不同形态镉在养殖对虾体内蓄积及其毒性的对比研究

研究以南美白对虾Penaeus vannamei为实验对象、富含镉的鱿鱼膏作为有机镉的添加原料、CdCl2作为无机镉的添加剂,对比研究了镉的不同形态——无机镉和有机镉在对虾体内的蓄积规律及其毒性。结果表明,有机镉和无机镉在对虾体内有相似的蓄积规律,主要蓄积于虾头脏中,在对虾各组织中的镉含量与养殖时间及饲料中镉浓度都呈正相关,相同浓度的两种形态的镉在对虾3种组织中的蓄积趋势基本相似。但同时间点,无机镉实验组在对虾的3种组织中的蓄积量要高于同浓度有机镉实验组。有机镉实验组比无机镉实验组的死亡率略高。此实验旨在为我国养殖水产品的安全生产、保护食用者的健康安全提供一定的科学数据。     

絮团浓度对革胡子鲇零换水养殖效果的影响

为研究絮团浓度对革胡子鲇零换水养殖效果的影响,在不额外添加有机碳源（只利用饲料中的碳）的革胡子鲇（）养殖系统中,设置了平均絮团质量浓度为561.18 mg/L和780.41 mg/L两个处理组,比较了两实验组的水质、菌群结构、鱼生长及氮利用效率。结果表明,两种浓度絮团条件下,总氨氮（total ammonia nitrogen,TAN）和亚硝酸氮（NO₂^--N）能分别维持1.84 mg/L和1.79 mg/L以下。两处理组间pH、溶解氧（dissolved oxygen,DO）、TAN、NO₂^--N、氮素利用效率及主要生长指标无显著差异（-N）浓度（822.0 mg/L）明显高于低浓度絮团组（623.33 mg/L）。高通量测序分析菌群结构结果表明,两组间门水平的菌群组成种类及优势度无显著性差异（<0.05）。两处理组中的革胡子鲇存活率分别达到（91.11±1.53）%和（94.44±2.08）%,饲料系数为（1.41±0.18）和（1.27±0.26）,特殊生长率为（2.13±0.04）%/d和（2.19±0.08）%/d,均无显著差异（>0.05）。两实验组饲料氮的利用率分别达到了72.17%和71.34%。综合以上结果认为,仅利用饲料中的碳既能维持革胡子鲇的零换水养殖且能取得较高的氮素利用效率,两种絮团浓度对革胡子鲇的生长无显著影响,高浓度絮团组中的硝化作用更明显。     

不同卤虫混养比例对生物絮凝系统凡纳滨对虾标粗效果的影响

在生物絮凝凡纳滨对虾养殖系统中,分别以100%、50%、0%的比例投喂活的卤虫幼体(Artemia spp)和饲料(分别记为A组,AF组和F组),研究其对养殖过程中氮素转化途径及转化效率的影响。卤虫以湿质量计算,饲料以干质量计算。试验结果显示,A组亚硝酸盐浓度显著低于另外2组(P<0.05);各组氨氮浓度在养殖第7天时达到峰值,此后迅速降低并维持在1 mg/L以下,3组之间差异不显著(P>0.05);3组硝酸盐浓度均无积累,且略有下降;养殖30 d后,A组对虾存活率(35.67%)显著高于其余两组(均低于30%)(P<0.05);A组对虾终末平均体质量为(1.92±0.96)g,显著低于AF组的(2.99±1.85)g和F组的(3.25±1.23)g(P<0.05),原因可能是卤虫的营养成分相比配合饲料较为单一。     

一株高效氨氮及亚硝态氮去除功能菌株的分离鉴定及在生物絮团对虾养殖中的应用

从凡纳滨对虾(Litopenaeus vannamei)养殖水体中分离出具有高效氨氮及亚硝态氮去除功能的菌株Y2,生理生化和16SrRNA基因序列比对分析结果显示该菌株为麦氏交替单胞菌(Alteromonas macleodii)。进一步通过生长实验进行温度、酸碱度、盐度的培养条件优化,利用抗生素药敏实验筛选菌株特定抗性;通过卤虫浸泡感染的方法检测麦氏交替单胞菌Y2的安全性,并测定海水培养液OD_(600)及含氮无机污染物的浓度,探究菌株Y2生长与水体中氨氮、亚硝态氮、硝态氮之间的动态变化关系;通过28d对虾养殖试验,监测水质、生物絮团形成量、致病菌数量及对虾成活率生长速率,进一步阐明菌株在实际养殖中的功效。结果表明,该菌株Y2对苯唑西林、克林霉素有抗性;对卤虫的48 h半致死浓度高于1.9×10~8 cfu/mL,显著高于哈氏弧菌(10~2 cfu/mL)。此外,该菌具有持续去除水体中氨氮、亚硝态氮的功能。在养殖实验中能抑制潜在病原菌弧菌生长、提高对虾存活率及生长率,并且能在水体中稳定存活较长时间。综上所述,菌株Y2是养殖用益生菌制剂的优良备选菌株,可作为生物絮团养殖系统中调节水质的关键菌株。     

生物絮团对仿刺参幼参生长与酶活性的影响

 以仿刺参幼参(Apostichopus japonicus)为研究对象, 采用发酵法培养生物絮团, 在室内塑料水槽中进行为期30 d的幼参培育实验。选择蔗糖作为碳源, 并设置饵料替代(0、10%、15%和20%共计4个梯度)和换水频次 (3 d/次和7 d/次两种)正交实验, 分析其对幼参生长、成活及其体内消化酶、免疫性酶活性和可溶性蛋白含量的影响, 为生物絮团培育幼参技术确定最佳投饵量和换水频次等参数提供依据。结果表明, 实验期间处理组淀粉酶(AMS)活性总体均高于对照组, 生物絮团可以提高幼参淀粉酶活性; 第15天时, 每3 d换水1次并替代15%饵料的处理组幼参体壁中超氧化物歧化酶(SOD, 32.9 U/mg prot)及碱性磷酸酶(AKP, 146.8 U/g prot)活性高于其他3组和对照组(P<0.05); 而每7 d换水1次且替代20%饵料组SOD(35.3 U/mg prot)及AKP酶活性(158.8 U/g prot)均明显高于对照组(P< 0.05)。第30天时, 每7 d换水1次且替代10%饵料组幼参淀粉酶和SOD活性均比15 d有所升高, 尤其AKP活性明显升高; 其特定生长率(4.12 %/d)与成活率(98.9%)均最高。每7 d换水1次且替代15%饵料组体壁中可溶性蛋白含量(10.9 mg/g)最高, 均明显高于对照组(P <0.05); 但与替代10%饵料组(9.3 mg/g)差异不显著。而每3 d换水1次且替代20%饵料组幼参成活率(91.8%)最低, 其可溶性蛋白含量与其他3组和对照组差异不显著(P>0.05)。适当降低换水频次和减少投饵量适于生物絮团系统中幼参的生长、存活与可溶性蛋白质积累。

     

Dietary Lactobacillus plantarum supplementation decreases tissue lead accumulation and alleviates lead toxicity in Nile tilapia (Oreochromis niloticus)

Pollution by the heavy metal lead (Pb) has become a threat to both aquaculture and food safety. In this study, the protective effects of a selected probiotic with good Pb binding capacity (Lactobacillus plantarumCCFM8661) against waterborne Pb exposure were evaluated in Nile tilapia (Oreochromis niloticus). One hundred and eighty fish were divided into four groups as control, Pb‐only, Pb‐plus‐CCFM8661 and CCFM8661‐only. Fish were exposed to a dose of waterborne Pb level at 1 mg L^?1 for 4 weeks, and the probiotic was administered at 10⁸ CFU g^?1 in fish diet twice daily. The results showed that dietary supplementation of CCFM8661 ameliorated the growth performance and prevented the death of Pb‐exposed fish. Cotreatment with Pb and CCFM8661 also effectively decreased Pb accumulation in kidney, liver, gonad, brain, gills and muscle. Moreover, the administration of this probiotic alleviated Pb‐induced oxidative stress, recovered digestive enzyme activities and blood δ‐aminolevulinic acid dehydratase activity, reversed alterations in innate immune status and decreased the frequencies of the nuclear abnormalities in peripheral blood erythrocytes of fish. These results suggested that CCFM8661 may be a novel dietary supplement against Pb toxicity at least in tilapia.     

Effects of bioflocs on dietary protein requirement in juvenile whiteleg Shrimp,Litopenaeus vannamei

A feeding trial was carried out to determine the effects of bioflocs on dietary protein requirement in juvenile whiteleg shrimp, Litopenaeus vannamei. Four bioflocs treatments (BFT) and one control group were managed: BFT fed diets 25% of crude protein (CP) (BFT‐25%), 30% CP (BFT‐30%), 35% CP (BFT‐35%) and 40% CP (BFT‐40%), and clear water control without bioflocs fed with 40% CP (CW‐40%). Triplicate groups of shrimp (initial body weight, 1.3 g) were fed one of the test diets at a ratio of 7% body weight daily for 8 weeks. At the end of the feeding trial, significantly (P < 0.05) higher weight gain and specific growth rate were obtained in shrimp fed BFT‐35% and BFT‐40% compared to BFT‐25% and BFT‐30%. Shrimp fed BFT‐35% exhibited the lowest feed conversion ratio. Significantly higher muscle nucleic acid indices were also recorded such as DNA content in BFT‐30%, RNA content in BFT‐35% and RNA/DNA ratio than that of shrimp fed control. Total protein level in the haemolymph of shrimp fed BFT‐40% was significantly higher than those of shrimp fed BFT‐25% and BFT‐30%. Therefore, the present results demonstrated that, when L. vannamei juveniles were reared in bioflocs‐based tanks, dietary protein level could be reduced from 40% to 35% without any adverse effect on shrimp growth performance, body composition and haemolymph characteristics. [Correction added on 20 May 2015, after first online publication: sentence modified to clarify the reduction in dietary protein level.].     

诺氟沙星在西伯利亚鲟体内蓄积规律及其对组织的病理损伤

为了确定诺氟沙星在鲟养殖中的科学使用方法,对不同剂量、不同给药次数情况下诺氟沙星在西伯利亚鲟(Acipenser baerii)体内蓄积规律及毒性进行了研究。分别以0、30 mg/kg、50 mg/kg、100 mg/kg的剂量对西伯利亚鲟连续口灌诺氟沙星3~5 d,每天1次,并于停药后24 h及240 h采集实验鱼血、肝、肾及软骨组织,对4种组织中药物蓄积量进行测定,并对肝、肾和软骨组织进行切片观察。实验结果表明:随着给药剂量增加、给药次数增多,实验鱼4种组织中诺氟沙星浓度逐渐升高,浓度由高到低依次为为:肾、软骨、肝、血清,且血清中药物浓度远远低于另外3种组织。相同给药剂量、不同给药次数时血清中药物浓度无显著差异;而肝、肾和软骨中均差异显著,停药240 h后,显著性消失。切片结果表明,50 mg/kg剂量连续给药5 d后,实验鲟肝、肾组织开始结构损伤变化,100 mg/kg剂量连续给药3~5 d后,损伤情况持续加重,停药240 h后,肝组织损伤情况有逐渐恢复趋势,而肾组织未见明显恢复趋势;而100 mg/kg连续给药3~5 d后,软骨组织出现软骨膜内层细胞减少;停药240 h后有恢复趋势。研究结果表明,诺氟沙星在鲟中使用剂量应小于50 mg/kg,连续给药次数低于5次,以避免对鲟肝组织造成损伤,引起肾不可逆损伤及影响软骨细胞发育和再生,对软骨组织造成潜在影响。     

一种微生物絮团的生化分析及其对对虾免疫力的影响

利用红糖与尿素为碳氮源在自然海水中培养微生物絮团,获得絮团产物,对该产物离心后进行初步的生化分析表明,絮团产物上清液中微生物胞外产物重均分子量为213281Da。絮团沉淀物中多糖含量占29.6%,氨基酸含量占12.6%。将絮团产物按0、0.02、0.1、0.5、2.5%的比例添加至低蛋白饲料中投喂凡纳滨对虾 (Litopenaeus vannamei),14d后分别测定实验对虾血清溶菌活力、抗菌活力和酚氧化酶活力,结果显示在饲料中添加微生物絮团浓度为2.5%的对虾血清中抗菌与溶菌活力最高(P<0.05),添加微生物絮团浓度为0.5%与2.5%的对虾血清中酚氧化酶活力较低蛋白饵料对照组显著提高(P<0.05)。用哈维氏弧菌(Vibrio harveyi)感染实验对虾后,结果显示饵料中添加0.1%微生物絮团产物组对虾的死亡率最低。综合分析认为对虾摄食微生物絮团后,能够显著提高对虾的非特异免疫力,抗微生物感染的能力得到增强。     

Carbon supplementation and microbial management to stimulate artemia biomass production in hypersaline culture conditions

Two Artemia culture experiments were conducted in a zero water exchange system at salinity 80 g L^?1. In Experiment I, different carbon sources including molasses, glucose, sucrose and corn flour were given to supplement suboptimal feeding with the microalgae Dunaliella viridis, whereas the control was fed only D. viridis. In Experiment II, molasses was supplemented to the culture medium, as well as the bacteria Alkalibacterium sp. or the archaea Halobacterium sp., isolated from the brine in the local saltponds. The control groups were fed only with D. viridis or with D. viridis and molasses. Our study shows that in laboratory culture biofloc development can be stimulated under hypersaline conditions. Supplementation of carbon sources, bacteria and archaea benefited biofloc development, water quality in terms of nitrogen load and enhanced Artemia production. Denaturing gradient gel electrophoresis analysis on the bioflocs also indicates an increased biodiversity and richness of the microbial community in the culture medium. These results need to be confirmed for large scale Artemia pond production, in which case, we recommend molasses as carbon source.     

Effect of bioflocs on growth and immune activity of Pacific white shrimp,Litopenaeus vannamei postlarvae

The bioflocs technology (BFT) for shrimp production has been proposed as a sustainable practice capable of reducing environmental impacts and preventing pathogen introduction. The microbial community associated with BFT not only detoxifies nutrients, but also can improve feed utilization and animal growth. Biofloc system contains abundant number of bacteria of which cell wall consists of various components such as bacterial lipopolysaccharide, peptidoglycan and β‐1, 3‐glucans, and is known as stimulating nonspecific immune activity of shrimp. Bioflocs, therefore, are assumed to enhance shrimp immunity because they consume the bioflocs as additional food source. Although there are benefits for having an in situ microbial community in BFT systems, better understanding on these microorganisms, in particular molecular level, is needed. A fourteen‐day culture trial was conducted with postlarvae of Litopenaeus vannamei in the presence and absence of bioflocs. To determine mRNA expression levels of shrimp, we selected six genes (prophenoloxidase1, prophenoloxidase2, prophenoloxidase activation enzyme, serine proteinase1, masquerade‐like proteinase, and ras‐related nuclear protein) which are involved in a series of responses known as the prophenoloxidase (proPO) cascade, one of the major innate immune responses in crustaceans. Significant differences in shrimp survival and final body weights were found between the clear water and in the biofloc treatments. mRNA expression levels were significantly higher in the biofloc treatment than the clear water control. These results suggest that the presence of bioflocs in the culture medium gives positive effect on growth and immune‐related genes expression in L.vannamei postlarvae.     

溴氰菊酯对日本对虾的急性毒性及积累试验研究

采用半静态换水补药的方法,开展溴氰菊酯对日本对虾的急性毒性及积累试验,并且记录下不同溴氰菊酯浓度下日本对虾的中毒症状。通过试验获得溴氰菊酯对日本对虾24h、48h、72h和96h的半致死浓度(LC50)值分别为0.00090mg/L、0.00050mg/L、0.00019mg/L、0.00012mg/L,96h安全质量浓度为0.046μg/L。通过药物积累试验表明在试验期间内,水体中溴氰菊酯浓度与受试生物体内溴氰菊酯的积累量成负相关。     

Effect of low salinity on microbial floc composition and performance of Litopenaeus vannamei (Boone) juveniles reared in a zero‐water‐exchange super‐intensive system

This study aimed to evaluate the effect of low salinity on the water quality, microbial flocs composition and performance of Litopenaeus vannamei juveniles reared over 40 days in a zero‐water‐exchange super‐intensive system at 0, 2, 4 and 25 g L^?1. At 0 g L^?1, the mortality was total at the 26th day, and consequently, these salinity data were not included in the statistical analysis. Among the water quality parameters, only pH and the total suspended solids concentration were significantly influenced by salinity. However, a trend towards intensification of the nitrification processes was observed as the salinity increased, with the lowest ammonia and the highest nitrite and nitrate concentrations found at 25 g L^?1. The concentrations of ciliates and flagellates diminished and increased, respectively, with the increase in salinity. Diatoms predominated at 25 g L^?1, whereas at 2 and 4 g L^?1, chlorophytes were more abundant. Microbial floc crude protein content was reduced with the increase in salinity, whereas ash content demonstrated the inverse trend. The best overall growth performance and survival were observed at 25 g L^?1. However, satisfactory productivity was also found at 4 g L^?1, suggesting the viability of rearing L. vannamei at low salinity under zero‐water‐exchange conditions.     

Effects of bioflocs on water quality,and survival,growth and digestive enzyme activities of Litopenaeus vannamei (Boone) in zero‐water exchange culture tanks

A 30‐day experiment was performed to investigate the effects of bioflocs on water quality, and survival, growth and digestive enzyme activities of the white shrimp Litopenaeus vannamei. Altogether 28 shrimp (7.4 ± 0.1 g) were stocked in each 150 L tank. Two bioflocs treatments and one control were managed: ‘bioflocs 1’ and ‘bioflocs 2’ based on two different densities of the bioflocs, and clean water control without the bioflocs. Brown sugar was added to the bioflocs 1 and bioflocs 2 treatment tanks accounting for 28% and 80% of the shrimp feed respectively (corresponding to proximate C/N ratios of 10 and 14 in daily additions of organic matter respectively), so as to promote bioflocs production and approximately 14 mL L^?1 in treatment bioflocs 1 and 20 mL L^?1 in treatment bioflocs 2 were maintained from day 15. Monitoring of selected water quality parameters throughout the whole experiment period showed that all parameters remained within recommended levels for shrimp culture in the bioflocs treatments at zero‐water exchange, especially low total ammonia nitrogen and nitrite nitrogen levels. By the end of the experiment, shrimp survival rates were above 86%, with no significant differences (P > 0.05) among the three groups. Both weight gain rate and special growth rate tended to increase in the bioflocs treatments compared to those in the control. Meanwhile, the overall specific activities of protease, amylase, cellulase and lipase of the shrimp in the bioflocs treatments were all higher than those in the control; and for the specific activity of the same digestive enzyme, the differences between the bioflocs treatments and the control performed inconsistently among different organs: hepatopancreas, stomach and intestine. Present results suggest that the bioflocs can not only maintain favourable water quality conditions for shrimp culture and help shrimp grow well in zero‐water exchange culture systems, but may also have a positive effect on digestive enzyme activities of the shrimp.     

Toxicity of chlorine to different sizes of black tiger shrimp (Penaeus monodon) in low-salinity shrimp pond water

An experiment was conducted, in a dark room with controlled temperature (27.3–28.4 °C), to determine the acute toxicity of chlorine concentration to black tiger shrimp (Penaeus monodon fabicus) of sizes 0.02 g, 2.75 g, 8.47 g and 23.65 g. Toxicity tests on each of these shrimp sizes were run in triplicate in glass jars under static conditions without media renewal. The concentration of active chlorine that killed 50% of the shrimp of each size after 24‐h exposure (LC₅₀‐24 h) was used as an indicator of acute toxicity. Chlorine concentrations applied in the shrimp toxicity test ranged from 2.0 to 14.5 mg L^?1 in shrimp pond water. As the test water contained total suspended solids of 22.0–85.0 mg L^?1 and total ammonia nitrogen of 0.18–0.40 mg L^?1, the resultant concentrations of combined residual chlorine ranged from 0.6 to 3.5 mg L^?1, which were the effective doses causing shrimp mortality. The test results showed that 24‐h LC₅₀ for average shrimp size at 0.02, 2.75, 8.47 and 23.65 g occurred in water containing combined residual chlorine at a concentration of 0.91, 1.39, 1.74 and 1.98 mg L^?1, for which the original application doses were 6.96, 2.05 11.50 and 13.34 mg L^?1 respectively.     

Dietary habits of grazers influence their suitability as biological controls of fouling macroalgae in ex situ mariculture

The dietary habits of the sea urchin Salmacis sphaeroides and the gastropod Trochus maculatus in ex situ mariculture were examined. Fouling algal assemblages on terracotta tiles were exposed to the grazers and compared. Except for Day 0, the assemblages on Days 2, 13 and 27 differed significantly across treatments. S. sphaeroides rapidly consumed most algae, leaving an assemblage dominated by turf algae and bare tile. T. maculatus primarily fed on green filamentous algae, resulting in an even distribution of other algal functional groups, while control tiles were dominated by green filamentous algae. Using three representative fouling algae species (Bryopsis corymbosa, Hypnea spinella and Lobophora variegata), the consumption rates of both grazers and dietary preferences of S. sphaeroides were examined through a single‐diet and a choice experiment respectively. The single‐diet experiment revealed differential algal consumption rates for S. sphaeroides (H. spinella = B. corymbosa > L. variegata) and T. maculatus (B. corymbosa > H. spinella = L. variegata). The choice experiment showed that S. sphaeroides preferred H. spinella over the other two species. These experiments highlighted the importance of understanding the dietary habits of grazers as this has direct implications on their effectiveness as biological controls of fouling macroalgae in mariculture.     

Zootechnical and physiological responses of whiteleg shrimp (Litopenaeus vannamei) postlarvae reared in bioflocs and subjected to stress conditions during nursery phase

The objective of this study was to assess zootechnical and physiological performance of Litopenaeus vannamei postlarvae (PL) reared in three environments (CW, clear water; B, biofloc; BS, biofloc with artificial substrates) at three stocking densities (300, 600, 900 PL/m³) for 8 weeks. At the end of experimentation, shrimp were subjected to hypoxia, and physiological response was again assessed. During rearing, low levels of total ammonia nitrogen, nitrite (NO₂^?) and nitrate (NO₃^?) were observed in B and BS for 600 and 900 PL/m³. For 300 PL/m³, a slight accumulation of NO₂^? and NO₃^? was detected. For the same stocking density, shrimp reared in B and BS showed significantly higher weights than those grown in CW, except for final weight. No significant differences were observed in survival. The use of biofloc and artificial substrates permitted doubling density from 300 to 600 PL/m³ without affecting growth, survival, feed conversion rate and obtaining twice the biomass. Shrimp grown in B and BS stored a surplus of glycogen and carbohydrates in their hepatopancreas, which probably gave them a better physiological capacity to counteract high‐stocking densities and hypoxia. A tendency of a higher adenylate energetic charge was observed in shrimp maintained in B and BS.     

珠江口海域双胞旋沟藻赤潮对卤虫幼体、鱼苗和虾苗的急性毒性

为研究2009年10月下旬在广东珠海海域爆发的双胞旋沟藻赤潮对养殖鱼类及水体中其它生物的影响,实验以卤虫幼体、金鼓鱼苗和凡纳滨对虾苗作为受试生物,在赤潮现场测试双胞旋沟藻对卤虫幼体、鱼苗和虾苗的急性毒性效应。结果显示,24 h双胞旋沟藻对卤虫幼体的LC₅₀(半致死浓度)为9.55×10⁴/mL,藻密度为2.5×10³/mL的双胞旋沟藻对卤虫幼体的LT₅₀(半致死时间)为48.5 h。60 h内该赤潮水体对鱼苗和虾苗的存活无不利影响,卤虫幼体和金鼓鱼苗均可摄食双胞旋沟藻,卤虫幼体对双胞旋沟藻的摄食率低。研究表明,双胞旋沟藻赤潮水体对卤虫幼体有一定的毒性作用,但在低藻密度条件下,卤虫幼体能以该藻为食并维持其生命,双胞旋沟藻对金鼓鱼苗和凡纳滨对虾苗无急性毒性作用。     

Inhibiting fungus on largemouth bass eggs with copper sulfate and its toxicity to fry and juveniles

This study determined the effectiveness of copper sulfate (CuSO₄) to inhibit fungal growth (caused by Saprolegnia spp.) on largemouth bass (LMB) eggs spawned on/in fiber mats in very high-alkalinity/-hardness waters; experiments also determined the toxicity of CuSO₄ to LMB fry and juveniles. An untreated control and three CuSO₄ concentrations (10, 20, and 40 mg/L) were tested under a flow-through scenario in the effectiveness experiment. Eggs were treated daily until hatching began. Fungal load at the time of hatch had a total area > 3.0 cm² in the untreated controls, total area 1.0 to <2.0 cm² in the 10 and 20 mg/L CuSO₄ treatments, and total area > 1.0 cm² in the 40 mg/L CuSO₄ treatments. Fungus samples were identified as Saprolegnia australis. The 24-hr median lethal concentration (LC50) values on the LMB yolk-sac and swim-up fry were 32.0 and 4.6 mg/L CuSO₄, respectively; the No Observed Effect Concentrations (NOEC) were 16.0 and 0.125 mg/L CuSO₄, respectively. Juvenile LMB were extremely tolerant to CuSO₄, and their 24-hr LC50 value was 185.5 mg/L; the NOEC was 64 mg/L. This study indicates that CuSO₄ can be an important resource for hatcheries to control egg fungus, especially in high-alkalinity/-hardness waters.     

Analysis of the relationship between luminescence and toxicity of <Emphasis Type="Italic">Vibrio carchariae</Emphasis> pathogenic to shrimp

ABSTRACT:   Aquaculture deterioration is caused by Vibrio harveyi , which is one of the main shrimp pathogens. Vibrio carchariae having the same phenotypic characteristics as V. harveyi was isolated from a shrimp farm and used in this study to investigate the relationship between luminescence and toxicity. Luminescence was verified by monitoring the expression of the LuxR gene. It was found that the relationship between the expression of LuxR and toxicity was the most significant factor related to luminescence. Results showed that LuxR expression was highest after 20 h of culture, which is comparable to the highest scintillation counter luminescence value (20 h). However, toxin levels in the culture broth were highest between 24 h-36 h of culture. Significant decrease in the toxicity level was observed after 36 h. It was also found that there was a decrease in toxicity level after 12 h of incubation at room temperature of the V. carchariae culture supernatant. The effect of the addition of cell-free culture supernatant on the luminescence of V. carchariae was also determined. Results showed that the addition of cell-free supernatant from 24 h-old culture was most effective in inducing and maintaining luminescence.