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.     

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.     

低温驯化下锯缘青蟹肝胰腺的抗氧化效应及ATPase活性变化

采用生物化学方法对低温驯化的锯缘青蟹（Scylla serrata）肝胰腺中抗氧化酶（SOD、CAT和GPX）活性和脂类过氧化产物MDA含量以及Na^＋-K^＋ -ATPase、Mg^2＋ -ATPase、Ca^2＋ -ATPase和Ca^2＋ -Mg^2＋ -ATPase活性进行测定。结果显示，锯缘青蟹肝胰腺中抗氧化酶（SOD、CAT和GPX）活性随驯化温度的降低而降低；而MDA含量则是随驯化温度的降低而升高，其变化正好与抗氧化酶活性相反。Na^2＋ -K^＋ -ATPase、Mg^2＋ -ATPase和Ca^2＋ -Mg^2＋ -ATPase活性均是随驯化温度的降低而升高；而Ca^2＋ -ATPase活性没有表现出这一明显变化趋势，但低温驯化下仍然是酶活性升高。锯缘青蟹低温驯化下抗氧化酶活性降低表明其清除活性氧能力下降，从而导致MDA在肝胰腺中积累。ATPase活性低温驯化下升高，说明其表现出明显的温度补偿效应（低温使酶活性下降，同时又诱导酶合成增加，从而使酶浓度增加，其总的酶活性仍能维持机体正常的生理功能），但各种ATPase活性的温度补偿存在差异。     

锯缘青蟹苗种培育的科技进展

锯缘青蟹是我国南方沿海各省传统养殖的海水蟹类,在当前农业产业结构调整中被列为主要发展品种之一。鉴于苗种是限制青蟹养殖业发展的主要因素,本文根据目前的研究现状对青蟹的种质、性成熟机制,产卵、孵化条件,幼体培育过程中营养条件、盐度、温度、光照、疾病等,以及从大眼幼体到仔蟹的中间培育技术等作了简要归纳,并对研究现状和进入产业化急需解决的问题进行了探讨。     

锯缘青蟹蜕皮抑制激素cDNA的分子克隆及其表达分析

根据近缘种类同源序列设计简并引物,采用逆转录聚合酶链式反应(RT—PCR)技术,首次扩增获得锯缘青蟹(Scylla serrata)眼柄组织中编码蜕皮抑制激素(MIH)成熟肽全长cDNA序列及部分信号肽序列。将该序列克隆到pUCm—T载体上进行序列测定。结果表明,编码锯缘青蟹MIH成熟肽的cDNA由234个碱基组成,由此推测MIH成熟肽含78个氨基酸残基。该序列不仅与其它短尾类甲壳动物的MIH氨基酸序列具有高度的同源性(79％～9l％),还与该激素同一家族的性腺抑制激素、大颚器抑制激素的氨基酸序列具有较高的相似性。RNA斑点杂交结果显示,MIH基因在眼柄神经节及脑组织中均有表达,而在肌肉、中肠腺中不表达。     

温度对锯缘青蟹幼体存活与发育的影响

锯缘青蟹溞状幼体生长发育的适温范围为25—30℃。在该范围内,随着幼体发育,其生存最适温度逐渐上升。各期溞状幼体的发育均随温度的提高而加快,从孵化至第一次变态,30℃时平均发育时间比 25℃时短 6天。温度对溞状幼体的变态过程亦有明显影响,水温大于或达到 30℃时不利于变态的进行,但变态后的大眼幼体对高温适应力增强,35℃时仍可正常生长发育。不同批孵化的幼体在相同温度下存活与发育有明显差异。在对后期溞状幼体相对不适的 25℃下,溞状幼体发育期数变异的出现率较高。     

一株锯缘青蟹呼肠孤病毒的分离纯化及鉴定

在研究锯缘青蟹病害的过程中,从广东某养殖场分离到一株呼肠孤病毒(命名为SsRV)。病毒粒子为球状,直径约45 nm。病毒粒子基因组为12个节段的双链RNA;在1%琼脂糖电泳中SsRV基因组呈1/5/6带型,其分子量分别为3.8,2.5,2.4,2.0,1.9,1.8,1.3,1.2,1.1,1.1,1.0,1.0 kbp。根据病毒的宿主范围、基因组节段数及电泳型,此病毒很可能与地中海滨蟹呼肠孤病毒P和W 2共同构成呼肠孤病毒科一个新的属。     

锯缘青蟹常见病害及其防治技术

综合报道了由细菌、真菌、寄生虫和环境变化引起的锯缘青蟹常见病害及防治措施,由细菌引起的病害有弧菌病、丝状细菌病、甲壳溃疡病和黑鳃病;由真菌引起的病害有霉菌病,由寄生虫引起的病害有蟹奴病、纤毛虫病、藤壶病、甲壳溃疡病和黑鳃病;由真菌引起的病害有霉菌病;由寄生虫引起的病害有蟹奴病、纤毛虫病、藤壶病、由环境变化引起的病害有白芒病、黄斑病、水肿病和蜕壳不遂症。     

Optimal first feed organism for South African mud crab <Emphasis Type="Italic">Scylla serrata</Emphasis> (Forskål) larvae

It is not known whether rotifers or Artemia nauplii are the best first food for South African mud crab Scylla serrata larvae. In order to test this, larvae were fed with five different test diets. These were rotifers for the first 8 days and newly hatched EG^® type Artemia nauplii (San Francisco Bay) from day 6 onwards (treatment R6A); newly hatched EG^® type Artemia nauplii throughout the rearing period (treatment EG); newly hatched Vinh-Chau strain (Vietnam) Artemia nauplii throughout the rearing period (treatment VC); decapsulated cysts of EG^® type Artemia throughout the rearing period (treatment DECAP); or decapsulated cysts supplemented with low densities of Artemia EG type Artemia nauplii (treatment MIX). Two experiments were conducted approximately 1 month apart using larvae from two different female crabs. Although results showed it is possible to rear S. serrata larvae through metamorphosis on Artemia nauplii exclusively, larval performance (development, survival and successful metamorphosis) was enhanced by the inclusion of rotifers as a first feed.No significant difference in performance was recorded between larvae fed on the two strains of Artemia nauplii. Larvae fed on decapsulated cysts in treatments DECAP and MIX performed poorly, but there were indications that decapsulated cysts and other inert diets may have potential as supplements to live food in the rearing of S. serrata larvae.     

Extension of nursery culture of Scylla serrata (Forsskål) juveniles in net cages and ponds

To address the preference of mud crab farmers for larger size Scylla serrata juveniles (5.0–10 g body weight or BW; 3.0–5.0 cm internal carapace width or ICW), a study was conducted to compare the growth and survival of crab juveniles (2.0–5.0 g BW; 1.0–3.0 cm ICW) produced a month after stocking of megalopae in net cages when reared further in net cages installed in earthen ponds or when stocked directly in earthen ponds. In a 3 × 2 factorial experiment, three stocking densities (1, 3 and 5 ind m⁻²), two types of rearing units (net cages or earthen pond) were used. Megalopae were grown to juvenile stage for 30 days in net cages set inside a 4000 m² brackishwater pond and fed brown mussel (Modiolus metcalfei). Crab juveniles were then transferred to either net cages (mesh size of 1.0 mm) or earthen ponds at three stocking densities. After 1 month, no interaction between stocking density and rearing unit was detected so data were pooled for each stocking density and rearing unit. There were no significant differences in the growth or survival rate of crab juveniles across stocking density treatments. Regardless of stocking density, survival in net cages was higher (77.11±6.62%) than in ponds (40.41±3.59%). Growth, however, was significantly higher for crab juveniles reared in earthen ponds. The range of mean BW of 10.5–16.0 g and an ICW of 3.78–4.33 cm obtained are within the size range preferred by mud crab operators for stocking grow‐out ponds.