Effects of salinity on growth,nutrient composition,fatty acid composition and energy metabolism of Scylla paramamosain during indoor overwintering

Three salinities (4‰, 12‰ and 25‰) were selected to determine the effects of different salinities on the growth, survival, nutrition and energy metabolism of Scylla paramamosain during indoor overwintering. Growth performance (survival rate, condition factor, hepatopancreatic index, weight gain rate and specific growth rate), nutrient composition (ash, moisture, crude fat, crude protein and total nitrogen), fatty acids, energy metabolites (glycogen, glucose, triglycerides, cholesterol and lactic acid) and energy metabolic enzymes (hexokinase, pyruvate kinase, lactate dehydrogenase and succinate dehydrogenase) were measured and calculated. The results showed that S. paramamosain exhibited the best growth and survival at 25‰ and worst at 4‰ after overwintering. In addition to consuming crude fat, excess protein was also broken down to provide energy in the 4‰ and 12‰ groups. The content of unsaturated fatty acids in the 25‰ group was higher after overwintering. Glycogen and glucose consumption and triglycerides, cholesterol and lactic acid production were lowest in the 25‰ group. The activity of hexokinase, pyruvate kinase, lactate dehydrogenase and succinate dehydrogenase was highest in the 4‰ group and lowest in the 25‰ group. The activity of hexokinase, pyruvate kinase, lactate dehydrogenase and succinate dehydrogenase in the hepatopancreas was higher than in the muscle. In conclusion, S. paramamosain uses less energy, has more unsaturated fatty acids and has a higher survival rate at a salinity of 25‰ after overwintering. The results of this study provide helpful information the indoor overwintering S. paramamosain in aquaculture production systems.     

Effects of dietary phospholipids levels on growth performance,lipid metabolism,and antioxidant capacity of the early juvenile green mud crab,Scylla paramamosain (Estampador)

Four iso‐nitrogenous and iso‐lipidic diets were designed to investigate the effects of dietary phospholipids (PL) levels (with 0%, 1%, 2%, and 4% PL supplementation) on growth performance, lipid metabolism, and antioxidant capacity in early juvenile green mud crab (Scylla paramamosain). There were three replicates of 28 crabs (initial body weight from 42.02 to 42.44 mg) for each diet treatment, and growth trial lasted for 8 weeks. At the end of the growth trial, there was no significant difference in survival among all treatments. Crabs fed diet with 2% PL obtained highest weight gain (WG) and specific growth rate than other crabs. The molting frequency was not affected by different dietary PL addition. Besides, the contents of whole body lipid and long chain highly unsaturated fatty acids significantly increased with elevating dietary PL levels. In the hepatopancreas, crabs fed diet with 0% PL had significantly higher malondialdehyde concentration than other crabs. And crabs fed diet with 2% PL obtained significantly higher superoxide dismutase activity than crabs fed diets with 0% and 4% PL. Moreover, the mRNA expression of Na⁺/K⁺‐ATPase was significantly down‐regulated with dietary PL supplementation over 2%. Based on the second order polynomial regression analysis of WG, 2.37% dietary PL level was the optimal demand for early juvenile S. paramamosain. Moreover, we found crabs fed diet with 2% PL obtained better antioxidant capacity than other crabs.     

Proximate Composition and Antioxidant Properties of Orange Mud Crab,Scylla olivacea

The proximate composition and antioxidant properties of the muscle tissues of Scylla olivacea are reported herein. The carbohydrate content was in the range of 1.52% to 3.07%, while protein varied from 13.30% to 17.28%. Meanwhile, the fat content for S. olivacea was found to be ranging from 0.20% to 0.57%. The moisture content in S. olivacea was 60.00%. Generally, no significant differences were observed in both male and female tissues of S. olivacea regarding its total phenolic content, 2,2-Diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) scavenging, and superoxide dismutase activities. However, significant differences were observed for the total flavonoid content and activity of catalase. The present results revealed the nutritional information and enzymatic and nonenzymatic antioxidant status of the tissues of S. olivacea.     

氨氮对拟穴青蟹的急性毒性及对其血清免疫相关酶活力的影响

采用静水法研究氨氮对拟穴青蟹(Scylla paramamosain)的急性毒性及在氨氮初始浓度分别为0(C0,对照组)、10(C10组)、20(C20组)、30(C30组)、40(C40组)、50 mg/L(C50组),胁迫时间分别为0、6、24、48、72 h的条件下对其血清中碱性磷酸酶(AKP)、酸性磷酸酶(ACP)、溶菌酶(LZM)、超氧化物歧化酶(SOD)和酚氧化酶(PO)活力的影响。结果显示,总氨氮对拟穴青蟹24 h和48 h的半致死浓度分别为104.793、66.124 mg/L,安全浓度为7.90 mg/L,非离子氨对拟穴青蟹24 h和48 h的半致死浓度分别为8.396、5.298 mg/L,安全浓度为0.63 mg/L。在胁迫6、24、48与72 h时,各实验组的LZM活力均显著低于对照组(P0.01)。相较于对照组,C10、C20及C40组在24 h的AKP、ACP活力均显著升高(P0.05)。C20组在24 h的SOD活力则显著低于其他胁迫时间点(P0.05)。胁迫72 h时,C30、C40及C50组的PO活力显著高于对照组(P0.05)。该实验条件下,不高于40 mg/L的氨氮可在24 h内使拟穴青蟹血清中的AKP与ACP活力显著升高,而50 mg/L的氨氮则对其具有抑制作用;各实验组浓度氨氮均在72 h内对拟穴青蟹血清中的LZM活力具有显著的抑制作用,对PO活力具有明显的刺激作用,对SOD活力无显著影响。     

Effects of tank colour on larval survival and development of mud crab Scylla serrata (Forskål)

Hatchery culture of mud crabs has not yet achieved commercial viability despite decades of research efforts. Further research is therefore needed to better understand larval culture requirements of the crab. Based on anecdotal observations, an experiment was carried out to test whether the background colour of the culture vessel affected larval culture success. Newly hatched larvae of Scylla serrata were reared in culture vessels of five colours, i.e., black, dark green, maroon, sky blue and white. Larval survival and development were monitored daily until all of them either moulted to the first crab stage or died. The results showed clear effects of background colour on larval survival. A general tendency of higher larval survival in darker‐coloured backgrounds was evident. In particular, overall zoeal survival for larvae reared in black vessels was significantly higher than those reared in white ones. Background colour also appeared to affect larval development. Larvae reared in darker backgrounds generally had shorter development times and more synchronized moulting. A significant delay in zoeal development was observed in larvae reared in white vessels. Dark backgrounds possibly facilitated more efficient feeding, reduced settlement of larvae at the bottom of the vessels as well as minimized stress. This result appears to be the first to demonstrate that background colour can significantly affect larval survival and development of a crustacean species.     

Chemical constituents in the abdominal muscle of cultured mud crab Scylla serrata in relation to seasonal variation and maturation

ABSTRACT:     Seasonal changes in levels of chemical constituents in the abdominal muscle of male and female mud crab Scylla serrata were investigated. The gonadosomatic index in the female crab was higher in October and August, of which the muscle yield, glycogen, and total amount of adenosine 5'-triphosphate (ATP)-related compounds (ARC) in the October sample were the highest throughout the year, but the total amount of free amino acids (FAA) was the lowest. The total FAA and individual FAA such as glycine, alanine, and arginine increased in the August and November female samples, while that in the male specimens was higher in January, March, and August. The total ARC in both crabs was lower in the samples collected from winter than in other seasons whereas glycinebetaine was higher in winter and early spring. Glutamic acid, glycine, alanine, arginine, glycinebetaine, and adenosine monophosphate might be responsible for the taste of mud crab. Their level together was relatively higher in the August and January male samples, and in the August and November female specimens. However, the correlation between the taste component content and degree of gonad maturation was low.     

拟穴青蟹软壳蟹与硬壳蟹营养品质和风味差异综合比较分析

为明确在最佳收集时间段内不同时间点的软壳蟹和硬壳蟹营养与风味物质的差异,本试验采用顶空固相微萃取(SPME)、气质联用(GS-MS)方法比较了拟穴青蟹硬壳蟹与蜕壳后0~48 h软壳蟹肌肉和肝胰腺2种组织中水分、灰分、氨基酸、矿物质元素、脂肪酸及挥发性物质含量。结果表明,软壳蟹2种组织在蜕壳0 h水分含量最高,硬壳蟹灰分含量显著(P<0.05)高于各时间点软壳蟹。除肝胰腺中胱氨酸和丙氨酸外,2种组织硬壳蟹其他氨基酸含量均高于软壳蟹,其中亮氨酸含量差异显著(P<0.05);在肌肉和肝胰腺组织中,分别有12和14种氨基酸含量均在蜕壳后6 h最高。软壳蟹2种组织Ca、Mg和Fe含量高于硬壳蟹,但差异不显著;蜕壳0 h 软壳蟹肝胰腺组织中Ca含量显著高于其他时间点(P<0.05)。蜕壳后24 h软壳蟹肌肉和0 h肝胰腺组织中∑PUFA均高于其他时间点。2种组织中挥发性物质包括烷烃类、醛类、酮类、醇类、芳香烃类、酯类、酚类和醚类化合物,总体相对含量有差异,但差异不显著。综上比较,拟穴青蟹软壳蟹蜕壳后0~6 h肝胰腺和肌肉比其他时间点更具营养、风味更加,是制取软壳蟹最佳时间。本研究结果为软壳蟹生产、营养和风味评价、市场价值评估提供了一定的参考。     

Diet particle size preference and optimal ration for mud crab, Scylla serrata, larvae fed microbound diets

This paper reports on experiments to determine particle size preference and optimal ration for the various larval stages of the mud crab, Scylla serrata, fed microbound diets (MBD). All experiments used ¹⁴C-labelled rotifers as components of MBD, and ingestion was determined by assessing the ¹⁴C content of S. serrata larvae after feeding on the MBD. Five size ranges of MBD (<150, 150–250, 250–400, 400–600 and 600–800 μm) were used to assess ingestion by Zoea I, Zoea III, Zoea V and Megalopa. All were fed a ration equivalent to twice the equivalent dry weight of live foods provided to each larval stage under standard rearing conditions (standard ration). MBD particle size preference increased with increasing larval development. Highest ingestion rates by Zoea I, Zoea III, Zoea V and Megalopa were found for particle size ranges of <150, 150–250, 250–400 and 400–600 μm, respectively. MBD within these particle size ranges were used in subsequent experiments to assessed optimum rations for each of the four larval stages. Larvae were fed rations based on multiples or fractions of the standard ration (100%): 12.5%, 25%, 50%, 100%, 200% and 300%. There were no significant increases in ingestion, for any of the four larval stages, when ration was increased above 100%. For Zoea I, Zoea III and Zoea V larvae, there was no significant difference in the rate of MBD ingestion when ration was reduced to 50%; however, a 25% ration brought about a significant decrease in ingestion. There was no significant decrease in the rate of ingestion by Megalopa when ration was reduced from 100% to either 50%, 25% or 12.5%. The results suggest that rations currently used for larval rearing of S. serrata may be excessive. Little is currently known of the feeding behaviour and nutritional requirements of S. serrata larvae, and the results of this study are a significant development in this field.     

Formalin as an alternative to trifluralin as prophylaxis against fungal infection in mud crab Scylla serrata (Forsskål) larvae

The toxicity of formalin and trifluralin to the larval stages of the mud crab Scylla serrata was compared in a static bioassay. Prophylactic doses of 5, 10, 15, 20 and 25 μg L⁻¹ formalin and 0.05, 0.1, 0.2, 0.4 and 0.8 μg L⁻¹ trifluralin were used. Toxicity was assessed on the basis of survival of larvae after 24, 48, 72 and 96 h exposure to the test chemicals and metamorphosis to the next larval stage. Result shows that larval survival in all stages was significantly reduced at concentrations of 20 and 25 μg L⁻¹ formalin whereas larvae were able to tolerate all trifluralin treatments. However, larvae became more tolerant to high formalin concentrations as the larval stage progressed. Survival was better at 5, 10 and 15 μg L⁻¹ formalin and in all trifluralin treatments than the control in almost all the larval stages. Faster metamorphosis was observed at 5 and 10 μg L⁻¹ formalin and 0.05, 0.1 and 0.2 μg L⁻¹ trifluralin concentrations. Doses of formalin and trifluralin obtained from the toxicity experiments were applied as prophylaxis to newly hatched larvae in white plastic basins. Prophylactic doses of 5 and 10 μg L⁻¹ formalin and 0.05 and 0.1 μg L⁻¹ trifluralin applied every other day were found to be effective in enhancing survival and larval development to megalopa compared with control. However, no megalopae survived to crab instar in all formalin treatments. Although the use of fungicides in rearing systems resulted in higher survival compared with controls, other strategies (i.e. maintenance of good water quality and hygienic practices in the hatchery) should be further investigated as an alternative to the use of chemicals in hatcheries.     

Reproductive performance and offspring quality in mud crab (Scylla paramamosain) broodstock fed different diets

A 2-month feeding trial was conducted toevaluate the reproductive performance andoffspring quality of mud crab (Scyllaparamamosain) females fed either a mixture offresh food items (squid, shrimp, trash fish andArtemia biomass) or two experimentaldiets developed for penaeids. Before testinitiation, mud crab females with an averageindividual wet weight of 200–300 g wereacclimated for 2–3 days and reared together inone concrete tank of 2.0 × 0.5 × 8 m untilspawning. After spawning, the spent spawnerswere unilaterally eyestalk ablated and randomlydivided (20 animals/treatment) over three tanksof the same size and subjected to the dietarytreatments. Spent spawners were used toeliminate the effect of feeding history.There were only minor differences inreproductive performance between dietarytreatments. No differences were observed in theduration of the latency period from eyestalkablation to spawning. Fecundity was onlymarginally higher for the broodstock fed thecontrol diet. Also egg quality seemed onlyslightly affected by the treatments. Egghatching rates were slightly higher in crabsfed the formulated diets compared to thosecrabs fed the fresh diet. The onlystatistically significant difference (p < 0.05) observed however was in egg hatchingrate between the control diet and diet A2. Incontrast, the crabs fed the fresh diet producedstronger larvae as determined by a starvationtest.We therefore conclude that artificial dietsresulted in reproduction success comparable tothe use of fresh food. The nutritionalcomposition of the artificial diets couldhowever be improved in order to produce larvaeof optimal quality. Based on our researchfindings, the protein level and n-3 HUFA levelin the diet warrants further investigation inthis respect.