Factors affecting nest-site choice and reproductive success of Curlews Numenius arquata on farmland

Nest-site choice and reproductive success of Curlews Numenius arquata in different habitats were studied at a mixed farmland site (grasslands and flooded tilled fields relatively common) and at an arable farmland site (dry tilled fields more dominant than at the mixed site) in central Sweden. At both sites Curlews preferred to nest on grassland and fallow fields, where hatching success was higher than on tillage fields. Nests were also situated further away from forest edges than random sites, but hatching success did not vary with distance to the forest edge. Only 35.6% of the pairs were estimated to hatch young. The main cause of nest loss was predation and the second most important factor was destruction by farming practices, which was an important factor in tillage early in season. Surprisingly, nest survival was higher at the arable than at the mixed farmland site, probably being an effect of the increased proportion of fallowing during recent years. Mortality of chicks was 79.7% before fledgling age (both sites combined) and, surprisingly, chick survival was lower on meadows than on arable fields and leys. The mean production of young was only 0.25 fledglings per pair, which is lower than in areas less affected by farming practice. The low production of young is probably an important factor in the decline of Curlew populations on Swedish farmland. On bogs 1.4 fledglings per pair were produced, indicating that reproductive success of Curlews is higher in more natural habitats.     

Resistance of nicotiana benthamiana to phytophthora infestans is mediated by the recognition of the elicitor protein INF1

Phytophthora infestans, the agent of potato and tomato late blight disease, produces a 10-kD extracellular protein, INF1 elicitin. INF1 induces a hypersensitive response in a restricted number of plants, particularly those of the genus Nicotiana. In virulence assays with different P. infestans isolates, five Nicotiana species displayed resistance responses. In all of the interactions, after inoculation with P. infestans zoospores, penetration of an epidermal cell was observed, followed by localized necrosis typical of a hypersensitive response. To determine whether INF1 functions as an avirulence factor in these interactions, we adopted a gene-silencing strategy to inhibit INF1 production. Several transformants deficient in inf1 mRNA and INF1 protein were obtained. These strains remained pathogenic on host plants. However, in contrast to the wild-type and control transformant strains, INF1-deficient strains induced disease lesions when inoculated on N. benthamiana. These results demonstrate that the elicitin INF1 functions as an avirulence factor in the interaction between N. benthamiana and P. infestans.     

Establishment and maintenance of nuclear position during zoospore formation in allomyces macrogynus: roles of the cytoskeleton

The involvement of the microtubule (MT) and actin microfilament (MF) cytoskeletons in establishing nuclear positions during zoosporogenesis in Allomyces macrogynus was assessed using selective cytoskeletal disrupting treatments and documented with light microscopy. These experiments were coupled with low-speed centrifugation studies to determine the degree to which cytoskeletal elements anchor nuclear position. At the onset of zoospore formation, nuclei were positioned only in cortical cytoplasmic regions of the zoosporangia (ZS). Immunofluorescence microscopy revealed that MTs primarily emanated from centrosomal regions into the surrounding cytoplasm at this stage. During delimitation of the cytoplasm into individual uninucleate zoospores, nuclei migrated from cortical regions to become distributed throughout the cytoplasm. Coincident with nuclear migrations, MTs were primarily organized at and emanated from nuclear surfaces, forming extensive perinuclear arrays. Nuclear migrations were suppressed in ZS induced to sporulate in the presence of cytochalasin D, an actin MF inhibiting compound. Disruption of MTs with nocodazole did not block nuclear migrations, although resultant nuclear spacing was irregular. Centrifugation treatments of control and drug-treated ZS demonstrated that nuclear positions were stabilized by perinuclear MT arrays. The results indicate that nuclear motility in ZS of A. macrogynus is the result of an actin-based system while perinuclear MTs arrays function to establish and fix nuclear position during zoospore formation. Copyright 1998 Academic Press.     

青冈林土壤动物群落结构在落叶分解过程中的演替变化

１９９３年５月－１９９５年４月,采用落叶袋法研究了中亚热带青冈（Ｃｙｃｌｏｂａｌａｎｏｐｓｉｓｇｌａｕｃａ）林土壤动物在落叶分离过程中的演替,变化,用多样性指数,演替指数,相似系数分析土壤动物群落结构的季节变化和在落叶分解过程中的演替,分解出现的类群,密度最高的为蜱螨目（Ａｃａｒｉｎａ）其次为弹尾目（Ｃｏｌｌｅｍｂｏｌａ）,二者个体数之和占总数的９２．７％,其他依次为：双翅目（Ｄｉｐｔｅｒａ）膜翅     

Sex roles, parental effort and offspring desertion in the monogamous Eurasian Curlew Numenius arquata

The reasons for female desertion of offspring and the evolution of predominantly male care among monogamous bird species are not clearly understood. We studied parental effort during the incubation and chick rearing periods in the Eurasian Curlew Numenius arquata in western Finland, and compared timing of brood desertion with other populations in Europe. Males and females contributed equally to incubation and showed no differences in the intensity of mobbing behaviour towards a potential nest predator (stuffed crow) shortly after hatching. However, females deserted their offspring approximately halfway through the brooding period ( c. 16 d after hatching), while males remained with chicks until independence ( c. 35 d). Females with late-laid clutches deserted their offspring sooner after hatching than those with clutches produced earlier in the season. Curlew females deserted younger chicks in northeast Europe, where laying dates were later, breeding seasons shorter and migration distances were longer, than in western and central Europe. We suggest that the most likely reasons for offspring desertion by females may be associated with increased female survivorship and maintenance of pairbond between years.     

台湾铗蠓吸血和生殖的观察

实验室条件下,台湾铗蠓[Forcipomyia (Lasiohelea)taiwana]吸食小鸡、小白鼠乳鼠的血液,吸血率为7.07%±1.64和65.70%±5.41.亦能通过人胎盘膜进行离体喂血,吸血率为35.44%±6.91.80对成蠓用人工交配的方法其交配率达到19%,但未授精.雌蠓未交配能吸血、产卵但不孵化.雌蠓饱血一次,发育成熟的卵平均为49.23±21.33个,实际产出的卵平均为35.35±22.38个.关于交配和产卵习性也做了观察.     

Adaptive evolution of G-protein coupled receptor genes

The phylogeny and patterns of nucleotide substitutions in the visual pigment genes, adrenergic receptor genes, muscarinic receptor genes, and in the human mas oncogene were studied by comparing their DNA sequences. The evolutionary tree obtained shows that the visual pigment genes and mas oncogene form one cluster and that the receptor genes form another. In the evolution of rhodopsin genes, synonymous substitutions outnumber nonsynonymous substitutions. This is consistent with the neutral theory of molecular evolution. However, the early evolutionary stages of alpha- and beta-adrenergic and muscarinic receptors are notable for significantly more nonsynonymous substitutions than synonymous substitutions, suggesting the acquisition of novel functional adaptations. Variable rates of nonsynonymous changes in different domains of these proteins reveal DNA segments that might have been important in their functional adaptations.      

超氧阴离子自由基对绿豆黄化幼苗ACC合酶的影响

以0．5、5和50mmol／L的连二亚硫酸钠(Na2S2O4)为外源超氧阴离子自由基(O2^-)源,处理20min能明显提高绿豆黄化幼苗ACC合酶(ACC synthase,ACS,EC4．4．1．14)的活性。超氧阴离子自由基的特异性清除剂超氧化物歧化酶(superoxide dismutase,SOD)和1,4-二氮杂二环(2,2,2)辛烷[1,4-diazabicyclo(2,2,2)Octane,DABCO]能抑制Na2S2O4的这种作用,显示Na2S2O4产生的O2^-;引起了ACC合酶活性的升高。但Na2S2O4处理较长时间,ACC合酶活性开始下降,处理60min的ACC合酶活性明显低于对照,SOD和DABCO的加入有助于抑制ACC合酶活性的降低,表明超氧阴离子自由基对ACC合酶活性具有促进和抑制作用并存的“双重性”影响。研究表明,外源Na2S2O4处理20min能明显降低以S-腺苷蛋氨酸(S-adenosylmethionine,SAM)为底物的ACC合酶的Km值,处理60min反而提高了ACC合酶的Km值,表明O2^-;是通过改变ACC合酶对底物SAM的亲和力,从而影响其活性的。     

俄罗斯水稻种质资源的苗期耐盐鉴定

采用在沿海滩涂用海水灌溉的方法,对从俄罗斯引进的104份水稻种质资源进行了苗期耐盐性鉴定.结果表明,随着海水灌溉时间延长,土壤电导率和盐度逐渐增加,水稻受盐害的程度加剧,不同材料之间差异明显.敏感对照日本晴在海水灌溉第9天全部死亡.根据国际水稻所水稻耐盐性9级分级方法进行苗期耐盐性评价,从俄罗斯资源中筛选出1级耐盐材料2份, 3级耐盐材料14份,两次重复鉴定结果基本一致.试验结果表明,水稻耐盐性受生态环境影响较大,有必要对引进的资源进行重新筛选和评价.