Study on Leaching Loss of Nitrogen in Ricefields by Using Large Undisturbed Monolith Lysimeters

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Effects of Biomineral Liquid from Spartina alterniflora on Growth,Body Color and Nutritional Components of Ricefield Eels,Monopterus albus

[Objective]The paper was to develop new fodder additives and to strengthen comprehensive utilization of Spartina alterniflora resources.[Method]The effects of biomineral liquid from S.alterniflora on growth,nutritional components of ricefield eels were studied.[Result]（1）0.5%of biomineral liquid had significant effect on weight gain rate,which was 8.37%higher than that in control group（P〈0.01）.Further supply of biomineral liquid could not increase the weight gain rate.Furthermore,biomineral liquid had no effect on the survival rate of ricefield eels.（2）Ricefield eels had certain changes in body color in the0.5%biomineral liquid group,and some ricefield eels were yellowing.（3）The contents of Cr,Fe,Zn in body of ricefield eels in treatment group were significantly higher than that in control group,but was lower than that in wild eel group,and the content of Se in treatment group was lower than that in control group and wild group（P〈0.01）.（4）The contents of K,Mg in muscle of ricefield eels in treatment group were higher than those in control group and wild eel group.The contents of ash and Ca in treatment group were close to that in control group but were higher than that in wild eel group.The content of crude fat in treatment group was close to that in wild eel group but was lower than that in control group.The contents of Zn,Se,Ni in treatment group were higher than that in control group and wild eel group,and the contents of Cr,Fe,Cu were close to that in control group and were higher than that in wild eel group（P〈0.01）.No significant differences were observed in the contents of moisture,crude fat and P among the three groups（P〉0.05）.[Conclusion]Addition of biomineral liquid from S.alterniflora could speed up the growth of ricefield eels and significantly improve their flesh quality,but had no significant effect on survival rate of ricefield eels.

Immatures of Lutzia fuscana(Wiedemann,1820)(Diptera:Culicidae) in ricefields:implications for biological control of vector mosquitoes

Objective:Rice fields are dynamic mosquito larval habitats with assemblage of different predator taxa,including the larva of the mosquitoes Lutzia.Entomological surveillance in the ricefields is essential to evaluate the potential of these predators as biological resource to regulate vector mosquito population.In view of this,a survey of ricefields for immatures of different mosquito species including Lutzia was conducted.Methods:Survey of selected ricefields was carried out to evaluate the species composition of mosquitoes.Laboratory evaluation of the immatures of Lutzia mosquitoes was carried out to assess its predation potential using mosquitoes and chironomid as preys.Results:The survey revealed the presence of five mosquito species belonging to the genera Anopheles and Culex and the predatory immatures of the mosquito Lutzia Juscana(Wiedemann,1820).The ratio of prey and predatory larva ranged between 1.46 and 4.78 during the study period,with a significant correlation on the relative abundance of the larval stages of Lt.Juscana and Anopheles and Culex larvae.Under laboratory conditions,a single IV instar larvae of Lt.fuscana was found to consume on an average 5 to 15 equivalent instars of Anopheles sp.and Culex sp.larvae per day depending on its age.The prey consumption reduced with the larval stage approaching pupation.When provided with equal numbers of chironomid and Anopheles or Culex larvae,larva of Lt.fuscana consumed mosquito larvae significantly more compared to chironomids.Conclusion: The survey results and the preliminary study on predation are suggestive of the role of Lt.Juscana in the regulation of vector mosquito populations naturally in the ricefields.Since Lt.Juscana is common in many Asian countries,further studies on bioecology will be helpful to justify their use in mosquito control programme.

Interdependence between Natural Habitats and Ricefields for Rice Pest Management in the Agusan Marsh Floodplain

This paper describes how aquatic insect diversity in major natural habitats of Agusan marsh relates with nearby ricefields to determine the interdependence between them for sustainable rice production through natural pest control and for conservation of aquatic fauna in the marsh. Sampling for one year including two cropping seasons of rice production was conducted in various natural habitats of the marsh and in the adjoining rice fields. Both the natural habitats and rice fields were characterized in relation to determining habitat suitability for aquatic insects. The sedge-dominated swamp had the highest diversity among the natural habitats, while the fern-dominated swamp had the lowest. In the adjacent ricefields, diversity was similarly highest in the site near the sedge-dominated swamp, while the lowest was in the ricefields adjoining the Sago forest. Species composition of aquatic insects among the habitats differed between the wet and dry seasons. However, similarity patterns exist between natural habitats and rice fields. The closer similarity in species composition between natural habitats and ricefields indicates habitat connectivity which is an important consideration in planning and effective pest management and ecologically sound rice farming in the marsh.

Lysimetry study on the leaching loss of nitrogen from double-rice-cropped ricefield

The effect of N fertilizer application in ricefield on the environmental quality of ground-water was evaluated using large undisturbedmonolith lysimeters.Soil in lysimeters wassilty-clay-loamy paddy soil(Haplaquept)with apH of 6.5,15.4g/kg organic C,1.55g/kg to-tal N,88 mg/kg available N,399 mg/kg A1-abbas-P,67.5 mg/kg exchangeable K,and14.1 cmol/kg CEC.The lysimetry experiment was laid out atHangzhou during the early-rice season(ER,May-Jul)and late-rice season(LR,Jul-Oct)in 1991-1994.Three plot treatments were es-tablished,i.e.,urea plot(UN,applied urea150 kgN/ha per cropping season),ammoniumbicarbonate plot(CN,applied ammonium bi-carbonate 150 kgN/ha per cropping season),and control plot(CK,no N application).Allof the plots also received single superphosphateat 45 kg P/ha and KC1 at 75 kg K/ha.The

稻田使用溴氰菊酯农药对水生生物的安全评价

研究了在稻田－鱼塘生态系统中，模拟稻田使用溴氰菊酯后遇大雨，田水中残留农药流入鱼塘，对塘内水生生物的危害影响。结果表明：供试的鱼、贝类未发现死亡现象；残留、毒性测定结果与危害性实测结果相符。排水口附近供试虾类大量死亡。排水口较远处，虾类的危害影响较轻。虾类对溴氰菊酯有明显的回避性，自然水域中虾类的危害程度比关在网箱内的要小。鱼塘中浮游动物受害十分严重，但２周后即可恢复正常。使用溴氰菊酯农药对稻田养鱼无危害影响。

池塘和稻田养殖克氏原螯虾肠道微生物对比分析

为探究池塘和稻田养殖模式下克氏原螯虾肠道微生物组成的差异,采用16S rRNA高通量测序方法分析了对两种养殖模式下克氏原螯虾肠道的微生物多样性和群落结构。结果显示,所有样品共检出2007个种水平上的分类操作单元(operational taxonomic units,OTU),归属于37个门,其中池塘养殖克氏原螯虾的肠道微生物有1260个OTU,稻田养殖克氏原螯虾的肠道微生物有1840个OTU,两种模式下克氏原螯虾的肠道微生物共同的OTU有1093个;两种模式下的肠道微生物优势菌均为厚壁菌门,其中池塘模式中占比67.40%,稻田模式中占比为32.69%;对两种模式的克氏原螯虾肠道微生物进行Alpha多样性分析显示,池塘养殖克氏原螯虾肠道微生物多样性的Shannon、ACE和Chao指数均低于稻田养殖克氏原螯虾肠道微生物的指数,差异均达到极显著的水平;物种差异分析显示,在门水平上有21个门差异达到显著水平,其中有12个门差异达到极显著水平;在OTU水平上,有364个OTU差异达到显著水平,其中有106个OTU差异达到极显著水平。研究表明,池塘和稻田养殖克氏原螯虾肠道微生物在物种组成上、多样性上都存在明显差异,针对两种模式的养殖管理应有所区分,由于池塘模式下肠道微生物多样性较低,因此,需要更多地注重虾类健康状况动态,加强管理。

免疫多糖对受免黄鳝免疫保护力的增强作用

在饲料中添加不同剂量的免疫多糖(酵母细胞壁),连续投喂经注射接种嗜水气单胞菌(Aeromonashydrophila)脂多糖(lipopolysaccharide,LPS)的黄鳝(Monopterus albus)28 d后,通过测定供试黄鳝的增重量、血清中凝集抗体效价、溶菌酶活性、谷丙转氨酶(SGPT)活性、血清总蛋白含量、白细胞吞噬活性以及活菌攻毒后的免疫保护率(RPS),探讨了将LPS作为免疫原、免疫多糖(酵母细胞壁)作为免疫刺激剂结合使用对受免黄鳝免疫保护力的增强作用。结果表明,用添加100.0 mg/kg免疫多糖(酵母细胞壁)的饲料投喂受免黄鳝,不仅可以提高受免黄鳝对A.hydrophila LPS的免疫应答水平,也可以增强黄鳝的非特异性免疫力和抵抗A.hydrophi-la人工感染的能力,同时也证明了在饲料中添加免疫多糖(酵母细胞壁)对黄鳝的生长速度和肝脏功能均无不良影响。

黄鳝性腺自然逆转过程中vasa基因的表达分析

本研究采用RNA反义探针原位杂交技术,对vasa基因在黄鳝(Monopterusalbus)性腺发育过程中的表达情况进行了分析。结果表明:vasamRNA在Ⅰ、Ⅱ、Ⅲ期卵母细胞的胞质中均匀分布,在Ⅳ、Ⅴ期卵母细胞中vasamRNA有向胞质外周皮层迁移集中的趋势,但不明显;退化的卵粒也呈现vasamRNA阳性反应;在Ⅲ、Ⅳ期卵巢的被膜中检测到带有vasa阳性信号的细胞,这些细胞可能是待向精原细胞分化、迁移到卵巢被膜上的原始生殖细胞(Primordialgermcell,PGC),在性逆转过程中这些PGC可能由卵巢被膜迁移到精小叶中并发育成精子;在成熟精巢中,vasa在精原细胞和初级精母细胞中表达。进一步采用碱性磷酸酶染色法分析黄鳝卵巢及精巢后发现:在卵巢中,除了卵母细胞外,卵巢被膜中也检测到了带有碱性磷酸酶阳性信号的细胞;在成熟精巢中,只在生殖腺囊内的雄性生殖细胞中检测到碱性磷酸酶,而精巢被膜中没有检测到带有碱性磷酸酶阳性信号的细胞。本研究结果初步表明:黄鳝的雄性生殖细胞可能起源于雌性阶段卵巢被膜中的原始生殖细胞[动物学报51(3):469-475,2005]。

外源性褪黑激素对黄鳝性腺发育及性腺激素分泌的影响

通过注射实验研究了外源性褪黑激素对黄鳝性腺发育及性腺激素分泌的影响。结果表明，处于不同性腺发育时期的黄鳝对外源褪黑激素的反应存在季节性差异。注射褪黑激素对Ⅳ期黄鳝的性腺发育具有剂量依存的促进与抑制的双重调节作用，但对Ⅴ期（排卵前期）个体没有显著影响。单次注射外源褪黑激素对黄鳝血清性类固醇激素（睾酮和雌二醇）水平具有一定的刺激作用，然而不同生殖时期的黄鳝对褪黑激素的反应差异很大，敏感时期出现在性腺发育的静止期。上述结果暗示，褪黑激素影响黄鳝性腺发育的关键时间可能是在性腺静止期，亦即Ⅳ期或／和Ⅳ期之前。

黄鳝对饲料中胆碱的需要量

用添加胆碱含量为0、0 1%、0 3%、0 5%、0 8%、1 0%、1 2%、1 5%和2 0%(均为质量分数)的配合饲料,在水泥池中(2m×6m×0 8m)饲养黄鳝,试验时间为90d。结果表明,随着饲料中胆碱含量的增加,黄鳝的生长加快,饲料系数降低,肝体指数减小;当饲料中胆碱添加量为0 8%～1 2%时,黄鳝的生长率最高,饲料系数最低,肝体指数、肝脏脂肪含量较小,与用动物饵料养殖的效果基本接近。这表明黄鳝饲料中胆碱的添加量不应少于0 8%,以0 8%～1 2%为宜。

黄鳝肠道益生菌HY-136的鉴定与系统发育分析

对分离自健康黄鳝肠道118株菌进行点种法病原菌拮抗试验,结合产酶能力分析试验结果,得到了对病原菌拮抗作用显著和产酶能力较强的拟选菌株HY-136。通过对该菌株进行形态观察,常规生理生化鉴定和应用API 50 CHB鉴定盒鉴定,结果表明该菌与枯草芽孢杆菌属的形态及生理生化特征相似;进一步利用PCR技术对该菌株16S rRNA序列作测定与分析,序列结果在GenBank中进行Blast同源序列检索,并用Mage4.0软件与芽孢杆菌属的其它菌种进行序列分析比对,结果表明其与已报道的枯草芽孢杆菌序列(登录号为EU346662)具有99.8%的同源性,且二者在所构建的系统发育树上处于同一个分支。确定菌株HY-136为枯草芽孢杆菌(Bacillus subtilis)。

环境因子对黄鳝血清褪黑激素水平的影响

研究光周期和水温这 2种重要的环境因子对黄鳝血清褪黑激素水平的影响。结果表明 :1)连续光照可导致黄鳝血清褪黑激素水平的昼夜节律消失 ;连续黑暗环境中黄鳝血清褪黑激素水平仍保持昼夜节律性 ,但波动幅度变窄 ;光暗颠倒导致黄鳝血清褪黑激素水平出现 180度移位。从而说明黄鳝血清褪黑激素水平的相位变化基本能反映出光周期的时程改变。 2 )在一定的温度范围 (15～ 2 1℃ )内 ,黄鳝血清褪黑激素水平保持相对稳定 ;高温 (31℃ )则刺激黄鳝血清褪黑激素水平显著升高 (P <0 .0 0 1)。由此可见 ,黄鳝血清褪黑激素水平受到环境光周期与水温的协同调节。温度相关性的幅度变化协同光周期依赖性的时相变化 ,可能是调节褪黑激素发挥生殖调节作用的 2种重要方式。

免疫多糖(酵母细胞壁)对黄鳝免疫保护力的增强作用

在饲料中添加不同剂量的免疫多糖(酵母细胞壁),连续投喂经注射接种嗜水气单胞菌(Aeromonashydrophila)脂多糖(Lipopolysaccharide,LPS)的黄鳝(Monopterus albus)28 d后,通过测定供试黄鳝的增重量、血清中凝集抗体效价、溶菌酶活性、谷丙转氨酶活性(SGPT)、血清总蛋白含量、白细胞吞噬活性以及活菌攻毒后的免疫保护率(RPS),探讨了将LPS作为免疫原、免疫多糖作为免疫刺激剂结合使用对受免黄鳝免疫保护力的增强作用。结果表明,用添加100.0 mg/kg免疫多糖的饲料投喂受免黄鳝,不仅可以提高受免黄鳝对A.hydrophila LPS的免疫应答水平,也可以增强黄鳝的非特异性免疫力和抵抗A.hydrophila人工感染的能力,同时也证明了在饲料中添加免疫多糖对黄鳝的生长速度和肝脏功能均无不良影响。

两种不同体色黄鳝的染色体组型

采用PHA和秋水仙素活体注射法,首次对洞庭湖区两种不同体色黄鳝进行肾细胞染色体标本制备,并对其染色体数目及组型进行比较分析.结果表明,两种不同体色黄鳝的染色体数目相同,2N =24,且全部为端部着丝粒染色体;但两种不同体色黄鳝的染色体相对长度存在一定差异：黄鳝A的染色体相对长度为11.45±0.06～6.15±0.03,黄鳝B的染色体相对长度为11.53±0.01～5.23±0.09.试验结果为进一步研究洞庭湖区黄鳝种质资源的遗传多样性提供了基础性资料.

饥饿对黄鳝性腺发育及血清褪黑激素水平的影响

研究了饥饿对黄鳝（MonopterusalbusZuiew）性腺发育的影响，并试图与血清中褪黑激素水平的变化相联系．实验结果表明，6周饥饿促进黄鳝性转变，6周和1周饥饿皆导致血清褪黑激素水平的午夜值明显高于对照组（p＜0．05和p＜0．001）．由此推论，饥饿促进黄鳝性转变可能是通过提高血清褪黑激素水平来实现的．

褪黑激素在黄鳝体内分布与生殖季节性变化

选用处于不同性腺发育阶段的黄鳝，采用放射免疫技术测定了脑、眼、小肠、肝、肾、脾、心、皮肤和肌肉等组织以及血清中褪黑激素的含量．结果表明，褪黑激素在黄鳝体内的多数组织中存在（皮肤和肌肉除外），其含量顺序为：眼＞全脑＞血清＞肝＞小肠＞肾＞脾＞心．黄鳝脑内，以下丘脑和垂体的褪黑激素水平最高，嗅叶、视盖与小脑居中，端脑及延髓最低．

产卵与黄鳝性转化关联研究

对产卵与未产卵黄鳝的专池周年培育,结果表明,黄鳝与常规鱼类类似,亲鳝在人工养殖条件下培育,性腺可正常发育。已产卵黄缮第2年雄化率为22.2％,间性率为27.7％,保持雌性率为51.1％。未产卵黄缮雄化率为0％.间性率为11％,保持雌性者为89％。怀卵未产黄鳝性转化率低,黄鳝正常产卵后与怀卵未产黄鳝相比较性转化率有极显著差异(P<0.01)。

硫酸铜等4种药物对黄鳝鱼种的急性毒性试验

选用4种常用药物对黄鳝进行急性致毒试验。根据24 h半致死浓度TLm24的大小来判断药物对黄鳝的毒性大小。结果显示,可将其由高到低排列如下:硫酸铜>敌百虫>溴氯海因>二氧化氯。并根据TLm24和TLm48计算了各种药物的使用安全浓度。此4种药物的安全浓度分别为2.1 mg/L,2.27 mg/L,3.07 mg/L,4.6 mg/L。

pH对黄鳝消化酶活性的影响研究

研究了pH对黄鳝（Monopterus albus）消化道内蛋白酶、胰蛋白酶、淀粉酶和脂肪酶的活性影响。结果表明，pH会影响黄鳝消化道内消化酶的活性，在pH6．5～10．0范围内，随着pH的升高，酶活性逐渐增加．但pH继续升高到一定值后，则会逐渐降低。其蛋白酶的适宜pH为8．5～9．0，胰蛋白酶的适宜pH为8．0～8．5，淀粉酶的适宜pH为7．0～8．0，脂肪酶的适宜pH为7．0～7．5。