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146 results for “Brain size”

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dryad36/100

Data from: Effects of maternal age and environmental enrichment on learning ability and brain size

It is well known that maternal age at reproduction affects offspring lifespan and some other fitness-related traits, but it remains understudied whether maternal senescence affects how offspring respond to their environments. Early environment often plays a significant role in the development of an animal's behavioral phenotype. For example, complex environments can promote changes in cognitive ability and brain morphology in young animals. Here, we study whether and how maternal effect senescence influences offspring plasticity in cognition, group behavior, and brain morphology in response to environmental complexity. For this, juvenile three-spined sticklebacks from young and old mothers (i.e. 1-year and 2-years-old) were exposed to different levels of environmental enrichment and complexity (i.e. none, simple and complex), and their behavior, cognitive ability, and brain size were measured. Exposing fish to enriched conditions improved individual learning ability assessed by a repeated detour-reaching task, increased the size of the whole brain, and decreased aggressive interactions in the shoal. Maternal age did not influence the inhibitory control, learning ability, and group behavioral responses of offspring to the experimental environmental change. However, maternal age affected how some brain regions of offspring changed in response to environmental complexity. In offspring from old mothers, those exposed to the complex environment had larger telencephalons and cerebellums than those who experienced simpler environments. Our results suggest that maternal effect senescence may influence how offspring invest in brain functions related to cognition in response to environmental complexity.

opencc-zeroJun 2024View details →

dryad36/100

Fast life-histories are associated with larger brain size in killifishes

The high energetic demands associated with the vertebrate brain are proposed to result in a trade-off between the pace of life-history and relative brain size. However, because both life-history and brain size also have a strong relationship with body size, any associations between the pace of life-history and relative brain size may be confounded by coevolution with body size. Studies on systems where contrasts in the pace of life-history occur without concordant contrasts in body size could therefore add to our understanding of the potential coevolution between relative brain size and life-history. Using one such system - 21 species of killifish - we employed a common garden design across two ontogenetic stages to investigate the association between relative brain size and the pace of life-history. Contrary to predictions, we found that relative brain size was larger in adult fast-living killifishes, compared to slow-living species. Although we found no differences in relative brain size between juvenile killifishes. Our results suggest that fast- and slow-living killifishes do not exhibit the predicted trade-off between brain size and life-history. Instead, fast and slow-living killifishes could differ in the ontogenetic timing of somatic vs. neural growth or inhabit environments that differ considerably in cognitive demands.

opencc-zeroDec 2020View details →

dryad36/100

Brain size variation along altitudinal gradients in the Asiatic Toad (Bufo gargarizans)

Size changes of brain and brain regions along altitudinal gradients provide insight into the trade-off between energetic expenditure and cognitive capacity. We investigated the brain size variations of the Asiatic Toad (Bufo gargarizans) across altitudes from 700m to 3200m. A total of 325 individuals from 11 sites and two transects were sampled. To reduce confounding factors, all sampling sites within each transect were within a maximum distance of 85km and minimum altitudinal difference close to 2000 m. Brains were dissected and five regions were both measured directly and with 3D CT scan. There is a significant negative correlation between the relative whole brain volume (to snout-vent length) and altitude. Furthermore, the relative volumes (to whole brain volume) of optic tectum and cerebellum also decrease along the altitudinal gradients, except the telencephalon, which increases along the altitudinal gradients. Therefore, our results are mostly consistent with the expensive tissue hypothesis and the functional constraint hypothesis. We suggest that most current hypotheses are not mutually exclusive and data supporting one hypothesis are often partially consistent with others. More researches on mechanisms are needed to explain the brain size evolution in realistic adaptation events.

opencc-zeroSep 2021View details →

dryad36/100

Seasonal variation of behavior and brain size in a freshwater fish

Teleost fishes occupy a range of ecosystem and habitat types subject to large seasonal fluctuations. Temperate fishes in particular, survive large seasonal shifts in temperature, light availability, and access to certain habitats. Mobile species like lake trout (Salvelinus namaycush) can behaviorally respond to seasonal variation by shifting their habitat deeper and further offshore in response to warmer surface water temperatures during the summer. During cooler seasons, use of more structurally complex nearshore zones by lake trout could increase cognitive demands and potentially result in a larger relative brain size during those periods. Yet, there is limited understanding of how such behavioral responses to a seasonally shifting environment might shape, or be shaped by, the nervous system. Here we quantified variation in relative brain size and the size of five externally visible brain regions in lake trout, across six consecutive seasons in two different lakes. Acoustic telemetry data from one of our study lakes was collected during the study period from a different subset of individuals and used to infer relationships between brain size and seasonal behaviors (habitat use and movement rate). Our results indicated that lake trout relative brain size was larger in the fall and winter compared to the spring and summer in both lakes. Larger brains coincided with increased use of nearshore habitats and increased horizontal movement rates in the fall and winter based on acoustic telemetry. The telencephalon followed the same pattern as whole brain size, while the other brain regions (cerebellum, optic tectum, olfactory bulbs, hypothalamus) were only smaller in the spring. These findings provide evidence that flexibility in brain size could underpin shifts in behavior, which could potentially subserve functions associated with differential habitat use during cold and warm seasons and allow fish to succeed in seasonally variable environments.

opencc-zeroJan 2023View details →

dryad36/100

Data for: Phylogenetically controlled life history trait meta-analysis in cetaceans reveals unexpected negative brain size and longevity correlation

The identification of patterns in trait evolution is essential to understand the interaction of evolutionary forces, and provides useful information for species management. Cetaceans are a phylogenetically well-resolved infraorder that exhibit distinct trait variation across behavioural, molecular and life history dimensions, yet few researchers have applied a meta-analytic or comparative approach to these traits. To understand cetacean trait evolution, we used a phylogenetic generalised least squares approach to examine the cognitive buffer hypothesis (CBH). A large brain should buffer individuals against environmental challenges through increasing survival rates, and a longer lifespan should buffer individuals against the cost of extended development for larger brains according to the CBH, leading to an expected positive correlation between brain size and lifespan. In contrast to this expectation, previously observed in taxa including primates, we found a negative correlation between brain size and lifespan in cetaceans. This suggests cetaceans experience selective pressures different from most other mammals in these traits but may be more similar to some social mammalian carnivores that display alloparenting. We also provide a comprehensive dataset to explore additional aspects of trait evolution but which would greatly benefit from studies on behavioural ecology across cetaceans and increased focus on data-deficient species.

opencc-zeroFeb 2023View details →

dryad36/100

Data from: Relative brain size is associated with natal dispersal rate and species' vulnerability to climate change in seabirds

The cognitive buffer hypothesis proposes that species with larger brains (relative to their body size) exhibit greater behavioural flexibility, conferring an advantage in unpredictable or novel environments. Therefore, behavioural flexibility – and relative brain size – are likely to be important predictors of a species' vulnerability to anthropogenic pressures and, ultimately, extinction risk. However, current evidence linking brain size to species vulnerability and extinction risk is inconclusive. Furthermore, studies examining the relationship between relative brain size and behavioural flexibility have mainly focused on foraging innovations, whilst other forms of behavioural flexibility remain unexplored. In this study, we collate species-specific information and examine links between relative brain size, rates of natal and adult dispersal (a measure of flexibility in breeding site fidelity), vulnerability to six anthropogenic threats and extinction risk for 131 species of seabird. We focused our study on seabirds, a highly threatened group that displays large variation in both relative brain size and dispersal behaviour. We found a significant positive relationship between relative brain size and natal dispersal rate, suggesting that relative brain size could enhance flexibility in breeding site choice in seabirds, consistent with the cognitive buffer hypothesis. However, this relationship does not persist when we consider adult dispersal, possibly reflecting constraints imposed by mate selection and knowledge transfer in seabirds. We also show that relative brain size is negatively associated with vulnerability to climate change. These findings have immediate application for predicting interspecific variation in species' vulnerability to climate change and identifying priority species for conservation.

opencc-zeroFeb 2023View details →

dryad36/100

Behavior and brain size of larval zebrafish exposed to environmentally relevant concentrations of betamethylamino- L-alanine (BMAA)

Harmful algal blooms (HABs) release toxic compounds in water and are increasing in frequency worldwide. The neurotoxin β-methylamino-L-alanine (BMAA) is released by HABs and has garnered much attention over the past twenty years due to its association with human neurodegenerative disorders, but its effects on wildlife are still largely unknown. This study characterized the effects of chronic exposure to environmentally relevant concentrations of BMAA on the behavior and brain size of developing zebrafish (Danio rerio). Zebrafish were continuously exposed to 0, 1, 10, or 100 μg/L waterborne BMAA between 0- and 5-days post-fertilization (dpf) before the onset of exogenous feeding. At 5 dpf, locomotion and responses to vibrational and visual stimuli were assessed. Following behavioral testing, larvae body and brain size were measured. Survival between 0 and 5 dpf did not differ between treatments. Moreover, BMAA exposure did not affect thigmotaxis, startle response magnitude, habituation to repeated presentation of vibrational startling stimuli, or relative brain size. A moderate increase in overall activity was observed in larvae exposed to 10 ug/L BMAA under light, but this effect was not seen in dark conditions, indicating that visual processing may have been affected by chronic BMAA exposure. Thus, our results show that passive continuous exposure to environmentally relevant concentrations of BMAA prior to first feeding in zebrafish does not affect overall brain development, locomotion, anxiety, and motor neuron-mediated reflexes, but suggest targeted neurotoxicity within the visual system.

opencc-zeroMar 2023View details →

dryad36/100

Both diet and sociality affect primate brain-size evolution

Increased brain size in humans and other primates is hypothesized to confer cognitive benefits but brings costs associated with growing and maintaining energetically expensive neural tissue. Previous studies have argued that changes in either diet or levels of sociality led to shifts in brain size, but results were equivocal. Here we test these hypotheses using phylogenetic comparative methods designed to jointly account for and estimate the effects of adaptation and phylogeny. Using the largest current sample of primate brain and body sizes with observation error, complemented by newly compiled diet and sociality data, we show that both diet and sociality have influenced the evolution of brain size. Shifting from simple to more complex levels of sociality resulted in relatively larger brains, while shifting to a more folivorous diet led to relatively smaller brains. While our results support the role of sociality, they modify a range of ecological hypotheses centered on the importance of frugivory and instead indicate that digestive costs associated with increased folivory may have resulted in relatively smaller brains.

opencc-zeroJun 2023View details →

dryad36/100