Survival Of Crab Research Articles

Success Rate Of Mangrove Crab (Scylla Serrata) Molting With Different Salinity Treatments In Controlled Containers

Market demand for mud crab (Scylla serrata) is increasing so that its catch in nature is high in the long term. The growth of mud crabs (Scylla serrata) occurs through molting (molting) mechanisms. Softshell crab has a higher economic value than hard shell crab. The purpose of this study was to assess the molting rate of mud crab (Scylla serrata) with different salinity treatments in controlled containers. The study used a completely randomized design (CRD) with three treatments of 20 ppt, 25 ppt, and 30 ppt salinity with three replications. The crabs used are mud crabs (Scylla serrata) measuring 80-175 grams with the carapace still hard. The test parameters include the weight gain and absolute length of the individual, daily growth rate, molting percentage, and survival and mortality rates. Besides, the chemical-chemical parameters of the culture media water and the effectiveness of using controlled containers were also observed. The research data were analyzed descriptively quantitatively. The difference in treatment and the use of controlled containers had a significant effect on the 95% significance level (α = 0.05) on all parameters of the response to treatment. Absolute individual weight values 40.6 – 47.41 grams, absolute individual length 2.6 – 3.2 cm, molting percentage 75 – 100%, daily growth rate 1.3 – 1.6 grams, 75 – 100% survival and mortality of mud crab (Scylla serrata) 25-16.7%. Optimal salinity level at 20 ppt. Water quality parameters during the study were still feasible for mangrove crab (Scylla serrata) cultivation. Controlled containers using a water rotation system are quite effective for the cultivation of mud crab (Scylla serrata).

Effect of dietary egg yolk lecithin levels on survival, growth, lipid metabolism, and antioxidant capacity of early juvenile green mud crab Scylla paramamosain

This study investigated the effects of different dietary egg yolk lecithin levels (with 0% (EL0), 1% (EL1), 2% (EL2), 3% (EL3), and 4% (EL4) EL supplementation) on survival, growth, lipid metabolism, and antioxidant capacity of the early juvenile green mud crab (Scylla paramamosain). Total of 420 crabs (initial weight 8.14 ± 0.30 mg) were randomly assigned into five experimental groups (with 3 replicates). At the end of the eight-week culture experiment, the highest survival (92.86 ± 4.52%) was obtained in EL3 group. Significantly higher growth performance (final body weight (FBW), weight gain (WG), and specific growth rate (SGR)) was also observed in the EL3 group, and there was no significant difference from the EL2 group. The highest molting frequency (MF) and transcription level of ecdysone receptor (EcR) gene were also obtained in EL2 group suggested that EL could increase the MF of early juvenile S. paramamosain by up-regulating the mRNA expression of EcR and ultimately promote its growth. In addition, the higher body lipid composition along with increased EL levels suggested that EL could promote lipid absorption and disposition in S. paramamosain. Compared with other crabs, the crabs in EL2 group had significantly higher ∑n-3/∑n-6 ratio. The highest transcription level of fatty acid binding proteins (FABPs) gene also observed in EL2 group. Furthermore, the crabs in EL4 group had significantly lower transcription level of fatty acid synthase (FAS) gene. This result implied that feeding of EL supress the fatty acids synthesis but induce fatty acid transport genes in S. paramamosain. In the hepatopancreas, the content of thiobarbituric acid reactive substances (TBARS) decreased significantly with the dietary EL addition. Meanwhile, significantly higher superoxide dismutase (SOD) activity was observed in the EL2 and EL3 groups. This indicated that dietary EL improved the antioxidant capacity of S. paramamosain. According to the polynomial regression analysis of SGR, 2.56% dietary EL level could achieve the maximum growth of early juvenile S. paramamosain.

Substitution of fish meal with soybean meal for juvenile Chinese mitten crab ( Eriocheir sinensis ) reared at three salinities: Effects on survival, growth, antioxidant capacity and body composition

A 60-day feeding experiment was conducted to evaluate the survival, growth, antioxidant capacity and body composition of the juvenile Chinese mitten crab (Eriocheir sinensis) reared at three salinities (0.5‰, 2‰ and 6‰) in response to the different substitution levels (0%, 24%, 39%, 57% and 100%) of fish meal (FM) by soybean meal (SBM). The five diets were named as S0, S24, S39, S57 and S100 respectively. Results showed that survival rate (SR) was only significantly affected by the substitution level at the salinity of 0.5‰, with significantly higher SR observed in S39 (p < 0.05). At the salinity of 0.5‰ and 2‰, the significantly higher weight gain rate (WGR) was observed in S39 and S57 respectively (p < 0.05). At the salinity of 6‰, WGR was significantly improved by partial or complete substitution of FM by SBM. At each salinity, the highest GSH-Px activity and lowest MDA content were observed in the treatments of S57, which were comparable to that fed S0. At the salinity of 6‰, the activities of SOD and CAT were significantly decreased in S100 than that in the other treatments (p < 0.05). The proline content significantly increased as the substitution level increased at the salinity of 2‰. At the salinity of 6‰, the contents of proline, glutamine, cysteine, methionine and lysine, first significantly increased and then decreased (p < 0.05), with the highest value observed in the treatment of S39 or S57. These results indicated that the optimal substitution level of FM by SBM was estimated to be 39% and 57% in the diets of E. sinensis at the salinity of 0.5‰ and 2‰ respectively. Although the FM can be completely replaced by SBM without negatively affecting the survival and growth performance at the salinity of 6‰, the antioxidant capacity was reduced to a large extent.

N-acetylcysteine provides protection against the toxicity of dietary T-2 toxin in juvenile Chinese mitten crab (Eriocheir sinensis)

The present research aimed to investigate the protection of N-acetylcysteine (NAC) on T-2 toxin-induced toxicity in Chinese mitten crab (Eriocheir sinensis). Crabs (0.27 ± 0.00 g) were fed four different diets (Control, T-2, 0.05% NAC + T-2 and 0.1% NAC + T-2) for 8 weeks. The results showed that T-2 toxin decreased growth performance, and induced oxidative stress, immunodepression and apoptosis in juvenile crabs. Crabs with NAC had higher weight gain, specific growth rate and hepatosomatic index than those in the T-2 group. The 0.1% NAC elevated crab survival and oxygen consumption rate and decreased alanine transaminase and aspartate transaminase in the serum of crabs fed T-2 toxin. Reactive oxygen species and malonaldehyde levels of hemolymph and hepatopancreas in crabs fed NAC were significantly lower than those in the T-2 group, while glutathione peroxidase, total antioxidant capacity, γ-glutamylcysteine synthetase activities and glutathione content significantly increased with 0.1% NAC. Total hemocyte count, respiratory burst activity, total protein, acid phosphatase (ACP) in hemolymph and ACP, alkaline phosphatase (AKP) in hepatopancreas were significantly enhanced with 0.1% NAC. Phagocytosis and AKP in hemolymph were significantly enhanced with 0.05% NAC supplementation. Furthermore, the mRNA expressions of antimicrobial peptides (ALF1, ALF2, crustin-1 and crustin-2) and peroxinectin were up-regulated with NAC. Besides NAC down-regulated the mRNA expressions of Relish, lipopolysaccharide-induced TNF-alpha factor, caspase-3, caspase-8 and p53 genes, and the ratio of Bax to Bcl-2 in the hepatopancreas. Our findings indicate that dietary NAC could improve the growth performance and survival of juvenile Chinese mitten crab fed T-2 toxin. The 0.1% NAC could effectively alleviate oxidative stress, immunodepression and apoptosis induced by T-2 toxin.

Improving Survival of Juvenile Scalloped Spiny Lobster (Panulirus homarus) and Crucifix Crab (Charybdis feriatus) Using Shelter and Live Prey.

Simple SummaryFighting with each other is a major problem in lobster and crab aquaculture. Reducing the fighting behavior of lobsters and crabs can improve survival during the culturing process. Juvenile lobsters and crabs were both cultured under different shelters (seaweed and cotton filter) and live prey conditions. Groups with shelter and co-culturing with live prey showed a better survival rate for both juvenile lobsters and crabs. Although providing shelter is currently the main method for reducing agonistic behavior, it must be continually altered as the lobsters and crabs grow. Live prey can grow and attract lobsters and crabs to hunt them, and live prey can be supplemented at any time. They can also be used as an additional source of income during the harvest season.Cannibalism is a major problem in lobster and crab aquaculture. Reducing the aggressive characteristics of lobsters and crabs can improve survival during the culturing process. In this study, juvenile scalloped spiny lobsters (Panulirus homarus) and crucifix crabs (Charybdis feriatus) were both cultured under different shelter and live prey conditions. Groups with shelter (seaweed and cotton filter) showed a better survival rate than the control group (no shelter; p < 0.05) for both Pa. homarus and Char. feriatus. Co-culturing with live prey (Litopenaeus vannamei) significantly benefited the juveniles of Pa. homarus and visibly increased the survival of juvenile Char. feriatus. Although providing shelter is currently the main method for reducing agonistic behavior, it must be continually altered as the lobsters and crabs grow. Live prey can grow and attract lobsters and crabs to hunt them, and live prey can be supplemented at any time. They can also be used as an additional source of income during the harvest season.

Growth and survival of Mud Crab, Scylla serrata, reared in bottom and floating cages within Mida Creek mangroves, coastal Kenya

Abstract Mud Crab fattening is a relatively new business idea in Kenya and is highly lucrative due to the reasonable prices offered at tourist hotels. This study was aimed at developing appropriate culture techniques for Mud Crabs to maximize harvestable biomass by the local communities and avoid recruitment overfishing. Growth and survival rates for mixed sex Mud Crabs was investigated for a period of 230 days in Mida Creek, Kenya, using bottom and floating cages, and two feed types in a crab fattening experiment. Crabs attained harvestable weight by the third month for both floating (466.2 ± 137 g) and bottom cages (542.2 ± 109.3 g). There was no significant difference in mean total weight of mixed-sex crabs in the two culture systems (t = 1.75, p&amp;gt;0.05), however males showed significantly higher total weight gain compared to females. A higher overall survival rate was found for crabs cultured in floating cages (63.8%), compared to bottom cages (44.9%). There was no significant difference in growth performance between crabs fed gastropod tissues and those fed fish offal. The long-term specific growth rate for floating cages (0.69 g d-1) was not significantly different from that of bottom cages (0.92 g d-1). An analysis of potential return on investment showed the floating cages to be more profitable per production cycle compared to the bottom ones. The floating cage system and mono-sex male crab culture are recommended to farmers within mangrove tidal flats in Kenya.

Utilization of Trash Fish for Cultivation of Crablet Mud Crab (Scylla serrata)

The high demand for mud crabs in North Kalimantan causes catch to increase in the wild. If it is not balanced with efforts to increase its aquaculture of mud crab, in the future there will be a decline in population. This study aims to determine the growth and survival rate of mud crab seed (crablet, Scylla serrata) in the application method of different types of trash fish. This research used a completely randomized design with 4 treatments and 3 replications. The Crablet used carapace width average 0.07-0.09 cm and weigh average 0.05-0.07 g with total 150 crablets. The treatments applied by trash fish were (A) Tilapia Fish (Oreochromis mossambicus), (B) Longfin Herrings Fish (Ilisha elongata), (C) Sword Fish (Trichiurus lepturus) and (D) Snails (Telescopium telescopium). The results were The best weight growth of crablet occurs in the treatment of T. lepturus (P&gt;0.05) and the highest of survival rates of crablet were found in treatment T. telescopium (P&lt;0.05) than the other. The trash fish were used turned out to be able survival of crablet mud crab (Scylla serrata).

Effect of Water Temperature on Survival, Growth and Molting Cycle During Early Crablet Instar of Mud Crab, Scylla paramamosain (Estampador, 1950)

This study aimed to determine the effect of rearing water temperature on survival, growth and molting cycle of the mud crab, S. paramamosain from Megalopa up to 1st crablet instar (Crablet 1) and from Crablet 1 to 2nd crablet instar (Crablet 2). Different water temperature regimes were implemented i.e. 20 °C, 24 °C, 28 °C, 32 °C, 36 °C and ambient temperature. The observed parameters were: successful molting from Megalopa to Crablet 1 and from Crablet 1 to Crablet 2, survival in Crablet 1 and Crablet 2, growth (carapace increment of crablets), Specific Growth Rate of carapace width (SGRCW) and, molting interval (in days) from Megalopa to Crablet 1 and from Crablet 1 to Crablet 2. The results showed that the highest survival rate from Megalopa to Crablet 1 was found at 24 and 28 °C where both could reach up to 100%. At water temperature of 32 °C and ambient temperature, the survival rate were 96.66%. The lowest survival rate was found at 20 °C and 36 °C treatments (p 0.05), but there were significant differences in molting intervals (p < 0.05) for both Megalopa to Crablet 1 and Crablet 1 to Crablet 2 phases. Treatment of ambient temperature (27–30 °C) had the fastest molting interval from Megalopa to Crablet 1 but its value not significantly different with treatment of 24, 28 and 32 °C. The fastest molting interval from Crablet 1 to Crablet 2 was found at 32 °C which was 2.96 days (p < 0.01). Based on this study, it is recommended that rearing from Megalopa to Crablet 1 should take place at a temperature of 28 °C while, in Crablet 1 to Crablet 2 phase, a temperature of 28 to 32 °C is recommended.

Thermal stress: The role of body size and the giant major claw in survival and heat transfer of a fiddler crab (Leptuca pugilator)

Mobile intertidal crabs are often exposed to the sun while displaying outside of moist and cooler breeding burrows, which imposes increased heat stress and water. Individuals of a field population in mid-summer of the fiddler crab Leptuca pugilator had body temperatures that declined with increasing body size. All crabs were cooler than the sediment surface. Laboratory experiments simulated a male leaving its burrow and standing on hot sand heated by the sun. Smaller crabs succumbed to thermal stress sooner than larger crabs. Incapacitation keyed to field sediment temperatures occurred usually in about 30 min. Water loss ranged 1–8% at incapacity Small crabs heated up as fast as large crabs. Males with a major claw gained body heat more than clawless males and succumbed sooner. The major cheliped loses water proportionally more slowly than the body, which is likely explained by the more impervious surface of the claw, suggesting the claw might be a heat sink. I hypothesized that heat may be accumulated in the relatively impermeable major cheliped and transferred to the body, increasing thermal stress in the body where crucial organs must function. Several experiments were done to attempt to demonstrate body part differences in heating or heat transfer between cheliped and body. Thermal images demonstrated a temperature excess in the manus, and a lower temperature of the dactyl, consistent with the impermeability of the manus and its larger surface area intercepting heat, and perhaps radiation from the dactyl. Immersion of major claws in warm and cold water demonstrated heat transfer between cheliped and body. If claws are painted black, they heat up faster than unpainted claws, but there was no evidence of the transfer of increased heat to the body when claws were darkened. Thus the potential for heat transfer between claw and body is probably quite limited, which is further suggested by the very narrow connection at the basal ischium segment of the cheliped.The results suggest that smaller male fiddler crabs may have reduced success in the upper intertidal partially because of their higher vulnerability to thermal stress. Smaller males may choose to avoid the hotter upper intertidal until they become larger. Experimental results show no evidence for the role of the major claw in alleviating thermal stress to the fiddler crab carapace.

Bioecology of Coconut Crab (Birgus latro L.) on Kaledupa Island

Bioecology of Coconut crab (Birgus latro L.) On Kaledupa Island, the objective of the research is to know the Biological characteristics (morphometric measurements in the length and width of the carapax, cephlathorax added rostrum (Cp + r) and body weight) and to know the Ecological characteristic (population size) Coconut crab which is on the island of Kaledupa. Sampling technique used the CMRR (Capture-Mark-ReleaseRecapture) method. Data analysis techniques used: (1) Coconut crab morphometry. Data were analyzed descriptively by calculating the average length and width of the carapax, cephalothorax + rostrum length and body weight, (2) Data on sex ratio and population estimation were analyzed quantitatively. Based on the result of the analysis, the highest morphometric measurements are the length of the carapax with an average of 6.37 cm, the width of the carapax 6.03 cm, the length of the cephalothorax + rostrum 10.06 cm, which is located at the location of Station I (Hoga island, Furake sub-village). This is because of this station has unspoiled environmental conditions and there are burrows or caves where the Coconut crab is hiding, where the station belongs to the Wakatobi National Park which is a protected area, and has coconut and other shrub vegetation. These are a food source of Coconut crab s, so this area is ideal for the survival of Coconut crab. The lowest morphometry measurements obtained by carapax length with a mean of 5.62 cm, carapax width of 5.49 cm, length of cephalothorax + rostrum of 9.044 cm, which is found at the location of Station II (Sombano village). This is thought to be the condition of habitats that have been converted into other uses such as the opening of plantation land, so many of the Coconut crab hide outs are damaged. The comparison of male and female sex ratio is 13 Male: 7 Female.

Effects of antibiotics and deep seawater on the survival and molting interval of the Japanese giant spider crab Macrocheira kaempferi in captivity during critical early life stages

Effects of antibiotics and deep seawater on the survival and molting interval of the Japanese giant spider crab <I>Macrocheira kaempferi</I> in captivity during critical early life stages

Growth and Survival of Blue Swimming Crab (Portunus pelagicus L.)In Different Rearing Substrates and Stocking Densities

The study of the growth and survival of blue swimming crabs is important to optimize its production and explore the development of net-cage crab culture as the culture scheme for production of blue swimming crabs. This paper investigates the growth and survival rate of Portunus pelagicus at 15 and 30 days of culture using two rearing substrates (net and sand) and three stocking densities (15, 30 and 45 crabs/m2). Physicochemical parameters such as the dissolved oxygen, salinity, water temperature, and water transparency were also gathered across the days of culture to explain other factors that may influence survival rate of crabs during culture. Results showed no significant differences for both growth rate in terms of carapace width and body weight and survival rate. Significant interaction between the stocking rate and rearing substrates on the growth rate in terms of carapace width during the 15 days of culture were observed. Poor growth and survival rates of the crabs may have been the result of cannibalism and poor quality of bottom substrates like silt and abrupt change of water quality namely salinity and transparency. It is recommended to validate the results in a more favorable rearing environment. Management strategies to control predation may be tested and implemented when culturing blue swimming crabs in cages and pens.

Growth, molting duration and carapace hardness of blue swimming crab, Portunus pelagicus, instars at different water temperatures

Survival and growth of blue swimming crab, Portunus pelagicus from instar 1 stage to instar 8 stage (C1 to C8), molting duration and time of hardening from instar C7 to C8 were examined at 24 °C, 28 °C and 32 °C. The carapace width decreased with increasing temperature, whereas the intermolt period also decreased. The inter-molt period of crab molted from C1 to C8 was 59.23 ± 4.22 days, 48.19 ± 3.52 days, and 38.66 ± 2.15 at 24 °C, 28 °C, and 32 °C, respectively. The survival of crabs from C1-C2 stage to C7-C8 stage range from 70% to 80% and the present study showed that survival decreases at the highest temperature of 32 °C. The time spent for complete molting of crab from emergence of swimming legs to chelae was 181, 123, and 103 s, at 24 °C, 28 °C, and 32 °C, respectively. The harding time (time required for hardening) of the carapace was 16–17 h, 12–13 h, and 9–10 h at 24 °C, 28 °C, and 32 °C, respectively. It is concluded that crab instars reared at high temperature of 32 °C decrease intermolt period, duration of exuviation and harding time. Data on molting time and carapace hardiness can be used for assessing the suitable time for stocking and changing the water culture.

Effect of temperature stress on the survival of juvenile Chinese mitten crab (Eriocheir sinensis)

Eriocheir sinensis is belongs to Crustacea, which is an important aquaculture specie. To discuss the temperature tolerance of Eriocheir sinensis, the survival rate of juvenile crabs of Eriocheir sinensis was determined in this paper by a series of temperature setting (normal temperature, 25°C, 30°C, 32°C, 34°C, 35°C, 36°C, 38°C, 40 °C). The results indicated that except the normal temperature level, mortality rate almost reached 100% for other temperature. Time of all crabs death of 30℃, 35℃, 40℃ was different. Only 10 minutes all crabs died for 40℃ level, while 3 days and 7 days for 35 ℃ and 30℃ respectively. In addition to normal temperature condition, minimum survival time of the juvenile crabs of Eriocheir sinensis at other temperature condition were no more than 24 h. Before the 8th day, the death case of 30℃ and normal temperature was different, change of turning slope for concentration of NH3-N and TN was contrary. Under normal temperature, the behavior of abdomen extension was not observed in juvenile crabs but the percentage time of abdomen extension was relatively long at 25℃. This research studies the influence of temperature stress on the survival of juvenile crabs of Eriocheir sinensis in expectation of providing reference for the production and transportation of juvenile crab of Eriocheir sinensis.

Winter is (not) coming: Warming temperatures will affect the overwinter behavior and survival of blue crab.

Understanding how increases in water temperature may affect winter dormancy period duration and overwinter survival are important for the effective conservation and management of estuarine species in the face of a warming climate. In this study, we determined the length of the overwintering period and the probability of overwinter survival of blue crab (Callinectes sapidus), an ecologically and economically important estuarine crustacean. Overwintering period length and probability of overwinter survival were determined using projected water temperatures up to the year 2100, derived from a harmonic model that utilized air temperatures from multi-model ensemble of regional-scale climate projections. Our estimates of warming water temperatures by 2100 in Chesapeake Bay indicate that winters will be up to 50% shorter and overwinter survival will increase by at least 20% compared to current conditions. The warmer conditions will lead to faster and prolonged seasonal growth, which, when combined with lower winter mortality, will lead to increased population productivity. The level of expression of this increased productivity will depend on the response of other elements of the Chesapeake Bay food web, as well as possible changes to fishery management policies over the same time period.

Impact of different rearing systems on survival, growth and quality of mud crab (Scylla paramamosain) megalopae reared from early zoeae

This study aimed to compare the effects of four different rearing systems—namely clear water, green water, recirculating water and biofloc water systems—on survival, growth and quality of mud crab (Scylla paramamosain) megalopae reared from early zoeae. Twelve 60-L plastic buckets filled with 50 L of disinfected seawater were stocked with 20 larvae of zoea 1 (Z1) L−1. The larvae were fed both probiotic-enriched L-strain rotifers (Brachionus plicatilis) and probiotic-enriched Artemia (Artemia franciscana) in all systems. After 20 days of culture, the green water system resulted in the highest survival to megalopae than all the other systems. The survival of megalopae reared under the biofloc water system was similar to that of the clear water system, but both systems exhibited higher survival than the recirculating water system. However, larval growth performance was not affected by the various rearing systems. The quality of megalopae produced under these systems was determined by ammonia and simulated transport stress tests. The ammonia stress test did not show a significant difference in the quality of megalopae, but the simulated transport stress test demonstrated a significant effect of rearing system on the quality of mud crab megalopae. The resistance to the air exposure until the end of the 48 h of transport was observed in the green water system. Overall, the results of the present study revealed that the green water system is the most suitable for rearing Scylla paramamosain larvae from Z1 to megalopa stage.

Induction of moulting in hatchery‐reared mangrove crabScylla serratajuveniles through temperature manipulation or autotomy

The effects of temperature and autotomy of chelipeds on survival, growth and moulting of mangrove crab (Scylla serrata) juveniles were investigated under laboratory conditions for 60 days. Hatchery-produced crabs with 2.0–2.3 cm internal carapace width (1.7–2.2 g body weight) at intermoult stage were exposed to one of four temperature treatments (constant 29, 32 or 35°C, or ambient [24–31°C]) or subjected to cheliped autotomy. All crabs held at 35°C had 100% mortality due to incomplete moulting during first moult. The mean survival of crabs at termination was 58%, 64% and 50% for ambient temperature, 29 and 32°C respectively. Specific growth rate (SGR) of crabs in the ambient and 29°C were comparable but significantly lower than those at 32°C. The moult interval of the crabs was significantly shorter in treatments with constant water temperature of 29 and 32°C compared with ambient temperature. The survival of crabs with intact chelipeds was comparable with those with one or two autotomized chelipeds. Crabs with intact or one autotomized chelipeds had significantly higher SGR than crabs with both chelipeds autotomized in the first moult. On the second moult, however, high SGR was observed in crabs with two chelipeds autotomized. The moult interval was significantly shorter in the autotomized crabs compared with crabs with intact chelipeds. The results suggest that the optimum water temperature for rearing S. serrata juveniles ranges from 29 to 32°C. Likewise, autotomy of chelipeds can promote moulting without adversely affecting survival of crabs.

Effects of the glyphosate-based herbicide roundup on the survival, immune response, digestive activities and gut microbiota of the Chinese mitten crab, Eriocheir sinensis

Glyphosate is one of the most widely used pesticides in the world and can be transported easily by surface runoff, air, and rivers, potentially affecting aquaculture. In this study, the survival rate, intestinal and hepatopancreatic immune and digestive functions, and the intestinal microbial diversity of Chinese mitten crab (Eriocheir sinensis) were evaluated after 7 days of exposure to glyphosate (48.945 mg/L from 1/2 96-h LC50 value). The results showed that glyphosate significantly reduced the survival rate of E. sinensis. After exposure to glyphosate, the totoal antioxidant capacity (T-AOC) in the midgut and hindgut of E. sinensis was significantly decreased, and malondialdehyde (MDA) content in the midgut was significantly increased (P < 0.05). After glyphosate exposure, the activities of digestive enzymes (including lipase and amylase) in the intestinal tract were significantly decreased and trypsin was significantly increased, while three enzymes in the hepatopancreas were significantly increased (P < 0.05). Using high-throughput sequencing analysis of the gut microbiota, the results showed that glyphosate significantly decreased the diversity of E. sinensis gut microbiota, while significantly increasing the taxonomic richness of Bacteroidetes and Proteobacteria (P < 0.05). This study suggested that these bacteria may be involved in glyphosate effects on survival by regulation of immune and digestive function.

Dietary Aroclor 1254-Induced Toxicity on Antioxidant Capacity, Immunity and Energy Metabolism in Chinese Mitten Crab Eriocheir sinensis: Amelioration by Vitamin A.

Effects of dietary Polychlorinated biphenyl (PCB) exposure and dietary vitamin A supplementation on Chinese mitten crab Eriocheir sinensis were studied with the aim to explain dietary PCB toxicity and toxic alleviation by vitamin A intake in crab. Four diets were used including three experimental diets containing 0, 80000 or 240000 IU/kg vitamin A with each experimental diet containing 10 mg PCB/kg diet, and a control diet (without vitamin A and PCB supplementation) in 56 days feeding trial. Crabs fed the PCB-only diet had significantly lower weight gain than those fed the control diet. No significant difference was observed in crab survival among all groups. Crabs fed the PCB-only diet had a significantly higher malondialdehyde content and antioxidase superoxide dismutase activity in the serum and hepatopancreas, and higher erythromycin N-demethylase and glutathione S-transferase activities in the hepatopancreas than those fed the control diet. However, supplementation of dietary vitamin A decreased the levels of all these parameters. The hepatopancreatic cytochrome P450 2 and 4 (CYP2, CYP4), fatty acid binding proteins 3 and 10 (FABP3, FABP10) and intracellular lipolytic enzyme (IL) Messenger Ribonucleic Acid (mRNA) levels in the PCB-only group were significantly higher than those in the control group, and dietary 240000 IU/kg vitamin A supplementation decreased hepatopancreatic CYP4, FABP3, FABP10 and IL enzyme mRNA level. The crabs fed 80000 IU/kg vitamin A supplementation diet had the highest level of retinoid X receptor mRNA in the hepatopancreas. The structure of the hepatopancreas was damaged and the deposit of lipid droplets decreased with dietary PCB exposure. Both levels of vitamin A supplementation alleviated the damage and increased lipid droplets in the hepatopancreas. Dietary PCB exposure significantly reduced total hemocyte count (THC), and phenoloxidase, acid phosphatase activities in the serum. Post-challenge survival of crab in the experimental PCB-only diet group was low compared with that in the control. Supplementation of 240000 IU/kg vitamin A significantly increased the THC and phenoloxidase activity in the serum and post-challenge survival compared with those in the PCB-only group. This study indicates that dietary vitamin A can improve the antioxidant capacity, immune response, detoxification enzymes activities, energy metabolism and hepatopancreas tissue structure of Chinese mitten crab fed PCB contaminated diets.

Survival, molting pattern, and growth of early blue swimmer crab, Portunus pelagicus, juveniles fed diets containing varying levels of cholesterol

AbstractThis study examined the effects of dietary cholesterol on the survival, molting pattern, and growth of early juveniles of the blue swimmer crab, Portunus pelagicus. Seven isocaloric diets were formulated to contain cholesterol at 0 (basal diet), 2.5, 5.0, 7.5, 10, 12.5, and 15 g/kg diet dry weight. Survival ranged from 20 to 47.5%, with the highest survival recorded for crabs fed the diet supplemented with 10 g/kg cholesterol, while the lowest survival was demonstrated by crabs fed the basal diet. The highest occurrence of molt death syndrome was found for crabs fed the diet with cholesterol supplementation of 15 g/kg. A general trend of decreasing development time to the crab 3 (C3) stage was observed with increasing dietary cholesterol supplementation up to a level of 10 g/kg, but this then decreased as dietary cholesterol level was increased to 12.5 and 15 g/kg. The specific growth rates of crabs, calculated for dry weight, carapace width, and carapace length, followed a similar trend. Our results suggest that, under the current feeding conditions, a dietary cholesterol level of 10 g/kg appears to be optimal for the culture of early juveniles of P. pelagicus.