Phenotypic plasticity of nest-mate recognition cues in formica exsecta ants

It is well established that many ant species have evolved qualitatively distinct species-specific chemical profile that are stable overlarge geographical distances. Within these species profiles quantitative variations in the chemical profile allows distinct colony-specific odours to arise (chemotypes) that are shared by all colony members. This help maintains social cohesion, includingdefence of their colonies against all intruders, including con-specifics. How these colony -level chemotypes are maintainedamong nest-mates has long been debated. The two main theories are; each ant is able to biochemically adjust its chemical profileto‘match’that of its nest-mates and or the queen, or all nest-mates share their individually generated chemical profile viatrophollaxis resulting in an average nest-mate profile. This‘mixing’idea is better known as theGestaltmodel. Unfortunately,it has been very difficult to experimentally test these two ideas in a single experimental design. However, it is now possible usingthe antFormica exsectabecause the compounds used in nest-mate recognition compounds are known. We demonstrate thatworkers adjust their profile to‘match’the dominant chemical profile within that colony, hence maintaining the colony-specificchemotype and indicates that a‘gestalt’mechanism, i.e. profile mixing, plays no or only a minor role

The Old Ladies of the Seed Harvester ant Pogonomyrmex Rugosus: Foraging Performed by Two Groups of Workers

We examined temporal polyethism in Pogonomyrmex rugosus, predicting a pattern of decreasing age from foragers to nest maintenance workers to individuals that were recruited to harvest a temporary food source. Nest maintenance workers were younger than foragers, as indicated by their heavier mass and lower mandibular wear. In contrast, recruited foragers were similar in mass to foragers but they displayed higher mandibular wear, suggesting that they were at least as old as foragers. Longevity estimates for marked individuals of these two latter task groups showed mixed results. Higher mandibular wear of recruited foragers suggests that they did not follow the normal sequence for temporal polyethism, but rather that they functioned as seed-millers, which should more quickly abrade their dentition. This would be the first demonstration of specialist milling individuals in a monomorphic seed-harvester ant

Synaptic Wnt signaling—a contributor to major psychiatric disorders?

Wnt signaling is a key pathway that helps organize development of the nervous system. It influences cell proliferation, cell fate, and cell migration in the developing nervous system, as well as axon guidance, dendrite development, and synapse formation. Given this wide range of roles, dysregulation of Wnt signaling could have any number of deleterious effects on neural development and thereby contribute in many different ways to the pathogenesis of neurodevelopmental disorders. Some major psychiatric disorders, including schizophrenia, bipolar disorder, and autism spectrum disorders, are coming to be understood as subtle dysregulations of nervous system development, particularly of synapse formation and maintenance. This review will therefore touch on the importance of Wnt signaling to neurodevelopment generally, while focusing on accumulating evidence for a synaptic role of Wnt signaling. These observations will be discussed in the context of current understanding of the neurodevelopmental bases of major psychiatric diseases, spotlighting schizophrenia, bipolar disorder, and autism spectrum disorder. In short, this review will focus on the potential role of synapse formation and maintenance in major psychiatric disorders and summarize evidence that defective Wnt signaling could contribute to their pathogenesis via effects on these late neural differentiation processes

Nest and colony-specific spectra in the weaver ant Oecophylla smaragdina

Animals in social groups need to differentiate between group members and others. In very large groups, such as those formed by many ant species, it is not possible to rely on individually specific cues to identify colonymates. Instead, recognition must be based on the colony-specific cues. Individual ant colonies tend to have a specific chemical gestalt that is maintained by the continual exchange of chemicals between workers. In very large polydomous colonies, the exchange of chemicals may be limited between nests within the colony, resulting in inter-nest variation in colony odour that might hinder identification of colonymates or conspecific intruders. We used near-infrared spectroscopy to explore variation in the chemical profile between and within colonies of the weaver ant Oecophylla smaragdina. We found that differences between colonies were reflected in the position, amplitude and width of spectral peaks, while differences between nests within colonies were reflected mainly in amplitude. Furthermore, in the context of colonymate recognition, the behaviour of the ants themselves was positively correlated with colony-specific spectral characteristics, rather than with nest-specific characteristics. Thus, colony spectra have features that are not obscured by intra-colonial variation and may potentially encode the chemical characteristics used by workers to identify colonymates

Bubbles and long-range dependence in asset prices volatilities

A model for a financial asset is constructed with two types of agents. The agents differ in terms of their beliefs. The proportions of the two types change over time according to a stochastic process which models the interaction between the agents. Thus, unlike other models, agents do not persist in holding "wrong" beliefs. Bubble-like phenomena in the asset price occur. We consider several tests for detecting long range dependence and change-points in the conditional variance process. Although the model seems to generate long-memory properties of the volatility series, we show that this is due to the switching of regimes which are detected by the tests we propose

A guide to the computation of stationarity tests

Stationarity test, KPSS test, LMC test, Optimal bandwidth selection, Long-run variance estimation, Purchasing Power Parity,