Telomeres are DNA-protein complexes at the ends of chromosomes that control genomic integrity but appear to become shorter with age and stress. To test whether stress causes telomere attrition, we exposed offspring wild-caught house mice (Mus musculus) stressful conditions examined changes in length over six months. We found females males reproductive (either or without crowding) had significantly telomeres than controls, crowding were not crowded. Our results indicate alters dynamics,...

Flexible or innovative behavior is advantageous, especially when animals are exposed to frequent and unpredictable environmental perturbations. Improved cognitive abilities can help respond quickly adequately dynamics, therefore changing environments may select for higher abilities. Increased be attained, instance, if change during ontogeny triggers plastic adaptive responses improving the learning capacity of individuals. We tested fishes in response experimental variation quality ontogeny....

Predation is thought to shape the macroscopic properties of animal groups, making moving groups more cohesive and coordinated. Precisely how predation has shaped individuals' fine-scale social interactions in natural populations, however, unknown. Using high-resolution tracking data shoaling fish (Poecilia reticulata) from populations differing pressure, we show adapts interaction rules. Fish originating high environments formed larger, cohesive, but not polarized than low environments. a...

Telomeres--the terminal caps of chromosomes--become shorter as individuals age, and there is much interest in determining what causes telomere attrition since this process may play a role biological aging. The leading hypothesis that due to inflammation, exposure infectious agents, other types oxidative stress, which damage telomeres impair their repair mechanisms. Several lines evidence support hypothesis, including observational findings people exposed diseases have telomeres. Experimental...

It has become increasingly clear that a larger brain can confer cognitive benefits. Yet not all of the numerous aspects cognition seem to be affected by size. Recent evidence suggests some more basic forms cognition, for instance colour vision, are influenced We therefore hypothesize is especially beneficial distinct and gradually complex cognition. To test this hypothesis, we assessed performance size selected female guppies ( Poecilia reticulata ) in two differ complexity. In standard...

Abstract There is remarkable diversity in brain size among vertebrates, but surprisingly little known about how ecological species interactions impact the evolution of size. Using guppies, artificially selected for large and small brains, we determined affects survival under predation threat a naturalistic environment. We cohoused mixed groups small‐ large‐brained individuals six semi‐natural streams with their natural predator, pike cichlid, monitored weekly censuses over 5 months. found...

Brain size varies dramatically among vertebrates, and selection for increased cognitive abilities is thought to be the key force underlying evolution of a large brain.Indeed, numerous comparative studies suggest positive relationships between cognitively demanding aspects behavior brain controlled body size.However, experimental evidence link relative ability surprisingly scarce date stems from single study on selected guppies (Poecilia reticulata), where large-brained females were shown...

Social animals can greatly benefit from well-developed social skills. Because the frequency and diversity of interactions often increase with size groups, benefits advanced skills be expected to group size. Variation in arises during ontogeny, depending on early experience. Whether variation social-group sizes affects development related changes brain structures remains unexplored. We investigated whether, a cooperatively breeding cichlid, (1) shapes behavior (2) induces lasting plastic...

The brain is one of the most energetically expensive organs in vertebrate body. Consequently, energetic requirements encephalization are suggested to impose considerable constraints on size evolution. Three main hypotheses concerning how might affect evolution predict covariation between investment and (1) into other costly tissues, (2) overall metabolic rate, (3) reproductive investment. To date, these have mainly been tested homeothermic animals existing data inconclusive. However, there...

Animal personalities range from individuals that are shy, cautious, and easily stressed (a "reactive" personality type) to bold, innovative, quick learn novel tasks, but also prone routine formation "proactive" type). Although differences should have important consequences for fitness, their underlying mechanisms remain poorly understood. Here, we investigated how genetic variation in brain size affects personality. We put selection lines of large- small-brained guppies (Poecilia...

There is remarkable diversity in brain anatomy among vertebrates and evidence accumulating that predatory interactions are crucially important for this diversity. To test hypothesis, we collected female guppies (Poecilia reticulata) from 16 wild populations related their to several aspects of predation pressure ecosystem, such as the biomass four major predators (one prawn three fish species), predator (number species each site). We found localities with higher had relatively larger...

Large brains are thought to result from selection for cognitive benefits, but how enhanced cognition leads increased fitness remains poorly understood. One explanation is that ability results in improved monitoring and assessment of predator threats. Here, we use male female guppies ( Poecilia reticulata ), artificially selected large small brain size, provide an experimental evaluation this hypothesis. We examined their behavioural response as singletons, pairs or shoals four towards a...

Variation in brain size and cognitive ability affects mate quality assessment underlies variation choice.

Brain size differs substantially among species, and several hypotheses have been proposed to explain the evolution of brain size. Because is most energetically expensive organs in vertebrate body, trade-offs hypothesized exert constraints on evolution. Prominently, tissue hypothesis (ETH) proposes that reducing another organ, such as gut, should compensate for cost a large brain. But energetic may also drive covariation between other costly traits—such body maintenance, locomotion, or...

Neurons are the basic computational units of brain, but brain size is predominant surrogate measure functional capacity in comparative and cognitive neuroscience. This approach based on assumption that larger brains harbor higher numbers neurons their connections, therefore have a information-processing capacity. However, recent studies shown mass may be less strongly correlated with neuron counts than previously thought. Till now, no experimental test has been conducted to examine...

While crypsis is a prominent antipredator adaptation, the role of brain in predator-driven evolution remains controversial. Resolving this controversy requires contextualizing with established traits and predation pressure. We hypothesize that reduced risk through relaxes predation-driven selection on provide comparative evidence across 102 Chinese frog species for our hypothesis. Specifically, phylogenetic path analysis reveals an indirect relationship between mediated by size. This result...

Selection pressures that act differently on males and females produce numerous differences between the sexes in morphology behaviour. However, apart from controversial report have slightly heavier brains than humans, evidence for substantial sexual dimorphism brain size is scarce. This apparent uniformity surprising given sexually distinct selection are ubiquitous one of most plastic vertebrate organs. Here we demonstrate highest level ever reported any vertebrate: male three-spined...

• We previously selected for large and small brain size in guppies. Large-brained females outperformed small-brained a learning task. Healy Rowe challenged our interpretations of larger brains = better learning. Here we argue why think they are mistaken.

Brain sizes vary substantially across vertebrate taxa, yet, the evolution of brain size appears tightly linked to life histories. For example, larger brained species generally live longer than smaller species. A requires more time grow and develop at a cost exceeded gestation period delayed weaning age. The slower development may be compensated by better homeostasis control increased cognitive abilities, both which should increase survival probabilities hence span. To date, this relationship...

Abstract The challenges of seasonal environments are thought to contribute brain evolution, but in which way is debated. According the Cognitive Buffer Hypothesis (CBH) size should increase with seasonality, as cognitive benefits a larger help overcoming periods food scarcity via, for instance, increased behavioral flexibility. However, line Expensive Brain Framework (EBF) decrease seasonality because smaller confers energetic scarcity. Empirical evidence inconclusive and mostly limited...