Temporal changes in ascendance and in‐season exploitation of Atlantic salmon,Salmo salar,inferred by a video camera array

Abstract Weekly exploitation rates of Atlantic salmon, Salmo salar L., in the River Utsjoki, Finland, were estimated from catch reports during the 2003, 2004, 2006 and 2007 seasons, and recordings of all Atlantic salmon ascending the river using a submerged video camera array. In all years, mean weekly fishing mortality rates were significantly higher in June than July to August, with a falling trend throughout the fishing season. Owing to overlap in size between one‐sea‐winter (1SW) and multi‐sea‐winter (MSW) salmon, the estimated fishing mortality rates were based on all sea‐age categories combined. By the second week in June, 18.3–34.7% of large salmon (only MSW) had ascended, compared with 2.2–6.4% of small salmon (1SW and some MSW). Indirectly, the earlier start of ascent of large salmon to River Utsjoki indicated that in‐river fishing mortality of MSW salmon is higher than for 1SW salmon. A later opening of the fishing season may be used to reduce the in‐river fishing mortality, especially for the MSW component.     

In vitro interactions between Neoparamoeba sp. and Atlantic salmon epithelial cells

Neoparamoeba sp., including the putative aetiological agent of amoebic gill disease in cultured fish (N. pemaquidensis), were incubated in vitro with an Atlantic salmon gill epithelium (RGE-2) cell line. Proliferation by the amoeba population was dependent upon culture osmolarity; no growth occurred at 330 mm x kg(-1) but a sixfold increase was observed at 1000 mm x kg(-1). At 780 mm x kg(-1) there was a fourfold increase in the amoeba population but a concurrent decrease in RGE-2 cell density that was significantly greater than that caused by the high culture osmolarity alone. This apparent cytopathic effect (CPE) developed rapidly and resulted in complete cytolysis of the monolayer in 5 days. CPE occurred in multiple foci and presented as cell vacuolation, rounding and clumping, and the rapid clearance of large areas of the cell monolayer. The possibility that CPE is because of the presence of Neoparamoeba sp. derived cytolytic products is discussed in the context of the pathology of the disease in vivo and the occurrence of secreted cytopathogenic compounds in other amoeba species.     

微生物发酵对罗非鱼下脚料蛋白酶解液脱腥去苦效果比较

以嗜热链球菌(Streptococus thermophilus)、保加利亚乳杆菌(Lactobacillus bulgaricus)和瑞士乳杆菌(L.helveticus)及2种酿酒酵母菌(Saccharomyces cerevisiae)为菌种,对罗非鱼(Oreochromis niloticus)下脚料蛋白酶解液进行发酵,利用感官评定法,比较不同微生物发酵对酶解液脱腥去苦效果.试验结果表明,乳酸菌脱腥效果优于酵母菌,其中以嗜热链球菌脱腥效果最好,其适宜的发酵条件为接种量10%,发酵温度42℃,发酵时间9 h.微生物发酵去苦效果不明显.     

High yield and rapid growth of Neoparamoeba pemaquidensis in co-culture with a rainbow trout gill-derived cell line RTgill-W1

Neoparamoeba pemaquidensis is an ubiquitous amphizoic marine protozoan and has been implicated as the causative agent for several diseases in marine organisms, most notably amoebic gill disease (AGD) in Atlantic salmon. Despite several reports on the pathology of AGD, relatively little is known about the protozoan and its relationship to host cells. In this study, an in vitro approach using monolayers of a rainbow trout gill cell line (RTgill-W1, ATCC CRL-2523) was used to rapidly grow large numbers of N. pemaquidensis (ATCC 50172) and investigate cell-pathogen interactions. Established cell lines derived from other tissues of rainbow trout and other fish species were also evaluated for amoeba growth support. The amoebae showed preference and highest yield when grown with RTgill-W1 over nine other tested fish cell lines. Amoeba yields could reach as high as 5 x 10(5) cells mL(-1) within 3 days of growth on the gill cell monolayers. The amoebae caused visible focal lesions in RTgill-W1 monolayers within 24 h of exposure and rapidly proliferated and spread with cytopathic effects destroying the neighbouring pavement-like cells within 48-72 h after initial exposure in media above 700 mOsm kg(-1). Disruption of the integrity of the gill cell monolayers could be noted within 30 min of exposure to the amoeba suspensions by changes in transepithelial resistance (TER) compared with control cell monolayers maintained in the exposure media. This was significantly different by 2 h (P < 0.05) compared with control cells and remained significantly different (P < 0.01) for the remaining 72 h that the TER was monitored. The RTgill-W1 cell line is thus a convenient model for growing N. pemaquidensis and for studying host-pathogen interactions in AGD.     

Development and application of fluorescence in situ hybridization (FISH) method for simple and rapid identification of the toxic dinoflagellates Alexandrium tamarense and Alexandrium catenella in cultured and natural seawater

ABSTRACT:   The toxic dinoflagellates Alexandrium tamarense (Lebour) Balech and A. catenella (Whedon and Kofoid) Balech produce potent neurotoxins, such as saxitoxin and gonyautoxin and have been mainly responsible for paralytic shellfish poisoning (PSP) in Japan. To prevent a negative effect on the fishery industry, it is necessary to identify these toxic species precisely and rapidly before and during the bloom. In this paper, a rapid and simple protocol of a fluorescence in situ hybridization (FISH) method using ribosomal RNA (rRNA)-targeted probes has been established for identifying the cultured strains and natural cells of A. tamarense and A. catenella . Using the FISH method established in this study, it was possible to identify these toxic species species-specifically and rapidly, within 30 min. The procedure of detection constituted three steps: (i) fixation/dehydration; (ii) hybridization; and (iii) washing; this made the identification simple. Moreover, this method did not require either special techniques or equipment, and the cost for detection was low. The specificity, rapidity, and simplicity of the developed method suggest that it might be useful for routine monitoring of these toxic microalgae.     

Effects of enhanced supplies of nitrogen and sulphur on rhizosphere and soil chemistry in a Norway spruce stand in SW Sweden

Rhizophere and bulk soil chemistry were investigated in a Norway spruce stand in SW Sweden. The rhizosphere and bulk soil chemistry in water extracts in control plots (C) and plots repeatedly treated with ammonium sulphate (NS) were compared. Treatment regime was started in 1988. Cylindrical core samples of the LFH-layer and mineral soil layers were collected in 1992 and used for water extract analyses. Samples of soil from LFH-layer and mineral soil layers were taken in 1991 and 1993 for determination of CEC and base saturation. Soil pH and NH₄-N, NO₃-N and SO₄-S, Al, Ca, K and Mg concentrations in water extracts were measured for rhizosphere and bulk soils. The pH-values of bulk and rhizosphere soils in NS plots decreased compared with those in control plots, whereas concentrations of NH₄-N, NO₃-N, SO₄-S, base cations and Al in water extract increased. In both bulk and rhizosphere soils the concentration of NH₄-N was much higher than that of NO₃-N. A significant difference in the pH and Mg concentration of bulk and rhizosphere soil between the treated and control plots was found only in the 0–10 cm layer. For all layers, there was a significant difference in NH₄-N concentrations in the bulk and rhizosphere soil between the NS treatment and control plots. Concentrations of exchangeable base cations and the base saturation level in the LFH-layer decreased in the NS plots. The concentration of extractable SO₄-S increased in the NS plots. The NS treatment enhanced the amount of litter in L-layer, owing to increases in needle biomass and litterfall but led to losses of base cations, mainly K and Mg, from LFH-layer. It was concluded that the NS treatment displaced cations from exchangeable sites in the LFH-layer leading to higher concentrations of these elements in both rhizosphere and bulk soil.     

黄土区不同地类土壤水分入渗与模拟研究

以晋西黄土区为研究对象,研究黄土区土壤的水分入渗规律。为了更好地研究不同环境因子（尤其是立地、坡度、植被）对于土壤入渗性能的影响,在不同的土地利用条件下,对不同地貌部位进行了野外入渗实验。研究结果表明土壤渗透率随时间的变化规律是:在开始时渗透率最大,继之随时间而降低;林地累计入渗量明显高于其它用地。此外,林地的土壤入渗速率为最优,道路路面为最小。研究表明Philip方程能够很好地对当地土壤入渗进行模拟。     

苏云金芽孢杆菌对黄河鲤血液免疫效果研究

研究了苏云金芽孢杆菌对黄河鲤血液免疫应答的影响.将苏云金芽孢杆菌按1.0×10~(11)、3.0×10~(11)、5.0×10~(11) cfu/kg 3个浓度添加在鱼用全价颗粒饲料中,投喂经嗜水气单胞菌疫苗免疫组(A_0～A_3)和未免疫组(B_0～B_3)黄河鲤,分别于0、15、30、40 d时检测各组黄河鲤白细胞吞噬活性、血清溶菌酶活性以及血清凝集抗体效价,并进行攻毒试验.结果表明:添加苏云金芽孢杆菌可使黄河鲤血液中白细胞吞噬活性和血清溶菌酶活性显著提高.添加组与对照组差异显著(P<0.05),添加浓度越高,血液白细胞活性和溶菌酶活性越强.免疫组与未免疫组白细胞吞噬活性差异不显著(P>0.05),而溶菌酶活性差异显著(P<0.05).在停止投喂后10 d,白细胞活性、血清溶菌酶活性逐渐下降,但差异不显著(P>0.05).添加苏云金芽孢杆菌还可提高黄河鲤的凝集抗体效价及攻毒后的存活率,其中,当菌株添加浓度为5.0×10~(11) cfu/kg时,受免疫的黄河鲤免疫保护率最高.即投喂苏云金芽孢杆菌对黄河鲤血液免疫应答有明显促进作用.     

汉语思维方式及写作经验在中国学生英语写作中的迁移现象

语言迁移现象会在语言学习的各个方面发生，正迁移对英语学习有促进作用，负迁移则有阻碍作用。写作教学是外语教学中的难点之一和薄弱环节，更容易发生负迁移。运用对比错误分析方法，对中国学生写作时容易发生的汉语负迁移现象进行了分析，试图对我国英语写作教学的改进提供一己之见。     

First approach to studying the genetics of the meagre (Argyrosomus regius; Asso, 1801) using three multigene families

The meagre (Argyrosomus regius) is a commercially important species for fisheries, and aquaculture production has been increasing in recent years. However, this growing importance has not been matched by increased genetic knowledge of the species. For this reason, an initial approach has been made to understanding the genetics of the meagre, using three particular multigene families (45S and 5S ribosomal DNA and U2 snRNA gene) as both molecular and cytogenetic markers. Only one type of 5S rDNA and only one ITS‐1 (from 45S rDNA) were obtained, and these therefore could provide the basis for the development of genetic markers for this species. However, the U2 snRNA gene produced a multi‐band electrophoretic pattern, and some of these bands were demonstrated to be linked with the U1 snRNA gene. This linkage could also provide a good species‐specific marker which could be useful for tracing the evolutionary history of the Sciaenidae family. In this study, we have described for the first time the karyotype of the meagre: this is composed of 48 acrocentric chromosomes. Each of the three gene families were localized on different chromosome pairs, although the U2 snRNA gene probe was also located scattered throughout the genome of the meagre, as expected by the amplification pattern.