Scylla Olivacea Research Articles

The Effect of Fresh Feed Combinations on Survival Rate, Growth, and Production of Mud Crab (Scylla olivacea) Cultured by Silvofishery Model

The Effect of Fresh Feed Combinations on Survival Rate, Growth, and Production of Mud Crab (Scylla olivacea) Cultured by Silvofishery Model

Experimental infection of Enterocytozoon hepatopanaei parasite (EHP) of penaeid shrimp in Indian marine crabs.

Enterocytozoon hepatopanaei parasite (EHP) is identified as an emerging pathogenic microsporidium parasite in shrimp culture industry. Though the etiology, disease pattern and sustainability of shrimp are well known, significantly less research has been carried out about the disease transmission and symptoms of infected aquatic animals. The present study aims is to determine the disease carrier status of five different species of Indian marine crabs (Scylla olivacea, Scylla serrata, Portunus pelagicus, Ocypode quadrata and Portunus sanquinolentus) using EHP. At the first instance, oral infection and intramuscular injection were performed to determine the susceptibility of the parasite at 50days post-infection and it was observed that there was no mortality. The experimental infected crabs were confirmed by polymerase chain reaction, bioassay and histopathology. The crabs were EHP-PCR positive at 5th day post-infection (d.p.i) in gills, heart, hepatopancreas, haemolymph and muscle tissue. However, after 5th d.p.i EHP was PCR negative in all the tissue samples. There were no mortalities and histological changes in the negative group and experimental group. Therefore, marine crabs are found to be not suitable hosts for replicating EHP spores but crabs fecal matters are PCR positive till 5th d.p.i. Therefore, marine crabs are having the possibilities of acceptance as a vector for Enterocytozoon hepatopanaei in shrimp. Shrimp farmers need to take necessary action to control this deadly infection in shrimp ponds.

Development of semi-moist formulated feed for female orange mud crabs, Scylla olivacea (Herbst, 1796) broodstocks with graded lipid levels

The present study examined the physical characteristics of semi-moist formulated feeds to the reproductive maturation of female orange mud crab, Scylla olivacea. In this study, two experiments were conducted. The first experiment compared four types of natural diets; fish offal (discarded organ), mangrove clams (Polymesoda erosa), black devil snail (Faunus ater), and commercial shrimp feeds (control), to select the basal diet for the formulation of feeds. Proximate compositions of the different diets revealed that the mangrove clam, P. erosa (protein = 81.63 % and lipid = 13.54 %) is the most suitable ingredients for the mud crabs’ diet. Fatty acid analysis also showed that mangrove clams had the highest concentration of ARA, EPA, and DHA at 0.56 %, 1.62 %, and 2.68 % respectively. In the second experiment, four isonitrogenous feed (~42 %) with different lipid percentages; T1: 6 %, T2: 8 %, T3: 10 %, and T4: 12 % were formulated to investigate the effects of the lipid inclusion on maturation of mud crabs. The effects of different levels of lipid on palatability, feed water stability, nutrient leaching, buoyancy, and total solids were studied prior to feeding experimentation. The palatability tests showed high attractability of the crabs towards the feeds. Meanwhile, high water stability (dry matter retention) were recorded in all experimental feeds after long immersion hours, with low nutrient leaching, and low solids disintegration. Later, feeding trial on 120 matured female mud crabs (carapace width: 10.24 ± 0.66 cm and body weight: 186.42 ± 37.90 g) revealed that the semi-moist formulated feeds are readily accepted by the crabs. The crabs from all treatments recorded positive body weight gain (BWG) and specific growth rate (SGR) with crabs fed T4 dominating (BWG = 11.43 g, 14.65 g, and 12.13 g; SGR = 0.35 %day-1, 0.13 %day-1, and 0.08 %day-1 during 30-, 60-, and 90-day of feeding trials respectively) (p < 0.05). Similarly, morphological results showed that high GSI was noted in S. olivacea fed with T4, increasing at subsequent feeding trials (10.44 %, 11.03 %, and 14.51 %) (p < 0.05), which were inversely proportional with the HSI (8.92 %, 5.11 %, and 4.76 %) (p < 0.05) compared to other treatments, probably contributed by the high percentage of lipid inclusion. These findings demonstrate that diets contained 12 % lipid and 42 % protein (T4) is ideal for somatic and reproductive growth of S. olivacea. Yet, a nutrient dose-response study is expected to be carried out in the future to estimate the optimum lipid level required for reproductive and growth performance in S. olivacea.

Acceleration of Ovarian Maturation in the Female Mud Crab With RNA Interference of the Vitellogenesis-Inhibiting Hormone (VIH)

In the present study, double strand RNA technology (dsRNA) was used to inhibit transcripts of vitellogenesis-inhibiting hormone (VIH) that mainly synthesized and secreted from the central nervous system in Scylla olivacea females. The results presented in this study clearly demonstrate the potential dsRNA-VIH was highly effective to inhibit VIH in the eyestalks of females injected with dsRNA-VIH on the 3rd, 7th and 14th day, respectively. The dsRNA-VIH injections were performed at 14-day intervals, a single dsRNA dose of 0.6 µg/gram body weight was enough to suppress VIH expression until 14th day after injection. The dsRNA-VIH injection significantly increased gonad-somatic index (GSI) and hemolymph vitellin level at day 14 and 28 when compared with control groups. The histological observation found that the number of oocyte step 4 in dsRNA-VIH group was significantly higher than that of the control group. Also, dsRNA-VIH has stimulatory function on other reproduction-related genes such as the Scyol-PGES and Scyol-ESULT that both genes gradually increased their expressions in brain and ventral nerve cord. In conclusion, the silence of VIH gene could reduce the production of VIH from eyestalk and brain that affected other downstream genes related to ovarian maturation in the mud crab.

Comparative Analyses of Scylla olivacea Gut Microbiota Composition and Function Suggest the Capacity for Polyunsaturated Fatty Acid Biosynthesis.

Although numerous studies in aquatic organisms have linked lipid metabolism with intestinal bacterial structure, the possibility of the gut microbiota participating in the biosynthesis of beneficial long-chain polyunsaturated fatty acid (LC-PUFA) remains vague. We profiled the gut microbiota of the mud crab Scylla olivacea fed with either a LC-PUFA rich (FO) or a LC-PUFA-poor but C18-PUFA substrate-rich (LOCO) diet. Additionally, a diet with a similar profile as LOCO but with the inclusion of an antibiotic, oxolinic acid (LOCOAB), was also used to further demarcate the possibility of LC-PUFA biosynthesis in gut microbiota. Compared to diet FO treatment, crabs fed diet LOCO contained a higher proportion of Proteobacteria, notably two known taxonomy groups with PUFA biosynthesis capacity, Vibrio and Shewanella. Annotation of metagenomic datasets also revealed enrichment in the KEGG pathway of unsaturated fatty acid biosynthesis and polyketide synthase-like system sequences with this diet. Intriguingly, diet LOCOAB impeded the presence of Vibrio and Shewanella and with it, the function of unsaturated fatty acid biosynthesis. However, there was an increase in the function of short-chain fatty acid production, accompanied by a shift towards the abundance of phyla Bacteroidota and Spirochaetota. Collectively, these results exemplified bacterial communities and their corresponding PUFA biosynthesis pathways in the microbiota of an aquatic crustacean species.

Morphological, Histological, and Physiological Responses of Female Orange Mud Crab, Scylla olivacea (Herbst, 1796), Fed with Different Dietary Lipid Levels

The main focus of the study was to assess the effect of lipid levels on the reproduction of the female orange mud crab, Scylla olivacea. Four isonitrogenous feed (~420 g/kg) were formulated with different lipid percentages: T 1 = 60 g / kg , T 2 = 80 g / kg , T 3 = 100 g / kg , and T 4 = 120 g / kg . A feeding trial was carried out on 120 matured female mud crabs for 90 days with 30 replicates in each treatment. Based on the morphological, histological, and hormonal analysis of each crab, the performances of each experimental diet were tested. The results of the experiment disclosed positive body weight gain (BWG) and specific growth rate (SGR), with the highest value recorded in crabs that were fed T4 (BWG: 14.43 ± 1.14 g ; SGR: 0.10 ± 0.01 % da y − 1 ). The highest gonado-somatic index (GSI) and hepato-somatic index (HSI) were noted in mud crabs that were fed T4, each with a value of 14.51 ± 1.13 % and 5.23 ± 0.55 % , respectively ( P &lt; 0.05 ). The histological assessment revealed that the highest oocyte diameter was recorded in mud crabs fed T4 ( 192.80 ± 21.93 μm), where the oocyte diameter was correlated with the progesterone (Pg) concentrations in the ovary with r = 0.73 . Evidence also indicated that Pg and estradiol (E2) are important in the ovarian development in S. olivacea and their concentrations were affected by the lipid levels. An overall analysis revealed that 120 g/kg of lipid in the diet contributes to optimal reproductive performance in Scylla olivacea. Yet, a further experiment is expected to be carried out in the future to determine the nutrient-dose response as 120 g/kg lipid may not be the optimum lipid level for reproductive and growth performance in S. olivacea. Moreover, the extrapolation of data from this study can be used as guidelines in feed formulation for developments in future research in adult crustaceans.

Effects of water parameters on population structure of mud crab from Buntal Mangroves, Kuching, Sarawak, Malaysia: A GLM analysis

Abstract. Shakawi AMHA, Hassan R, Mustapah DS. 2022. Effects of water parameters on population structure of mud crab from Buntal Mangroves, Kuching, Sarawak, Malaysia: A GLM analysis. Biodiversitas 23: 2580-2585. Buntal Mangroves, Kuching, Sarawak, Malaysia, is an area that is abundant with biological resources but contains minimal biodiversity information. Mud crab fisheries by the locals exist on small scales at Buntal Mangroves, but there is a tendency to overfish due to the increasing demand for this resource. The relationship between the population structure of mud crabs and the environmental factors in Buntal Mangroves has not been explored. Therefore, this study aimed to apply the generalized linear models (GLM) for analyzing the population structure of mud crabs with selected water parameters in Buntal Mangroves. Scylla olivacea (Herbst, 1796) has the highest abundance in Buntal compared to S. tranquebarica (Fabricius, 1798) and other types of mud crab. Three GLM with carapace length, carapace width, and body weight as dependent variables were constructed. These GLMs with gamma-distributed response variables indicated that depth, pH, salinity, and turbidity positively affected body weight, carapace width, and carapace length, while temperature had a negative impact on the dependent variables. The results emphasized the importance of adopting the GLM to describe a relationship where the response variable followed a non-normal distribution. The findings provide a basis for future studies at Buntal Mangroves, not only for conservation purposes but also to support the utilization of this valuable resource sustainably.

Water flow velocity influence the gonad maturation, glucose and energy levels of mud crab, Scylla olivacea

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.

Population dynamics of mud crab, Scylla olivacea (Herbst, 1796) from the Sundarbans of Bangladesh

AbstractThe Sundarbans mangrove regions are the home of the mud crab (Scylla olivacea) business, as forest areas are potential places for random crab harvesting, trading, and exporting overseas seafood markets. Since the mud crab was being captured on a large‐scale in the wild for various purposes, estimation of population parameters were immediately done in terms of body weight and length‐frequency data collected from different locations in the forest of southwestern Bangladesh to understand the status of the stock. Recruitment pattern, growth parameters, mortality rates, and exploitation levels (E) were estimated to understand the population dynamics of S. olivacea. Asymptotic carapace widths (CW∝) were 14.70 and 14.18 cm, and growth co‐efficients (K) were 0.47 and 0.50 year–1 for male and female S. olivacea, respectively. The fishing mortalities were 2.32 and 1.13 year–1 and natural mortalities were 1.39 and 1.46 year–1 for males and females, respectively. Year‐round recruitment of this species takes place in the wild with a peak between June and November. The E for S. olivacea was found to be 0.63 for the male and 0.44 for the female. In summery, the stock of S. olivacea is found to be overexploited in the Sundarbans of Bangladesh. Therefore, mud crab resources should be taken into consideration under suitable fisheries management policies to conserve this national treasure in this delta. It is supposed that the findings will draw the attention of the scientists in the fields of aquatic biology, ecology, and management of the Sundarbans in restoring the mud crab population.

Larval rearing of orange mud crab, Scylla olivacea: improving survival rate and shortening metamorphosis period

Orange mud crab (Scylla olivacea) is an important aquaculture species in Southeast Asian countries, especially in the Southwest costal region of Bangladesh. Due to unavailability of hatchery produced seeds the farming of S. olivacea in exclusively depends on the wild for small juveniles resulting in exploitation of this species in Bangladesh. The development of proper hatchery techniques considering better understandings related to larval development are needed to increase the survival and growth rate of S. olivacea in hatchery conditions. Therefore, this study aimed to optimize the water treatment strategy for the upgrading of water quality, minimizing mortality and shortening the metamorphosis duration during larval rearing of mud crab. Newly hatched larvae were reared in three different rearing conditions where the water was treated with both prebiotic (Super-TCT-Biotic, 5 ppm) and probiotics (Fish probiotic, 0.5 ppm) in treatment-1 (T1) but only prophylaxis (mixure of 0.025 ppm Teflan and 0.3 ppm Furazolidone) in treatment-2 (T2). In treatment-3 (T3), prebiotic (5 ppm) and probiotics (0.5 ppm) were combinedly used during first 10 days and prophylaxis (0.3 ppm) was also used from day 14 to day 25. The stocking density was maintained as 50 zoea.L-1 and rotifer, liquid rotifer, enriched Artemia and liquid Artemia were used as feed for the larval growth. The findings revealed that hydrological parameters viz., temperature, salinity, pH, dissolved oxygen and ammonia in all the treatments were similar and found within the acceptable ranges for mud crab larvae rearing. The value of larval stage index (LSI) was found significantly higher (p&lt;0.05) on 21st day of rearing in T3 (6.87±0.06) than T1 (6.74±0.04) and T2 (6.61±0.07). Between, zoea1 and crablet phase, the significantly higher survival rate was observed in T3 (7.00±1.00) than T1 (5.00±0.00) and T2 (4.00±1.00). The result of the present study suggested that combined water treatment with prebiotic, probiotic and prophylaxis can shorten the metamorphosis period and enhance the survival rate of S. olivacea.

Unbaited Light-Emitting Diode Traps Performance for Catching Orange Mud Crabs

Mud crabs (Scylla spp.) are a vital fishery resource and targeted for a valuable source of income for coastal communities throughout the Indo-Pacific region. Baited traps are a considerable expense in crustacean fishing. Hence, the present study was performed to investigate the catchability of Scylla olivacea in response to light-emitting diodes (LEDs) in captivity and field conditions. We used a new experimental setup in the captivity condition that revealed most S. olivacea were attracted to green, blue, and white LED lights and no attractive effect by red LED lights similar to the controls. Field studies have shown that the catch per unit of effort (CPUE) of S. olivacea and other organisms, including bycatch species, is significantly higher when conventional mackerel and chicken head baits are used. However, unbaited traps equipped with green LED lights produced low CPUE of S. olivacea. Moreover, baited trap with chicken head, mackerel and green LED caught 4.52 %, 7.28 % and 2.18% more CPUE of S. olivacea compare to empty trap, respectively. Besides, both the mackerel and chicken head treatments resulted in the higher average CPUE of S. olivacea than did the green LED treatments; 0.66, 0.38 and 0.13 per trap. No significant differences were detected in the average carapace width of S. olivacea across all treatments. Our findings demonstrated that mud crabs can be captured using artificial lights, like other aquatic species but further in-depth studies and specific modifications to improve the performance of LED lights are warranted.

Effects of Rotifer Feeding Frequency on Growth and Survival Rate of Early Larval Stages of Mud Crab, Scylla olivacea

Crustacean larvae have the characteristics of living as carnivorous organisms. This has an impact on the length of gut evacuation time which affects the feeding pattern of the larvae. The feeding strategy of mud crab larvae is modulated by the length of gut evacuation time. Another factor that can be subject to modulation is the frequency of feeding. This research aimed to evaluate rotifer frequency feeding of early larvae stages of mud crab, Scylla olivacea. This research was conducted at the Mariculture Fisheries Center, Ambon with an indoor system. This research began with carrying out parental maintenance to produce larvae. Larvae are fed with rotifers with different frequencies. The treatments were the frequency of feeding rotifers, namely: Treatment 1 (F1) was the frequency of 1x a day (9:00 am); Treatment 2 (F2) was a frequency of 2x a day (9:00 am &amp; 13:00 pm) and Treatment 3 (F3) was a frequency of 3x a day (9:00am, 13:00pm &amp; 17:00pm). Each treatment was given 3 replications. Based on the results of this study, it showed that feeding with a frequency of three times a day (F3 treatment) was able to have a positive effect on the survival rate of zoea larvae which on the third day was 58% and the fourth day was 22% higher than the F1 and F2 treatments. The growth of larvae showed that F3 treatment was higher than F1 and F2 on the sixth day with an increase in the absolute value of growth of 0.12044 mm compared to F1 of 0.05531 mm and F2 of 0.03253 mm. Keywords: frequency of feeding, growth, larvae, survival rate, mud crab

Utilization of Feed and Growth Performance of Mud Crabs: The Effect of Herbal Extracts as Functional Feed Additives

This study aimed to analyze the effect of herbal extracts as functional feed additives on the utilization of feed and growth performance of orange mud crabs (Scylla olivacea). The test animals used were 60 crabs for each treatment dose. The crabs are kept individually in a crab box which was placed on a floating bamboo raft. This was to enable floating on the surface of the pond water which had a depth of ±80 cm. The treatments tested were four doses of a combination herbal extract from Morus alba, Curcuma xanthorrhiza, and Boesenbergia rotunda, namely 0, 200, 400, 600 mg kg-1 of feed. Formulated feed with the protein content of 41.93%, fat 7.43%, Nitrogen Free Extract (NFE) 29.33%, and crude fiber 7.82% was given at a dose of 5% body weight every day. Based on one-way ANOVA, the results showed that the dose of herbal extracts influences the feed utilization and growth performance of mud crabs. The dose of herbal extract 600 mg kg-1 of feed provided higher feed utilization and growth performance (LSD Test: P&lt;0.1). Significant differences were found between feed utilization and growth performance of mud crabs after molting and non-molting. In molting mud crabs, treatment with herbal extract 600 mg kg-1 obtained an average weight gain of ±60.73 from the initial weight, compared to control crabs (without herbal extracts) gaining an average weight gain of ±43.73%. However, in non-molting crabs, ±5.44 and ±6.42 weight gain was observed, respectively. Significant differences also occurred between treatments for specific growth rates, feed consumption, feed efficiency, and condition factors. These results provided information that herbal extracts are potentially as feed additives to increase feed utilization and growth performance, as well as stimulate molting in crab cultivation.

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

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

Nursery rearing of orange mud crab, Scylla olivacea (Herbst, 1896): Optimizing pond habitat and stocking density

Nursery rearing of orange mud crab, Scylla olivacea (Herbst, 1896): Optimizing pond habitat and stocking density

The effect of lipid level on the growth and reproductive performance of female orange mud crab, Scylla olivacea (Herbst, 1796), during the fattening period

This experiment aimed to evaluate the efficiency of formulated feeds with different lipid levels (T1 = 60 g/kg, T2 = 80 g/kg, T3 = 100 g/kg and T4 = 120 g/kg) in the biochemical composition of female orange mud crab, Scylla olivacea, during the fattening period. Experiments were conducted on 120 crabs with BW and CW of 186.42 ± 37.90 g and 10.24 ± 0.66 cm, respectively, for 90 days. The crabs were reared in tanks, and dissections were performed in 10 individuals per treatment every 30 days. Overall assessments disclosed that mud crabs fed the T4 showed the highest BWG (1.80 ± 0.78 g, 13.78 ± 1.81 g and 14.51 ± 3.81 g), SGR (0.03 ± 0.02%day−1, 0.19 ± 0.01%day−1 and 0.28 ± 0.02%day−1), GSI (9.90 ± 1.05%, 11.31 ± 1.68% and 17.30 ± 2.13%) and HSI (4.17 ± 0.52%, 5.22 ± 0.40% and 5.06 ± 0.45%) during fattening periods. Meanwhile, EPA and DHA were the most important fatty acids required for maturing ovaries in mud crabs. During 60- and 90-day culture period, higher EPA and DHA were noted in the ovary of mud crabs fed with T4 (EPA: 4.79 mg/g and 6.69 mg/g; DHA: 4.55 mg/g and 6.85 mg/g) compared with hepatopancreas (EPA: 1.84mg/g and 2.47 mg/g; DHA: 3.28 mg/g and 3.71 mg/g) (p < .05). The low fatty acid composition in the hepatopancreas indicates a nutrient transfer from the hepatopancreas to the ovaries for maturation. Two-way ANOVA suggested that 120 g/kg of feed with 60–90 days of duration would be the best for crab rearing.

Structure-Based Functional Analysis of a Hormone Belonging to an Ecdysozoan Peptide Superfamily: Revelation of a Common Molecular Architecture and Residues Possibly for Receptor Interaction.

A neuropeptide (Sco-CHH-L), belonging to the crustacean hyperglycemic hormone (CHH) superfamily and preferentially expressed in the pericardial organs (POs) of the mud crab Scylla olivacea, was functionally and structurally studied. Its expression levels were significantly higher than the alternative splice form (Sco-CHH) in the POs, and increased significantly after the animals were subjected to a hypo-osmotic stress. Sco-CHH-L, but not Sco-CHH, significantly stimulated in vitro the Na+, K+-ATPase activity in the posterior (6th) gills. Furthermore, the solution structure of Sco-CHH-L was resolved using nuclear magnetic resonance spectroscopy, revealing that it has an N-terminal tail, three α-helices (α2, Gly9−Asn28; α3, His34−Gly38; and α5, Glu62−Arg72), and a π-helix (π4, Cys43−Tyr54), and is structurally constrained by a pattern of disulfide bonds (Cys7–Cys43, Cys23–Cys39, and Cys26–Cys52), which is characteristic of the CHH superfamily-peptides. Sco-CHH-L is topologically most similar to the molt-inhibiting hormone from the Kuruma prawn Marsupenaeus japonicus with a backbone root-mean-square-deviation of 3.12 Å. Ten residues of Sco-CHH-L were chosen for alanine-substitution, and the resulting mutants were functionally tested using the gill Na+, K+-ATPase activity assay, showing that the functionally important residues (I2, F3, E45, D69, I71, and G73) are located at either end of the sequence, which are sterically close to each other and presumably constitute the receptor binding sites. Sco-CHH-L was compared with other members of the superfamily, revealing a folding pattern, which is suggested to be common for the crustacean members of the superfamily, with the properties of the residues constituting the presumed receptor binding sites being the major factors dictating the ligand–receptor binding specificity.

Comparative growth and morphometric assessment between cultures of wild and hatchery-produced mud crabs

This paper reports the comparative growth, nutritional performance, and morphometric variation between wild and hatchery-reared juvenile mud crabs (Scylla olivacea) in earthen ponds. The crabs were fed daily with boiled tilapia paste at a feeding rate of 5–8% body weight for the first two weeks, followed by feeding with chopped eviscerated tilapia until termination of the experiment. Selected phenotypic trains, including carapace width (CW), carapace length (CL) and abdominal width (AW), were measured weekly. The protein content of the muscle (21.13%), gill (13.51%) and egg (43.28%) were significantly higher in the hatchery-sourced compared to wild female crabs (muscle = 19.15%; gill = 10.09%; egg = 38.15%). Likewise, the hatchery sourced crabs exhibited higher lipid content in the muscle (2.45–2.51%) and eggs (7.51%) compared to the wild counterparts (muscle = 1.45–1.47%; egg = 6.15%). These findings suggested a superior nutritional quality of the hatchery-reared compared to the wild-sourced crabs. Although some selected phenotypic traits did not vary among the wild and hatchery-reared crabs (p < 0.05), their survival rates varied significantly depending on the stocking density (p < 0.05). Overall, the findings suggest that the growth characteristics of the hatchery produced and wild-sourced crab were similar, which will help to remove the misconception among the crab farmers about the hatchery seeds and promote diversification of the crab production system for long-term sustainability.

Molecular and allergenic characterization of recombinant tropomyosin from mud crab Scylla olivacea.

Tropomyosin is a major allergen in crustaceans, including mud crab species, but its molecular and allergenic properties in Scylla olivacea are not well known. Thus, this study aimed to produce the recombinant tropomyosin protein from S. olivacea and subsequently investigate its IgE reactivity. The tropomyosin gene was cloned and expressed in the Escherichia coli system, followed by SDS-PAGE and immunoblotting test to identify the allergenic potential of the recombinant protein. The 855-base pair of tropomyosin gene produced was found to be 99.18% homologous to Scylla serrata. Its 284 amino acids matched the tropomyosin of crustaceans, arachnids, insects, and Klebsiella pneumoniae, ranging from 79.03 to 95.77%. The tropomyosin contained 89.44% alpha-helix folding with a tertiary structure of two-chain alpha-helical coiled-coil structures comprising a homodimer heptad chain. IPTG-induced histidine tagged-recombinant tropomyosin was purified at the size of 42kDa and confirmed as tropomyosin using anti-tropomyosin monoclonal antibodies. The IgE binding of recombinant tropomyosin protein was reactive in 90.9% (20/22) of the sera from crab-allergic patients. This study has successfully produced an allergenic recombinant tropomyosin from S. olivacea. This recombinant tropomyosin may be used as a specific allergen for the diagnosis of allergy.

DNA barcoding of brackish and marine water fishes and shellfishes of Sundarbans, the world's largest mangrove ecosystem.

The present study aims to apply a DNA barcoding tool through amplifying two mitochondrial candidate genes i.e., COI and 16S rRNA for accurate identification of fish, aquatic molluscs and crustaceans of Sundarbans mangrove wetland, to build a reference library of fish and shellfishes of this unique ecosystems. A total of 185 mitochondrial COI barcode sequences and 59 partial sequences of the 16S rRNA gene were obtained from 120 genera, 65 families and 21 orders of fish, crustaceans and molluscs. The collected samples were first identified by examining morphometric characteristics and then assessed by DNA barcoding. The COI and 16S rRNA sequences of fishes and crustaceans were clearly discriminated among genera in their phylogenies. The average Kimura two-parameter (K2P) distances of COI barcode sequences within species, genera, and families of fishes are 1.57±0.06%, 15.16±0.23%, and 17.79±0.02%, respectively, and for 16S rRNA sequences, these values are 1.74±.8%, 0.97±.8%, and 4.29±1.3%, respectively. The minimum and maximum K2P distance based divergences in COI sequences of fishes are 0.19% and 36.27%, respectively. In crustaceans, the K2P distances within genera, families, and orders are 1.4±0.03%, 17.73±0.15%, and 22.81±0.02%, respectively and the minimum and maximum divergences are 0.2% and 33.93%, respectively. Additionally, the present study resolves the misidentification of the mud crab species of the Sundarbans as Scylla olivacea which was previously stated as Scylla serrata. In case of molluscs, values of interspecific divergence ranges from 17.43% to 66.3% in the barcoded species. The present study describes the development of a molecular and morphometric cross-referenced inventory of fish and shellfish of the Sundarbans. This inventory will be useful in future biodiversity studies and in forming future conservation plan.