Abstract: The most abundant intestinal immunoglobulin and first line of specific immunological defense against environmental antigens is secretory immunoglobulin A. To better understand the effect of repeated stress on the secretion of intestinal IgA, the effects of restraint stress on IgA concentration and mRNA expression of the gene for the alpha-chain of IgA was assessed in both the duodenum and ileum of the rats. Restraint stress induced an increase in intestinal IgA, which was blocked by an adrenalectomy, suggesting a role of catecholamines and glucocorticoids. Whereas the blocking of glucocorticoid receptors by RU-486 did not affect the increased IgA concentration, it did reduce IgA alpha-chain mRNA expression in both segments, indicating a possible mediation on the part of glucocorticoids in IgA secretion by individual cells. Treatment with corticosterone significantly increased both the IgA concentration and IgA alpha-chain mRNA expression in ileum but not in duodenum, suggesting that glucocorticoids may act directly on IgA-antibody forming cells to increase IgA secretion in the former segment. A probable role by catecholamines was evidenced by the reduction in IgA concentration and IgA alpha-chain mRNA expression in both segments after a chemical sympathectomy with 6-hydroxydopamine (6-OHDA). Additionally, norepinephrine significantly reduced IgA alpha-chain mRNA levels but increased pIgR mRNA expression and IgA concentration in both intestinal segments. We propose that the increased intestinal IgA levels caused by repeated restraint stress is likely due to the effects of catecholamines on the transport of plgA across the epithelium.

Abstract: A group of animals can only move cohesively, if group members “somehow” reach a consensus about the timing (e.g., start) and the spatial direction/destination of the collective movement. Timing and spatial decisions usually differ with respect to the continuity of their cost/benefit distribution in such a way that, in principle, compromises are much more feasible in timing decision (e.g. median preferred time) than they are in spatial decisions. The consequence is that consensus costs connected to collective timing decisions are usually less skewed amongst group members than are consensus costs connected to spatial decisions. This, in turn, influences the evolution of decision sharing: sharing in timing decisions is most likely to evolve when conflicts are high relative to group cohesion benefits, while sharing in spatial decisions is most likely to evolve in the opposite situation. We discuss the implications of these differences for the study of collective movement decisions.

Abstract: The environment of animals is often heterogeneous, containing zones that may be dedicated specifically to resting, drinking or feeding. These functional zones may spread over a more or a less extensive area. Thus, mobile animals may have to move from one patch to another when resources are locally depleted or when they need to change activity. The mechanisms involved in collective movement appear simple at first glance, but a brief reflection shows the real difficulty of the problem in terms of the numerous environmental, physical, physiological and social parameters involved. This review is mainly concerned with collective movements, which are characterised by a directional and temporal coordination, where individuals mutually influence each other, meaning this coordination mainly depends on social interactions ([Huth and Wissel, 1992], [Warburton and Lazarus, 1991], [Couzin and Krause, 2003] and [Couzin et al., 2002]). In literature, two types of movement are discussed: large-scale movement and small-scale movement. First, we define these types of movement and then discuss the behavioural mechanisms involved. Secondly, we show that short and long movement but also moving and stopping may result from the outcome of parameters modulation underpinning collective decision-making.

Abstract: Besides focusing on the adaptive significance of collective movements, it is crucial to study the mechanisms and dynamics of decision-making processes at the individual level underlying the higher-scale collective movements. It is now commonly admitted that collective decisions emerge from interactions between individuals, but how individual decisions are taken, i.e. how far they are modulated by the behaviour of other group members, is an under-investigated question. Classically, collective movements are viewed as the outcome of one individual's initiation (the leader) for departure, by which all or some of the other group members abide. Individuals assuming leadership have often been considered to hold a specific social status. This hierarchical or centralized control model has been challenged by recent theoretical and experimental findings, suggesting that leadership can be more distributed. Moreover, self-organized processes can account for collective movements in many different species, even in those that are characterized by high cognitive complexity. In this review, we point out that decision-making for moving collectively can be reached by a combination of different rules, i.e. individualized (based on inter-individual differences in physiology, energetic state, social status, etc.) and self-organized (based on simple response) ones for any species, context and group size.

Abstract: Abstract When living in a group, individuals have to make trade-offs, and compromise, in order to balance the advantages and disadvantages of group life. Strategies that enable individuals to achieve this typically affect inter-individual interactions resulting in nonrandom associations. Studying the patterns of this assortativity using social network analyses can allow us to explore how individual behavior influences what happens at the group, or population level. Understanding the consequences of these interactions at multiple scales may allow us to better understand the fitness implications for individuals. Social network analyses offer the tools to achieve this. This special issue aims to highlight the benefits of social network analysis for the study of primate behaviour, assessing it's suitability for analyzing individual social characteristics as well as group/population patterns. In this introduction to the special issue, we first introduce social network theory, then demonstrate with examples how social networks can influence individual and collective behaviors, and finally conclude with some outstanding questions for future primatological research. Am. J. Primatol. 73:703?719, 2011. ? 2011 Wiley-Liss, Inc.