Colour constancy in insects

Colour constancy is the perceptual phenomenon that the colour of an object appears largely unchanged, even if the spectral composition of the illuminating light changes. Colour constancy has been found in all insect species so far tested. Especially the pollinating insects offer a remarkable opportunity to study the ecological significance of colour constancy since they spend much of their adult lives identifying and choosing between colour targets (flowers) under continuously changing ambient lighting conditions. In bees, whose colour vision is best studied among the insects, the compensation provided by colour constancy is only partial and its efficiency depends on the area of colour space. There is no evidence for complete ‘discounting’ of the illuminant in bees, and the spectral composition of the light can itself be used as adaptive information. In patchy illumination, bees adjust their spatial foraging to minimise transitions between variously illuminated zones. Modelling allows the quantification of the adaptive benefits of various colour constancy mechanisms in the economy of nature. We also discuss the neural mechanisms and cognitive operations that might underpin colour constancy in insects.     

昆虫单眼的结构和功能

大多数昆虫的视觉器官除了复眼外还有一些简单的小眼,称为单眼。昆虫成虫和半变态类若虫的单眼称为背单眼,位于头顶两复眼之间。背单眼在数目和结构上都有较大变化,但基本结构包括角膜晶体、一层角膜生成细胞(覆盖在角膜晶体上)、视网膜(由大约1000个感光细胞构成,视类群而不同)。背单眼对弱光比较敏感,但在图像感知方面的作用并不显著;它是一种“激发器官”,可以增加复眼的感知能力。全变态昆虫的幼虫既没有复眼也没有背单眼,但在其头部两侧有些类似复眼小眼的侧单眼。侧单眼的结构也与小眼相似,包括角膜,晶体和由一些视网膜细胞组成的视杆。侧单眼是完全变态类昆虫幼虫仅有的感光器官,与复眼一样,它们可以感知颜色、形状、距离等等。     

Retinal development in the lobster Homarus americanus. Comparison with compound eyes of insects and other crustaceans

Pattern formation and ommatidial differentiation were examined in the developing retina of the lobster Homarus americanus using light and electron microscopy. In the lobster the retina differentiates from the surface ectoderm that covers the optic primordia. Initially a single band of proliferation moves across this surface ectoderm. Immediately following this wave of proliferation, rows of ommatidial cell clusters appear. The earliest cell clusters are often seen adjacent to dividing cells of the proliferation band. The changing organization of the first seven rows of ommatidial clusters, visible at the surface of the retina, reveals events in early ommatidial differentiation. A rosette-like cluster of 18 cells forms the first row. Each stage following the rosette clusters occurs in a separate staggered row. Developing ommatidia have a central cluster of retinula cells, whose organization changes at each stage. Four cone cells enclose the retinula cells in each cluster and extend to the surface. In the seventh row, rhabdome formation begins and the retinula cells recede, leaving only cone cells visible at the retinal surface. This change initiates the two-tiered organization of the adult ommatidium. In 70% embryos, asymmetries in the position of the R8 axon around R7 create an equatorial line separating the dorsal and ventral halves of the retina. Possible mechanisms for the formation of these asymmetries are discussed. Postembryonic growth of the retina continues in stage VI juvenile animals along the ventral edge of the retina.     

Pheromones in the life of insects

Life in insect societies asks for a permanent flow of information, often carried by rather simple organic molecules. Some originate from plants as odours of blossoms or exudates from trees. Especially important are the intra- and interspecific combinations of compounds produced by the insects themselves. These are called pheromones or ecto-hormones and serve a variety of tasks. The paper deals mainly with honeybee pheromones, but takes also into consideration those of wasps and hornets. Effects of pheromones are monitored ethologically by direct observation and filming as well as in a more quantitative manner with using direct and indirect calorimetry. In all experimental set-ups alarm pheromones were used as controls. They show an up to fourfold increase of activity after a few seconds, determined for small groups of insects as well as for a whole hornet nest placed in a 25-l calorimeter. A variety of cosmetics like soaps, shampoos, lotions and perfumes are included in the investigations because of repeated reports about unwarranted insect attacks which are said to be provoked by such products. None of the applied substances provoked a significant reaction of the bees (p > 0.05). A short appendix discusses the still questionable existence of pheromones in man, which were confirmed under laboratory conditions, but not yet for daily life.     

Corazonin in insects

Corazonin is a peptidergic neurohormone of insects that is expressed in neurosecretory neurons of the pars lateralis of the protocerebrum and transported via nervi corporis cardiaci to the storage lobes of the corpora cardiaca. This peptide occurs with a single isoform in all insects studied so far, with the exception of the Coleoptera in which no corazonin form could be detected. Very few modifications of [Arg(7)]-corazonin, originally isolated from cockroaches, are known, namely [His(7)]-corazonin which is expressed in certain locusts and the stick insect Carausius morosus, and [Thr(4), His(7)]-corazonin recently described from the honey bee Apis mellifera. In this study, we performed a comprehensive screening for corazonin in the different insect groups after detecting of a fourth isoform in a crane fly, Tipula sp. ([Gln(10)]-corazonin). [Arg(7)]-corazonin is distributed in most major lineages of insects, and is thus the ancient form which was present at the time the phylum Insecta evolved. The replacement of Arg with His at position 7 from the N-terminus occurred several times in the evolution of insects. The third isoform, [Thr(4), His(7)]-corazonin, seems to be restricted to bees (Apidae); whereas wasps (Vespidae) and a bumble bee (Apidae) express other corazonins, specifically [His(7)]-corazonin and [Tyr(3), Gln(7), Gln(10)]-corazonin, respectively. A novel corazonin form, [His(4), Gln(7)]-corazonin, was also detected in all South African members of the newly described insect order Mantophasmatodea. The [His(4), Gln(7)]-corazonin separates these species from the Namibian Mantophasmatodea which express [Arg(7)]-corazonin and can be used as a distinct character to distinguish these morphologically similar insects.     

Polyphenism in insects

Polyphenism is the phenomenon where two or more distinct phenotypes are produced by the same genotype. Examples of polyphenism provide some of the most compelling systems for the study of epigenetics. Polyphenisms are a major reason for the success of the insects, allowing them to partition life history stages (with larvae dedicated to feeding and growth, and adults dedicated to reproduction and dispersal), to adopt different phenotypes that best suit predictable environmental changes (seasonal morphs), to cope with temporally heterogeneous environments (dispersal morphs), and to partition labour within social groups (the castes of eusocial insects). We survey the status of research on?some of the best known examples of insect polyphenism, in each case considering the environmental cues that trigger shifts in phenotype, the neurochemical and hormonal pathways that mediate the transformation, the molecular genetic and epigenetic mechanisms involved in initiating and maintaining the polyphenism, and the adaptive and life-history significance of the phenomenon. We conclude by highlighting some of the common features?of these examples and consider future avenues for research on polyphenism.     

Flightlessness in insects

The evolution of wings is heralded as the most important event in the diversification of insects, yet flight-wing loss has occurred in nearly all pterygote insect orders. Flight loss is especially prevalent among taxa inhabiting historically stable habitats. Recent studies of wing-polymorphic species have revealed numerous selective trade-offs in the reproductive potentials of winged versus flightless forms. A diverse set of environmental factors, both biotic and abiotic, trigger flight loss in alary polyphenic taxa, presumably by influencing juvenile hormone titers. Phylogenetic comparisons promise to elucidate much about the historical contexts and consequences of flight loss.     

昆虫的雌雄嵌合现象

探讨了昆虫雌雄嵌合体的类型、类群、发生机制、对昆虫生物学的影响 ,以及其在胚胎发育学、比较形态学、神经系统调控机理上的应用。并对 1 980～ 2 0 0 0年《动物学记录》中收入的雌雄嵌合体记录进了行整理 ,共发现 1 3目 69科昆虫有雌雄嵌合体记载。文中还整理了中国现有的雌雄嵌合体记录     

Cognition in insects

A traditional view of cognition is that it involves an internal process that represents, tracks or predicts an external process. This is not a general characteristic of all complex neural processing or feedback control, but rather implies specific forms of processing giving rise to specific behavioural capabilities. In this paper, I will review the evidence for such capabilities in insect navigation and learning. Do insects know where they are, or do they only know what to do? Do they learn what stimuli mean, or do they only learn how to behave?     

Cognition in insects

A traditional view of cognition is that it involves an internal process that represents, tracks or predicts an external process. This is not a general characteristic of all complex neural processing or feedback control, but rather implies specific forms of processing giving rise to specific behavioural capabilities. In this paper, I will review the evidence for such capabilities in insect navigation and learning. Do insects know where they are, or do they only know what to do? Do they learn what stimuli mean, or do they only learn how to behave?     

昆虫的肢体自残现象

该文主要就昆虫的肢体自残现象发生的种类和虫态、被残器官和部位、自残发生的原因、自残对昆虫个体的有利及不利影响进行了综述,并简单地讨论了肢体自残现象在进化上的意义。     

昆虫的微孢子虫病

介绍了昆虫微孢子虫病的病理学、传播途径、寄主特异性、病害管理以及利用昆虫微孢子虫作为生物杀虫剂的应用等方面的研究进展 ,以期为益虫微孢子虫病害的防治和昆虫微孢子虫杀虫剂的研制提参考。