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Many animals use motion vision information to control dynamic behaviors. Predatory animals, for example, show an exquisite ability to detect rapidly moving prey followed by pursuit and capture. Such target detection is not only used by predators but can also play an important role in conspecific interactions. Male hoverflies (Eristalis tenax), for example, vigorously defend their territories against conspecific intruders. Visual target detection is believed to be subserved by specialized target tuned neurons that are found in a range of species, including cats, zebrafish, and insects. However, how these target-tuned neurons respond to actual pursuit trajectories is currently not well understood. To redress his, we recorded extracellularly from target selective descending neurons (TSDNs) in maleEristalis tenaxhoverflies. We show that the neurons have dorso-frontal receptive fields, with a preferred direction up and away from the visual midline. We next reconstructed visual flow-fields as experienced during pursuits of artificial targets (black beads). We recorded TSDN responses to six reconstructed pursuits and found that each neuron responded consistently at remarkably specific time points, but that these time points differed between neurons. We compared the observed spike probability with the spike probability predicted from each neuron’s receptive field and size tuning, and found a correlation coefficient of 0.35. Interestingly, however, the overall response rate was low, with individual neurons responding to only a small part of each reconstructed pursuit. In contrast, the TSDN population responded to a substantially larger proportion of the pursuits (up to a median of 23%). This large variation between neurons could be useful if different neurons control different parts of the behavioral output.Significance statementDescending neurons constitute less than 1% of the nervous system, yet have to convey all requisite information from the brain to the body. They are therefore a crucial bottleneck in sensorimotor transformation. Descending target tuned neurons in male hoverflies (Eristalis tenax), for example, are believed to play a key role in territory defense and pursuit of conspecifics. However, this has not been tested using visual stimuli resembling reconstructed target pursuits. We here found that the observed neural responses to reconstructed pursuits are stronger than those predicted from responses to simpler stimuli. In addition, while the responses to simple stimuli suggested a homogenous population of neurons, the reconstructed pursuits showed important differences between individual neurons. Our data thus highlight the need for using more naturalistic stimuli when deciphering neural function.

The Green Weaver ants, Oecophylla smaragdina are iconic animals known for their extreme cooperative behaviour where they bridge gaps by linking to each other to build living chains. They are visually oriented animals, build chains towards closer targets, use celestial compass cues for navigation and are visual predators. Here, we describe their visual sensory capacity. The major workers of O. smaragdina have more ommatidia (804) in each eye compared to minor workers (508), but the facet diameters are comparable between both castes. We measured the impulse responses of the compound eye and found their response duration (42 ms) was similar to that seen in other slow-moving ants. We determined the flicker fusion frequency of the compound eye at the brightest light intensity to be 132 Hz, which is relatively fast for a walking insect suggesting the visual system is well suited for a diurnal lifestyle. Using pattern-electroretinography we identified the compound eye has a spatial resolving power of 0.5 cycles deg−1 and reached peak contrast sensitivity of 2.9 (35% Michelson contrast threshold) at 0.05 cycles deg−1. We discuss the relationship of spatial resolution and contrast sensitivity, with number of ommatidia and size of the lens.

The ability to visualize small moving objects is vital for the survival of many animals, as these could represent predators or prey. For example, predatory insects, including dragonflies, robber flies and killer flies, perform elegant, high-speed pursuits of both biological and artificial targets. Many non-predatory insects, including male hoverflies and blowflies, also pursue targets during territorial or courtship interactions. To date, most hoverfly pursuits were studied outdoors. To investigate naturalistic hoverfly (Eristalis tenax) pursuits under more controlled settings, we constructed an indoor arena that was large enough to encourage naturalistic behavior. We presented artificial beads of different sizes, moving at different speeds, and filmed pursuits with two cameras, allowing subsequent 3D reconstruction of the hoverfly and bead position as a function of time. We show that maleE. tenaxhoverflies are unlikely to use strict heuristic rules based on angular size or speed to determine when to start pursuit, at least in our indoor setting. We found that hoverflies pursued faster beads when the trajectory involved flying downwards towards the bead. Furthermore, we show that target pursuit behavior can be broken down into two stages. In the first stage the hoverfly attempts to rapidly decreases the distance to the target by intercepting it at high speed. During the second stage the hoverfly’s forward speed is correlated with the speed of the bead, so that the hoverfly remains close, but without catching it. This may be similar to dragonfly shadowing behavior, previously coined ‘motion camouflage’.

Responding rapidly to visual stimuli is fundamental for many animals. For example, predatory birds and insects alike have amazing target detection abilities, with incredibly short neural and behavioral delays, enabling efficient prey capture. Similarly, looming objects need to be rapidly avoided to ensure immediate survival, as these could represent approaching predators. MaleEristalis tenaxhoverflies are non-predatory, highly territorial insects, that perform high-speed pursuits of conspecifics and other territorial intruders. During the initial stages of the pursuit the retinal projection of the target is very small, but grows to a larger object before physical interaction. Supporting such behaviors,E. tenaxand other insects have both target-tuned and loom-sensitive neurons in the optic lobes and the descending pathways. We here show that these visual stimuli are not necessarily encoded in parallel. Indeed, we describe a class of descending neurons that respond to small targets, to looming and to widefield stimuli. We show that these neurons have two distinct receptive fields where the dorsal receptive field is sensitive to the motion of small targets and the ventral receptive field responds to larger objects or widefield stimuli. Our data suggest that the two receptive fields have different pre-synaptic input, where the inputs are not linearly summed. This novel and unique arrangement could support different behaviors, including obstacle avoidance, flower landing, target pursuit or capture.Significance StatementIf you are playing baseball, when the ball is far away, it appears as a very small object on your retina. However, as the ball gets closer, its image becomes a rapidly expanding object. Here, we show that within the hoverfly visual system, a single neuron could respond to both of these images. Indeed, we found a class of descending neurons with dual sensitivity, separated into two distinct parts of the visual field. The neurons have a more dorsal receptive field that is sensitive to small targets and a more ventral receptive field that is sensitive to larger objects.

The Green Weaver ants, Oecophylla smaragdina are iconic animals known for their extreme cooperative behaviour where they bridge gaps by linking to each other to build living chains. They are visually oriented animals, build chains towards closer targets, use celestial compass cues for navigation and are visual predators. Here, we describe their visual sensory capacity. The major workers of O. smaragdina have more ommatidia (804) in each eye compared to minor workers (508), but the facet diameters are comparable between both castes. We measured the impulse responses of the compound eye and found their response duration (42ms) was similar to that seen in other slow-moving ants. We determined the temporal resolution of the compound eye at the brightest light intensity to be 131.54 Hz, which is relatively fast for a walking insect suggesting the visual system is well suited for a diurnal lifestyle. Using pattern-electroretinography we identified the compound eye has a spatial resolving power of 0.52 cycles deg− 1 and reached peak contrast sensitivity of 2.88 (34.67% Michelson contrast threshold) at 0.05 cycles deg− 1. We discuss the relationship of spatial resolution and contrast sensitivity, with number of ommatidia and size of the lens.

Ligand-protected gold clusters with an asymmetric nature have emerged as a novel class of chiral compounds, but the origins of their chiroptical activities associated with helical charge movements in electronic transitions remain unexplored. Herein, we perform experimental and theoretical studies on the structures and chiroptical properties of Au-13 clusters protected by mono- and di-phosphine ligands. Based on the experimental reevaluation of diphosphine-ligated Au-13 clusters, we show that these surface ligands slightly twist the Au-13 cores from a true icosahedron to generate intrinsic chirality in the gold frameworks. Theoretical investigation of a monophosphine-ligated cluster model reproduced the experimentally observed circular dichroism (CD) spectrum, indicating that such a torsional twist of the Au-13 core, rather than the surrounding chiral environment by helically arranged diphosphine ligands, contributes to the appearance of the chiroptical response. We also show that the calculated CD signals are dependent on the degree of asymmetry (torsion angle between the two equatorial Au-5 pentagons), and provide a visual understanding of the origin of helical charge movements with transition-moment and transition-density analyses. This work provides novel insights into the chiroptical activities of ligand-protected metal clusters with intrinsically chiral cores.

A esquizofrenia (SCZ) pode ser caracterizada pela integração alterada não apenas em termos de pensamentos e sentimentos, mas também a nível de processamento neural. De acordo com essa caracterização, sugere-se que a atividade oscilatória gama (>30 Hz), possível mecanismo de integração de processos neurais, esteja alterada no transtorno. O presente estudo examinou a integração semântica, um aspecto específico de integração de processos neurais, por meio da análise da atividade gama durante priming semântico. Nossa hipótese foi que, se a integração semântica estiver prejudicada na SCZ, então a modulação da atividade gama por priming semântico seria menor no transtorno em comparação ao grupo controle. Dados eletroencefalográficos foram coletados de dezoito pacientes com SCZ (n=14 analisados) e de quarenta e três controles de desenvolvimento típico (DT) (n=30 analisados) durante a realização de uma tarefa de priming semântico. Nessa tarefa, palavras prime (ex.: BOLA) eram seguidas por imagens alvo congruentes (ex.: imagem de uma bola) ou incongruentes (ex.: imagem de um garfo). As medidas comportamentais de acurácia, tempo de reação e escore de diferença de priming, assim como as medidas eletroencefalográficas de potência evocada e induzida, conectividade baseada em sincronia de fase, coeficiente de agrupamento e comprimento de trajetória - todas na banda de frequência gama (30-50 Hz) - foram analisadas em resposta à imagem alvo. O priming semântico foi definido como a diferença dessas medidas entre as condições congruente e incongruente. Nas medidas comportamentais, o menor tempo de reação na condição congruente do que na incongruente indicou que o priming semântico ocorreu, e este não diferiu entre os grupos, conforme indicado pelo escore de diferença de priming; ademais, pacientes com SCZ apresentaram menor acurácia do que os controles. Já em relação às medidas eletroencefalográficas, não foram encontradas diferenças significativas entre as condições em nenhum dos grupos, sugerindo ausência de priming semântico nessas medidas. Porém, a potência da atividade gama evocada e induzida foi maior no grupo SCZ independentemente da condição. Embora nossos resultados não permitam concluir se a integração semântica está alterada na SCZ, eles sugerem que a atividade oscilatória gama não é modulada por priming semântico na tarefa em questão. Ademais, o achado inesperado de potência gama aumentada na SCZ independentemente da condição pode indicar um processamento neural excessivo que acaba por prejudicar a performance cognitiva. Entretanto, é possível que o pequeno tamanho amostral, principalmente do grupo SCZ, tenha encoberto outras diferenças entre grupos e condições Schizophrenia (SCZ) is characterised by altered integration not only in thoughts and behaviours but also at the neural level. Accordingly, oscillatory gamma activity (>30 Hz) - a candidate mechanism of neural processing integration - is suggested to be altered in the disorder. The present study examined semantic integration, a particular aspect of neural integration, by means of gamma activity during semantic priming. We hypothesized that if semantic integration is impaired in the disorder, then the modulation of gamma activity by semantic priming would be decreased in SCZ compared with typically developing (TD) controls. Electroencephalographic data were collected from eighteen patients with SCZ (n=14 analysed) and forty-three TD controls (n=30 analysed) during a semantic priming task. In this task, prime words (e.g.: BALL) were followed by congruent (e.g.: image of a ball) or incongruent (e.g.: image of a fork) target images. The behavioural measures accuracy, reaction time and priming difference score, as well as the electroencephalographic measures evoked and induced power, phase-based connectivity, clustering coefficient and path length were analysed in the gamma frequency band (30-50 Hz) in response to the target image. Semantic priming was defined as the difference between the congruent and incongruent condition in these measures. In the behavioural measures, the shorter reaction time in the congruent compared to the incongruent condition indicated that semantic priming occurred, and this did not differ between groups as indicated by the priming score difference; in addition, patients with SCZ showed lower accuracy than controls. In the electroencephalographic measures, no significant differences between conditions in either group were found, suggesting the absence of semantic priming in these measures. However, evoked and induced gamma power were increased in the SCZ group regardless of condition. While these results were not conclusive of whether semantic integration is altered in SCZ, they suggest that oscillatory gamma activity is not modulated by semantic priming in our task. In addition, the unexpected finding that gamma activity power is increased in SCZ irrespective of condition might indicate excessive neural processing that impairs cognitive performance. Nonetheless, it is possible that the small sample size, particularly in the SCZ group, has masked other significant differences between groups and conditions

Most animals rely on vision to perform a range of behavioural tasks and variations in the anatomy and physiology of the eye likely reflect differences in habitat and life history. Moreover, eye design represents a balance between often conflicting requirements for gathering different forms of visual information. The trade-off between spatial resolving power and contrast sensitivity is common to all visual systems, and European honeybees (Apis mellifera) present an important opportunity to better understand this trade-off. Vision has been studied extensively in A. mellifera as it is vital for foraging, navigation and communication. Consequently, spatial resolving power and contrast sensitivity in A. mellifera have been measured using several methodologies; however, there is considerable variation in estimates between methodologies. We assess pattern electroretinography (pERG) as a new method for assessing the trade-off between visual spatial and contrast information in A. mellifera. pERG has the benefit of measuring spatial contrast sensitivity from higher order visual processing neurons in the eye. Spatial resolving power of A. mellifera estimated from pERG was 0.54 cycles per degree (cpd), and contrast sensitivity was 16.9. pERG estimates of contrast sensitivity were comparable to previous behavioural studies. Estimates of spatial resolving power reflected anatomical estimates in the frontal region of the eye, which corresponds to the region stimulated by pERG. Apis mellifera has similar spatial contrast sensitivity to other hymenopteran insects with similar facet diameter (Myrmecia ant species). Our results support the idea that eye anatomy has a substantial effect on spatial contrast sensitivity in compound eyes.

Nocturnal insects likely have evolved distinct physiological adaptations to enhance sensitivity for tasks, such as catching moving prey, where the signal-noise ratio of visual information is typically low. Using electroretinogram recordings, we measured the impulse response and the flicker fusion frequency (FFF) in six congeneric species of

A general problem of sensory systems is how to simultaneously encode prevailing input as well as deviations from this baseline. A new study shows how the fly visual system has solved this by using parallel processing.

In addition to the compound eyes insects possess simple eyes known as ocelli. Input from the ocelli modulates optomotor responses, flight-time initiation and phototactic responses, behaviours that are predominantly mediated by the compound eyes. In this study, using pattern electroretinography (pERG), we investigated the contribution of the compound eyes to ocellar spatial vision in the diurnal Australian bull ant, Myrmecia tarsata by measuring the contrast sensitivity and spatial resolving power of the ocellar second-order neurons under various occlusion conditions. Furthermore, in four species of Myrmecia ants active at different times of the day and in European honeybee, Apis mellifera, we characterized the ocellar visual properties when both visual systems were available. Among the ants, we found that the time of activity had no significant effect on ocellar spatial vision. Comparing day-active ants and the honeybee we did not find any significant effect of locomotion on ocellar spatial vision. In M. tarsata, when the compound eyes were occluded, the amplitude of the pERG signal from the ocelli reduced by three times compared to conditions when the compound eyes were available. The signals from the compound eyes maintained the maximum contrast sensitivity of the ocelli as 13 (7.7%), and the spatial resolving power as 0.29 cpd. We conclude that ocellar spatial vison improves significantly with input from the compound eyes, with a noticeably larger improvement in contrast sensitivity than in spatial resolving power.

Ligand-protected gold clusters with an asymmetric nature have emerged as a novel class of chiral compounds, but the origins of their chiroptical activities associated with helical charge movements in electronic transitions remain unexplored. Herein, we perform experimental and theoretical studies on the structures and chiroptical properties of Au

Colour signals, and the ability to detect them, are important for many animals and can be vital to their survival and fitness. Fiddler crabs use colour information to detect and recognise conspecifics, but their colour vision capabilities remain unclear. Many studies have attempted to measure their spectral sensitivity and identify contributing retinular cells, but the existing evidence is inconclusive. We used electroretinogram (ERG) measurements and intracellular recordings from retinular cells to estimate the spectral sensitivity of Gelasimus dampieri and to track diurnal changes in spectral sensitivity. G. dampieri has a broad spectral sensitivity and is most sensitive to wavelengths between 420 to 460 nm. Selective adaptation experiments uncovered an ultraviolet (UV) retinular cell with a peak sensitivity shorter than 360 nm. The species’ spectral sensitivity above 400 nm is too broad to be fitted by a single visual pigment and using optical modelling we provide evidence that at least two medium-wavelength sensitive (MWS) visual pigments are contained within a second blue-green sensitive retinular cell. We also found an approximate 25 nm diurnal shift in spectral sensitivity towards longer wavelengths in the evening in both ERG and intracellular recordings. Whether the shift is caused by screening pigment migration or changes in opsin expression remains unclear, but the observation shows the diel dynamism of colour vision in this species. Together, these findings support the notion that G. dampieri possesses the minimum requirement for colour vision, with UV and blue/green receptors, and help to explain some of the inconsistent results of previous research.

Visual navigation is a benchmark information processing task that can be used to identify the consequence of being active in dim-light environments. Visual navigational information that animals use during the day includes celestial cues such as the sun or the pattern of polarized skylight and terrestrial cues such as the entire panorama, canopy pattern, or significant salient features in the landscape. At night, some of these navigational cues are either unavailable or are significantly dimmer or less conspicuous than during the day. Even under these circumstances, animals navigate between locations of importance. Ants are a tractable system for studying navigation during day and night because the fine scale movement of individual animals can be recorded in high spatial and temporal detail. Ant species range from being strictly diurnal, crepuscular, and nocturnal. In addition, a number of species have the ability to change from a day- to a night-active lifestyle owing to environmental demands. Ants also offer an opportunity to identify the evolution of sensory structures for discrete temporal niches not only between species but also within a single species. Their unique caste system with an exclusive pedestrian mode of locomotion in workers and an exclusive life on the wing in males allows us to disentangle sensory adaptations that cater for different lifestyles. In this article, we review the visual navigational abilities of nocturnal ants and identify the optical and physiological adaptations they have evolved for being efficient visual navigators in dim-light.

The US Preventative Services Task Force assessed the efficacy of breast cancer screening according to the sum of its benefits and disadvantages. We estimate that the balance of the benefits and disadvantages varies among women depending on their demographic background. Between March 2016 and March 2017, we conducted a questionnaire survey among Japanese women who underwent population-based or opportunistic breast cancer screening at our multicenter institutions. We investigated the behavior modification among women after being informed about the benefits and disadvantages of breast cancer screening depending on their demographic background. Out of 3032 questionnaires that were returned, 2936 (96.8%) were evaluated. The percentage of women with prior knowledge about the benefits and disadvantages of breast cancer screening before reading the leaflets that we created was 24%. However, 95% of the women were willing to undergo screening next time, despite knowing the disadvantages. Regarding overdiagnosis, the young women tended to choose usual treatment, and the elderly women tended to choose active surveillance. In response to the question on the significance of screening, the young women wished to avoid death by breast cancer; whereas, the elderly women wished to live a safe life. Our results indicate that the information of disadvantages does not lead to a reduction in screening rates. Additionally, we found that the balance between the benefits and disadvantages of breast cancer screening varies among women depending on their demographic background, especially age.

Visual systems play a vital role in guiding the behaviour of animals. Understanding the visual information animals are able to acquire is therefore key to understanding their visually-mediated decision making. Compound eyes, the dominant eye type in arthropods, are inherently low-resolution structures. Their ability to resolve spatial detail depends on sampling resolution (interommatidial angle) and the quality of ommatidial optics. Current techniques for estimating interommatidial angles are difficult, and generally require in vivo measurements. Here, we present a new method for estimating interommatidial angles based on the detailed analysis of 3D Micro-CT images of fixed samples. Using custom-made MATLAB software we determine the optical axes of individual ommatidia and project these axes into the three-dimensional space around the animal. The combined viewing directions of all ommatidia, estimated from geometrical optics, allow us to estimate interommatidial angles and map the animal's sampling resolution across its entire visual field. The resulting topographic representations of visual acuity match very closely the previously published data obtained from both fiddler and grapsid crabs. However, the new method provides additional detail that was not previously detectable and reveals that fiddler crabs, rather than having a single horizontal visual streak as is common in flat world inhabitants, likely have two parallel streaks located just above and below the visual horizon. A key advantage of our approach is that it can be used on appropriately preserved specimens allowing the technique to be applied to animals such as deep-sea crustaceans that are inaccessible or unsuitable for in vivo approaches.

Few walking insects possess simple eyes known as the ocelli. The role of the ocelli in walking insects such as ants has been less explored. Physiological and behavioural evidence in the desert ant, Cataglyphis bicolor, indicates that ocellar receptors are polarisation sensitive and are used to derive compass information from the pattern of polarised skylight. The ability to detect polarised skylight can also be inferred from the structure and the organisation of the ocellar retina. However, the functional anatomy of the desert ant ocelli has not been investigated. Here we characterised the anatomical organisation of the ocelli in three species of desert ants. The two congeneric species of Cataglyphis we studied had a fused rhabdom, but differed in their organisation of the retina. In Cataglyphis bicolor, each retinula cell contributed microvilli in one orientation enabling them to compare e-vector intensities. In Cataglyphis fortis, some retinula cells contributed microvilli in more than one orientation, indicating that not all cells are polarisation sensitive. The desert ant Melophorus bagoti had an unusual ocellar retina with a hexagonal or pentagonal rhabdomere arrangement forming an open rhabdom. Each retinula cell contributed microvilli in more than one orientation, making them unlikely to be polarisation detectors.

The eyes of most animals exhibit a trade-off between spatial resolving power and absolute sensitivity, which likely reflects functional adaptations for the animals' visual ecology. When animals operate in dim light conditions, the sensitivity of an eye needs to be increased because the signal-noise ratio of visual information is typically low, even though this potentially compromises spatial resolving power. Here, we investigated the spatial resolving power and contrast sensitivity in two congeneric ant species: the diurnal-crepuscular Myrmecia tarsata and the nocturnal Myrmecia midas using pattern electroretinography (PERG). Both ant species have a specialised zone in the medio-frontal region of the eye that has enlarged facets compared to the rest of the eye. Using the PERG technique, we found that spatial resolving power was 0.60 cycles per degree (cpd) in M. tarsata, while it was 0.57 cpd in M. midas. This variation in spatial resolving power is explained by differences in ommatidial facet diameters, which were significantly larger in the nocturnal M. midas. The contrast sensitivity reached a maximum of 15.5 at 0.1 cpd in M. tarsata and 21.2 at 0.05 cpd in M. midas. The contrast sensitivity functions did not differ significantly between the two species. In the diurnal-crepuscular M. tarsata, the specialised eye region with the largest facets provides both high spatial resolving power and contrast sensitivity making it an “acute zone”. In contrast, in the nocturnal M. midas the specialised eye region with the largest facets improves the eye's sensitivity, making it a “bright zone”. The increased sensitivity would be important under low luminance conditions and/or for discriminating objects of low contrast. We conclude that even closely related species active at different ambient light intensities have evolved different strategies to optimise their visual system to match their respective visual ecologies.

Queens of social insects make all mate-choice decisions on a single day, except in honeybees whose queens can conduct mating flights for several days even when already inseminated by a number of drones. Honeybees therefore appear to have a unique, evolutionarily derived form of sexual conflict: a queen’s decision to pursue risky additional mating flights is driven by later-life fitness gains from genetically more diverse worker-offspring but reduces paternity shares of the drones she already mated with. We used artificial insemination, RNA-sequencing and electroretinography to show that seminal fluid induces a decline in queen vision by perturbing the phototransduction pathway within 24–48 hr. Follow up field trials revealed that queens receiving seminal fluid flew two days earlier than sister queens inseminated with saline, and failed more often to return. These findings are consistent with seminal fluid components manipulating queen eyesight to reduce queen promiscuity across mating flights., eLife digest For social insects like honeybees it is beneficial if their queens mate with many males, because genetic diversity can protect the hive against parasites. Early in life, a honeybee queen has a short period of time in which she can fly out to mate with males before returning to the hive with all the sperm needed to last for a lifetime. Queens that have mated on their first flight may embark on additional mating flights over a few consecutive days to further increase genetic variability in their offspring. This is problematic for a male that has already mated because the more males that inseminate the queen the fewer offspring will carry on his specific genes. This results in sexual conflict between males and queens over the number of mating flights. In many animals, males manipulate females using molecules in seminal fluid to reduce the chances of the female mating again and honeybee males may use a similar strategy. Previous studies revealed that insemination alters the activity of genes related to vision in a honeybee queen’s brain. This could be one way for the males to prevent queens from embarking on additional mating flights. Now, Liberti et al. find support for this idea by showing that seminal fluid can indeed trigger changes in the activity of vision-related genes in the brains of honeybee queens, which in turn reduce a queen’s opportunity to complete additional mating flights. Queens inseminated with seminal fluid were less responsive to light compared to queens that were exposed to saline instead. Electronic tracking devices affixed to queens showed that the seminal fluid-exposed queens left for mating flights sooner but were more likely to get lost and to not return to their hives compared to the saline-exposed queens. The experiments support the idea of a sexual arms race in honeybees. Males use seminal fluid to cause rapid deteriorating vision in queens, thus reducing their likelihood of leaving the hive to mate again and to find males when they do fly again. The queens try to counteract these effects by leaving for mating flights sooner, thereby increasing offspring genetic diversity and the success of their colonies. Further studies will be needed to find out how the honeybee sexual arms race varies across seasons, bee races, and geographic ranges. Such information will be useful for honeybee breeding programs, which rely on queen mating success and hive genetic diversity to ensure hive health.

Vision is crucial for animals to find prey, locate conspecifics and navigate within cluttered landscapes. Animals need to discriminate objects against a visually noisy background. However, the ability to detect spatial information is limited by eye size. In insects, as individuals become smaller, the space available for the eyes reduces, which affects the number of ommatidia, the size of the lens and the downstream information-processing capabilities. The evolution of small body size in a lineage, known as miniaturisation, is common in insects. Here, using pattern electroretinography with vertical sinusoidal gratings as stimuli, we studied how miniaturisation affects spatial resolving power and contrast sensitivity in four diurnal ants that live in a similar environment but vary in their body and eye size. We found that ants with fewer and smaller ommatidial facets had lower spatial resolving power and contrast sensitivity. The spatial resolving power was maximum in the largest ant Myrmecia tarsata at 0.60 cycles deg−1 compared with that of the ant with smallest eyes Rhytidoponera inornata at 0.48 cycles deg−1. Maximum contrast sensitivity (minimum contrast threshold) in M. tarsata (2627 facets) was 15.51 (6.4% contrast detection threshold) at 0.1 cycles deg−1, while the smallest ant R. inornata (227 facets) had a maximum contrast sensitivity of 1.34 (74.1% contrast detection threshold) at 0.05 cycles deg−1. Miniaturisation thus dramatically decreases maximum contrast sensitivity and also reduces spatial resolution, which could have implications for visually guided behaviours. This is the first study to physiologically investigate contrast sensitivity in the context of insect allometry.

Behavioral traits can differ between individuals in a population and affect their fitness if they differentially influence survivorship in a microhabitat scale. This may occur when individuals experience different predation risks between microhabitats. In this study, we investigated boldness, exploration, and their correlation depending on the microhabitat of origin in the hermit crab Clibanarius symmetricus. Individuals of both sexes were collected from four microhabitats with different levels of predation exposure within the intertidal zone of a mangrove. We conducted experiments introducing the hermit crabs to a new standard environment and simulated predation attempts to assess exploration and boldness. Latency to re-emerge from the shell (boldness) was consistent and not affected by size, sex, or microhabitat type, but was slightly different between years. Exploration, in turn, varied only according to the microhabitat from which individuals were collected. Hermit crabs from the less risky environments explored the experimental arena for longer than individuals from the microhabitat most exposed to predators. This behavioral consistency in exploration activity can influence microhabitat choice in C. symmetricus. In addition, boldness and exploration were weakly correlated in a behavioral syndrome. Therefore, predation exposure can be a source of variation in exploration-avoidance personalities and can indirectly influence the expression of boldness in C. symmetricus. We conclude that personality traits can coevolve and have implications for habitat choice, but traditional theories of individual behavioral consistency still lack a unified theoretical background linking animal personality to niche specialization with empirical support.

Mangroves have a relevant ecosystem function due to their efficiency in blue carbon sequestration. Autotrophic carbon conservation in mangroves remains controversial. In this sense, autotrophic nutrient assimilation by crabs can highlight their ecosystem function. This study aims to identify the relationship between quality sources and food partitioning in two leaf-eating crabs, Ucides cordatus and Goniopsis cruentata. Quantification of the litterfall biomass, analysis of the soil, the C/N ratio and stable isotopes (δ13C and δ15N) were used to evaluate food sources and crab tissues in two mangrove forests. The litterfall and soil C contents and C/N ratios of the Pacoti River (PR) were higher than those of the Jaguaribe River. The higher C/N ratios of the litterfall of the PR led to higher nitrogen ingestion from complementary food sources (soil and omnivorous invertebrates). The nutritional requirements and food partitioning behavior of both species emphasize the ecosystem functions of leaf-eating crabs concerning the assimilation and conservation of autotrophic carbon and nitrogen in mangroves.

In addition to compound eyes, honeybees (Apis mellifera) possess three single-lens eyes called ocelli located on the top of the head. Ocelli are involved in head-attitude control and in some insects have been shown to provide celestial compass information. Anatomical and early electrophysiological studies have suggested that UV and blue–green photoreceptors in ocelli are polarization sensitive. However, their retinal distribution and receptor characteristics have not been documented. Here, we used intracellular electrophysiology to determine the relationship between the spectral and polarization sensitivity of the photoreceptors and their position within the visual field of the ocelli. We first determined a photoreceptor9s spectral response through a series of monochromatic flashes (340–600 nm). We found UV and green receptors, with peak sensitivities at 360 and 500 nm, respectively. We subsequently measured polarization sensitivity at the photoreceptor9s peak sensitivity wavelength by rotating a polarizer with monochromatic flashes. Polarization sensitivity (PS) values were significantly higher in UV receptors (3.8±1.5, N=61) than in green receptors (2.1±0.6, N=60). Interestingly, most receptors with receptive fields below 35 deg elevation were sensitive to vertically polarized light while the receptors with visual fields above 35 deg were sensitive to a wide range of polarization angles. These results agree well with anatomical measurements showing differences in rhabdom orientations between dorsal and ventral retinae. We discuss the functional significance of the distribution of polarization sensitivities across the visual field of ocelli by highlighting the information the ocelli are able to extract from the bee9s visual environment.

Summary The compound eyes of the Eastern Pale Clouded Yellow butterfly, Colias erate, contain three types of ommatidia (I, II and III), identifiable by the differing arrangements of pigment clusters around the rhabdoms. The pigment color is red in all ommatidial types except for type II ommatidia of females, where the pigment is orange. Intracellular recordings demonstrated that the spectral sensitivities of the proximal photoreceptors (R5-8) of all ommatidia in both sexes are strongly tuned by the perirhabdomal pigments. These pigments act as long-pass filters, shifting the peak sensitivities into the wavelength range above 600 nm. Due to the sex-specific pigments in type II ommatidia, the spectral sensitivities of the R5-8 photoreceptors of females peaked at 620 nm while those in males peaked at 660 nm. The measured spectral sensitivities could be well reproduced by an optical model assuming a long-wavelength-absorbing visual pigment with peak absorbance at 565 nm. Whereas the sexual dimorphism was unequivocally demonstrated for the ventral eye region, dimorphism in the dorsal region was not found. Presumably the ventral region is adapted for sexual behaviors such as courtship and oviposition.

Species composition, reproduction and body size of mud crabs, genus Scylla de Haan, 1833, were investigated using gill nets from October 2008 to October 2009 in Urado Bay, Japan. Three mud crab species were identified in the area, with S. paramamosain Estampador, 1949 being the dominant species (74% of the catch), followed by S. serrata (Forskal, 1775) (23%) and S. olivacea (Herbst, 1796) (3%). We found temporal changes in species composition with abundances of S. serrata increasing towards the summer season. Ovigerous females of S. paramamosain and S. olivacea occur between January and October, peaking in the warm (May-July) and rainy (June-July) seasons, but we found no berried females of S. serrata. The female-biased sex ratios of S. paramamosain and S. serrata, and the larger body size of females during the period from autumn (November) to early spring (April), suggest that large gravid females may have migrated offshore before the spawning season. The mean body size of females and males of S. paramamosain and S. serrata tended to increase and the mating activity was high between May and October, showing the moulting and growth season.

The fishery biology of mud crabs Scylla spp. was examined using baited traps and gill nets from September 2001 to August 2005 at Iriomote Island, Japan. To elucidate the growth of the crabs, artificially produced S. serrata juveniles were released and recaptured at the study site. The sizes at which 50% of females and males of S. serrata reached sexual maturity (SM50) were estimated as an external carapace width (ECW) based on the morphology of the abdomen and the chela respectively. Two species, S. serrata and S. olivacea, were identified in the area with S. serrata being the dominant species (>95% of the catch). Changes in the mean ECW and the results of the release and recapture experiments suggested that the recruitment of young crabs to the fishery occurred from December/January to April/May. The SM50 of females and males occurred at 132.4 and 150.7 mm ECW respectively. The body size composition of S. serrata revealed that immature crabs comprised approximately 40 and 65% of the catch for females and males respectively. To maintain a sustainable fishery for S. serrata, a minimum landing size based on the SM50 estimates should be implemented as a fishing regulation.

Perchlorate concentrations in raw and tap water in Osaka, Japan, were determined by IC-MS/MS. The concentrations of perchlorate in raw water and tap water were in the ranges from

Previously, we showed that the enzymes aspartokinase (AK) and dihydrodipicolinate synthase (DDPS), which are involved in l -lysine biosynthesis in the Gram-negative obligate methylotroph Methylophilus methylotrophus AS1, were inhibited by allosteric effectors, including l -lysine. To elucidate further the regulation of l -lysine biosynthesis in M. methylotrophus, we cloned the genes encoding three other enzymes involved in this pathway, l -aspartate-β-semialdehyde dehydrogenase, dihydrodipicolinate reductase (DDPR) and diaminopimelate decarboxylase, and examined their properties. DDPR was markedly inhibited by l -lysine. Based on this and our previous results, we constructed an l -lysine-producing strain of M. methylotrophus by introducing well-characterized genes encoding desensitized forms of AK and DDPS, as well as dapB (encoding DDPR) from Escherichia coli, using a broad host range plasmid. l -Lysine production was significantly increased by employing an S-(2-aminoethyl)-l-cysteine ( l -lysine analog)-resistant mutant as the host. This derivative accumulated l -lysine at a concentration of 1 g l−1 of medium using methanol as a carbon source.

We investigated the stridulatory courtship initiated by male-male contact after agonistic encounters and the effect of dominance status on subsequent reproductive behavior in the cricket Gryllus bimaculatus. When two male crickets were kept together in a small area, their dominance status was quickly established through fighting or non-fighting interactions. Approximately 10 min after pairing, most dominant males produced calling and/or courtship songs in the presence of subordinate males. This behavior appeared to be triggered by some contact chemicals on the body surface of the males. Stimulation using the forewing of a neutral male induced courtship in dominant males at a higher level compared with neutral males which were not previously paired with males. These observations suggest that the sexual motivation in dominant males increased because of previous agonistic interactions. In contrast, subordinate males remained silent. Stimulation using the male forewing induced stridulation to a lesser degree in subordinate males than in neutral males, suggesting decreased sexual motivation in subordinate males. Furthermore, only 40% of subordinate males exhibited courtship behavior under triadic conditions (dominant male, subordinate male and female) in contrast with 100% in male-female pairs. This result reveals that subordinate males, being less sexually motivated, are continuously suppressed in their courtship by intermittent attacks by the nearby dominant males. In the other triadic condition where the males were allowed to copulate, 65% of the dominant males copulated, while none of the subordinates did. These results suggest that dominant males have a greater chance to copulate and produce offspring.

The Saccharomyces cerevisiae mutant strains blocked in the protein secretion pathway are not able to induce sexual aggregation. We have utilized the defect of aggregation to concentrate the secretion-deficient cells and identified a new gene which functions in the process of intracellular protein transport. The new mutant, uso1, is temperature sensitive for growth and protein secretion. At the restrictive temperature (37 degrees C), uso1 mutant accumulated the core-glycosylated precursor form of the exported protein invertase in the cells. Ultrastructural study of the mutant fixed by the freeze-substitution method revealed expansion of the nuclear envelope lumen and accumulation of the ER at the restrictive temperature. Abnormally oriented bundles of microtubules were often found in the nucleus. The USO1 gene was cloned by complementation of the uso1 temperature-sensitive growth defect. DNA sequence analysis revealed a hydrophilic protein of 1790 amino acids with a COOH-terminal 1,100-amino acid-long alpha-helical structure characteristic of the coiled-coil rod region of the cytoskeleton-related proteins. These observations suggest that Uso1 protein plays a role as a cytoskeletal component in the protein transport from the ER to the later secretory compartments.

Ants are thought to be special among Hymenopterans in having only dichromatic colour vision based on two spectrally distinct photoreceptors. Many ants are highly visual animals, however, and use vision extensively for navigation. We show here that two congeneric day- and night-active Australian ants have three spectrally distinct photoreceptor types, potentially supporting trichromatic colour vision. Electroretinogram recordings show the presence of three spectral sensitivities with peaks (λmax) at 370, 450 and 550 nm in the night-activeMyrmecia vindexand peaks at 370, 470 and 510 nm in the day-activeMyrmecia croslandi. Intracellular electrophysiology on individual photoreceptors confirmed that the night-activeM. vindexhas three spectral sensitivities with peaks (λmax) at 370, 430 and 550 nm. A large number of the intracellular recordings in the night-activeM. vindexshow unusually broad-band spectral sensitivities, suggesting that photoreceptors may be coupled. Spectral measurements at different temporal frequencies revealed that the ultraviolet receptors are comparatively slow. We discuss the adaptive significance and the probability of trichromacy inMyrmeciaants in the context of dim light vision and visual navigation.

The L-lysine biosynthetic pathway of the gram-negative obligate methylotroph Methylophilus methylotrophus AS1 was examined through characterization of the enzymes aspartokinase (AK), aspartsemialdehyde dehydrogenase, dihydrodipicolinate synthase (DDPS), dihydrodipicolinate reductase, and diaminopimelate decarboxylase. The AK was inhibited by L-threonine and by a combination of L-threonine and L-lysine, but not by L-lysine alone, and the activity of DDPS was moderately reduced by L-lysine. In an L-lysine producing mutant (G49), isolated as an S-(2-aminoethyl)-L-cysteine (lysine analog) resistant strain, both AK and DDPS were partially resistant to feedback inhibition. The ask and dapA genes encoding AK and DDPS respectively were isolated from the parental strain, AS1, and its G49 derivative. Comparison of the sequences revealed a point mutation in each of these genes in G49. The mutation in the ask gene altered aspartic acid in a key region involved in the allosteric regulation common to AKs, while a novel mutation in the dapA gene altered tyrosine-106, which was assumed to be involved in the binding of L-lysine to DDPS.

Aspartokinase III (AKIII), one of three isozymes of Escherichia coli K-12, is inhibited allosterically by L-lysine. This enzyme is encoded by the lysC gene and has 449 amino acid residues. We analyzed the feedback inhibition site of AKIII by generating various lysC mutants in a plasmid vector. These mutants conferred resistance to L-lysine and/or an L-lysine analogue on their host. The inhibitory effects of L-lysine on and heat tolerance of 14 mutant enzymes were examined and DNA sequencing showed that the types of mutants were 12. Two hot spots, amino acid residue positions 318-325 and 345-352, were detected in the C-terminal region of AKIII and these enzyme regions may be important in L-lysine-mediated feedback inhibition of AKIII. Feedback resistant lysC relieved on L-threonine hyper-producing strain, B-3996, from reduced L-threonine productivity by addition of L-lysine, and furthermore increased L-threonine productivity even when no addition of L-lysine. It suggested that the bottleneck of L-threonine production of B-3996 was AK and feedback resistant lysC was effective because of the strict inhibition by cytoplasmic L-lysine.

The compound eye of Colias erate is composed of about 6,500 ommatidia, eachcontaining nine photoreceptors (R1-9), forming a tiered rhabdom, surrounded by fourreddish pigments. The ommatidia are divided into three types (I-III) due to thearrangement of perirhabdormal pigment spots and expression pattern of four opsinmRNAs. The opsins are already identified: they are short (CeUV), two middle (CeV1,CeV2) and L (CeL)-absorbing types. In the thesis research, I studied the physiologicalbasis of color vision in the Eastern Pale Clouded yellow butterfly, Colias erate Esper, indetail focusing on the production mechanism of the variety of spectral photoreceptors.Following General Introduction, I describe a few basic properties of the Colias eye inChapter 1. The basic properties are the eyeshine, which is a reflection from the tapetum atthe bottom of the ommatidia, and the spectral sensitivity of the entire eye. The eyeshine ofthe dorsal region has identical reflectance spectrum in both sexes. In the ventral region ofmales, type I ommatidia reflect 660 nm and type II and III ommatidia reflect 730 nm. Infemales, type II ommatidia have broadband reflection from 620 to 730 nm, while type Iand III respectively reflect 660 nm and 730 nm as in males. Remarkable sexual differenceof eyeshine spectrum in type II ommatidia is attributable to the female-specific orangepigment. Regionalization was also found in the eye spectral sensitivity determined byelectroretinography. Dorsal region of the retina is relatively more sensitive below 420 nmrange, whereas the ventral region is more sensitive in the wavelength range of 420 nm to550 nm. This is probably because of the differential distribution of different ommatidialtypes.Four of nine photoreceptor cells contribute their rhabdomeral microvilli to the distaltier of the tired Colias rhabdom. In chapter 2, I analyzed the visual pigments and spectralsensitivities of individual photoreceptors in the distal tier in both sexes of Colias erate. Asubset of photoreceptor cells expresses a newly discovered middle wavelength-absorbingopsin, Colias erate Blue (CeB), in addition to two previously described middlewavelength-absorbing opsins, CeV1 and CeV2. The other photoreceptors either coexpressCeV1 and CeV2, or exclusively express a short wavelength-absorbing opsin, CeUV, or along wavelength-absorbing opsin, CeL. Males and females have the same visualpigment expression patterns, but the photoreceptor spectral sensitivities are sexuallydimorphic. The photoreceptors coexpressing three middle wavelength-absorbing opsinsare broad-blue receptors in males, but in females they are narrow-blue receptors. Thosewith CeV1 and CeV2 are violet receptors in females, while they are shouldered-bluereceptors in males. The sexual dimorphism in spectral sensitivity is caused by asex-specific distribution of fluorescent pigment that functions as a spectral filter.In chapter 3, I demonstrated by intracellular recording that the spectralsensitivities of the proximal photoreceptors (R5-8) of all ommatidia in both sexes arestrongly tuned by the perirhabdomal pigments. These act as long-pass filters, shifting thepeak sensitivities into the wavelength range above 600 nm. Due to the sex-specificpigments in type II ommatidia, the spectral sensitivities of the R5-8 photoreceptors offemales peaked at 620 nm while those in males peaked at 660 nm. The measuredspectral sensitivities could be well reproduced by an optical model assuming a longwavelength-absorbing visual pigment with peak absorbance at 565 nm. Whereas thesexual dimorphism was unequivocally demonstrated for the ventral eye region,dimorphism in the dorsal region was not found. Presumably the ventral region isstrongly related to sexual behaviors such as courtship and oviposition.I demonstrated in this thesis that males and females of Colias have different setof eight classes of spectral photoreceptor in the ventral region of the eye. On the otherhand, I did not detect any sexual dimorphism in the dorsal retina. The eight types ofphotoreceptor identified in the Colias ventral retina are generated by 1) duplication ofopsin genes, 2) expression of multiple opsins in single photoreceptors and 3) the filteringeffect of the fluorescent and perirhabdomal pigment. Together with previous studies,especially on the small white, Pieris rapae, and the Japanese yellow swallowtail Papilioxuthus, these mechanisms underlying various spectral receptors appear to be widespreadamong butterflies.