Behavioural Components of pheromonal aggregation in Aphis fabae Scopoli

Adult apterous A. fabae were made to walk along straight catwalks between muslin walls behind part of which other, settled aphids were confined. Individuals walking past these concealed aphids were arrested there and started to probe or turn, showing a positive taxis, inverse orthokinesis, and probably also inverse klinokinesis, all presumably in response to aphid odour. Walking aphids also responded to the visual stimulus of a black vertical stripe by turning towards it and this response was stronger than the olfactory orientation response and seemed to inhibit it. On the other hand, aphid odour enhanced the visual orientation response to the stripe.     

Mechanisms of black and white stripe pattern formation in the cuticles of insect larvae

Molecular mechanisms that produce pigment patterns in the insect cuticle were studied. Larvae of the armyworm Pseudaletia separata have stripe patterns that run longitudinally along the body axis. The pattern in the cuticle became clear by being emphasized by the increasing contrast between the black and white colors of the lines after the last larval molt. We demonstrated that dopa decarboxylase (DDC) mRNA as well as protein are expressed specifically in the epidermal cells under the black stripes. The pigmentation on the stripes was clearly diminished by injection of a DDC inhibitor (m-hydroxybenzylhydrazine) to penultimate instar larvae for 1 day before molting, suggesting that DDC contributes to the production of melanin. Further, electron microscopic observation showed that the epidermal cells under the gap cuticle region (white stripe) between the black stripes contain many uric acid granules, which gives a white color. Our findings suggest that the spatially regulated expression of DDC in the epidermal cells produces the black stripes while abundant granules of uric acid in the cells generate the white stripes in the cuticle. Based on these results, we concluded that this heterogeneity in the epidermal cells forms cuticular stripe patterns in the armyworm larvae.     

Retinal scanning and visual inputs in freely walking crickets

ABSTRACT. Freely walking crickets were filmed from above during their visual orientation towards a black stripe. A frame-by-frame analysis enabled head and body movements to be recorded. The animals walk in 200ms bouts (runs) separated by pauses of similar duration. During each run, rotations of the body axis are observed and some corrections of the course direction occur between successive runs. Generally, the crickets do not walk straight ahead but slightly sideways. Because no lateral head movements were observed during visually orientated locomotion, retinal scanning results from both rotations of the body axis and translation of the head. While walking, one of the target edges is maintained by the cricket on a relatively limited area of the retina, generally between 10 and 25 laterally. Thus, the cricket often records three pieces of information about each edge: one in the monocular visual field, and two in the binocular visual field. Nevertheless, between two pauses, the images of each edge shift asymmetrically on the retinae. Such movement could prevent receptor adaptation by modulation of the ommatidial excitation, or by stimulation of the neighbouring ommatidia. It is also suggested that antennal movements are influenced by the positions of the visually fixated target edges.     

A colour and size dimorphism in the green swordtail (population Jalapa): female mate choice,male–male competition,and male mating strategies

Two types of males are present in the Jalapa population of Xiphophorus helleri: Males with a black or dark brownish mid-lateral stripe ("black males") mature earlier and are smaller than males with a red or brownish mid-lateral stripe ("red males"). We tested the hypothesis that the colour patterns of red males may be regarded as ornaments, which evolved as the result of inter- and/or intrasexual selection. As predicted, in choice tests females exhibited a strong preference for red versus black males. Furthermore, in competition experiments red males became dominant over black males with no exception, both when body size was equal and even when red males were 3–5 mm smaller than black males. However, contrary to our prediction, sneak–chase behaviour in black males was not detected, and courtship displays occurred at similar rates in both morphs. Red males are always heterozygous, with one allele for red and another for black colouration. This genetic constraint potentially prevents the extinction of the black morph. Possibly, the colour patterns of red males are functioning as indicators of heterozygosity. According to the "heterozygosity theory of mate choice", the female's preference for red males may be adaptive.     

Visual lateral fixation and tracking in the haematophagous bug Triatoma infestans

Summary Triatoma bugs turn away from a vertical black stripe on the inner surface of a rotating or oscillating drum by keeping it in the lateral visual field at an angle relative to the long axis of the body. The value of depends on the angular velocity w of the drum. Below w=5° s^–1, increases with increasing w, and the stripe can lie to either side of the animal. Occasionally, the bugs switch between these two tracking modes. Above w=5° s^–1, remains nearly constant at about 120° and the stripe lags behind the animal. We call this lateral tracking. At velocities over 5° s^–1 the animals track the leading edge of a wide black stripe in the same manner as they track a narrow stripe. Below 5° s^–1 they walk towards the centre of the stripe (skototaxis). Objects moving towards the insect above the horizon are also fixated at an angle of about 120°. Lateral tracking is mediated mainly by the dorsal part of the visual field, as can be shown by occluding either the dorsal or ventral halves of the eyes. The walking speed of the bugs increases significantly during lateral tracking of an oscillating stripe compared with that during frontal fixation of a stationary one. We therefore interpret lateral tracking as an escape response.     

Evolution of colour patterns in East African cichlid fish

African cichlid fishes have undergone outbursts of explosive speciation in several lakes, accompanied by rapid radiations in coloration and ecology. Little is known about the evolutionary forces that triggered these events but a hypothesis, published by Wallace Dominey in 1984, has figured prominently. It states that the evolution of colour patterns is driven by sexual selection and that these colour patterns are important in interspecific mate choice, a combination which holds the potential for rapid speciation. Here we present phylogenetic analyses that describe major events in colour evolution and test predictions yielded by Dominey's hypothesis. We assembled information on stripe patterns and the presence or absence of nuptial coloration from more than 700 cichlid species representing more than 90 taxa for which molecular phylogenetic hypotheses were available. We show that sexual selection is most likely the selection force that made male nuptial coloration arise and evolve quickly. In contrast, stripe patterns, though phylogenetically not conserved either, are constrained ecologically. The evolution of vertical bar patterns is associated with structurally complex habitats, such as rocky substrates or vegetation. The evolution of a horizontal stripe is associated with a piscivorous feeding mode. Horizontal stripes are also associated with shoaling behaviour. Strength of sexual selection, measured in terms of the mating system (weak in monogamous, strong in promiscuous species), has no detectable effects on stripe pattern evolution. In promiscuous species the frequency of difference between sister species in nuptial hue is higher than in pair bonding and harem forming species, but the frequency of difference in stripe pattern is lower. We argue that differences between the two components of coloration in their exposure to natural selection explain their very different evolutionary behaviour. Finally, we suggest that habitat-mediated selection upon chromomotor flexibility, a special form of phenotypic plasticity found in the river-dwelling outgroups of the lake-dwelling cichlids, explains the rapid and recurrent ecology-associated radiation of stripe patterns in lake environments, a new hypothesis that yields experimentally testable predictions.     

Rotational and translational movement features of the pelvis and thorax during adult human locomotion

The kinematics of the pelvis and thorax are important in gait studies since their movement patterns are closely related to gait efficiency and 'smoothness' of locomotion. The purpose of this study was to identify features of normal gait patterns for later comparisons with pathological and developmental gait patterns. A two camera SELSPOT system interfaced with an HP1000 minicomputer was used to obtain three-dimensional kinematic/temporal data for the pelvis and thorax. Data from treadmill walking of eight adults were used for within subject (at different speeds) analyses. The analyses revealed a very complex pattern with a set of breakpoints which was consistent over all subjects. Some features were invariant over a range of walking speeds although the total range of motion changed considerably.     

Isolation and characterization of the mating type locus of Mycosphaerella fijiensis, the causal agent of black leaf streak disease of banana

Idiomorphs mat1-1 and mat1-2 from Mycosphaerella fijiensis , the causal agent of black leaf streak disease of banana, were isolated. Degenerate oligos were used to amplify the HMG box of the mat1-2 idiomorph from M. fijiensis , showing homology with the HMG box of Mycosphaerella graminicola. Using a DNA walking strategy, anchored on the DNA lyase gene towards the HMG box, a 9-kb-long region of mat1-2 was obtained. A 5-kb fragment from the mat1-1 region was obtained by long-range PCR using primers on the flanking regions, which have close to 100% identity between both idiomorphs. High-identity (77–89%), inverted regions within both idiomorphs were found, which suggest unique inversion events, which have not been found before, and that could have been significant in the evolution of this species. The predicted genes showed the conserved introns in both idiomorphs as well as an additional intron within the alpha box. The implications for the evolution of species in the Mycosphaerella complex on banana are discussed.     

Changing visual responsiveness in pregnant and larvipositing tsetse flies, Glossina morsitans

ABSTRACT. Direct observations on the spontaneous activity and visually-evoked responses of pregnant female Glossina morsitans morsitans Westw. were made hourly during the photophase over the 4 days around larviposition. Visual stimulation was by a 5-wide vertical black stripe moving laterally, 4 times min^-1 at c. 5 s^-1. The numbers of take-offs and the numbers of females taking off were recorded, both in response to the stimulus and spontaneously in its absence. The visual responsiveness paralled both the day-to-day changes and the altered circadian patterns of spontaneous activity reported previously (Brady & Gibson, 1983), being very low for the 48 h before parturition. It did not, however, rise in parallel with the increase in spontaneous activity during the last 3–4 h before parturition, and the proportion of flights oriented towards the moving stripe was also much reduced at that time. The significance of this changing responsiveness to slow movement is discussed, and its potential enhancement of any behavioural avoidance of aerosol, non-residual insecticide spraying during late pregnancy is noted.     

The walking gaits of some species of Pecora

A method is presented for defining the walking gaits of quadrupeds from films so that they can be compared in closely related species. Differences in walking patterns of 18 pecoran species belonging to four families are discussed with respect to anatomy and environment. Variation in the walk patterns of members within a species are assessed. They are found to vary often with the speed at which the walk is executed, with the terrain, with the presence of heavy horns or antlers and with age. The time taken for one walking stride increases with the increase in length of the legs, but the legs swing forward more rapidly than they would if they acted passively like cylindrical pendulums.     

The effects of natural substrate discontinuities on the quadrupedal gait kinematics of free‐ranging Saimiri sciureus

Wild primates encounter complex matrices of substrates that differ in size, orientation, height, and compliance, and often move on multiple, discontinuous substrates within a single bout of locomotion. Our current understanding of primate gait is limited by artificial laboratory settings in which primate quadrupedal gait has primarily been studied. This study analyzes wild Saimiri sciureus (common squirrel monkey) gait on discontinuous substrates to capture the realistic effects of the complex arboreal habitat on walking kinematics. We collected high‐speed video footage at Tiputini Biodiversity Station, Ecuador between August and October 2017. Overall, the squirrel monkeys used more asymmetrical walking gaits than symmetrical gaits, and specifically asymmetrical lateral sequence walking gaits when moving across discontinuous substrates. When individuals used symmetrical gaits, they used diagonal sequence gaits more than lateral sequence gaits. In addition, individuals were more likely to change their footfall sequence during strides on discontinuous substrates. Squirrel monkeys increased the time lag between touchdowns both of ipsilaterally paired limbs (pair lag) and of the paired forelimbs (forelimb lag) when walking across discontinuous substrates compared to continuous substrates. Results indicate that gait flexibility and the ability to alter footfall patterns during quadrupedal walking may be critical for primates to safely move in their complex arboreal habitats. Notably, wild squirrel monkey quadrupedalism is diverse and flexible with high proportions of asymmetrical walking. Studying kinematics in the wild is critical for understanding the complexity of primate quadrupedalism.     

No association between the melanocortin-1 receptor (MC1R) and black belly stripe size variation in the Great Tit Parus major

Capsule The Great Tit Parus major displays a black melanin breast patch stripe (black tie or black belly stripe) which shows great variation and its size correlates with male breeding success, survival and dominance. We investigated for associations between the melanocortin-1 receptor (MC1R) polymorphism, which has an important function in melanin colouration, and the size of the black belly stripe but were unable to detect any polymorphism in this gene. Variation in the size of the melanin-based black belly stripe may therefore be regulated through genetic variation at other genes or via modification of the gene expression inside the melanocortin system and melanogenesis.     

Relevance of visual and olfactory cues for host location in the mustard leaf beetle Phaedon cochleariae

The relevance of visual and olfactory cues for host‐plant location is investigated in males and females of the oligophagous mustard leaf beetle Phaedon cochleariae Fabricius (Coleoptera: Chrysomelidae). Different objects are offered in a walking arena and the behaviour of beetles is observed. Beetles orient toward vertically or horizontally striped black and white pattern independent of stripe orientation. The results suggest that contrast facilitates orientation in the field, whereas the pattern itself may be less important for host location in dense vegetation. The response to green and yellow objects is tested to investigate discrimination abilities between young (green) and mature (yellow) leaves. Beetles prefer green over yellow independent of material (cardboard or leaves of Nasturtium officinale R. Br., Brassicaceae). Preference behaviour tested in a dual‐choice contact assay coincides with visual preferences, where adults prefer young, more nutritious leaves for feeding and oviposition. Furthermore, females discriminate between visual cues of green leaves and green cardboard, whereas males do not, indicating that females are more sensitive in colour discrimination. Differences in colour wavelength influence the choice of beetle behaviour more strongly than differences in intensity. Both sexes of P. cochleariae prefer volatiles of the host plant N. officinale, whereas only females respond to the main volatile compound 2‐phenylethyl isothiocyanate. Given a choice between visual and olfactory cues, males orientate towards the colour cues, whereas females do not show any preferences. In males, visual cues may thus override olfactory cues, whereas, in females, both are equally important, which may reflect different ecological requirements and/or physiological abilities.     

The generalization of directional visual stimuli in the honey bee, Apis mellifera

In transfer tests the ability of bees to generalize visual stimuli was tested by using differently inclined stripes and stripe patterns offered on a vertical screen. After having been trained to single stripes or equidistant stripe patterns, which were orientated by α₊ = 45° to the horizontal, the bees had to discriminate between the training direction α₊ and the competition direction α_c = 135° by means of special stripe configurations. These transfer patterns were obtained by varying different stimulus parameters of the original training stripes, for example by (1) reversing contrast between a stripe and the surrounding visual field, (2) changing the ratio of length/width and by this the dimensions of the stripe, and (3) inserting white intervals into the black stripes. In all three test series the bees succeeded in detecting the α₊-direction along a broad range of stimulus variations. As the bees in the transfer tests positively responded to patterns, which on the other side were significantly discriminated from the training pattern (control tests), the information about the direction of the visual cue had been transferred to a new pattern configuration never seen by the bees during the training situation.     

Artificial neural network model for the generation of muscle activation patterns for human locomotion.

Skilled locomotor behaviour requires information from various levels within the central nervous system (CNS). Mathematical models have permitted researchers to simulate various mechanisms in order to understand the organization of the locomotor control system. While it is difficult to adequately characterize the numerous inputs to the locomotor control system, an alternative strategy may be to use a kinematic movement plan to represent the complex inputs to the locomotor control system based on the possibility that the CNS may plan movements at a kinematic level. We propose the use of artificial neural network (ANN) models to represent the transformation of a kinematic plan into the necessary motor patterns. Essentially, kinematic representation of the actual limb movement was used as the input to an ANN model which generated the EMG activity of 8 muscles of the lower limb and trunk. Data from a wide variety of gait conditions was necessary to develop a robust model that could accommodate various environmental conditions encountered during everyday activity. A total of 120 walking strides representing normal walking and ten conditions where the normal gait was modified in terms of cadence, stride length, stance width or required foot clearance. The final network was assessed on its ability to predict the EMG activity on individual walking trials as well as its ability to represent the general activation pattern of a particular gait condition. The predicted EMG patterns closely matched those recorded experimentally, exhibiting the appropriate magnitude and temporal phasing required for each modification. Only 2 of the 96 muscle/gait conditions had RMS errors above 0.10, only 5 muscle/gait conditions exhibited correlations below 0.80 (most were above 0.90) and only 25 muscle/gait conditions deviated outside the normal range of muscle activity for more than 25% of the gait cycle. These results indicate the ability of single network ANNs to represent the transformation between a kinematic movement plan and the necessary muscle activations for normal steady state locomotion but they were also able to generate muscle activation patterns for conditions requiring changes in walking speed, foot placement and foot clearance. The abilities of this type of network have implications towards both the fundamental understanding of the control of locomotion and practical realizations of artificial control systems for use in rehabilitation medicine.     

The role of retinula cell types in fixation behaviour of walkingDrosophila melanogaster

Summary Fixation behaviour of free walking wild typeDrosophila and various retinal mutants was tested in a circular arena. Optomotor response was also measured as a test of the function of R1-6.ora andsev,ora do not fixate a narrow stripe (10° or 20°, Fig. 1) but are able to orient towards broad stripes (110° or 180°, Fig. 1). The behaviour ofsev is not different from wild type. Fixation behaviour ofw rdgB is similar toora (Figs. 5, 6). The mutantora has a maximum optomotor response at low contrast frequencies (Fig. 2), but the threshold for this response is at least one log unit higher than in wild type orsev (Fig. 8). The light intensity threshold at 550 nm of fixation to a broad stripe (110°) is 1–2 log units higher inora than in wildtype, and 4 log units higher insev,ora and the structural brain mutantVam (Fig. 7).The conclusions are that retinula cells R1-6 mediate fixation to a narrow stripe at high and low ambient light intensities, and to a broad stripe at low ambient light levels. R8, possibly in conjunction with R1-6, contributes to orientation towards broad stripes at high light intensities. This hypothesis is supported by evidence that blue-adapted white-eyed flies are able to orient towards a broad stripe at high blue light intensities (Figs. 9 and 12). Blue adaptation totally eliminates the optomotor response (Figs. 10, 11) and so the optomotor response observed inora at low contrast frequencies (Figs. 2 and 8) is most likely due to the small remnants of the rhabdomeres of R1-6 that remain.Abbreviations PDA prolonged depolarising afterpotential - ERG electroretinogram     

Feather ornaments are dynamic traits in the Great Tit Parus major

In behavioural studies it has been common to quantify plumage colours or ornaments over a range of dates and link them to fitness characteristics without accounting for seasonal changes in these traits. Such changes are likely to be widespread among birds, yet we lack assessments of this variability within individuals. We studied both within‐ and between‐individual temporal changes in Great Tit Parus major ornaments, specifically the melanin‐based black breast stripe and the pigment‐free white cheek patch. During the non‐breeding season both ornaments varied. In juveniles and adult females, the area of the breast stripe first rose and then, from near the end of December, decreased. In adult males there was a linear decrease. In the cheek patch, the irregularity of the cheek borders showed either a linear (adults) or a non‐linear (juveniles) increase as the season progressed. In individuals repeatedly sampled during the same winter, the decrease in the size of the breast stripe was larger for males than females and there was an overall decrease in the regularity of the cheek borders. There was no relationship between the size of the breast stripe and the white cheek patch irregularities or the cheek patch area. These results imply that more attention should be paid to quantification, within individuals, of the components of expression of phenotypic traits. In addition, we suggest that further research should focus on explaining the causes and functions of ornament change.     

昆虫着色及体表黑色斑纹和斑点形成机制研究进展

昆虫在生长发育的过程中,会不断受到捕食者的攻击,为逃避被捕食在长期的适应进化中展现出各种适应性的形态特征,体色和斑纹的适应性变化是其中重要的防御策略。昆虫多样的着色模式常用于释放警告信号或者模仿宿主植物,避免被其他动物捕食并且加速逃避学习,而且在寻求伴侣、适应地理、调节体温和抵抗紫外线等方面发挥重要的生物功能,是昆虫学研究的热点之一。鳞翅目昆虫具有分布广、种类多的特点,大量的斑点和斑纹模式常见于鳞翅目昆虫中,其生物学功能比其他动物更明显。近年来研究发现色素色和结构色是昆虫主要的着色模式,眼色素、黑色素以及喋啶类色素是影响昆虫着色最重要的色素;而昆虫的寄主、环境因素、激素显著影响昆虫多样性着色模式的形成。利用定位克隆、经典遗传连锁图谱、RNA干涉、基因组编辑、高通量测序等技术分离鉴定出了多个调控鳞翅目昆虫着色的关键基因。研究表明, TH, DDC, yellow, laccase2, ebony, AA-NAT, tan和GTPCHI是昆虫色素合成信号通路中的关键基因,而多效性基因spz3, apt-like和wnt1以及20E诱导的转录因子E75A和spalt通过影响鳞翅目昆虫黑色素合成信号通路的活性从而调控黑色素的合成与沉积。本文对昆虫体色和斑纹多样性的形成和影响因素,昆虫着色类型及物质基础,以及黑色斑点和斑纹形成和调节机制方面的研究进展作了整理和总结,以期为今后着色基因的利用以及害虫防治提供理论参考。