Growth Of Crabs Research Articles

Mud crab, Scylla tranquebarica (Fabricius, 1798), crablet grow‐out in lined ponds with different stocking densities to support soft‐shell crab production

AbstractCrab stocking densities in brackish water ponds can influence crab growth rate, survival, and production volume. This study aimed to determine the optimum grow‐out stocking density for Scylla tranquebarica crablets reared in lined ponds to supply the soft‐shell crab industry. Three stocking density treatments (1, 4, and 8 ind./m2) were applied to crablets reared in lined ponds for 90 days. The crablets were fed low‐value fish (Leiognathus equula) at an initial rate of 100% of total body weight for two weeks, reduced to 3% toward the end of the study. Crablets stocked at 1 and 4 ind./m2 had a significantly (p < 0.05) higher net growth (NG) and daily growth rate (DGR) than crablets stocked at 8 ind./m2. Deformed crabs were also most common at the highest stocking density. The intermediate stocking rate achieved moderate survival and feed conversion rates, with the highest crab production volume (19.65 ± 0.10 kg/100 m2) and net income (6845.60 US$/Ha/2 crops/year). Based on these findings, a stocking rate of around 4 ind./m2 is recommended for the grow‐out of S. tranquebarica crablets in lined ponds.

Balancing act: How cholesterol and phospholipids influence juvenile mud crab Scylla paramamosain growth and lipid metabolism

A 2 × 3 two-factor experiment was designed to assess the effects of dietary cholesterol (CHO) and phospholipids (PLs) on growth and lipid metabolism in early juvenile mud crabs (0.01 g crab−1). The experimental diets were designed with two CHO levels: 0.40 % (LCH) and 0.80 % (HCH), and three PLs levels: 1.80 % (LPL), 2.50 % (MPL), and 3.20 % (HPL). The 58-day aquaculture trial demonstrated that the LCH-HPL group achieved the best growth performance in mud crabs, characterized by the highest final body weight, weight gain, and specific growth rate. Regarding whole-body composition, dietary PLs increased total cholesterol (T-CHO), PLs, triglyceride (TG), and crude lipid content in the LCH groups. Mud crabs in the HCH groups had a higher proportion of saturated fatty acids, a lower proportion of monounsaturated fatty acids, and increased gene expression of sterol regulatory element binding protein 1c (srebp-1c) and fatty acid synthase (fas) compared to those in the LCH groups. As the dietary PLs increased, mud crabs in the LCH groups exhibited up-regulation in the expression of genes, including srebp-1c, fas, elongation of very long-chain fatty acid protein 4 (elovl4), elovl6, and Δ9-fatty acid desaturase (Δ9-fad). In the HCH groups, elevated dietary PLs resulted in the down-regulation of fatty acid binding protein (fabp) gene expression. In addition, high levels of dietary CHO and PLs (HCH-HPL) inhibited the catalase activity of mud crabs, resulting in a significant increase in the malondialdehyde content. Correlation analysis revealed that dietary CHO was positively correlated with the expression of long-chain polyunsaturated fatty acids synthesizing genes, and dietary PLs were positively correlated with the whole-body lipid content of mud crabs. Additionally, a positive correlation was found between the growth performance and whole-body content of crude protein, crude lipid, and antioxidant capacity in mud crabs.

Quercetin supplementation improved the growth and health of juvenile Chinese mitten crabs (Eriocheir sinensis) fed low-fishmeal diets

The substitution of fishmeal with plant proteins can induce oxidative stress in aquatic animals and impair their growth and health. Quercetin is a potent natural antioxidant, but its specific effects on the growth and health of Chinese mitten crabs, as well as the underlying molecular mechanisms, remain unclear. This study aimed to investigate the impact of quercetin on the growth, physiological and biochemical parameters, gut microbiota, and transcriptome of juvenile Chinese mitten crabs (Eriocheir sinensis). Crabs (0.53 ± 0.01 g) were randomly divided into seven groups. One group was fed a diet containing normal fishmeal (35 % fishmeal), whereas the other six groups were fed diets containing low levels of fishmeal (15 % fishmeal) supplemented with different levels of quercetin (0, 250, 500, 1000, 2000, or 4000 mg/kg). Each group had four replicate tanks with 40 crabs per 300 L tank, and the experiment lasted for 56 days. The growth performance of the 35 % fishmeal group was significantly greater than that of the 15 % fishmeal group without quercetin. However, quercetin significantly increased the weight gain rate and specific growth rate of juvenile crabs, especially in the 1000 mg/kg quercetin group, where these rates exceeded those of the normal fishmeal group. The antioxidant capacity and immunity of the 35 % fishmeal group were significantly greater than those of the 15 % fishmeal group. However, quercetin supplementation promoted the antioxidant capacity and immunity of the crabs. Quercetin supplementation at 4000 mg/kg changed the gut microbiota structure by decreasing beneficial bacteria and increasing pathogenic bacteria. Quercetin supplementation enhanced the growth performance and antioxidant capacity of Chinese mitten crabs by increasing glutamate metabolism, pantothenic acid and Coenzyme A biosynthesis, sphingolipid metabolism, arachidonic acid metabolism, and cysteine and methionine metabolism. This study revealedthat dietary supplementation with quercetin can promote Chinese mitten crab growth, antioxidant capacity, and nonspecific immunity; improve gut morphology; and promote gut microbiota homeostasis. The optimal dietary concentration of 688–695 mg/kg is recommended on the basis of weight gain and specific growth rate analyses.

Comparative analysis of cholesterol and its alternative squalene: The impact on growth and lipid metabolism in coin-sized Eriocheir sinensis

Cholesterol is crucial for the growth and development of crabs, but its high cost limits its widespread use in feed. Squalene, a key precursor in cholesterol synthesis, has the potential to replace cholesterol, but its effectiveness in promoting crab growth and cholesterol levels remains unclear. This study investigated the cholesterol and squalene requirements of coin-sized Eriocheir sinensis, the impact of cholesterol and squalene on growth and lipid metabolism, and the relative bioavailability of squalene. A total of 420 coin-sized crabs were divided into seven experimental groups and fed different diets for eight weeks. The diets included three cholesterol levels at 0 % (Control), 0.2 %, and 0.4 %, and four squalene levels at 0.05 %, 0.1 %, 0.2 %, and 0.4 %. Here, we reported that both 0.2 % and 0.4 % cholesterol significantly increased final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) of coin-sized crabs, and 0.2 % cholesterol showed the best growth-promoting effect. Similarly, increasing dietary squalene levels significantly enhanced FBW, WGR, and SGR, with 0.4 % squalene providing the best growth-promoting effect. Additionally, 0.4 % squalene significantly decreased hepatopancreas index (HSI), but did not affect molting frequency (MF). Interestingly, although squalene and cholesterol exerted opposite effects on biochemical indices such as cholesterol and triglyceride levels in the hemolymph, both promoted cholesterol deposition in the hepatopancreas. Relative bioavailability of squalene compared to cholesterol on growth and cholesterol deposition was 82.61 % and 81.73 %, respectively, which might be closely related to lipid metabolism-related genes. In conclusion, the study revealed that similar to cholesterol, squalene was important for crab growth and cholesterol deposition, and squalene could serve as a potential substitute to reduce the reliance on cholesterol in crab feed.

Comparative analysis of embryonic development and growth performance among two mud crab species and their hybrids

In modern aquaculture, inter-specific hybridization enhances traits, but its effects on embryonic development and growth in mud crabs (genus Scylla) remain underexplored. This study investigated the embryonic development and growth performance of Scylla paramamosain, Scylla serrata, and their hybrid offspring from reciprocal crosses. We found that S. paramamosain and the hybrid (S. paramamosain ♀ × S. serrata ♂) produced smaller eggs with shorter development periods than S. serrata and the hybrid (S. serrata ♀ × S. paramamosain ♂). Both hybrids exhibited higher growth rates in the crablet stage than their purebred parents. Notably, the hybrid (S. serrata ♀ × S. paramamosain ♂) demonstrated significant heterosis in body weight and height, while the hybrid (S. paramamosain ♀ × S. serrata ♂) showed single-parent heterosis. While the shape of the frontal lobe spines in hybrids depended on the male parent. Development durations varied, with the longest observed in the hybrid (S. paramamosain ♂ × S. serrata ♀). Discriminant analysis of growth traits showed high accuracy across developmental stages, supporting the potential of inter-specific hybridization for enhancing mud crab aquaculture. This research provides valuable insights and germplasm resources for the aquaculture industry.

The impact of using predigested feed on growth and molting frequency in blue swimming crab (Portunus pelagicus) enlargement

Abstract Blue swimming crab is one of the leading fishery export commodities which occupies the 3rd largest position after tuna and shrimp. Crab maintenance so far uses rasbora fish feed which has several drawbacks, including inappropriate nutrition, depending on the season, and is difficult to handle. Therefore, simple artificial feed is needed to support crab growth. The purpose of this study was to determine the effect of artificial feeding supplemented with pancreatic extract on crab growth. The research design used in this study was completely randomized design (CRD) with different concentrations of pancreatic extract (0%, 3%, 6%, 9%). Parameters observed included water quality (temperature, dissolved oxygen, pH, salinity, and ammonia), feed proximate, crab biology. The results of this study indicate that the water quality in this study supports the life of blue swimming crabs. The feed proximate results show that the proximate value is in accordance with the crab’s needs. The results of swimming crab biology showed that the highest growth of crab was owned by the artificial feed + 9% pancreas and the lowest was in the trash fish treatment. Based on the results it can be seen that the best treatment to support the life of the blue swimming crab is artificial feed + 9% pancreas. Predigestion feed with the help of pancreatic extract concentrations can increase crab growth compared to ordinary feed or rasbora fish feed.

The effectiveness of crab apartment to shelter egg berried female of blue swimming crab (Portunus pelagicus) in Rembang, Central Java, Indonesia

Abstract Blue swimming crab is an Indonesian fishery commodity with high economic value for export to America, Asia, and Europe. The increase in crab fishing activities every year results in diminishing stocks in nature, in addition to predator attacks around spawning areas. The purpose of this study was to determine the growth of blue swimming crabs and identify types of fish in the crab apartment shelters in Rembang Regency, Central Java Province, from March to May 2023. The egg berried female crabs were put in a floating apartment for three months and monitored every 2 weeks to determine the growth of the hatched crab eggs. Our observations showed as many as 50 egg berried female crab with with an average size of 8–10 cm and a weight of 40–65 g. There were other marine organisms found in the shelter, including rabbit fish, shrimp, small crabs, and therapon-perch. Rabbit fish and therapon-perch often result in reduced juveniles. Therefore, add and installing shelter is highly recommended to the entry of these fish. This study found crab apartment brings positive impacts on the survival of hacthing crabs and protected them from the threat of predatory fish.

Effects of Dietary Bio-Fermented Selenium Supplementation on Growth, Immune Performance, and Intestinal Microflora of Chinese Mitten Crabs, Eriocheir sinensis.

Selenium is a vital trace mineral that is crucial for maintaining regular biological processes in aquatic animals. In this study, a four-week dietary trial was carried out to assess the impact of bio-fermented selenium (Bio-Se) on the growth and immune response of Chinese mitten crabs, Eriocheir sinensis. The crabs were randomly allocated to five dietary treatment groups, each receiving a different dose of Bio-Se. The doses included 0, 0.3, 0.6, 1.5, and 3.0 mg/kg and were accurately measured in basal diet formulations. The results showed the weight gain rate (WGR), specific growth rate (SGR), and survival rate (SR) in the 1.5 mg/kg Bio-Se group were the highest, and 3.0 mg/kg of Bio-Se has an inhibitory effect on the WGR, SGR, and SR. The activities of the immune enzymes, including glutathione peroxidase (GPX), superoxide dismutase (SOD), and acid phosphatase (ACP), of the hepatopancreas were significantly (p < 0.05) increased in the 1.5 mg/kg Bio-Se group, while they decreased (p < 0.05) in the 3.0 mg/kg feeding group compared to the 0 mg/kg feeding group. The concentration of maleic dialdehyde (MDA) exhibited the opposite pattern. Similarly, the mRNA expression levels of antimicrobial peptides (ALF-1, Crus-1, and LYS), ERK, and Relish genes were also observed to be the highest in the 1.5 mg/kg Bio-Se group compared with the other groups. Furthermore, the administration of 1.5 mg/kg of Bio-Se resulted in an increase in the thickness of the intestinal plica and mucosal layer, as well as in alterations in the intestinal microbial profile and bacterial diversity compared to the dose of 0 mg/kg of Bio-Se. Notably, the population of the beneficial bacterial phylum Fusobacteria was increased after crabs were fed the 1.5 mg/kg Bio-Se diet. In conclusion, the oral administration of 1.5 mg/kg of Bio-Se improved the growth efficiency, antioxidant capabilities, immunity, and intestinal health of E. sinensis. Through a broken-line analysis of the WGR against dietary Bio-Se levels, optimal dietary Bio-Se levels were determined to be 1.1 mg/kg. These findings contribute valuable insights to the understanding of crab cultivation and nutrition.

Effects of dietary defatted black soldier fly (Hermetia illucens) larvae meal substituting fish meal on growth, antioxidative capacity, immunity, intestinal histology and microbiota of juvenile Chinese mitten crab (Eriocheir sinensis)

This study evaluated the effects of replacing dietary fish meal (FM) with defatted black soldier fly (Hermetia illucens) larvae meal (DBSFLM) on growth, non-specific immunity, antioxidative capacity, intestinal histology and microbiota of juvenile Chinese mitten crab (Eriocheir sinensis). A control diet was designed to contain 200 g/kg FM (Con), then 25 %, 50 %, 75 %, and 100 % of dietary FM was replaced by DBSFLM, referring to DBSFLM25, DBSFLM50, DBSFLM75 and DBSFLM100, respectively. The five isoproteic and isolipidic diets were fed to crab (7.15 ± 0.10 g) for 8 weeks. The results indicated that the final weight, weight gain, feed conversion ratio and survival of DBSFLM25 and DBSFLM50 groups all reached the same level as Con (P > 0.05). The proper DBSFLM replacement on WG and FCR from broken line model were 49.70 % and 52.90 %, respectively. For immune enzyme activity, ACP, ALP, and LZM activities showed a trend of first increasing and then decreasing, the DBSFLM50 group had the highest activity, and the DBSFLM100 group was significantly lower than the DBSFLM50 group (P < 0.05). In terms of antioxidant capacity, the T-AOC, T-SOD, GSH-Px activities and MDA content of DBSFLM25 DBSFLM50 and DBSFLM75 groups all shows no significant difference with Con (P > 0.05), the DBSFLM100 group has the lowest antioxidant enzyme activities and highest MDA content. The intestinal number of folds and folds height in DBSFLM25 and DBSFLM50 groups reached the same level as Con (P > 0.05). The abundance of intestinal harmful bacteria Vibrio was enhanced with the increase of dietary DBSFLM level (P < 0.05). In conclusion, the recommended level of replacing FM with DBSFLM was at 50 % (100 g/kg) without negative effect on growth, non-specific immunity, antioxidative capacity, intestinal histology and microbiota of Chinese mitten crab.

Exploring the effects of dietary cholesterol on growth, immunity, and lipid metabolism of juvenile Chinese mitten crabs (Eriocheir sinensis)

This study aims to investigate the nutritional needs and physiological functions of dietary cholesterol in juvenile Chinese mitten crabs (Eriocheir sinensis). In the 8-week feeding experiment, we evaluated the effects of various cholesterol levels (0 control, 0.6, 1.3, 2.6, 5.9, 12.0 g/kg diet) on growth, immune capacity, lipid metabolism, molting, and cholesterol and bile acid metabolism. Crabs (1.06 ± 0.04 g) were divided into six groups with four replicates of 40 crabs per tank. The highest weight gain was found in crabs fed 5.9 g/kg cholesterol (P < 0.05), while the highest molting frequency was observed in the 0.6 g/kg group (P < 0.05). Cholesterol significantly changed fatty acid composition in the hepatopancreas, and 5.9 g/kg cholesterol increased immune enzyme activities (acid phosphatase, alkaline phosphatase, and polyphenol oxidase) (P < 0.05). A 5.9 g/kg cholesterol significantly upregulated lipogenesis- and catabolism-related genes, while higher levels of cholesterol (12.0 g/kg) downregulated lipogenesis-related genes significantly (P < 0.05). Low cholesterol levels upregulated chitinase expression, while ecdysone receptor and molt-inhibiting hormone expressions were upregulated with cholesterol levels (P < 0.05). Cholesterol also upregulated the gene in bile acid metabolism. The total bile acids, the proportion of primary bile acids, and the content of primary bile acids increased significantly compared to the control. Based on quadratic regression model analysis, the optimal dietary cholesterol level for juvenile E. sinensis is 5.74–5.77 g/kg. The study suggests that cholesterol promotes growth and immunity in juvenile E. sinensis by regulating molting frequency, improving lipid and HUFA utilization, and increasing bile acids.

Size distribution and growth parameters of blue swimming crab (Portunus pelagicus, Linnaeus 1758) in Awur Bay, Jepara

Blue swimming crab (Portunus pelagicus) is a fishery commodity that has important economic value. One of the catch landings in Teluk Awur, Jepara is blue swimming crab. Intensive crab catching carried out with small sizes has an effect on decreasing crab stocks in the waters. This study aims to determine the size distribution, the relationship between carapace width and weight, growth parameters and recruitment patterns. The research was conducted in May, June, July and August 2022 in the waters of Teluk Awur, Jepara. Sampling using systematic sampling method. The data collected is carapace width (mm) and crab weight (grams). Data analysis was performed using FiSAT II software. The results of the analysis of the relationship between carapace width and weight showed that the growth of the male crab was positive allometric and the growth of the female crab was isometric, with the equation of the male crab W = 0.0000214cW3.251 and the female crab W = 0.0000232cW3.220. The growth parameters obtained by the equation of the male and female crabs were cWt = 158,55(1- e(-1,2(t+0,083))], and cWt = 158.55(1 – e(-0.67(t+0.152) ))). The peak of male crab recruitment was in October at 22,71%, while the female crab was in May at 13,52%, indicating that in that month new crab individuals were added. Based on these results, the stock of crab resources in Jepara's Awur Bay must always be considered and always support the recruitment process of crab. Beside that, the goverment can enforce management of crab fishing.Keywords: Allometric; Carapace Width; Crab; Recruitment

Effects of Dietary Glutamate on the Growth Performance and Antioxidant Capacity of Juvenile Chinese Mitten Crab (Eriocheir sinensis)

In order to explore the effects of glutamate on the growth performance, antioxidant capacity and protein metabolism of juvenile Chinese mitten crab, 0%, 1% and 2% glutamate were supplemented to low protein (30%) and normal protein (35%) diets, respectively. There were 5 parallel tanks in each treatment, and the feeding duration was 8 weeks. The results showed that dietary glutamate did not significantly affect the weight gain of Chinese mitten crab. Diets supplemented with 2% glutamate significantly decreased the crude protein of crabs. The T-AOC of crabs fed the 30% protein diets was significantly lower than crabs fed the 35% protein diets. At 30% protein level, the superoxide dismutase (SOD) activity significantly increased with the increase in glutamate content. Dietary glutamate significantly down-regulated the relative expressions of mTOR, PI3K, S6K1 and 4EBP at 35% protein level. In conclusion, dietary glutamate cannot significantly increase the growth of Chinese mitten crab, but it can improve the antioxidant capacity in Chinese mitten crab under low protein conditions.

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

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

The effect of different fresh feeds on the growth and molting period of mud crab (Scylla serrata) cultivated in a single room system

The effect of different fresh feeds on the growth and molting period of mud crab (Scylla serrata) cultivated in a single room system

Supplementation of yeast culture to low-fishmeal diets improves growth, intestinal health, and heat stress resistance in juvenile Chinese mitten crab (Eriocheir sinensis)

Yeast culture (YC), a microecological product derived from yeast fermentation, can enhance animal growth, health, and resistance to heat stress. However, its impact on the economically significant crustacean Eriocheir sinensis has not been demonstrated. This study investigated the effects of low-fishmeal YC on the growth, intestinal health, and heat stress resistance of juvenile Chinese mitten crabs. Crabs (0.72 ± 0.01 g) were distributed across 42 tanks, and 40 crabs were randomly maintained per tank in six replicates. The crabs were fed a control diet (35% fish meal) or six YC concentrations (15% fish meal; 0, 0.8, 1.6, 2.4, 3.2, or 4.0 g/kg) for 56 days. After sample collection, the remaining crabs were subjected to a 72-h heat stress challenge at 32 °C. A moderate-yield YC diet significantly improved weight gain, specific growth rate, and digestive enzyme activities (α-amylase, trypsin, and lipase) compared to those of crabs fed a 15% fishmeal diet without YC. Notably, the diet with 3.2 g/kg YC supplementation was performed as well as crabs fed a 35% fishmeal diet. YC also enhanced intestinal morphology in the low-fishmeal diet group and reduced oxidative damage by increasing the expression of genes related to the peritrophic membrane and tight junction proteins. Furthermore, YC supplementation diversified the intestinal microbiota, significantly increased the abundance of Firmicutes and the genus Shewanella, increased acetate and butyrate levels and decreased the abundance of Proteobacteria. Correlation analysis revealed that weight gain and specific growth rate were associated with most digestive activity and intestinal health indicators. Following heat stress challenge, YC protected against oxidative stress and enhanced serum immunity at elevated temperatures. This study indicated that incorporating YC in low-fishmeal diets significantly increases juvenile crab growth, improves intestinal health, and mitigates oxidative stress induced by temperature elevation. The optimal YC concentration was determined to be 2.71 g/kg through regression analysis.

Dietary arachidonic acid supplementation promoted cholesterol utilization, lipid deposition and molting for Scylla paramamosain

A six-week feeding trial was carried out to investigate the impact of dietary ARA and CHOL levels, and their interactions, on the growth, lipid metabolism, and molting response of juvenile mud crabs (Scylla paramamosain) with an initial weight of 17.46 ± 0.04 g. A 3 × 3 two-factor design was adopted for 9 experimental diets with 0%, 0.75% and 1.5% ARA levels and 0%, 0.75% and 1.5% CHOL supplemental levels, respectively. The results showed that ARA and CHOL had significant interaction effects on percent weight gain and specific growth rate. Percent weight gain and specific growth rate of crabs fed 0.75% ARA diet were significantly higher than those of crabs fed 0% ARA diet, but only when dietary CHOL content was 0.75%. ARA and CHOL levels had significant interaction on crude lipid content and percentage of Oil Red O staining area in the hepatopancreas, and when 0.75% ARA was supplemented to 0.75% CHOL diet, the levels of crude lipid and percentage of Oil Red O staining area in hepatopancreas were significantly up-regulated. Moreover, 0.75% CHOL diet that was supplemented with 0.75% ARA significantly up-regulated the levels of DHA, EPA, and ARA in the hepatopancreas. Additionally, significant interactions between ARA and CHOL were found in expression levels of genes related to long-chain polyunsaturated fatty acid anabolism (Δ9 fad, elovl4, elovl5 and elovl6), fatty acid anabolism and catabolism (aco3, cpt1 and acc), fatty acid transport (fabp1, fabp3 and fatp4), and lipid catabolism and anabolism (hsl, srebp1, lpl and hl) in the hepatopancreas. 1.5% dietary ARA significantly increased the content of serum T-CHO and the activity of hepatopancreatic LCAT. The addition of 1.5% dietary CHOL significantly reduced the concentration of 20E in the serum. Furthermore, both 0.75% and 1.5% dietary ARA reduced concentrations of MIH and CHH in the serum. Significant interactions between dietary ARA and CHOL were observed in the concentrations of 20E and MIH in the serum. Dietary ARA significantly increased the expression levels of dib, e74b, e75 and ftz-f1 in the hepatopancreas. In conclusion, adding 6.02–11.06 mg/kg ARA to 1.21–1.27 mg/kg CHOL diets or adding 6.04 mg/kg ARA to 6.17–7.02 mg/kg CHOL diets both promoted cholesterol metabolism, deposition of essential fatty acids and lipids, and activated ecr-mediated molting response pathway, with these positive benefits likely resulting from a significant increase in PG.

Effects of background color on survival, growth, and shell coloration of juvenile Chinese mitten crab (Eriocheir sinensis)

Background color is a crucial factor influencing the growth performance and feed utilization in crustaceans. However, little is known about its impacts on the culture performance of Chinese mitten crab (Eriocheir sinensis). In this study, we examined the impacts of six different background colors (white-W, black-BK, green-G, red-R, yellow-Y, and blue-BL) on growth, inter-molt period, and coloration and total carotenoids content of carapace of juvenile E. sinensis. The culture experiment comprised two trials: a 68-day individual culture, and a 30-day group culture. Individual culture results: No significant effects of background color were found on weight gain rate (WGR), specific growth rate (SGR), molting interval, carapace length and width, and survival rate (SR) of the juvenile crabs (P > 0.05). However, during the second molting cycle, the BL group exhibited the highest WGR, and the G group showed the lowest hepatopancreas index (HSI). Meanwhile, markedly lower feed conversion ratio (FCR) was obtained for the W group compared to the G and BK groups. Group culture results: Significantly higher SR was recorded for the BK group, and the highest limb loss rate was detected for Y group indicating the significant effects of background color on survival and aggressiveness of juvenile E. sinensis. Moreover, background color impacted the carapace coloration indices where the W, BK and Y groups showed the highest brightness (L*), redness (a*), and yellowness (b*) values, respectively. Furthermore, correlation analysis revealed a positive linear relationship between the L* value and background color (y =0.1638x+27.961, R2=0.613). In conclusion, our results demonstrated that background color significantly affects culture performance and carapace color. Black background color was shown to enhance the survival rate and reduce the limb amputation rate under group culture condition. These results provide new insights on the optimization of farming technology for juvenile E. sinensis.

Dynamics of Phytoplankton Communities and Environmental Drivers in Chinese Mitten Crab Aquaculture Ponds: Highlighting the Need for Cyanobacteria Control

Pond culture is the primary method for cultivating Chinese mitten crab (Eriocheir sinensis), with phytoplankton significantly influencing their growth. Green algae benefit crab growth by serving as supplementary food, while cyanobacteria, particularly during blooms, hinder it and pose health risks. Environmental changes in nutrient levels, temperature, and light significantly affect phytoplankton communities in ponds, impacting both ecosystem stability and crab growth. However, there is a limited understanding regarding the patterns of phytoplankton changes within adult Chinese mitten crab culture ponds. This study conducted monthly collection and analysis of phytoplankton throughout the culture cycle in typical adult Chinese mitten crab culture ponds, concurrently measuring physical and chemical water parameters to explore the correlation between phytoplankton changes and environmental factors. The results revealed distinct seasonal variations in phytoplankton composition. Chlorophyta and Bacillariophyta, such as Chlorella, Pediastrum, and Cocconeis, predominated in spring, while Chlorophyta and cyanobacteria, such as Volvox, Anabaena, and Microcystis, dominated in summer, and cyanobacteria and Bacillariophyta, such as Microcystis, Dolichospermum, and Cocconeis, prevailed in autumn. Total phytoplankton density consistently increased throughout the culture period. Microcystis constituted the majority of cyanobacteria biomass throughout most months. Although the total phytoplankton biomass fluctuated, cyanobacteria biomass consistently rose each month, reaching a peak of 61.7 mg/L in October. Water temperature and pH emerged as the primary environmental drivers influencing changes in phytoplankton community structure. Cyanobacteria density reached its peak between 18 and 26 °C and at a pH range of 7.5–8.5. These findings highlight the need for environmental regulation and cyanobacteria control in Chinese mitten crab culture ponds, thus promoting the health and sustainability of the Chinese mitten crab culture.

Crab bioturbation reduces carbon storage in salt marshes under more robust mechanisms than plant invasiveness

IntroductionThe macrobenthos are crucial for the stability of estuarine ecosystems due to their burrowing behavior in the sediment and their uptake of nutrients from plants. These activities lead to significant alterations in both the morphological and biogeochemical processes within the region.MethodsHowever, there is limited investigation into carbon cycling processes specifically related to crab bioturbation. Additionally, few studies have examined enzymatic activities and carbon fractions in sediments from crab burrow walls at different crab growth stages. This study aims to explore the impact of both plant invasiveness and crab bioturbation on carbon storage.ResultsOur findings suggest that plant invasion leads to higher organic accumulation due to the reduction of recalcitrant organic carbon (ROC) (decreased by 11.6% in invasive and 62.6% in native site from April to December), faster photosynthetic rates (25.8 μmol/m2 s in invasive and 10.7 μmol/m2 s in native site), and an increased presence of arbuscular mycorrhizal fungi (AMF) in the soil over time. However, the increase of easy oxidized carbon (EOC) may lead to less carbon storage in soil (increase by 67.7% in invasive and 48.8% in native site from April to December). In addition to invasiveness, the bioturbation activities of macrobenthos also affect carbon storage. Sediments from crab burrows exhibit higher EOC content (33.6% more than the bulk soil) and higher levels of carbon cycling-related enzymes, including S-ACT, S-β-GC, and S-ACP activities (24.2%, 8.99%, and 135.6% higher than the bulk soil, respectively).DiscussionThese changes contribute to reduced carbon accumulation in the soil. Therefore, crab bioturbation is a more significant factor affecting carbon sink capacity than plant invasion.

Morphometric relationships of blue swimming crab (&lt;em&gt;Portunus pelagicus&lt;/em&gt;, Linnaeus, 1758) caught in Negombo coastal waters in Sri Lanka.

Length-weight relationships provide information about the blue swimming crab (Portunus pelagicus) population for successful stock management. Morphometric measurements of Two hundred fifty (250) crab samples were obtained from April to November 2019, of which 128 were males, and 122 were females, showing a sex ratio of 1:1. Chi-square test indicated that the sex ratio was not significantly different from the expected value of 1:1 at 5% level of significance (χ2cal = 0.144, χ2tab = 3.84). Carapace width (CW) was measured at the nearest 0.001 cm using a vernier calliper, and total body weight (W) was measured at the nearest gram (g) using a digital scale. The carapace width of males ranged from 7.28 - 15.7 cm, whereas it varied from 3.06 - 15.8 cm in females. The body weight of male crabs varied from 22.45 - 334.6 g, and females had a range from 23.0 - 275.35 g. Length-weight relationships for male and female crabs were W=0.0495CW3.0469 (R2=0.8526) and W=0.063CW2.9428 (R2=0.8179) respectively. Student’s t-test showed that the growth of male crabs was positive allometric (t = 5.64, p&lt;0.05) and negative allometric (t = -8.21, p&lt;0.05) for females. The mean condition factors for males and females were 5.68±0.12 and 5.65±0.12, respectively, indicating no significant difference between males and females (p=0.882) by two-sample t-tests. Providing baseline data, the present study recommends further studies for successful utilization, development and management of this crab species as it has been recognized as a commercially valuable species with a high market demand.