Effect of cadmium on the cytoskeleton and morphology of gill chloride cells in parr and smolt Atlantic salmon (Salmo salar)

This study documented the effect of cadmium on salmon parr and smolt gill morphology. Cadmium-induced changes in chloride cell (CC) cytoskeletal elements were investigated, as well as the modifications of CC surface area and density. In cadmium-treated parr (10 µg Cd l^-1 for 2 days), immunofluorescent light microscopy revealed the appearance of an intense actin staining located in the CC apical part. Transmission electron microscopic observations revealed a change in the organization of the microfilaments at the CC apex, with the appearance of numerous aggregates of filamentous actin. Higher cadmium concentrations (30 and 50 µg l^-1) and prolonged treatment times (7 to 14 days) did not modify such reorganisation. Microtubules were not significantly affected by similar treatments. Further, scanning electron microscopic analysis revealed that cadmium induces a significant increase of parr CC surface area as early as the second day of exposure. After 2 days, mature CC density had also increased. In smolt, a rise in CC surface area was observed, although CC density did not significantly increase.     

Non-lethal loop-mediated isothermal amplification assay as a point-of-care diagnostics tool for Neoparamoeba perurans,the causative agent of amoebic gill disease

Neoparamoeba perurans is the causative agent of amoebic gill disease (AGD). Two loop-mediated isothermal amplification (LAMP) assays targeting the parasite 18S rRNA and the Atlantic salmon EF1α, used as internal control, were designed. The N. perurans LAMP assay did not amplify close relatives N. pemaquidensis and N. branchiphila, or the host DNA. This assay detected 10⁶ copies of the parasite 18S rRNA gene under 13 min and 10³ copies under 35 min. Five “fast-and-dirty” DNA extraction methods were compared with a reference method and further validated by TaqMan™ qPCR. Of those, the QuickExtract buffer was selected for field tests. Seventy-one non-lethal gill swabs were analysed from AGD-clinically infected Atlantic salmon. The pathogen was detected under 23 min in fish of gill score >2 and under 39 min for lower gill scores. About 1.6% of the tests were invalid (no amplification of the internal control). 100% of positives were obtained from swabs taken from fish showing gill score ˃3, but only ~50% of positives for lower gill scores. The present LAMP assay could be implemented as a point-of-care test for the on-site identification of N. perurans; however, further work is required to improve its performance for lower scores.     

镉对背角无齿蚌主要组织谷胱甘肽含量和相关酶活性的影响

为了进一步探明谷胱甘肽系统对镉引起的氧化损伤的防御作用,根据背角无齿蚌(Anodonta woodiana woodiana)96 h镉的半致死浓度,设置5个染毒组(4.22、8.43、16.86、33.72、67.45 mg·L-1)和1个对照组,处理24、48、72、96 h分别测定鳃与肝脏中还原型谷胱甘肽(GSH)、氧化型谷胱甘肽(GSSG)含量和谷胱甘肽硫转移酶(GST)、谷胱甘肽还原酶(GR)的活性。实验结果显示,与对照组相比,除48 h、4.22 mg·L-1处理组鳃中GSSG含量出现显著性升高(P0.05)外,GSH和GSSG含量均表现为显著或极显著性降低(P0.05,P0.01);随着时间的延长,GSH/GSSG比值在低浓度(4.22、8.43 mg·L-1)处理组先降后升,在高浓度(33.72、67.45 mg·L-1)处理组则逐渐下降,且与对照组相比差异显著(P0.05)。与对照组相比,在24 h鳃中GST活性呈梯度型降低(P0.01);在48、72、96 h GST活性整体呈升高趋势,且在低浓度组升高、高浓度组降低,呈现显著性或极显著性差异(P0.05,P0.01)。鳃中GR活性在48 h、8.43 mg·L-1,72 h、67.45 mg·L-1和96 h、4.22 mg·L-1处理组出现显著性升高。随着浓度的升高和时间的延长,肝脏中GSH含量和GSH/GSSG比值呈显著或极显著性降低(P0.05,P0.01)。肝脏中GST活性整体呈升高趋势且有极显著性差异(P0.01);在24 h、4.22 mg·L-1处理组GST活性达到最高。同一时间,随着镉浓度的升高,肝脏中GST活性逐渐降低。肝脏中GR活性整体呈升高趋势且有显著性或极显著性差异(P0.05,P0.01),在72 h、4.22 mg·L-1处理组浓度达到最高。研究表明,肝脏中GSH含量的变化对镉引起的损伤反应灵敏且发挥了重要作用,GST解毒酶对镉的毒性反应灵敏,且肝脏较鳃的反应迅速。GSH含量、GST活性和肝脏分别可以作为环境监测的生化指标和靶器官。     

育肥饲料中虾青素含量对雄性中华绒螯蟹肠道和鳃部可培养优势细菌数量和组成的影响

在育肥饲料中添加虾青素会影响中华绒螫蟹肠道及鳃内的可培养优势菌群以及机体的免疫力,本实验旨在探讨饲料中虾青素含量及养殖水体对其肠道和鳃部菌群的影响。采用不同虾青素含量的饲料(0.00、26.60、41.62、81.37和75.35 mg/kg,分别对应饲料1#~5#)对雄性中华绒螫蟹进行育肥70 d后,利用基础培养基和选择性培养基对其肠道、鳃及养殖水体中的细菌进行传统分离和纯化,所得菌株进行16S rRNA测序,再进行同源性分析后做系统进化树。结果发现,在分离获得的106株细菌(登录号:KU570293~KU570368,KU570370,KU570372~KU570383,KU601302~KU6013 16,KU720553)中,92株为优势菌株,其中,肠道、鳃部和水体各29、32和31株。肠道中的可培养优势细菌属于柠檬酸杆菌属、假单胞菌属和气单胞菌属;而鳃中可培养优势细菌属于柠檬酸杆菌属、芽孢杆菌属、假单胞菌属和气单胞菌属;养殖水体中可培养优势细菌属于芽孢杆菌属、气单胞菌属、柠檬酸杆菌属、假单胞菌属和黄杆菌属。饲料2#组肠道中可培养细菌总数最高(1.06×10~8cfu/g);饲料5#肠道中的潜在致病菌数量最低,但其可培养细菌总数显著高于其他饲料组;饲料3#组肠道和鳃中潜在致病菌数量相对较高。研究表明,饲料中添加不同含量的虾青素能够显著影响雄性中华绒螫蟹肠道和鳃中的菌群构成,但对水体中可培养细菌数量无显著影响。本研究首次对投喂不同含量虾青素饲料的育肥期雄性中华绒螫蟹肠道、鳃及养殖水体可培养的优势细菌数量和组成进行分析,探究了饲料中虾青素含量以及养殖水体与蟹肠道内可培养细菌之间的联系,为中华绒螫蟹营养免疫和菌群调控提供了理论基础。     

Effect of thin twine on gill net size-selectivity analyzed with the direct estimation method

ABSTRACT: To analyze the effect of thin twine on gill net size selectivity, a series of fishing experiments using gill nets of two twine thicknesses (no. 0.8 of 0.16 mm diameter and no. 3 of 0.28 mm diameter) and three nominal mesh sizes (41 mm, 46 mm and 51 mm) was conducted in outdoor water tanks containing a rainbow trout ( Oncorhynchus mykiss ) population of known size frequency. For nets of the same nominal mesh size, mesh openings of the no. 0.8 twine nets were approximately 2 mm larger than those of the no. 3 twine nets. The effects of both mesh opening and twine thickness are combined in the conventional analysis with the selectivity curve against fish length. Selectivity against the ratio of fish girth to mesh perimeter was calculated to avoid the direct effect of changes in mesh openings due to twine diameter at the same nominal mesh size. Results demonstrated that the thinner twine gill net was more likely to capture rainbow trout of smaller girth than the mesh perimeter. Fish with girths smaller than the mesh perimeter were often retained by the net with its body tangled by the thinner twine, possibly due to the increased flexibility of the thinner twine.     

鲤鱼烂鳃病病原菌的分离及其毒力研究

从患烂鳃病的鲤鱼鳃中分离得到烂鳃病病原菌９２０１，其菌落、菌体及生化等特征与草鱼鱼害粘球菌相似。９２０１的毒力与水温呈正相关，以１８ｈ菌龄毒力最强。在菌种保藏过程中，其毒力衰退较快，复壮后毒力有所恢复。     

双孢蘑菇子实体发育研究

初始原基球形至卵球形，内部菌丝交织、致密，边缘菌丝凝结或胶化。随着原基膨大，顶端边缘内凹出现菌盖原基，此时未发现菌柄原基分化，之后菌盖原基侧面的裂缝中出现栅栏状菌丝细胞并逐渐发育形成菌褶腔，子实层原基分化开始，同时菌柄原基也开始分化。在菌褶腔形成过程中，可观察到Y型菌褶。双孢蘑菇是半被果型发育中的副菌幕发育型，从发育顺序观察是菌盖发育型。     

Rearing unit-level factors associated with bacterial gill disease treatment in two Ontario, Canada government salmonid hatcheries

Early-rearing salmonids in Ontario Ministry of Natural Resources (OMNR) fish hatcheries have been consistently affected by bacterial gill disease (BGD) (causative agent: Flavobacterium branchiophilum) for many years. Separate retrospective epidemiological investigations of BGD treatments at two OMNR fish hatcheries (Hatcheries A and B) for the 1999 production year were conducted using on-site hatchery records. Both investigations were carried out at the rearing unit-level, with early-rearing (<9 months of age) “tank-lot” as the unit of analysis to identify unique fish populations over time. Multivariable repeated measures logistic regression models were created for both hatchery datasets, controlling for lot-level and species effects. For Hatchery A, the species brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) were significantly associated with BGD treatment, as well as lower water exchange rate, and higher feeding and mortality percentages during the 2 weeks previous to BGD treatment. At Hatchery B, the species brook trout (S. fontinalis) and splake (Salvelinus namaycush × S. fontinalis) were significantly associated with BGD treatment, as well as lower individual fish weights and treatment for BGD during the previous week. These results emphasize the importance of water quality, feeding rate, fish size and prior mortality on the development of BGD. Significant hatchery and species effects were evident, and future observational research on BGD must account for these factors in their design and analysis.     

Probarbus jullieni and Probarbus labeamajor: the management and conservation of two of the largest fish species in the Mekong River in southern Laos

• 1. Probarbus jullieni and Probarbus labeamajor are two of the largest carps in the Mekong River Basin, each reaching a maximum weight of about 70 kg. P. jullieni is listed in Appendix 1 of the Convention on the International Trade in Endangered Species, and both are listed on the IUCN Red List of Threatened Species, the first as ‘endangered’ and the second as ‘data deficient’.
• 2. Six years of quantitative monitoring of a large‐meshed gill net fishery for Probarbus just below the Khone Falls in Khong district, Champasak province, in southern Laos shows that 78% of the overall catch is comprised of Probarbus, with P. jullieni making up 65% of landings.
• 3. Over the 6‐year period catches of Probarbus declined significantly. However, catch‐per‐unit effort statistics do not indicate that the fishery is in decline, although fishers are convinced that real stock reductions are a large part of the reason for catch declines and decreases in fishing effort.
• 4. A number of ecological and social factors are affecting the number and quality of gill nets in use, the length of fishing seasons, and gill net efficiency, making it difficult to compare catch‐per‐unit effort between years.
• 5. There has been a shift from using large‐meshed gill nets for catching Probarbus to targeting smaller species using gill nets with smaller mesh‐sizes. This is an example of the ‘fishing down’ of a Mekong fish community, in which large long‐lived species are the first to be affected by heavy fishing pressure.

Copyright © 2006 John Wiley & Sons, Ltd.