 1, n = 2, 627; SH 2, n = 136; SH 3, n = 1; SH 4, n = 2) with intermediate characteristics were found, mostly at Sulu Sea. Discriminant Function Analysis revealed that all Scylla species, including SH 1 - 4, are distinguishable via their morphometric ratios. The most powerful discriminant ratios for each character and the top five discriminant ratios of males and females were suggested. The carapace width of SH 1 males and females were significantly smaller than pure species. Based on the discriminant ratios and the description of morphological characters, we hypothesize that the additional four groups of Scylla with intermediate characteristics could be presumed hybrids. Future work at the molecular level is urgently needed to validate this postulate.