Innervation and control of tension in abdominal muscles of Blaberus discoidalis and Gromphadorhina portentosa

In Blaberus discoidalis and Gromphadorhina portentosa, the distribution of motor axons to the muscles which control movements of the spiracular valves at both respiratory and non-respiratory spiracles is identical. Both fast and slowly contracting heads of the opener muscles are innervated by an excitatory motor axon. Physiological properties of the opener excitor axon correlate with valve function. The slowly contracting head of the opener muscle is, in addition, innervated by a common inhibitor which also occasionally innervates closer muscle fibers. Activation of the common inhibitor terminates contraction of slowly contracting opener muscle fibres and initiates a rapid relaxation of these fibres.     

Functional morphology of the spiracles in two species of Argasidae (Metastigmata: Acarina), with particular reference to responses to desiccation

Spiracle morphology of Argas persicus (Oken) and Omithodorus acinus Whittick is described and the differences between the two species are related to biological factors. Argasid and ixodid spiracle structures and functions are compared.     

肥须亚麻蝇幼虫不同发育阶段气门形态学变化

为了满足实际工作中利用蝇类幼虫日龄推断尸体死后间隔时间的需求,本文采用显微镜观察不同龄期肥须亚麻蝇 Parasarcophaga crassipalpis (Macquart)幼虫气门的形态学变化,通过计算机图像分析系统对幼虫的前、后气门等可用于判断幼虫生长发育的形态学指标进行测量。结果表明：肥须亚麻蝇幼虫前、后气门随时间而发生规律性的变化,幼虫前气门色素管部的平均光密度及其长宽比,以及后气门的平均光密度这 3 项指标是推算幼虫日龄较理想的指标,对法医学中尸体死亡时间的推测具有重要的指示意义。此外,叠龄期作为幼虫发育的必经阶段,可为特殊时间点的推测提供可靠依据。     

昆虫不连续气体交换

许多昆虫呼吸时气体交换是不连续的循环式进行的。根据气门开闭,一个典型的不连续气体交换循环（discontinuous gas exchangecycle, DGC）可以明显分为3个阶段: 关闭阶段,极少或没有气体交换;颤动阶段,气门迅速微开和关闭,O₂进入气管,少量CO₂释放;最后是开放阶段,大量的CO₂释放。该文综述了DGC特征及昆虫活动、温度、体重对DGC的影响,并讨论了DGC与呼吸失水、缺氧或高CO₂浓度环境有关的进化适应意义。     

The mating behaviour of tsetse flies (Glossina): a review

Abstract. The mode of reproduction of tsetse flies, by adenotrophic viviparity, is unusual among the Diptera and is associated with many unique aspects of the tsetse's mating system. Tsetse exist at relatively low densities in the environment but a combination of olfactory and visual stimuli brings males and virgin females together on or around host animals. The behavioural repertoire associated with mate location and identification, courtship and copulation is regulated by external physical and chemical stimuli as well as by internal physiological mechanisms. With a view to identifying stimuli that could be used to manipulate tsetse behaviour and exploited for control purposes, much progress has been made in recent years in elucidating the mating behaviour of tsetse and its regulatory mechanisms. This progress and the current state of understanding of tsetse mating behaviour is reviewed.     

Morphology and ultrastructure of spiracles in phlebotomine sandfly larvae

The morphology and ultrastructure of the larval spiracle system of three phlebotomine sandfly species, Phlebotomus perniciosus, P. perfiliewi and P. papatasi, were examined by scanning (SEM) and transmission (TEM) electron microscopy and by confocal scanning laser microscopy (CSLM). During larval development, thoracic and abdominal spiracles show considerable modifications. In fourth instar larvae, the spiracles consist of a plate with a sclerotized central portion and a peripheral circle of papillae. The latter is distinctive in the larvae of P. papatasi, which are readily distinguished from the other species. Opening clefts across the papillae communicate with an internal chamber that encircles an electrondense plug. Many cylindrical projections cross the chamber, uniting the central plug with the larval body, forming an air filter. Spiracular development in successive larval instars has both a taxonomic and adaptive value.     

Temperature effect on the predation rate of Anthocoris nemorum (Het.: Anthocoridae) on cabbage aphids (Hom.: Aphididae)

The temperature‐dependent predation by Anthocoris nemorum L. (Het.: Anthocoridae) on second instar Brevicoryne brassicae L. (Hom.: Aphididae) at constant temperatures of 12, 15 and 20°C increased linearly with temperature with a mean (±SE) consumption of 6.9 (±0.8), 9.28 (±1) and 15.9 (±0.8) respectively. The estimated lower temperature threshold for predation (T₀) was 6.4°C.     

Structural characterisation and functional significance of transient protein-protein interactions

Protein-protein complexes that dissociate and associate readily, often depending on the physiological condition or environment, play an important role in many biological processes. In order to characterise these "transient" protein-protein interactions, two sets of complexes were collected and analysed. The first set consists of 16 experimentally validated "weak" transient homodimers, which are known to exist as monomers and dimers at physiological concentration, with dissociation constants in the micromolar range. A set of 23 functionally validated transient (i.e. intracellular signalling) heterodimers comprise the second set. This set includes complexes that are more stable, with nanomolar binding affinities, and require a molecular trigger to form and break the interaction. In comparison to more stable homodimeric complexes, the weak homodimers demonstrate smaller contact areas between protomers and the interfaces are more planar and polar on average. The physicochemical and geometrical properties of these weak homodimers more closely resemble those of non-obligate hetero-oligomeric complexes, whose components can exist either as monomers or as complexes in vivo. In contrast to the weak transient dimers, "strong" transient dimers often undergo large conformational changes upon association/dissociation and are characterised with larger, less planar and sometimes more hydrophobic interfaces. From sequence alignments we find that the interface residues of the weak transient homodimers are generally more conserved than surface residues, consistent with being constrained to maintain the protein-protein interaction during evolution. Protein families that include members with different oligomeric states or structures are identified, and found to exhibit a lower sequence conservation at the interface. The results are discussed in terms of the physiological function and evolution of protein-protein interactions.     

Drift compensation and its sensory basis in waterstriders (Gerris paludum F.)

Summary Watestriders (Gerris paludum F.), displaced by flowing water or wind, compensate for this by periodic jumps against the direction of drift so that they keep their average position — relative to the river bank, for instance — constant over long periods of time. To identify the cues used by the animals to compensate for drift, they were kept on an artificial stream with visual patterns along one or both sides. The velocity of the water flow and the pattern motion were varied. It is not possible to induce compensatory jumps in darkness by water or air current alone. Visual cues are indispensable for the reaction. The product of jump amplitude and jump frequency equals the drift velocity on average. The jump amplitudes are more or less independent of the flow velocity while the jump frequency is adjusted to it.     

Male and female meiosis in diploid and colchitetraploid Phlox drummondii Hook. (Polemoniaceae)

Comparative studies on male and female meiosis in diploid (2n = 2x = 14) and colchitetraploid (2N = 4x = 28) ornamental Phlox drummondii reveal higher chiasma frequency in embryo-sac mother cells as compared with pollen mother cells in the diploid, and significant differences in the pairing properties of chromosomes in the pollen mother cells and embryo-sac mother cells of the colchitetraploid. Male meiosis in the colchicine-induced autotetraploid was abnormal with 51.70% of chromosomes associated in quadrivalents and tridents in 96% of the cells. This was followed by discordant anaphase I disjunction. In the female meiocytes the chromosomes formed 14 bivalents in 86.66% of the cells. Quadrivalents (1–3) appeared only in 13.34% of the cells. It is concluded that meiosis in male and female cells of the colchitetraploid is governed and regulated by different controlling systems of gene(s).     

Visual gaze control during peering flight manoeuvres in honeybees

As animals travel through the environment, powerful reflexes help stabilize their gaze by actively maintaining head and eyes in a level orientation. Gaze stabilization reduces motion blur and prevents image rotations. It also assists in depth perception based on translational optic flow. Here we describe side-to-side flight manoeuvres in honeybees and investigate how the bees’ gaze is stabilized against rotations during these movements. We used high-speed video equipment to record flight paths and head movements in honeybees visiting a feeder. We show that during their approach, bees generate lateral movements with a median amplitude of about 20 mm. These movements occur with a frequency of up to 7 Hz and are generated by periodic roll movements of the thorax with amplitudes of up to ±60°. During such thorax roll oscillations, the head is held close to horizontal, thereby minimizing rotational optic flow. By having bees fly through an oscillating, patterned drum, we show that head stabilization is based mainly on visual motion cues. Bees exposed to a continuously rotating drum, however, hold their head fixed at an oblique angle. This result shows that although gaze stabilization is driven by visual motion cues, it is limited by other mechanisms, such as the dorsal light response or gravity reception.     

Lateromyxa gallica N. G., N. Sp. (Vampyrellidae): A Filopodial Amoeboid Protist With A Novel Life Cycle and Conspicuous Ultrastructural Characters

ABSTRACT. A large, uni- or multinucleate vampyrellid rhizopod, Lateromyxa gallica n. g., n. sp., has been isolated several times from two lakes in central France between September 1973 and August 1989 and cultivated for several months or years under laboratory conditions. No essential variations of feeding behaviour were found over the time; all isolated strains invade the trichomes of the green alga Oedogonium and move, divide and encyst inside the vanished plant cells. Penetration is performed by attacking the cross walls and only primary attacks are directed against the lateral cell walls of the algae. These findings contrast with the behaviour, life cycles and fine structure of all known species of the genera Vampyrella, Hyalodiscus, Arachnula and Gobiella. The establishment of a new genus, Lateromyxa , with the type species Lateromyxa gallica is therefore proposed.     

A new method of studying predatory nematodes using a micropore system

We developed an innovative micropore system that enables us to directly observe the constrained behaviour of predatory nematodes. The results show that the new system provides a suitable environment for modelling the potential effects of these animals as biocontrol agents in their natural habitat.