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.     

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.     

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.     

Y-chromosome haplotype distribution in Han Chinese populations and modern human origin in East Asians

We investigated the distribution of Y-chromosome haplotype using 19 Y-SNPs in Han Chinese populations from 22 provinces of China. Our data indicate distinctive patterns of Y chromosome between southern and northern Han Chinese populations. The southern populations are much more polymorphic than northern populations. The latter has only a subset of the southern haplotypes. This result confirms the genetic difference observed between southern and northern ethnic populations in East Asia. It supports the hypothesis that the first settlement of modern humans of African origin occurred in the southern part of East Asia during the last Ice Age, and a northward migration led to the peopling of northern China.     

Cannabis sativa: volatile compounds from pollen and entire male and female plants of two variants, Northern Lights and Hawaian Indica

Sixty-eight compounds were identified by coupled gas chromatography and mass spectrometry (GC-MS) in the chemosphere of Cannabis sativa L. pollen and entire male and female plants of two cultivated varieties, Northern Lights and Hawaian Indica. Twenty-one and 28 substances, respectively, were present in pollen of the two forms. To conserve the natural composition of volatiles a delicate headspace method was employed. The two varieties represent different chemotypes which distinguish themselves, in the main quantitatively, in the setup of volatiles from pollen and entire male and female plants. Twenty compounds were monoterpenes, including the five major components: β-myrcene (E)-β-ocimene, terpinolene, β-pinene and limonene; 25 were sesquiterpenes, and the other 23 were of mixed biogenetic origin, including 3-methyl-1-butanol and benzylalcohol which occurred only in pollen; two pyrazines occurred only in Northern Lights females. Besides being of interest in natural products chemistry, the results should have relevance for plant systematics and for the pharmaceutical and technical applications of Cannabis . We demonstrate that the pollen has a distinct chemical character in possessing two exclusive volatiles, while lacking seven compounds occurring in males and females of both variants.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 387–397.     

我国城市地表径流污染治理技术探讨

城市地表径流是典型的非点源污染,具有地域范围广、随机性强、成因复杂等特点,已成为水环境污染的重要因素之一。本文提出由源处理、输移控制和汇处理组成的城市地表径流污染控制对策,并探讨了各种具体的城市径流污染控制与治理技术,认为初期雨水的有效截留将成为下一步的研究重点。     

镧系元素对海水小球藻的毒性效应

用评价化学品对藻类毒性的标准实验方法,研究了12种镧系元素对小球藻生长的抑制情况。结果表明,12种镧系元素抑制小球藻生长的96h半效应浓度(96h EC50 )均为2 9 0 0±0 5 0 μmol·L-1。对各剂量反应方程进行X2 检验,结果表明,符合精度要求,计算出的96h EC50 真实可靠。镧系元素对海水小球藻的生物毒性是相同的,此结果对探明镧系元素对藻类的生态毒理效应具有重要意义。