菊黄东方鲀发育早期的脂肪酸组成变化

采用生化分析手段对菊黄东方鲀的未受精卵、胚胎(出膜前,受精后80~85 h)、初孵仔鱼(0日龄)、开口前仔鱼(3日龄)的脂肪酸组成和含量进行了检测和分析。结果显示,菊黄东方鲀卵和鱼苗的水分含量随着个体发育出现升高趋势,而鱼苗总脂含量随着个体发育显著下降。各发育阶段的干样中检出8种饱和脂肪酸(SFA)、7种单不饱和脂肪酸(MUFA)和12种多不饱和脂肪酸(PUFA)。菊黄东方鲀未受精卵脂肪酸组成与其亲本卵巢非常相似;胚胎期的脂肪酸利用率高低顺序为SFA(15.08%)、MUFA(14.46%)、n6PUFA(10.20%)和n3PUFA(0.19%),以C16:0、C16:1、C18:1n9c和C18:2n6c为主要能量来源,n3PUFA被优先保存,特别是DHA得到完全保留;孵化后,在内源性营养阶段,仔鱼对n3PUFA利用迅速上升,仔鱼开口前的脂肪酸利用率高低顺序与胚胎期正好相反:n3PUFA(19.60%)、n6PUFA(16.98%)、SFA(13.50%)和MUFA(13.01%),以C18:2n6c、C22:5n3(DPA)、C20:5n3(EPA)、C22:6n3(DHA)、C18:1n9c和C16:0为主要能量来源,其中仔鱼对DHA实际利用量为最高(14.44 mg/g),仔鱼在开口前期n3PUFA(特别是DHA)被大量利用消耗。研究表明,菊黄东方鲀仔鱼发育需要消耗大量的n3PUFA(特别是DHA和EPA),并建议在菊黄东方鲀苗种培育开口阶段及时增加富含EPA和DHA饵料的投喂量,如海水的轮虫、藻类强化过的卤虫幼体,缓解苗种开口阶段成活率低下的问题。     

延迟投饵对杂交鲟仔鱼生长、存活和体成分的影响

以杂交鲟(Huso huso ×Acipenser baeri )仔鱼为研究对象,将其分为 8个处理组,每组100尾(各设2个平行组),分别在孵化后6 d(对照组)、8 d、10 d、12 d、14 d、16 d和18 d开始投喂冰冻卤虫和碎水蚯蚓(以质量比1:1混合),5 d后只投喂碎水蚯蚓。第8组为饥饿组,从不投饵。水温17 ℃,实验周期30 d。结果显示,仔鱼于孵出后8日龄进入混合营养期;10日龄左右是仔鱼开始加速生长的关键时期;12日龄仔鱼进入外源性营养期。随起始投饵时间的延迟,仔鱼的全长、湿重、干重和粗蛋白含量下降,鱼体水分含量则随之升高。但对照组、8日龄及10日龄起始投喂组之间的鱼体水分、粗蛋白、粗脂肪含量并没有显著差异(P>0.05),14日龄及其以后各起始投喂组仔鱼的生长和鱼体生化成分则与上述各组存在显著差异(P相似文献   

Effect of in vitro exposure to Vibrio vulnificus on hydroelectrolytic transport and structural changes of sea bream (Sparus aurata L.) intestine

The everted gut sac technique has been used to investigate the effect of Vibrio vulnificus on water and electrolyte (Na⁺, K⁺, Cl⁻, HCO₃ ⁻) transport on the intestine of sea bream (Sparus aurata L.). Both the anterior and the posterior intestine were incubated in a medium containing 10⁸ V. vulnificus cells ml⁻¹ at 25°C for 2 h. The presence of V. vulnificus resulted in a significant reduction (P < 0.05) of water absorption in the anterior intestine, while sodium absorption in the anterior (P < 0.01) and posterior (P < 0.05) intestine was elevated. Chloride absorption was increased, but the changed was not significant, while potassium absorption decreased significantly (P < 0.05), but only in the posterior intestine. Incubation the sea bream intestine with V. vulnificus did not affect carbonate secretion in the anterior segment, whereas high secretion was stimulated in the posterior segment (P < 0.01). Histological evaluations demonstrated damage in the anterior intestine of sea bream that was characterized by the detachment of degenerative enterocytes, alterations in the microvilli, and the presence of a heterogenous cell population, indicating inflammation. Based on our results, we conclude that V. vulnificus caused cell damage to the intestine of sea bream and that the anterior intestine is more susceptible than the posterior part of the intestine. Several hypotheses are suggested to explain our observations, such as the presence of higher numbers of villosities in the anterior intestine than in the posterior one and/or the presence of endogenous bacteria in the posterior intestine which may have a protector role.     

Two pathogens of Greenshell™ mussel larvae, Perna canaliculus: Vibrio splendidus and a V. coralliilyticus/neptunius-like isolate

Bacterial pathogens of Greenshell™ mussel (GSM) larvae can cause batch losses during hatchery production. Twenty-two isolates were screened using a larval bioassay. Two strains were identified as potential pathogens. Phenotypic identification of these strains revealed two non-reactive Gram-negative, oxidase positive rods. Sequencing of the 16S rRNA gene identified Vibrio splendidus and a V. coralliilyticus/neptunius -like isolate as pathogens of GSM larvae, with an ability to cause 83% and 75% larval mortality in vitro , respectively, at a concentration of 10² CFU mL⁻¹. Histopathology indicated that the route of infection was via the digestive system. Using healthy larvae as target hosts, Koch's postulates were confirmed for the two isolates. This is the first report on pathogens of GSM larvae.     

A method to determine protein digestibility of microdiets for larval and early juvenile fish

A method to evaluate protein quality using in vivo methods was developed for larval fish. FluoSpheres^® fluorescent microspheres (10 μm) were incorporated into two test diets, our standard zein microdiet (ZMD) and a microdiet with identical ingredients except for the replacement of high quality fish meal with the same product cooked for 24 h at 80 °C (ZMD-CF). Several trials were performed to design a reliable method to test digestibility using FluoSpheres^® as a marker. The developed in vivo technique was tested on 35 days posthatch (dph) larval Atlantic cod ( Gadus morhua L.) and two tropical fish species in the early juvenile stage. The method took into account loss of total protein to the faecal pellet and water column. Apparent digestibility of protein in larval cod fed ZMD was significantly higher than that of larvae fed ZMD-CF ( P  < 0.05). A growth study to validate differences between the two diets showed significant differences in growth and survival of larvae fed ZMD versus ZMD-CF ( P  < 0.05). Further validation of our results was indicated through the use of a pH-stat method using enzymes extracted from 35 dph larval cod guts. This novel technique will be advantageous for researchers to evaluate feed ingredients for larval marine fish and is adaptable to many different areas of larval fish nutrition.     

Immunostimulatory effects of dietary poly‐β‐hydroxybutyrate in European sea bass postlarvae

The stable production of high‐quality fry in marine aquaculture is still hampered by unpredictable mortality caused by infectious diseases during larval rearing. Consequently, the development of new biocontrol agents is crucial for a viable aquaculture industry. The bacterial energy storage compound poly‐β‐hydroxybutyrate (PHB) has been shown to exhibit beneficial properties on aquatic organisms such as enhanced survival, growth, disease resistance and a controlling effect on the gastrointestinal microbiota. However, the effect of PHB on the developing immune system of fish larvae has so far not been investigated. In this study, the effect of feeding PHB‐enriched Artemia nauplii on survival, growth and immune response in European sea bass (Dicentrarchus labrax) postlarvae was examined. Amorphous PHB was administered to 28‐day‐old sea bass postlarvae over a period of 10 days. The survival and growth performance were monitored, and the expression of 29 genes involved in immunity, growth, metabolism and stress‐response was measured. While the expression of the insulin‐like growth factor 1 (igf1), an indicator of relative growth, was upregulated in response to feeding PHB, the larval survival and growth performance remained unaffected. After 10 days of PHB treatment, the expression of the antimicrobial peptides dicentracin (dic) and hepcidin (hep) as well as mhc class IIa and mhc class IIb was elevated in the PHB fed postlarvae. This indicates that PHB is capable of stimulating the immune system of fish early life stages, which may be the cause of the increased resistance to diseases and robustness observed in previous studies.     

五种重金属对早繁鮸鱼胚胎和仔鱼的毒性效应

在水温27.5℃、盐度29条件下,研究了Cu2+、Cd2+、Zn2+、Cr6+和Pb2+5种重金属对早繁鮸鱼胚胎发育和初孵仔鱼的影响。结果表明:重金属在胚胎发育过程中引起各种畸形,如胚胎尾巴弯曲、初孵仔鱼不能出膜、胚胎死亡等;胚胎和初孵仔鱼上出现黑色颗粒,初孵仔鱼脊柱弯曲成L、V、S形或尾部没有展开呈逗号状,褶皱边缘被破坏等畸形。Cu2+、Cd2+、Zn2+、Cr6+和Pb2+5种重金属均延迟胚胎发育速率。综合孵化率、胚胎畸形和仔鱼畸形率等指标得出5种重金属对胚胎的毒性大小依次为Cu2+>Cd2+>Zn2+>Pb2+>Cr6+。计算了5种重金属对早繁鮸鱼初孵仔鱼的LC50和安全浓度,得出5种重金属对早繁鮸鱼初孵仔鱼毒性大小顺序为:Cu2+>Cd2+>Pb2+>Zn2+>Cr6+。     

Improved performance of gilthead sea bream, Sparus aurata, larvae after ozone disinfection of the eggs

Ozone (O₃) dissolved in seawater (ODS) was evaluated, as an egg disinfectant, on the spawn of captive gilthead sea bream, Sparus aurata, brood stock. Four contact times (CT) were tested (0.6, 1.2, 2.4 and 4.8 mg min L⁻¹) where CT was calculated by multiplying the dissolved O₃ concentration (0.3 mg L⁻¹) by different exposure periods (2, 4, 8, 16 min). There was also a disinfected seawater treatment that contained no O₃ or derived compounds (CT 0) and an untreated seawater control. All ODS treatments reduced egg surface bacterial counts to zero, which was significantly (P<0.05) lower than the CT 0 and the control groups (194 and 1320 plate⁻¹ respectively). Nevertheless, the hatching rate was high in the control and the CT treatments 0, 0.6 and 1.2 (88.7%, 87.3%, 89.5% and 83.7% respectively) while eggs exposed to a CT 2.4 and 4.8 hatched poorly (36.5% and 20.4% respectively), which was likely due, at least in part, to larvae unable to break the egg chorion successfully. Swim‐bladder inflation was significantly higher in the ODS groups (>97%) compared with the control and CT 0 treatments (ca. 70%). The results suggest that a 2‐min exposure of eggs to 0.3 mg O₃ L⁻¹ of ODS (CT 0.6) would improve current protocols in marine larviculture.