鳙鱼受精早期扫描电镜研究

镛鱼(Aristichthys nobilis)受精是精子通过卵膜孔附着于卵质膜表面精子穿入部的微绒毛,两者迅即发生融合,但未见到有明显的受精锥。授精一分钟,精子整个头部已与卵的质膜发生融合,并看到有精子整个尾部已被微绒毛包裹的情况。在受精精子附近有一尚未与卵完全分开的第一极体。本文还讨论了精子穿入部的功能。     

Ecology and management of exotic and endemic Asian longhorned beetle Anoplophora glabripennis

• 1 The Asian longhorned beetle is native to China and Korea, and was found for the first time outside its native habitat in the U.S.A. in 1996, with subsequent detections being made in Canada and several European countries.
• 2 We review the taxonomy, distribution, basic biology, behaviour, ecology and management of endemic and exotic Anoplophora glabripennis, including information that is available in the extensive Chinese literature.
• 3 This species has caused massive mortality of Populus species in China and models have demonstrated that it could become established in many locations worldwide.
• 4 Anoplophora glabripennis is polyphagous but prefers Acer, Salix and Populus, section Aigeiros.
• 5 Although A. glabripennis adults do not disperse far when surrounded by host trees, they have the potential to fly more than 2000 m in a season.
• 6 Volatile organic compounds from preferred host trees are attractive to A. glabripennis and this attraction is heightened by drought stress. Males and females orientate to a volatile released by female A. glabripennis and males attempt to copulate after contacting a sex pheromone on the female cuticle.
• 7 At present, A. glabripennis is being (or has been) eradicated from areas where it has been introduced. After detection, extensive surveys are conducted and, if breeding populations are detected, at the very least, infested trees are removed and destroyed. Close attention is paid to imported solid wood packaging material to prevent new introductions.
• 8 Standard practice to control A. glabripennis in China is to spray insecticides in tree canopies. In North America, largely as a preventative measure, systemic insecticides are injected into trees. Entomopathogenic fungi have been developed for the control of A. glabripennis, and entomopathogenic nematodes, coleopteran and hymenopteran parasitoids and predatory woodpeckers have been investigated as biocontrol agents.
• 9 Ecological control of A. glabripennis in China involves planting mixtures of preferred and nonpreferred tree species, and this practice can successfully prevent outbreaks.

     

华贵栉孔扇贝♀×栉孔扇贝♂远缘杂交的受精细胞学观察

用HOECHST33258对华贵栉孔扇贝(Chlamys nobilis)♀×栉孔扇贝(Chlamys farreri)♂的受精卵进行染色,在荧光显微镜下观察其受精细胞学过程。观察表明:栉孔扇贝的精子能够使华贵栉孔扇贝卵子受精。精子入卵后呈一圆形亮点,体积稍有膨大成球形;授精后成熟卵母细胞释放出第一极体和第二极体后,精核解凝、稀疏、泡状化,形成雄性原核(male pronucleus);雌性原核(female pronucleus)在完成两次成熟分裂之后,染色质去浓缩,扩散膨大;雌雄原核相互靠拢,当雌雄原核膨胀到最大程度时,发生融合,形成合子。受精卵能够正常发育,完成第一次卵裂,卵裂时细胞核分离未观察到异常现象。与华贵栉孔扇贝和栉孔扇贝种内交配对照组相比,异源受精卵的细胞学过程明显滞后,同时其发生过程具明显的不同步现象。实验中还观察到少数的雌核发育现象。     

First Report of Calonectria ilicicola Causing a New Disease on Laurus (Laurus nobilis) in Europe

Crown and root rot has been detected on potted Laurus nobilis plants in a nursery located in the Catania province (Italy). Perithecia referable to a Calonectria species were consistently detected on crowns and stems of symptomatic plants. Based on morphology, cultural features and molecular analysis, the species was identified as Calonectria ilicicola. Koch’s postulates were fulfilled by pathogenicity tests carried out on potted Laurus nobilis seedlings. To our knowledge, this is the first report of the occurrence of a disease caused by Ca. ilicicola on Laurus nobilis.     

台湾棘带吸虫囊蚴在鳙鳃丝、鳃耙上的分布

通过对鳙为期16个月的定期取样研究发现,1993年8月到1994年3月,台湾棘带吸虫的囊蚴主要分布在鳃耙上,1994年4月至11月,囊蚴则主要分布在鳃丝上;当鳙体长范围为30-90mm时,囊蚴主要分布在鳃耙上,当体长大于90mm时,囊蚴主要分布在鳃丝上,随着鳙的生长,鳃丝囊蚴所占的比例逐渐增大,从0增加到100%,而鳃耙囊蚴所占的比例逐渐减小,从100%下降到0;不同月份、不同体长组鳙其不同组鳃丝囊蚴分布规律相同,第2组鳃丝囊蚴分布较多,第3、第1、第4组鳃丝囊蚴分布依次减少：其不同组鳃耙囊蚴分布规律也相同,总是第1组鳃耙囊蚴分布较多,其余依次为第2、第3、第4组鳃耙;囊蚴在鳙鳃丝和鳃耙上的分布都呈聚集分布,且聚集的强度随囊蚴内种群密度的增高而增高。     

Sixteen polymorphic microsatellites in bighead carp (Aristichthys nobilis) and cross-amplification in silver carp (Hypophthalmichthys molitrix)

A (GT)(n) enriched partial genomic library of bighead carp (Aristichthys nobilis) was constructed by employing the (fast isolation by AFLP of sequences containing repeats) FIASCO protocol. Sixteen loci exhibited polymorphism with two to seven alleles/locus (mean 3.263) in a test population and the observed heterozygosity ranging from 0.100 to 0.690 (mean 0.392). Eleven of the 16 bighead carp microsatellites were found to be also polymorphic in silver carp. These polymorphic loci should provide sufficient level of genetic diversity to evaluate population structure of bighead carp.     

Vulnerability to cavitation of leaf minor veins: any impact on leaf gas exchange?

Vulnerability to cavitation of leaf minor veins and stems of Laurus nobilis L. was quantified together with that of leaflets, rachides and stems of Ceratonia siliqua L. during air‐dehydration of 3‐year‐old branches. Embolism was estimated by counting ultrasound acoustic emissions (UAE) and relating them to leaf water potential (Ψ_L). The threshold Ψ_L for cavitation was less negative in L. nobilis than in C. siliqua according to the known higher drought resistance of the latter species. Leaf minor vein cavitation was also quantified by infiltrating leaves with fluorescein at different dehydration levels and observing them under microscope. Distinct decreases in the functional integrity of minor veins were observed during leaf dehydration, with high correlation between the two variables. The relationship between leaf conductance to water vapour (g_L) and Ψ_L showed that stomata of L. nobilis closed in response to stem and not to leaf cavitation. However, in C. siliqua, g_L decreased in coincidence to the leaf cavitation threshold, which was, nevertheless, very close to that of the stem. The hypothesis that stem cavitation acts as a signal for stomatal closure was confirmed, while the same role for leaf cavitation remains an open problem.     

Transitions in photosynthetic parameters of midvein and interveinal regions of leaves and their importance during leaf growth and development

Abstract: The areal development of photosynthetic efficiency and growth patterns in expanding leaves of two different dicotyledonous species - Coccoloba uvifera and Sanchezia nobilis - was investigated by imaging both processes repeatedly over 32 days. Measurements were performed using combined imaging systems for chlorophyll fluorescence and growth, with the same spatial resolution. Significant differences in potential quantum yield of photosynthesis (F_v/F_m), a parameter indicating the functional status of photosystem II, were found between midvein and interveinal tissue. Although base-tip gradients and spatial patchiness were observed in the distribution of relative growth rate, neither midvein nor interveinal tissue showed such patterns in F_v/F_m. In young leaves, F_v/F_m of the midvein was higher than F_v/F_m of interveinal tissue. This difference declined gradually with time, and upon cessation of growth, F_v/F_m of interveinal regions exceeded those of midvein tissue. Images of chlorophyll fluorescence quenching showed that ΔF/F_m' in the different tissues correlated with F_v/F_m, indicating that, in these uniformly illuminated leaves, transitions in photosynthetic electron transport activity follow those of predawn quantum efficiency. We explore the implications of these observations during leaf development, discuss effects of sucrose delivery from veins to interveinal areas on relative rates of photosynthetic development in these tissues, and propose that the initially higher photosynthetic activity in the midvein compared to the intervein tissues may supply carbohydrates and energy for leaf growth processes.     

Axillary meristems and the development of epicormic buds in wollemi pine (Wollemia nobilis)

Intact trees of Wollemia nobilis Jones, Hill and Allen (Araucariaceae) routinely develop multiple coppice shoots as well as orthotropic epicormic shoots that become replacement or additional leaders. As these are unusual architectural features for the Araucariaceae, an investigation was made of the axillary meristems of the main stem and their role in the production of epicormic and possibly coppice shoots. Leaf axils, excised from the apex to the base of 2-m-high W. nobilis plants (seedling origin, ex situ grown), were examined anatomically. Small, endogenous, undifferentiated (no leaf primordia, no vascular or provascular connections) meristems were found in the axils from near the shoot apex. In the more proximal positions about half the meristems sampled did not differentiate further, but became tangentially elongated to compensate for increases in stem diameter. In the remaining axils the meristems slowly developed into bud primordia, although these buds usually developed few leaf primordia and their apical 'domes' were wide and flat. Associated vascular development was generally restricted to provascular dedifferentiation of the cortical parenchyma, with the procambium usually forming a 'closed loop' that did not extend back to the secondary vascular tissues. Development of the meristems was very uneven with adjacent axils often at widely differing stages of development into buds. The study shows that, unlike most conifers, W. nobilis possesses long-lived meristematic potential in most, if not all, leaf axils. Unlike other araucarias that have been investigated, many of the meristems in the orthotropic main stem will slowly develop into bud primordia beneath the bark in intact plants. It appears likely that this slow but continued development provides a ready source of additional or replacement leaders and thus new branches and leaves.