Should I stay or should I go? How activity synchronization affects fission decisions.

Group-living animals need to deal with conflicting interests to maintain cohesion. When the costs of doing so outweigh the benefits, the group may (temporarily) split into two or more subgroups. Conflicting interests can concern what activity to pursue or the direction of travel. Temporary group separation is a common feature in species with a high degree of fission-fusion dynamics. We investigated the role activity synchronization played in fission decisions in a spider monkey group living in the Otoch Ma'ax Yetel Kooh Nature Reserve, Yucatan, Mexico. For 21 months, we recorded every fission event occurring in the followed subgroup, as well as the subgroup activity. We classified the activity as 'synchronized' when at least 75% of subgroup members performed the same activity (resting, foraging, socializing or travelling); otherwise, we classified it as 'non-synchronized'. We found that fission events occurred more often when the activity was non-synchronized. In addition, when the activity was synchronized, fission events occurred more often when spider monkeys were travelling than when they were engaged in other subgroup activities. Our findings highlight the role of conflicting interests over the activity to pursue and travel direction in fission decisions.

The dawn of social bonds: what is the role of shared experiences in non-human animals?

Group-living animals can develop social bonds. Social bonds can be considered a type of social relationship characterized by frequent and consistent affiliative (non-reproductive) interactions. Social bonds with conspecifics bring many advantages, also in terms of direct fitness. A characteristic of social bonds is that they need time to develop. Several studies on humans have emphasized the fact that sharing experiences can affect the strength of social bonds. A similar trend can be spotted in non-human species. For example, a recent experiment showed that if chimpanzees watched a video together with a conspecific, they spent more time in proximity compared to conspecifics with whom they did not actively watch a video. Another experiment on fish showed that individuals who experienced a situation of high predation risk together, showed preference for each other compared to those who did not. As the link between shared experiences and social bonds is not explicitly recognized in non-human animals, the main goal of this work is to propose the exploration of this novel research path. This exploration would contribute to shed light on the evolutionary mechanisms of social bond (or friendship) development and maintenance between individuals in different vertebrate species, from fish to non-human primates.

Using multiplex networks to capture the multidimensional nature of social structure.

Network analysis has increasingly expanded our understanding of social structure in primates and other animal species. However, most studies use networks representing only one interaction type, when social relationships (and the emerging social structure) are the result of many types of interactions and their interplay through time. The recent development of tools facilitating the integrated analysis of multiple interaction types using multiplex networks has opened the possibility of extending the insight provided by social network analysis. We use a multiplex representation of interactions among the members of a group of wild Geoffroy's spider monkeys (Ateles geoffroyi), to study their social structure. We constructed a six-layered multiplex network based on three indices of overt social interactions (aggression, embraces, grooming) and three distance-based indices (contact, proximity, and association). With tools provided by the MuxViz software, we assessed the relevance of including all six indices in our analysis, the role of individuals in the network (through node versatility), and the presence of modules and non-random triadic structures or motifs. The multiplex provided information which was not equivalent to any individual layer or to the simple aggregation of layers. Network patterns based on associations did not correspond with those observed for overt-interactions or for the multiplex structure. Males were the most versatile individuals, while multiplex modularity and motifs highlighted the relevance of different interaction types for the overall connectivity of the network. We conclude that the multiplex approach improves on previous methods by retaining valuable information from each interaction type and how it is patterned among individuals.

Predation Attacks on Wild Spider Monkeys (Ateles geoffroyi).

We report 2 cases of predation on an adult and a subadult spider monkey (Ateles geoffroyi) by a puma (Puma concolor) and an unidentified terrestrial predator at the natural protected area of Otoch Ma'ax yetel Kooh, in the Yucatan Peninsula, Mexico. Although spider monkeys are believed to experience overall low predation pressure compared to other primate species, our observations show that predation occurs in the study area and therefore behavioral strategies are likely to be in place to reduce predation risk. Our observations are further evidence that terrestrial predators are a threat for both young and full-grown spider monkeys.

Homosexual Behavior Between Male Spider Monkeys (Ateles geoffroyi).

Homosexual behavior is defined as genital contact or genital manipulation between same-sex individuals. In nonhuman primates, it may regulate social relationships by serving as a means of reconciliation, tension alleviation, or alliance formation. Grappling is a rare and complex behavior, which most frequently occurs between same-sex individuals of the genus Ateles and can include mutual manipulation of the genitalia. Here we report three cases of penile-anal intromission during grappling between wild male spider monkeys living in the natural protected area of Otoch Ma'ax Yetel Kooh, Mexico. In all the observed cases, the same adult male was the actor. To our knowledge, this is the first report of penile-anal intromission between males in any New World primate species.

Upregulation of CRABP1 in human neuroblastoma cells overproducing the Alzheimer-typical Abeta42 reduces their differentiation potential.

BACKGROUND: Alzheimer's disease (AD) is characterized by neurodegeneration and changes in cellular processes, including neurogenesis. Proteolytic processing of the amyloid precursor protein (APP) plays a central role in AD. Owing to varying APP processing, several beta-amyloid peptides (Abeta) are generated. In contrast to the form with 40 amino acids (Abeta40), the variant with 42 amino acids (Abeta42) is thought to be the pathogenic form triggering the pathological cascade in AD. While total-Abeta effects have been studied extensively, little is known about specific genome-wide effects triggered by Abeta42 or Abeta40 derived from their direct precursor C99. METHODS: A combined transcriptomics/proteomics analysis was performed to measure the effects of intracellularly generated Abeta peptides in human neuroblastoma cells. Data was validated by real-time polymerase chain reaction (real-time PCR) and a functional validation was carried out using RNA interference. RESULTS: Here we studied the transcriptomic and proteomic responses to increased or decreased Abeta42 and Abeta40 levels generated in human neuroblastoma cells. Genome-wide expression profiles (Affymetrix) and proteomic approaches were combined to analyze the cellular response to the changed Abeta42- and Abeta40-levels. The cells responded to this challenge with significant changes in their expression pattern. We identified several dysregulated genes and proteins, but only the cellular retinoic acid binding protein 1 (CRABP1) was up-regulated exclusively in cells expressing an increased Abeta42/Abeta40 ratio. This consequently reduced all-trans retinoic acid (RA)-induced differentiation, validated by CRABP1 knock down, which led to recovery of the cellular response to RA treatment and cellular sprouting under physiological RA concentrations. Importantly, this effect was specific to the AD typical increase in the Abeta42/Abeta40 ratio, whereas a decreased ratio did not result in up-regulation of CRABP1. CONCLUSION: We conclude that increasing the Abeta42/Abeta40 ratio up-regulates CRABP1, which in turn reduces the differentiation potential of the human neuroblastoma cell line SH-SY5Y, but increases cell proliferation. This work might contribute to the better understanding of AD neurogenesis, currently a controversial topic.