Utilization of different raw and pre-gelatinized starch sources by juvenile yellowfin seabream Sparus latus

Raw corn starch (RCS), raw tapioca starch (RTS), raw potato starch (RPS), pre‐gelatinized corn starch (PCS), pre‐gelatinized tapioca starch (PTS) and pre‐gelatinized potato starch (PPS) were evaluated as starch sources in diets for yellowfin seabream Sparus latus in a 56‐day growth trial. Seven isonitrogenous semi‐purified diets comprising a non‐starch cellulose control diet and the six different starch sources holding 200 g kg⁻¹ starch each were prepared and fed to triplicate groups of juvenile yellowfin seabream S. latus. Fish were fed for 8 weeks. Weight gain (WG) and specific growth rate (SGR) for fish fed RCS, RTS and RPS diets were equal, as well as for fish fed PCS, PTS and PPS diets, but values in groups fed the raw starch sources were significantly higher compared with fish fed the pre‐gelatinized starches. Feed efficiency and protein efficiency ratio in fish fed different starch source diets showed no significant differences but were significantly higher than those fed a non‐starch control diet. Protein productive value was improved by starch incorporation to diets. PCS, PTS or PPS groups showed lower feed intake compared with RCS, RTS or RPS groups, and the differences were significant between PCS, PPS and RCS, RPS groups. Whole‐body protein and ash contents and muscle compositions were not affected by different starch sources. Whole‐body and liver lipid contents, liver moisture and glycogen contents were significantly affected by starch source. Values of hepatosomatic index, intraperitoneal fat ratio, viscerosomatic index and condition factor did not vary between experimental treatments. Plasma total protein concentration for RCS, RTS or RPS fed fish was significantly higher than that for PCS, PTS or PPS fed fish, but significantly lower than that for non‐starch fed fish. Plasma cholesterol and triacylglycerol concentrations were unaffected by starch source, but were significantly higher in fish fed the non‐starch control diets. Plasma glucose concentrations in all dietary groups were relatively stable. In conclusion, raw corn, tapioca and potato starches at a 200 g kg⁻¹ inclusion level were well utilized as energy sources by yellowfin seabream, which was evidenced by better WG and SGR. Pre‐gelatinization of the starches had no positive effect on starch utilization.     

维生素C对半滑舌鳎亲鱼繁殖性能及后代质量的影响

本试验旨在研究维生素C对半滑舌鳎亲鱼繁殖性能及后代质量的影响.在基础饲料中分别添加0.5％(C0.5组)、1.0％(C1.0组)和1.5％(C1.5组)的L-抗坏血酸-2-磷酸酯(作为维生素C添加剂),制成维生素C添加量分别为0.175％、0.350％和0.525％的3种试验饲料.每种试验饲料饲喂3.5龄滑舌鳎雌性亲鱼15尾[(1.15±0.11) kg/尾]和雄性亲鱼20尾[(0.25±0.05) kg/尾],饲喂2个月后人工育苗.结果表明:添加维生素C对半滑舌鳎雌性亲鱼的性腺指数和相对产卵量以及雄性亲鱼的精液浓度没有显著影响(P＞0.05),添加0.350％维生素C能显著提高雄性亲鱼的性腺指数(P＜0.05).随饲料中维生素C添加量的增加,上浮卵率和孵化率显著上升(P＜0.05),初孵仔鱼畸形率显著下降(P＜0.05).C1.0和C1.5组的卵径、受精率、初孵仔鱼体长以及血清中雌二醇和睾酮含量均显著高于C0.5组(P＜0.05),而C1.0与C1.5组之间无显著差异(P＞0.05).C1.5组卵中大油球直径显著高于C05组(P＜0.05).卵子和上浮卵中维生素C含量随饲料中维生素C添加量的增加呈上升趋势,但各试验组间无显著差异(P＞0.05).此外,饲料中添加维生素C能不同程度地提高亲鱼肝脏、卵巢、精巢和卵子中维生素C含量,提升亲鱼血清、肝脏、卵巢、精巢、卵子和精液中超氧化物歧化酶活性并相应降低丙二醛含量.由此可见,本试验条件下,饲料中添加高剂量(0.525％)的维生素C更有利于促进半滑舌鳎亲鱼性激素的合成,改善亲鱼的繁殖性能,提高精卵质量,促进受精卵孵化,减少仔鱼畸形.     

In vitro effect of the red alga Hydropuntia cornea (J. Agardh) on the respiratory burst activity of sole (Solea senegalensis, Kaup 1858) phagocytes

The stimulatory effect of different extracts from the red alga Hydropuntia cornea (formerly Gracilaria cornea) on the respiratory burst activity of sole phagocytes was evaluated in vitro. Aqueous and ethanolic extracts and extracellular polysaccharidic fractions from algal cultures were assayed. Phagocytes, isolated from sole kidney, were incubated in vitro with different algal fractions at concentrations of 10, 5, 2 and 1 mg mL⁻¹. As a positive control, commercial β‐glucan from the alga Euglena gracilis was used. The results obtained indicate that an ethanolic extract from H. cornea, at 10 mg mL⁻¹, is capable of enhancing superoxide anion production in sole phagocytes when the cells are incubated for 30 min with the bacterium P. damselae ssp. piscicida and the extract. On the other hand, the commercial β‐glucan leads to a significant increase at highest concentration, 10 mg mL⁻¹, after 30 min of incubation.     

Establishment and characterization of a liver cell line,ALL, derived from yellowfin sea bream,Acanthopagrus latus,and its application to fish virology

Yellowfin sea bream (Acanthopagrus latus) is an important economic fish, which is seriously threatened by various fish viruses. In this study, a cell line designated as ALL derived from the liver of yellowfin sea bream was developed and characterized. The cell line grew well in Dulbecco's modified Eagle's medium containing 10%–20% foetal bovine serum at 28°C. Amplification of the cytochrome B gene indicated that ALL cells originated from yellowfin sea bream. The modal chromosome number of ALL cells was 48. ALL cells were efficiently transfected with pEGFP-N3 plasmids, indicating the potential application of ALL cells in exogenous gene manipulation studies. ALL cells were susceptive to three main fish viruses, including viral haemorrhagic septicaemia virus (VHSV), red-spotted grouper nervous necrosis virus (RGNNV) and largemouth bass virus (LMBV). The replication of VHSV, RGNNV and LMBV in ALL cells was confirmed by quantitative real-time polymerase chain reaction, virus titre and transmission electron microscopy assays. Moreover, ALL cells could respond to VHSV, RGNNV and LMBV infections, as indicated by the differential expression of antiviral genes involving in the innate immune response. In conclusion, the newly established ALL cell line will be an excellent in vitro platform for the study of the virus–yellowfin sea bream interaction.     

Variation in the distribution of yellowfin sole Limanda aspera larvae in warm and cold years in the eastern Bering Sea

Multiyear periods of relatively cold temperatures (2007–2013) and warm temperatures (2001–2005 and 2014–2018) altered the eastern Bering Sea ecosystem, affecting ocean currents and wind patterns, plankton community, and spatial distribution of fishes. Yellowfin sole Limanda aspera larvae were collected from the inner domain (≤50 m depth) of the eastern Bering Sea among four warm years (2002, 2004, 2005, 2016), an average year (2006), and three cold years (2007, 2010, 2012). Spatial distribution and density of larvae among those years was analyzed using generalized additive models that included timing of sea-ice retreat, areal coverage of water ≤0°C, and water temperature as covariates. Analyses indicated a combination of temperature effects on the location and timing of spawning, and on egg and larval survival, may explain the variation in larval density and distribution among years. During warm years, higher density and wider spatial distribution of larvae may be due to earlier spawning, an expansion of the spawning area, and higher egg and larvae survival due to favorable temperatures. Larval distribution contracted shoreward, and density was lower during cold conditions and was likely due to fish spawning closer to shore to remain in preferred temperatures, later spawning, and increased mortality. Predicted drift trajectories from spawning areas showed that larvae would reach nursery grounds in most years. Years when the drift period was longer than the pelagic phase of the larvae occurred during both warm and cold conditions indicating that settlement outside of nursery areas could happen during either temperature condition.     

引起半滑舌鳎(Cynoglossus semilaevis Günther)鱼苗大规模死亡的神经坏死病毒病

2012和2013年,山东某育苗场15–20日龄的半滑舌鳎(Cynoglossus semilaevis Günther)鱼苗出现暴发性大规模死亡,7 d内死亡率高达90%–100%。本研究调查了疾病的发生情况和临床特征,采集病鱼样品进行了组织病理学检查,并运用RT-PCR方法进行了病原的检测和基因序列分析。结果发现,半滑舌鳎鱼苗一般在7月和8月发病,发病时养殖水温为22–24℃。病鱼游泳行为异常,表现为上下翻游、螺旋性游动、全身大幅度波浪状浮动症状,但病鱼体表无出血和溃疡症状。组织病理检查发现,病鱼脑和视网膜组织出现严重的空泡化及坏死。病鱼样品的RT-PCR检测结果全部呈鱼类神经坏死病毒阳性。对得到的RT-PCR产物测序,进行BLAST比对,发现该病毒与鱼类神经坏死病毒的赤点石斑鱼神经坏死病毒(Red-spotted grouper nervous necrosis virus, RGNNV)基因型的相似性达98%以上,而与鱼类神经坏死病毒的其他3个基因型：黄带拟鲹神经坏死病毒(Striped jack nervous necrosis virus,SJNNV)、红鳍东方鲀神经坏死病毒(Tiger puffer nervous necrosis virus, TPNNV)和条斑星鲽神经坏死病毒(Barfin flounder nervous necrosis virus,BFNNV)的相似性仅为71%–78%。由此可以判定,本研究发现的引起半滑舌鳎鱼苗大规模死亡的神经坏死病毒为RGNNV基因型,半滑舌鳎也是鱼类神经坏死病毒的天然宿主。该发现在半滑舌鳎疾病防治和鱼类神经坏死病毒的流行机制研究方面都具有重要意义。     

经济鳎类的疾病研究进展

近年来,随着经济鳎类养殖规模的不断扩大,各种病害也随之频繁发生。本文就国内外经济鳎类的疾病研究情况,阐述了引起鳎类爆发流行疾病的病原体,及该类疾病的病原检测、鉴定方法、防治方法、抗病基因的研究进展,以期为经济鳎类的疾病防治提供参考依据。     

Isolation of lymphocystis disease virus from sole, Solea senegalensis Kaup, and blackspot sea bream, Pagellus bogaraveo (Brunnich)

Two viruses were isolated from cultured sole, Solea senegalensis, and wild blackspot sea bream, Pagellus bogaraveo, and preliminarily characterized as lymphocystis disease viruses (LCDVs). Viral isolates were characterized by morphological, biochemical and biophysical properties. In addition, the susceptibility of four fish cell lines was also tested. LCDV isolates developed cytopathic effects on the SAF-1 cell line at 5 and 6 days post-infection and reached titres of 10(6) TCID50 mL(-1). The antigenic and structural protein analysis of the two new LCDV isolates showed identical profiles to that obtained for LCDV strain Leetown NFH (ATCC VR-342), used as a reference viral strain, and for an LCDV isolate collected from gilt-head sea bream, Sparus aurata, cultured in southern Spain. Molecular confirmation was performed by polymerase chain reaction. Specific primers for LCDV produced a 270-bp DNA fragment, the expected size for LCDV.