Arena Size Research Articles

Multiple factors, including arena size, shape the functional responses of ladybird beetles

Abstract Functional response studies are often used to determine the suitability of predators as biocontrol agents. Ladybird beetles (Coleoptera: Coccinellidae) are often used for the control of crop pests such as aphids. However, most functional response studies on coccinellids compare a limited number of species at different life stages, temperatures or sexes. A large‐scale comparison of ladybird beetle functional responses is needed to evaluate the utility of these species as potential biocontrol predators and to understand the traits that influence the interaction strength between ladybird beetles and their prey. We compiled 158 ladybird beetle functional responses from 30 studies and tested for effects of taxa, traits, temperature and arena size on functional response parameters using linear mixed‐effects models. Our results show that functional response parameters (handling time and space clearance rate) are affected by predator stage, predator mass, prey type, temperature and arena size. Although complicated by interaction terms, space clearance rate generally increased with predator size, temperature and predator stage, while handling time decreased with predator size, temperature and predator stage. Coleopteran prey induced the highest handling times. Our results also show that experimental arena size has a large, consistent effect on space clearance rate. Arena size is more important in determining foraging rates at low prey densities than any other factor considered here, including predator mass and temperature. Efforts to use laboratory‐based functional response experiments to evaluate the efficacy of biocontrol predators are therefore confounded by the choice of arena size. Synthesis and applications. In addition to confirming known body mass and temperature effects, our study reveals previously unclear age‐related effects and the importance of prey types, which can be used to optimize biocontrol programmes. The arena size effect is unexpected and problematic because failure to account for arena size precludes accurate comparison of biocontrol predator effectiveness. We suggest managers and biocontrol practitioners re‐evaluate the efficacy of candidate biocontrol predators, perhaps by statistically controlling for arena size to minimize the influence of this widely unconsidered factor on functional response estimates.

Consistency of fish-shoal social network structure under laboratory conditions.

We investigated the consistency of association network structure for groups of sticklebacks Gasterosteus aculeatus. Each group was observed twice and we varied the duration between observations and the size of the experimental arena that they were observed in. At the dyad level, we found positive correlations between dyad interaction frequencies across observations. At the group level we found variation in four network metrics between observations, but only in treatments where the duration between observations was short. Specifically, fish formed more and smaller groups in the second observation in this treatment. Fish were also organized into more subunits in the larger arenas. Finally, we saw positive correlations between some group network metrics across observations suggesting relative consistency at the group level. There are several processes that might drive these interaction patterns. Our findings have implications for experimental design and the comparison and integration of findings of experiments from different studies carried out under different conditions.

The purging of deleterious mutations in simple and complex mating environments

There is a general expectation that sexual selection should align with natural selection to aid the purging of deleterious mutations, yet experiments comparing purging under monogamy versus polygamy have provided mixed results. Recent studies suggest that this may be because the simplified mating environments used in these studies reduce the benefit of sexual selection through males and hamper natural selection through females by increasing costs associated with sexual conflict. To test the effect of the physical mating environment on purging, we use experimental evolution in Drosophila melanogaster to track the frequency of four separate deleterious mutations in replicate populations that experience polygamy under either a simple or structurally complex mating arena while controlling for arena size. Consistent with past results suggesting a greater net benefit of polygamy in a complex environment, two of the mutations were purged significantly faster in this environment. The other two mutations showed no significant difference between environments.

Toxicant induced behavioural aberrations in larval zebrafish are dependent on minor methodological alterations

Alterations in zebrafish motility are used to identify neurotoxic compounds, but few have reported how methodology may affect results. To investigate this, we exposed embryos to bisphenol A (BPA) or tetrabromobisphenol A (TBBPA) before assessing larval motility. Embryos were maintained on a day/night cycle (DN) or in constant darkness, were reared in 96 or 24 well plates (BPA only), and behavioural tests were carried out at 96, 100, or 118 (BPA only) hours post fertilisation (hpf). We found that the prior photo-regime, larval age, and/or arena size influence behavioural outcomes in response to toxicant exposure. For example, methodology determined whether 10μM BPA induced hyperactivity, hypoactivity, or had no behavioural effect. Furthermore, the minimum effect concentration was not consistent between different methodologies. Finally, we observed a mechanism previously used to explain hyperactivity following BPA exposure does not appear to explain the hypoactivity observed following minor alterations in methodology. Therefore, we demonstrate how methodology can have notable implications on dose responses and behavioural outcomes in larval zebrafish motility following identical chemical exposures. As such, our results have significant consequences for human and environmental risk assessment.

Mutual interference between adult females of Galendromus flumenis (Acari: Phytoseiidae) feeding on eggs of Banks grass mite decreases predation efficiency and increases emigration rate.

The Banks grass mite, Oligonychus pratensis (Banks) (Acari: Tetranychidae) causes significant damage to dates in California (USA), if not controlled. Studies are underway to develop biological control strategies against this pest in dates using the predatory mite Galendromus flumenis (Chant) (Acari: Phytoseiidae). In California date gardens, this predator is found in low numbers that are insufficient for the economic suppression of Banks grass mites, and our research aims to understand why it fails to keep up with prey densities. The hypothesis that prey density and predator interference interactively determine the predation efficiency of G. flumenis was tested. In addition, the effect of arena size and prey and predator density manipulations on the emigration rate of the predator was investigated. Our results indicate that the per capita predation rate of G. flumenis decreases steeply with increasing predator density due to mutual interference. Analysis of emigration data considering the arena size and predator numbers showed that the emigration rate of G. flumenis was higher from small arenas, and increased with increasing predator numbers. When emigration data were analyzed using prey and predator densities as independent variables, only the effect of predator density was significant, suggesting that higher predator density increases the emigration rate of G. flumenis. These results contribute to our understanding of the predator-prey interactions, and help in designing strategies for more efficient augmentative releases of G. flumenis.

Heterogeneous spatial representation by different subpopulations of neurons in the subiculum

The subiculum is a pivotal structure located in the hippocampal formation that receives inputs from grid and place cells and that mediates the output from the hippocampus to cortical and sub-cortical areas. Previous studies have demonstrated the existence of boundary vector cells (BVC) in the subiculum, as well as exceptional stability during recordings conducted in the dark, suggesting that the subiculum is involved in the coding of allocentric cues and also in path integration. In order to better understand the role of the subiculum in spatial processing and the coding of external cues, we recorded subicular units in freely moving rats while performing two experiments: the “size experiment” in which we modified the arena size, and the “barrier experiment” in which we inserted new barriers in a familiar open field thus dividing the enclosure into four comparable sub-chambers. We hypothesized that if physical boundaries were deterministic of the firing of subicular units a strong spatial replication pattern would be found in most spatially modulated units. In contrast, our results demonstrate heterogeneous space coding by different cell types: place cells, barrier-related units and BVC. We also found units characterized by narrow spike waveforms, most likely belonging to axonal recordings, that showed grid-like patterns. Our data indicate that the subiculum codes space in a flexible manner, and that it is involved in the processing of allocentric information, external cues and path integration, thus broadly supporting spatial navigation.

Mice Develop Efficient Strategies for Foraging and Navigation Using Complex Natural Stimuli

The ability to shift between multiple decision-making strategies during natural behavior allows animals tostrike a balance between flexibility and efficiency. We investigated odor-guided navigation by mice tounderstand how decision-making strategies are balanced during a complex natural behavior. Mice navigated to odor sources in an open arena using naturally fluctuating airborne odor cues as their positions were recorded precisely in real time. When mice had limited prior experience of source locations, theirsearch behavior was consistent witha gradient ascent algorithm that utilized directional cues in theplume to navigate to the odor source. Gradient climbing was effective because the arena size allowed animals to conduct their search mainly within the odor plume, with frequent odor contacts.With increased experience, mice shifted their strategy from this flexible, sensory-driven search behavior to a more efficient and stereotyped foraging approach that varied little in response to odor plumes. This study demonstrates that mice use prior knowledge to adaptively balance flexibility and efficiency during complex behavior guided by dynamic natural stimuli.

Or47b-neurons promote male-mating success in Drosophila.

Drosophila performs elaborate well-defined rituals of courtship, which involve several types of sensory inputs. Here, we report that Or47b-neurons promote male-mating success. Males with Or47b-neurons silenced/ablated exhibit reduced copulation frequency and increased copulation latency. Copulation latency of Or47b-manipulated flies increased proportionately with size of the assay arena, whereas in controls it remained unchanged. While competing for mates, Or47b-ablated males are outperformed by intact controls. These results suggest the role of Or47b-neurons in promoting male-mating success.

Bumblebees spontaneously map location of conspecific using geometry and features

Researchers of vertebrate navigation have investigated and debated intensely the existence of independent processes underlying spatial representation of environmental geometry and featural cues (e.g., landmarks). One of the most well-known behavioural instantiations of this dissociation originates from the differences in the way animals map locations in the surrounding environment with respect to the external cues such as boundaries or landmarks. Invertebrate researchers have joined this debate in the past few years, showing that insects can be trained to encode spatial locations using a variety of cues within small enclosures. In the present paper, we test insects in a non-rewarded, spontaneous navigation task. We observed bumblebees’ spatial navigation in response to the observed location of a conspecific, over manipulations of cue type and arena size. The results indicate that bumblebees spontaneously use both boundaries and features to guide their spatial behaviour. We discuss the similarities and differences in their behaviours to those of vertebrates and speculate on the implications of these findings.

Estimating location without external cues.

The ability to determine one's location is fundamental to spatial navigation. Here, it is shown that localization is theoretically possible without the use of external cues, and without knowledge of initial position or orientation. With only error-prone self-motion estimates as input, a fully disoriented agent can, in principle, determine its location in familiar spaces with 1-fold rotational symmetry. Surprisingly, localization does not require the sensing of any external cue, including the boundary. The combination of self-motion estimates and an internal map of the arena provide enough information for localization. This stands in conflict with the supposition that 2D arenas are analogous to open fields. Using a rodent error model, it is shown that the localization performance which can be achieved is enough to initiate and maintain stable firing patterns like those of grid cells, starting from full disorientation. Successful localization was achieved when the rotational asymmetry was due to the external boundary, an interior barrier or a void space within an arena. Optimal localization performance was found to depend on arena shape, arena size, local and global rotational asymmetry, and the structure of the path taken during localization. Since allothetic cues including visual and boundary contact cues were not present, localization necessarily relied on the fusion of idiothetic self-motion cues and memory of the boundary. Implications for spatial navigation mechanisms are discussed, including possible relationships with place field overdispersion and hippocampal reverse replay. Based on these results, experiments are suggested to identify if and where information fusion occurs in the mammalian spatial memory system.

Exploratory activity and habituation of Drosophila in confined domains

Animals use locomotion to find food, shelter, and escape routes as well as to locate predators, competitors, and mates. Thus, locomotion is related to many behavioral traits, and can be used to characterize these more complex facets of behavior. Exploratory behaviors are random and need to be assessed through stochastic analysis. By comparing ensembles of trajectories from Drosophila and a model animal, we identify a pair of principles that govern the stochastic motion of a specific species. The first depends on local cues and quantify directional persistence, i.e., the propensity of an animal to maintain direction; the second, its attraction to walls, is relevant for exploration in confined arenas. Statistical properties of exploratory activity in several types of arenas can be computed from these principles. A pair of spiral arenas are designed to demonstrate that centrophobicity, or fear of the center of an arena, is not a fundamental feature of exploration. xxxx We provide evidence to show that the decay in an animal’s activity following its introduction into a novel arena is correlated to its familiarity with the arena. We define two measures, coverage and habituation, to quantify familiarity. It is found that the relationship between activity and coverage is independent of the arena size. Finally, we use an analysis of exploration of mutant species to infer that in Drosophila, habituation relies on visual cues.

When Size Does Matter - Trends of SMEs Internationalization Strategies in Chinese Economy

The strategies of internationalization have been one of hottest topics in managerial literature in the last decade. Interestingly to notice how deep and unexpected changes have challenged the mainstream of international management theories. Recent studies shed light on learning and unlearning of internationalization practices; a research effort to figure out the continuous shift of strategic priorities which shape the companies’ strategic landscape. This paper illustrates a framework and some preliminary results aim to comprehend how and why MMNEs (Medium-size Multinational Entreprise) internationalization strategies deviate from the more established strategies of multinational and global companies (MNC). The differences concern both the modes and the actions (how) and the strategic drivers, such as resource availability and exploitation. In the international competitive arena size matters because it forces the innovation process of governance structure and forms. Evidences from the field compel SMEs to explore and implement new governance forms. The mere imitation of international modes from MNC is not feasible and sustainable.We study a sample of Italian SMEs, analyzing the strategy choice and the governance models adopted in China businesses, and the relationship between the headquarters and the local branches or firms. The qualitative analysis complies with the research requirement to collect evidences on a precise point in time and over a more extended period of time (time of entry in China). Qualitative analysis highlights both the feasibility and sustainability of governance models (criteria and components) and forms (model execution and implementation).This paper investigates the specificities of SMEs. Some of them are driven to search for innovative governance mechanisms and forms because of the weakness due to the size. But size, in term of resources, is not sufficient to explain the success or failure of internationalization objectives, in fact SMEs are required to be more innovative also on the institutional arrangement and governance forms because of factors, which affect the scope of their strategic landscape. The adaptation process and, in some cases, the innovative governance forms analyzed in our sample of cases (described in the paper) are strongly affected by the following factors: first, the size does not fit the potential or actual dimension of market (size factor); Second, increasing difficulties to access to the countries’ institutional externalities and strong reliance on the efficiency of markets in order to purchase product and services which they can not internalize (make or buy factor);. Third, negative effects because of 'nocritical mass', which prevents to reach arrangements with local and national government (government and local shareholders factor); Fourth, being part of the supply chain of larger firms (MNC) is a common entry mode in Chinese market; though many SMEs are suppliers of MNC and face difficulties to decrease dependence and to implement their autonomous strategies (supplier and value chain positioning factor); Last factor refers to the lack of resources (human, market, relational and financial assets) which drive SMEs to adopt lean organizational structures and to search for innovative governance models (resources based factors). Our results show that SMEs are more prone to differentiate the models of internationalization matching the requirements coming from different markets. We observe in MMNEs a strong emphasis on develop new governance models. And the varieties of growth strategies through single partnerships or a network of partnerships validates this path of adaptation/innovation. Our study explains these differences as an evolutionary path. It allows us to interpret the internationalization moves and actions along with two tiers issues: first, “onetime” approach to the emerging economies and innovative actions in designing and implementing governance mechanisms; Second, a longitudinal (over a certain period) set of adjustments to adapt the governance mechanisms. This paper contributes to the international management studies with the following results: observations of the managerial paradoxes of SMEs in large markets; evidences shedding light of the interplay between macroeconomic and industrial policies and the single firm’s strategies; signs of the role of SME to the economic development and growth and how the size of companies may explain and contribute to the competitiveness in various industries; proofs of how SMEs drive and promote innovation of governance models. Our results provide a framework and preliminary evidences which support some of the forecasts of “size paradigm” (p.e. the size of local market correlated to firms’ size).

Trust and arena size: expectations, institutions, and general trust, and critical population and group sizes

AbstractWhile trust and group size in socio-economic processes have been well investigated separately, approaches to synergize them have been rare. After addressing basic conditions for institutionalized cooperation, the agency capability of preferential mixing is introduced in order to determine the carrier group of an institution of cooperation. That platform typically assumes a meso-size smaller than the initial arena. Habituation and generalization within and across overlapping platforms then may lead to first contextual trust. This has to be carried over from individual platforms into the larger public of the whole economy to constitute general trust. The practical relevance of this analysis is illustrated through the fact that even superficially similar economies show different socio-economic performance and trajectories. Our results suggest investigating their inner deep structure of overlapping meso-sized platforms as a critical factor.

Short and Long Term Measures of Anxiety Exhibit Opposite Results

Animal models of human diseases of the central nervous system, generalized anxiety disorder included, are essential for the study of the brain-behavior interface and obligatory for drug development; yet, these models fail to yield new insights and efficacious drugs. By increasing testing duration hundredfold and arena size tenfold, and comparing the behavior of the common animal model to that of wild mice, we raise concerns that chronic anxiety might have been measured at the wrong time, for the wrong duration, and in the wrong animal. Furthermore, the mice start the experimental session with a short period of transient adaptation to the novel environment (habituation period) and a long period reflecting the respective trait of the mice. Using common measures of anxiety reveals that mice exhibit opposite results during these periods suggesting that chronic anxiety should be measured during the post-habituation period. We recommend tools for measuring the transient period, and provide suggestions for characterizing the post habituation period.

Manipulation of parasitoid state influences host exploitation by Diadromus pulchellus Wesmael (Hymenoptera: Ichneumonidae)

In biological control programs, it should be possible to manipulate agents during host specificity trials so that they exhibit a lower host acceptance threshold. This would help to ensure that any non-target species that could be attacked in the field will also be attacked in the laboratory and flagged as potential hosts. The question is how to encourage agents to express the widest possible host range during trials. This study examined the effects of variation in parasitoid state (mating status, nutritional status, age, host experience) and the test environment (competition, arena size, presence of host-damaged leek leaves) on the degree of host exploitation by Diadromus pulchellus Wesmael (Hymenoptera: Ichneumonidae). As a first step, this study looked for changes in oviposition by the parasitoid on its normal host, the leek moth, Acrolepiopsis assectella (Zeller) (Lepidoptera: Acrolepiidae). Each of the seven factors was tested independently to assess its effect on the number of parasitoid offspring produced and host mortality. Previous host experience led to a marginal increase, while competition led to a per-capita decrease, in the degree of host exploitation. In contrast, mating status, arena size and the presence of host-damaged leek leaves had no measurable effects. Finally, parasitoid age and nutritional status had strong effects in the opposite direction to predictions, with younger and sugar-fed individuals exhibiting higher host exploitation than older and sugar-starved parasitoids, respectively. This study suggests that a sound understanding of species-specific reproductive biology and parasitoid–host interactions is likely required before oviposition-enhancing parasitoid states can confidently be identified.

Factors influencing fluoxetine-induced sexual dysfunction in female rats

Treatment with selective serotonin reuptake inhibitors, such as fluoxetine, produces sexual side effects with low sexual desire being the most prevalent effect in females. In few studies have preclinical models for such antidepressant-induced sexual dysfunction been fruitful. In the current manuscript, the effects of fluoxetine on multiple measures of female sexual motivation and sexual receptivity were examined. Ovariectomized, Fischer rats were primed with 10μg estradiol benzoate and 500μg progesterone. Partner preference, active investigation of the male, and measures of sexual behavior were examined after injection with 15mg/kg fluoxetine. Factors (pretesting for sexual behavior, size of the test arena, non-contact time with a male) that differ among experiments designed to study antidepressant-induced female rat sexual dysfunction were studied.The male preference ratio was not affected by fluoxetine treatment but active investigation of the male was reduced; lordosis behavior was inhibited and pretesting for sexual receptivity amplified fluoxetine's inhibition; size of the testing arena or non-contact experience with the male had no effect. Regardless of test condition, when given the opportunity to escape from the male, fluoxetine-treated females displayed escape behavior. Measures of male preference and active investigation, but not lordosis behavior, appeared to be affected by fluoxetine's impact on activity. The collective data provided a behavioral profile of fluoxetine-induced sexual dysfunction. These findings reinforce the value of multiple measures when attempting to model antidepressant-induced female sexual dysfunction.

Spatial and temporal foraging patterns of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), for protein and implications for management

AbstractFruit flies require protein for reproductive development and actively feed upon protein sources in the field. Liquid protein baits mixed with insecticide are used routinely to manage pest fruit flies, such as Bactrocera tryoni (Froggatt). However, there are still some gaps in the underpinning science required to improve the efficacy of bait spray technology. The spatial and temporal foraging behaviour of B. tryoni in response to protein was investigated in the field. A series of linked trials using either wild flies in the open field or laboratory‐reared flies in field cages and a netted orchard were undertaken using nectarines and guavas. Key questions investigated were the fly's response to protein relative to: height of protein within the canopy, fruiting status of the tree, time of day, season and size of the experimental arena. Canopy height had a significant response on B. tryoni foraging, with more flies foraging on protein in the mid to upper canopy. Fruiting status also had a significant effect on foraging, with most flies responding to protein when applied to fruiting hosts. B. tryoni demonstrated a repeatable diurnal response pattern to protein, with the peak response being between 12:00–16:00 h. Season showed significant but unpredictable effects on fruit fly response to protein in the subtropical environment where the work was undertaken. Relative humidity, but not temperature or rainfall, was positively correlated with protein response. The number of B. tryoni responding to protein decreased dramatically as the spatial scale increased from field cage through to the open field. Based on these results, it is recommend that, to be most effective, protein bait sprays should be applied to the mid to upper canopies of fruiting hosts. Overall, the results show that the protein used, an industry standard, has very low attractancy to B. tryoni and that further work is urgently needed to develop more volatile protein baits.

Understanding spatio-temporal strategies of adult zebrafish exploration in the open field test

Zebrafish (Danio rerio) are emerging as a useful model organism for neuroscience research. Mounting evidence suggests that various traditional rodent paradigms may be adapted for testing zebrafish behavior. The open field test is a popular rodent test of novelty exploration, recently applied to zebrafish research. To better understand fish novelty behavior, we exposed adult zebrafish to two different open field arenas for 30min, assessing the amount and temporal patterning of their exploration. While (similar to rodents) zebrafish scale their locomotory activity depending on the size of the tank, the temporal patterning of their activity was independent of arena size. These observations strikingly parallel similar rodent behaviors, suggesting that spatio-temporal strategies of animal exploration may be evolutionarily conserved across vertebrate species. In addition, we found interesting oscillations in zebrafish exploration, with the per-minute distribution of their horizontal activity demonstrating sinusoidal-like patterns. While such patterning is not reported for rodents and other higher vertebrates, a nonlinear regression analysis confirmed the oscillation patterning of all assessed zebrafish behavioral endpoints in both open field arenas, revealing a potentially important aspect of novelty exploration in lower vertebrates.

Effect of prey stages of the two-spotted miteTetranychus urticaeon functional response of the coccinellid predatorStethorus gilvifrons

The effect of prey stages of the two-spotted spider mite Tetranychus urticae on the functional response of the coccinellid predator Stethorus gilvifrons was studied at 25±1 °C, 65±10% rh, and 16:8 h (L:D photoperiod). The functional response of S. gilvifrons female, to increasing prey stage density from 10–100 preys per patch, was of the curvilinear shape depicting Roger’s type II response with the highest consumption rate of larval prey stage. Results of the maximum likelihood analyses confirmed this type. By plotting a type II functional response model and polynomial logistic regression model to the numbers and proportions of consumed stages of T. urticae, respectively, the resulting regression lines fitted the data well. However, a composite waving form that appeared to be a decelerating (type II) response at low to medium prey densities and an accelerating (type III) response at high prey densities. We assume that the small size of experimental arena or predator feeding behaviour at low and high prey densities may have induced the modified type II response. A sensitivity analysis of the functional response model shows the crucial effect of prey stages on predation rates by S. gilvifrons. Theoretically, based on the lowest handling time for S. gilvifrons on larval stage of T. urticae, the maximum numbers of mites that could consume by a single female of S. gilvifrons within 24 h period were 77.42 larvae. These results improve our understanding of the interaction among S. gilvifrons and T. urtica stages and provide insights into the control of T. urticae.

A reduction from parity games to simple stochastic games

Games on graphs provide a natural model for reactive non-terminating systems. In such games, the interaction of two players on an arena results in an infinite path that describes a run of the system. Different settings are used to model various open systems in computer science, as for instance turn-based or concurrent moves, and deterministic or stochastic transitions. In this paper, we are interested in turn-based games, and specifically in deterministic parity games and stochastic reachability games (also known as simple stochastic games). We present a simple, direct and efficient reduction from deterministic parity games to simple stochastic games: it yields an arena whose size is linear up to a logarithmic factor in size of the original arena.