昆虫繁盛的原因探析

昆虫繁盛的最主要原因是其对陆地生活的成功适应。对昆虫的陆地生活适应性从昆虫如何保持体内水分、克服重力、呼吸空气、陆地繁殖、体躯小等几个方面进行了分析。     

MicroRNA在昆虫变态及生殖过程中的调控作用

MicroRNA（miRNA）是一类广泛存在于真核生物中的小分子非编码RNA,通过抑制靶基因的翻译过程或降解靶基因的mRNA,在转录后水平上调控基因表达。在昆虫中已报道了大量的miRNA,其中部分miRNA的功能得到了解析。在昆虫变态过程中,let-7, miR-100, miR-125, miR-34, miR-14, miR-8, miR-281和 miR-252-3p能够作用于保幼激素或蜕皮激素信号通路,影响昆虫蜕皮、化蛹或翅、足及神经系统的发育。在昆虫生殖阶段,bantam, miR-184和miR-275影响生殖干细胞的分化或卵子发生。本文在介绍miRNA生物合成和作用机制的基础上,重点对昆虫变态与生殖过程中miRNA的最新研究进展进行综述。     

妙趣横生话昆虫

对昆虫我们都很熟悉,成虫的身体分为头、胸、腹3个部分,头部的口器、触角、单眼和复眼形态各异;胸部的3对足和2对翅（也有的种类只有一对翅或缺翅）体现运动天赋;腹部是生殖与营养代谢的中心;坚硬的外骨骼不但对身体起保护作用,还装点了五彩斑斓的昆虫世界。     

“昆虫的生殖和发育”一节概念教学

以“昆虫的生殖和发育”一节课为例,阐述在初中生物学课堂中如何进行概念教学.在学生观察比较和分析归纳的基础上,教师力求在课堂教学过程中帮助学生形成概念,促使学生自主有效地构建概念.     

MicroRNA对不完全变态昆虫变态及生殖调控作用的研究进展

MicroRNAs(miRNAs)是一类在真核生物中由内源基因编码的小分子RNA,参与昆虫变态、生殖发育、细胞分化等多种重要生物学过程,在转录水平上发挥重要作用.在完全变态昆虫中,大量调控其变态及生殖的miRNA被广泛报道且进行了深入的研究,但miRNA调控不完全变态昆虫的变态及生殖发育的研究仍比较少,对其具体的调控机制也需要进一步阐明.为此,本文综述了近年来miRNA在调控不完全变态昆虫(以直翅目飞蝗Locusta migratoria、半翅目褐飞虱Nilaparvata lugens和蚜虫以及部分蜚蠊目昆虫为代表)的变态及生殖方面的研究进展,以期深化理解miRNA对不完全变态昆虫变态和生殖发育方面的机制,为害虫生态治理和综合防控提供科学依据.     

昆虫变态发育类型与调控机制

昆虫变态发育使得昆虫成为地球上种类最多、分布最广的动物种群。它特指末龄幼虫化蛹,或者蛹向成虫的转变过程。根据变态剧烈程度,可将昆虫变态发育简单分为增节变态、表变态、原变态、不完全变态及全变态5种类型。此外,昆虫变态发育是一个极其复杂的生物学过程,受到激素、基因、营养等多种因素的精密调控。本文简要介绍了昆虫变态发育的类型和分子调控机理方面的研究进展。     

昆虫分目“科普诗”

杨集昆先生在长年的昆虫教学过程中,曾以二十字来介绍什么是昆虫纲:“体分头胸腹,四翅并六足:生长多变态,昆虫百万数。”后又将代表我国昆虫大类群的32个目,各作一首,虽被视为“打油诗”或“顺口溜”,但对初学之士不无帮助,有益于科学普及。这里,我们将这些“科普诗”列出来,配之以图,让广大昆虫爱好者共赏之。     

珍稀昆虫蛩蠊目研究取得新进展

蛩蠊目（Grylloblattodea）起源古老,至少可追溯到上石炭纪（距今约3亿年）,特征原始,是昆虫纲孑遗类群之一,又被称为昆虫纲的“活化石”,在我国属一级保护昆虫。     

昆虫机器混合系统研究进展

昆虫机器混合系统是以昆虫为载体,运动性能优异的新型昆虫机器人.本文首先提出昆虫机器混合系统的定义,分析其主要特点;进而结合蜜蜂机器人的研制,评述该领域的主要研究成果.在此基础上,概括了昆虫机器混合系统的研究框架,从神经生理机制、行为刺激方法、电极组织接口、刺激控制微系统和无线数据传输等几个方面归纳其主要研究挑战,分析其发展趋势,并展望了实现生物智能和机器智能融合的昆虫机器混合系统.     

整合昆虫发育生物学和果蝇遗传学来研究昆虫发育与变态

成熟动物(昆虫)个体大小主要由生长持续时间和生长速度2个因素所决定。蜕皮激素和保幼激素协同调控昆虫发育变态,并决定昆虫生长持续时间;胰岛素、营养和细胞接触抑制等生长死亡信号及其传导途径控制细胞分裂、长大、分化、死亡,并最终决定昆虫的生长速度。最近研究成果表明,蜕皮激素信号和胰岛素信号相互影响,对昆虫个体大小起决定性的作用;脂肪体和营养代谢把这2条信号传导途径整合起来。科学家将会整合昆虫发育生物学和果蝇遗传学,抓住生长持续时间和生长速率2个关键因素,并以营养代谢和脂肪体为切入点来研究昆虫的发育变态。     

Assessing the contributions of multiple interacting traits to plant reproductive success: environmental dependence

The reproductive success of sibling cocklebur plants (Compositae: Xanthium strumarium) was monitored after growth at different levels of availability of water and nutrient resources. Variation in reproductive success among individual plants was related to physiological, structural, and phenological characteristics. Reproductive success increased with increased availability of resources, but the relative contribution of particular traits to reproductive success varied with resource availability. Allocation of biomass to different vegetative tissues, time to seedling emergence, degree of branching, transpiration rates, water use efficiency, the rate of decline in height growth after seedling emergence and final plant size all varied significantly with resource availability. However, the changes in each of these phenotypic traits across three garden environments did not always correlate with reproductive success. The shifts across environments in the apparent importance of somatic traits for reproductive success were attributed to plastic changes in the traits but also to changes in the phenotypic correlations of the traits with reproductive success.     

Phenotypic plasticity in life-history traits of femaleThalassoma bifasciatum (Pisces: Labridae): 2. Correlation of fecundity and growth rate in comparative studies

Synopsis The cost of reproduction is a central concept in theories of life-history evolution. One way to empirically examine the tradeoff between current reproduction and future reproductive prospects is to use natural intraspecific variation in life-history traits. However, this approach is complicated by the sensitivity of life-history traits to variation in the level of resources. We report here an attempt to measure the cost of increasing reproductive activity in populations of female bluehead wrasse,Thalassoma bifasciatum, a coral-reef fish. All of the significant correlations of fecundity and growth rate were positive, in contradiction to the tradeoff predicted by the cost concept. In one of two regions studied, the populations with relatively high mean growth rate had a relatively large mean fecundity. The trait means were also positively associated over time: in months of rapid growth, female reproductive activity was high. Even after removing the effects of habitat and time period in a comparison of individual traits, no growth cost to reproduction appears. Variation in the abundance of resources over space and time is likely to interfere with the measurement of the cost of reproduction in many natural systems.     

Reproductive traits in the tropical moss Octoblepharum albidum Hedw. differ between rainforest and coastal sites

Abstract

Octoblepharum albidum Hedw. is an autoicous moss commonly occurring in tropical savannas, dry forests, rainforests and coastal habitats. It frequently reproduces by spores and asexual structures (gemmae and protonemata or buds at leaf tips), making it a good model for understanding how reproductive traits change with respect to habitat type. Our aims were to characterize the different life-history traits in O. albidum relative to sexual and asexual cycles and to detect variations in reproductive performance among the different habitats, trade-offs among these traits, and relationships among reproductive traits and plant length. We studied colonies from two Atlantic rainforests and two coastal sites in north-eastern Brazil. Shoots in the coastal sites, compared to those of the forest sites, had higher numbers of sporophytes, male and female branches per shoot, male gametangia per sexual branch, and longer setae. Numbers of female gametangia per sexual branch did not differ between forest and coastal sites. A male-biased sex ratio of branches and gametangia occurred in all sites. Compared to gemmae, sporophytes and protonemata or buds were more likely to be found on longer shoots than on shorter ones, but this relationship was only applicable to forest sites. The abundant production of gemmae and protonemata or buds at leaf tips, and sporophytes (spores) in O. albidum are important components in explaining colonization success and maintenance in this tropical moss. Longer sporophytic setae in addition to a higher reproductive performance (especially for number of male gametangia and sporophytes per shoot) may favour spore dispersal and colonization in plants of coastal sites.     

Sodium activity of insect blood: physiological significance and relevance to the design of physiological saline.

The apparent activity coefficients for sodium (gamma'Na) in the blood of six insect species have been calculated from measurements made with sodium-selective electrodes and a flame photometer. In every case gamma Na was significantly lower than that for this cation in free solution (gammaNa). In Periplaneta americana gammaNa varied considerably, during a period of 90 days, so that a relatively constant sodium activity (aNa) was maintained in the blood in the face of large variations in the total sodium content measured by flame photometry. Despite the relative constancy of aNa (of around 0.088M) appreciable fluctuations were observed in the sodium and potassium content of nervous connective over a period of 140 days. The values of aNa and aK were used to devise a satisfactory cockroach saline for use in experiments with isolated nerve cords.     

Antennal sensilla of grasshoppers (Orthoptera: Acrididae) in relation to food preferences and habits

The external structure, i.e. number and distribution of sensillae on male and female antennae of 12 species of grasshoppers belonging to Pamphaginae, Catantopinae, Oedipodinae and Gomphocerinae in the grasslands of Inner Mongolia was investigated using scanning electron microscopy. Five major types of antennal sensillae were detected - trichoid, long basiconic, short basiconic, slender and short basiconic, and coeloconic sensillae. Total number of antennal sensillae varied among different sexes, subfamilies, feeding groups, life forms and eco-forms. Males showed significantly more sensillae than females, due to presence of more short basiconic and coeloconic sensillae. Species under Catantopinae showed more long basiconic sensillae than the others. The Oedipodinae had the highest number of slender and short basiconic sensillae and coeloconic sensillae, followed by Catantopinae and Gomphocerinae; while Pamphaginae had the fewest. The total number of sensillae showed the same trend for these two types amongst the subfamilies as well, species which prefer habits on the ground possessed fewer antennal sensillae than species which prefer to stay on plants. The maximal number of antennal sensillae were observed in hygrophytous species,Chorthippus albomarginatus, in the 12 grasshopper species investigated, although the data is not statistically significant. The general trend which emerged was that species feeding on grass possessed more antennal sensillae, particularly coeloconic sensillae, compared to other feeding group species.     

Antibiotic resistance and the evolution of group-beneficial traits. II: a metapopulation model

Inspired by the evolution of antibiotic resistance in bacteria, we have developed a model that examines the evolution of "producers" (who secrete a substance that breaks down antibiotics) and non-producers. In a previous study, we found that frequency-dependent selection could favor an intermediate frequency of producers in a single, large population. Here we develop a metapopulation model that examines the evolution of producers and non-producers. Our results indicate that in a metapopulation with many groups, each of size N, the equilibrial frequency of producers decreases with group size. Even when N is high (e.g. 150 individuals/group), however, a significant frequency of producers is still predicted. We also found that the equilibrial frequency of producers increases as the minimum numbers of producers necessary to provide protection to non-producers increases. Lastly, increasing the benefit/cost ratio (b/c) for producers increases their equilibrial frequency.