scholarly journals Large brains, short life: selection on brain size impacts intrinsic lifespan

2019 ◽  
Vol 15 (5) ◽  
pp. 20190137 ◽  
Author(s):  
Alexander Kotrschal ◽  
Alberto Corral-Lopez ◽  
Niclas Kolm
Keyword(s):  
Poecilia Reticulata ◽  
Brain Size ◽  
Positive Association ◽  
Energetic Cost ◽  
Accelerated Ageing ◽  
Extrinsic Mortality ◽  
Somatic Maintenance ◽  
Cognitive Benefits ◽  
In The Wild ◽  
Positive Correlations

The relationship between brain size and ageing is a paradox. The cognitive benefits of large brains should protect from extrinsic mortality and thus indirectly select for slower ageing. However, the substantial energetic cost of neural tissue may also impact the energetic budget of large-brained organisms, causing less investment in somatic maintenance and thereby faster ageing. While the positive association between brain size and survival in the wild is well established, no studies exist on the direct effects of brain size on ageing. Here we test how brain size influences intrinsic ageing in guppy ( Poecilia reticulata ) brain size selection lines with 12% difference in relative brain size. Measuring survival under benign conditions, we find that large-brained animals live 22% shorter than small-brained animals and the effect is similar in both males and females. Our results suggest a trade-off between investment into brain size and somatic maintenance. This implies that the link between brain size and ageing is contingent on the mechanism of mortality, and selection for positive correlations between brain size and ageing should occur mainly under cognition-driven survival benefits from increased brain size. We show that accelerated ageing can be a cost of evolving a larger brain.

scholarly journals Brain size affects performance in a reversal-learning test

2018 ◽  
Vol 285 (1871) ◽  
pp. 20172031 ◽  
Author(s):  
Séverine D. Buechel ◽  
Annika Boussard ◽  
Alexander Kotrschal ◽  
Wouter van der Bijl ◽  
Niclas Kolm
Keyword(s):  
Reversal Learning ◽  
Cognitive Complexity ◽  
Poecilia Reticulata ◽  
Brain Size ◽  
Learning Ability ◽  
Colour Discrimination ◽  
Reward Contingency ◽  
Cognitive Benefits ◽  
Learning Test ◽  
Basic Learning

It has become increasingly clear that a larger brain can confer cognitive benefits. Yet not all of the numerous aspects of cognition seem to be affected by brain size. Recent evidence suggests that some more basic forms of cognition, for instance colour vision, are not influenced by brain size. We therefore hypothesize that a larger brain is especially beneficial for distinct and gradually more complex aspects of cognition. To test this hypothesis, we assessed the performance of brain size selected female guppies ( Poecilia reticulata ) in two distinct aspects of cognition that differ in cognitive complexity. In a standard reversal-learning test we first investigated basic learning ability with a colour discrimination test, then reversed the reward contingency to specifically test for cognitive flexibility. We found that large-brained females outperformed small-brained females in the reversed-learning part of the test but not in the colour discrimination part of the test. Large-brained individuals are hence cognitively more flexible, which probably yields fitness benefits, as they may adapt more quickly to social and/or ecological cognitive challenges. Our results also suggest that a larger brain becomes especially advantageous with increasing cognitive complexity. These findings corroborate the significance of brain size for cognitive evolution.

scholarly journals Experimental translocations to low predation lead to non-parallel increases in relative brain size

2020 ◽  
Vol 16 (1) ◽  
pp. 20190654 ◽  
Author(s):  
David J. Mitchell ◽  
Regina Vega-Trejo ◽  
Alexander Kotrschal
Keyword(s):  
Poecilia Reticulata ◽  
Brain Size ◽  
Parallel Evolution ◽  
Brain Evolution ◽  
Common Garden ◽  
Brain Anatomy ◽  
In The Wild ◽  
High Predation ◽  
Relative Brain Size ◽  
Introduction Experiment

Predation is a near ubiquitous factor of nature and a powerful selective force on prey. Moreover, it has recently emerged as an important driver in the evolution of brain anatomy, though population comparisons show ambiguous results with considerable unexplained variation. Here, we test the reproducibility of reduced predation on evolutionary trajectories of brain evolution. We make use of an introduction experiment, whereby guppies ( Poecilia reticulata ) from a single high predation stream were introduced to four low predation streams. After 8–9 years of natural selection in the wild and two generations of common garden conditions in the laboratory, we quantified brain anatomy. Relative brain region sizes did not differ between populations. However, we found a general increase and striking variation in relative brain size of introduced populations, which varied from no change to a 12.5% increase in relative brain weight, relative to the ancestral high predation population. We interpret this as evidence for non-parallel evolution, which implies a weak or inconsistent association of relative brain size with fitness in low predation sites. The evolution of brain anatomy appears sensitive to unknown environmental factors, or contingent on either chance events or historical legacies of environmental change.

scholarly journals Brain size affects the behavioural response to predators in female guppies ( Poecilia reticulata )

2015 ◽  
Vol 282 (1812) ◽  
pp. 20151132 ◽  
Author(s):  
Wouter van der Bijl ◽  
Malin Thyselius ◽  
Alexander Kotrschal ◽  
Niclas Kolm
Keyword(s):  
Poecilia Reticulata ◽  
Brain Size ◽  
Sensory Information ◽  
Behavioural Response ◽  
General Idea ◽  
Risky Behaviour ◽  
Cognitive Benefits ◽  
Predator Response ◽  
Predator Model ◽  
Model Predator

Large brains are thought to result from selection for cognitive benefits, but how enhanced cognition leads to increased fitness remains poorly understood. One explanation is that increased cognitive ability results in improved monitoring and assessment of predator threats. Here, we use male and female guppies ( Poecilia reticulata ), artificially selected for large and small brain size, to provide an experimental evaluation of this hypothesis. We examined their behavioural response as singletons, pairs or shoals of four towards a model predator. Large-brained females, but not males, spent less time performing predator inspections, an inherently risky behaviour. Video analysis revealed that large-brained females were further away from the model predator when in pairs but that they habituated quickly towards the model when in shoals of four. Males stayed further away from the predator model than females but again we found no brain size effect in males. We conclude that differences in brain size affect the female predator response. Large-brained females might be able to assess risk better or need less sensory information to reach an accurate conclusion. Our results provide experimental support for the general idea that predation pressure is likely to be important for the evolution of brain size in prey species.

scholarly journals An integrative study of facultative personality calibration

2019 ◽  
Author(s):  
Christoph Julian von Borell ◽  
Tobias L. Kordsmeyer ◽  
Tanja M. Gerlach ◽  
Lars Penke
Keyword(s):  
Positive Association ◽  
Phenotypic Traits ◽  
Anthropometric Measures ◽  
Sociosexual Orientation ◽  
Physical Strength ◽  
Personality Differences ◽  
Two Samples ◽  
Integrative Study ◽  
Positive Correlations ◽  
3D Scans

The theory of facultative calibration, which explains personality differences as responses to variation in other phenotypic traits of individuals, received mixed results throughout the last years. Whereas there is strong evidence that individual differences in human behavior are correlated with the self-perception of other traits, it still needs to be questioned whether they are also adjusted to objective differences in body condition (i.e. formidability). In two independent studies (N1 = 119 men and 124 women, N2= 165 men) we tested hypotheses of facultative personality calibration in an integrative way, assessing various outcomes of previous studies in the same samples (including Anger Proneness, Extraversion, Neuroticism, Narcissism, Shyness, Vengefulness, and Sociosexual Orientation). Formidability was derived from assessments of physical strength and various anthropometric measures from full-body 3D scans and paired with measures of self-perceived and other-rated physical attractiveness (based on rotating morphometric 3D body models and facial photographs). We could replicate positive correlations with self-perceived attractiveness across outcomes, though these were not corroborated by more objective assessments of attractiveness: an effect of other-rated attractiveness was clearly not supported in our results for either sex, regardless of the personality outcome. Anthropometric measures and physical strength were also largely unrelated to personality, with the exception of Extraversion, Utility of Personal Aggression, and Sociosexual Orientation. While the two samples differed in their results for domain-level Extraversion, at least the Extraversion facets Activity and Assertiveness were related to strength and masculinity in men. For Sociosexual Orientation the results of our two samples varied more substantially, a positive association was only present in Study 2. Future studies need to clarify whether formidability, potentially an indicator of genetic quality for males, enhances their orientation and success in short-term mating. Furthermore we propose longitudinal twin-difference studies as means to evaluate the theory of personality recalibration in a more controlled manner.

scholarly journals Associations between %AA (20:4 n6) and Relative Amounts of Other Body Fatty Acids

2020 ◽  
Vol 3 (2) ◽  
pp. 01-12
Author(s):  
Arne Høstmark
Keyword(s):  
Fatty Acids ◽  
Concentration Distribution ◽  
Positive Association ◽  
Chicken Breast ◽  
Random Numbers ◽  
Regulatory Principle ◽  
Health And Disease ◽  
Group 2 ◽  
Positive Correlations ◽  
Group 1

Body fatty acids are important in health and disease. Previously, we reported a positive association between % AA (20:4 n6) and relative amounts of EPA (20:5 n3) and of some other fatty acids. We now study positive and negative correlations in general between %AA and percentages of other fatty acids, as observed in chicken breast muscle. Two groups of fatty acids were identified: Group 1) with relative amounts correlating negatively with %AA, and Group 2) with relative amounts correlating positively with %AA. With the positive correlations, but not with the negative ones, we obtained similar scatterplots using true and random numbers. This apparent discrepancy is probably related to differences in skewness of the concentration distribution of some fatty acids. Most of Group 2 fatty acids are eicosanoid or docosanoid precursors. The overall correlation outcome may be largely explained by the particular concentration ranges of the fatty acids. We therefore suggest Distribution Dependent Correlations to be an evolutionary regulatory principle, possibly ensuring balance between various eicosanoids and docosanoids.

scholarly journals Hibernation Patterns of the European Hedgehog, Erinaceus europaeus, at a Cornish Rescue Centre

Animals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1418
Author(s):  
Kathryn E. South ◽  
Kelly Haynes ◽  
Angus C. Jackson
Keyword(s):  
Weight Loss ◽  
Total Duration ◽  
Erinaceus Europaeus ◽  
Significant Difference ◽  
In Captivity ◽  
European Hedgehog ◽  
In The Wild ◽  
Positive Correlations ◽  
The Uk ◽  
Monitoring Protocols

The European hedgehog, Erinaceus europaeus, is frequently admitted to rescue centres in the UK. With many overwintering in captivity, there is cause to investigate hibernation patterns in order to inform and improve husbandry and monitoring protocols. Thirty-five hedgehogs were studied over two winters. Weight change during hibernation for the first winter was used to test for effects of disturbance on different aspects of hibernation, including total duration, frequency and duration of spontaneous arousals. There was no significant difference between the two winters for any of the four aspects studied. Significant positive correlations demonstrated that weight-loss increased with the duration of the hibernation period and with percent of nights spent asleep, but not with the number of arousal events. Thus, weight-loss appears more strongly associated with the proportion of time spent asleep than with the number of arousal events. This was surprising given the assumed energetic expense of repeated arousal and was potentially due to availability of food during arousals. In contrast with previous studies, larger hedgehogs lost less weight per day than did smaller hedgehogs. They also woke up more often (i.e., had more opportunities to feed), which may explain the unexpected pattern of weight-loss. Hibernatory behaviour in captivity differs from that in the wild, likely because of non-natural conditions in hutches and the immediate availability of food. This study provides a basis for further research into the monitoring and husbandry of hedgehogs such that it can be adapted for each individual according to pre-hibernation weight and behaviour during hibernation.

scholarly journals Parental care in the buffy-tufted-ear marmoset (Callithrix aurita) in wild and captive groups

2000 ◽  
Vol 60 (4) ◽  
pp. 667-672 ◽  
Author(s):  
C. V. SANTOS ◽  
M. M. MARTINS
Keyword(s):  
Parental Care ◽  
Breeding Pair ◽  
Energetic Cost ◽  
Environmental Pressures ◽  
Infant Carrying ◽  
Captive Group ◽  
In Captivity ◽  
In The Wild ◽  
Wild Group ◽  
Callithrix Aurita

Studies on cooperative care of offspring in callitrichid primates are biased in favor of observations in captivity. In the wild, however, individuals have to deal with environmental pressures, which may influence their social behavior. We compared the individual effort attributed to parental care offered by members of a wild group (couple, plus a subadult helper) and two captive groups (A: couple, plus an subadult helper, B: couple, plus four adult helpers) of the buffy-tufted-ear marmoset, Callithrix aurita, from weeks 1-12 after the infants' birth. The carrier (breeding male and female or helper) and the infant's feeding (food sharing and foraging for food) were recorded. Up to week four, while the wild breeding pair shared infant carrying at similar proportions, the male from captive group A carried 100% of the time. Adult helpers from group B were the main carriers. Carrying behavior extended up to week 12 only in the wild group. Food provisioning to the infant was observed earlier in the groups wild and A, but general proportion of feeding records was lower in the wild than in captivity. Energetic cost of travelling and searching for food may be associated with equal division of carrying behavior by the wild breeding pair. Higher proportions of carrying in the groups wild and B may have delayed the development of the infants' motor skills required in foraging. Our data agree with previous studies: the father's lower investment in carrying when adult helpers are present and lower contribution of subadult non-reproductive members.

scholarly journals Selection for brain size impairs innate, but not adaptive immune responses

2016 ◽  
Vol 283 (1826) ◽  
pp. 20152857 ◽  
Author(s):  
Alexander Kotrschal ◽  
Niclas Kolm ◽  
Dustin J. Penn
Keyword(s):  
Immune Responses ◽  
Poecilia Reticulata ◽  
Brain Size ◽  
Innate Immune Responses ◽  
Rejection Reaction ◽  
Trade Off ◽  
Large Brain ◽  
Rejection Response ◽  
Selection For ◽  
Acquired Immune Responses

Both the brain and the immune system are energetically demanding organs, and when natural selection favours increased investment into one, then the size or performance of the other should be reduced. While comparative analyses have attempted to test this potential evolutionary trade-off, the results remain inconclusive. To test this hypothesis, we compared the tissue graft rejection (an assay for measuring innate and acquired immune responses) in guppies ( Poecilia reticulata ) artificially selected for large and small relative brain size. Individual scales were transplanted between pairs of fish, creating reciprocal allografts, and the rejection reaction was scored over 8 days (before acquired immunity develops). Acquired immune responses were tested two weeks later, when the same pairs of fish received a second set of allografts and were scored again. Compared with large-brained animals, small-brained animals of both sexes mounted a significantly stronger rejection response to the first allograft. The rejection response to the second set of allografts did not differ between large- and small-brained fish. Our results show that selection for large brain size reduced innate immune responses to an allograft, which supports the hypothesis that there is a selective trade-off between investing into brain size and innate immunity.

scholarly journals The costs and benefits of flexibility as an expression of behavioural plasticity: a primate perspective

2013 ◽  
Vol 368 (1618) ◽  
pp. 20120339 ◽  
Author(s):  
Carel P. van Schaik
Keyword(s):  
Environmental Change ◽  
Local Adaptation ◽  
Geographical Variation ◽  
Brain Size ◽  
Behavioural Plasticity ◽  
High Plasticity ◽  
Costs And Benefits ◽  
Cognitive Benefits ◽  
Local Genotypes ◽  
Individual Decisions

Traditional neo-Darwinism ascribes geographical variation in morphology or in behaviour to varying selection on local genotypes. However, mobile and long-lived organisms cannot achieve local adaptation this way, leading to a renewed interest in plasticity. I examined geographical variation in orang-utan subsistence and social behaviour, and found this to be largely owing to behavioural plasticity, here called flexibility, both in the form of flexible individual decisions and of socially transmitted (cultural) innovations. Although comparison with other species is difficult, the extent of such flexibility is almost certainly limited by brain size. It is shown that brains can only increase relative to body size where the cognitive benefits they produce are reliably translated into improved survival rate. This means that organisms that are very small, face many predators, live in highly seasonal environments, or lack opportunities for social learning cannot evolve greater flexibility, and must achieve local adaptation through selection on specific genotypes. On the other hand, as body and brain size increase, local adaptation is increasingly achieved through selection on plasticity. The species involved are also generally those that most need it, being more mobile and longer-lived. Although high plasticity buffers against environmental change, the most flexible organisms face a clear limit because they respond slowly to selection. Thus, paradoxically, the largest-brained animals may actually be vulnerable to the more drastic forms of environmental change, such as those induced by human actions.

scholarly journals Effect of tag attachment on flight parameters and energetic cost across five raptor species

2021 ◽  
Author(s):  
Arianna Longarini ◽  
Olivier Duriez ◽  
Emily Shepard ◽  
Kamran Safi ◽  
Martin Wikelski ◽  
...  
Keyword(s):  
Energy Expenditure ◽  
Movement Ecology ◽  
Energetic Cost ◽  
Systematic Bias ◽  
Flight Performance ◽  
Different Types ◽  
Vertical Speed ◽  
In The Wild ◽  
Flight Parameters

Bio-logging devices play a fundamental and indispensable role in movement ecology studies, particularly in the wild. However, researchers are becoming increasingly aware of the potential effects that attaching devices can have on animals, particularly on their behaviour, energy expenditure and survival. The way a device is attached to an animal's body has also potential effects on the collected data, and quantifying the type and magnitude of potential bias is fundamental to enable researchers to combine and compare data from different studies. Since over two decades, large terrestrial birds have been in the focus of long-term movement ecology research, employing bio-logging devices attached with different types of harnesses. However, comparative studies investigating the effects of harness type on these species are scarce. In this study, we tested for potential differences in data collected by two commonly used harness types, backpack and leg-loop, on the flight performance of 10 individuals from five raptor species, equipped with high resolution bio-logging devices, in the same area and time. We explored the effect of harness type on vertical speed, horizontal speed, glide ratio, height above sea level, distance travelled, proportion of soaring and flapping behaviour, and VeDBA (a proxy for energy expenditure) between and within individuals, all used as fine-scale measures of flight performance. Birds equipped with leg-loops climbed up to 0.65 ms-1 faster, reached 19% greater heights while soaring and spent less time with active flight compared to birds equipped with backpacks, suggesting that backpack harnesses, compared to leg-loops, might cause additional drag that lowered the birds' flight performance. A lower rate of sinking while gliding, a slightly higher glide ratio, higher horizontal speed while soaring, and lower VeDBA, were also indicative of decreased drag using leg-loops. Our results, add to the pre-existing literature highlighting the design-related advantages of leg-loops, and they are in support of considering leg-loops as a better alternative to backpack harnesses for large soaring birds. Our study also highlights the importance of investigating how the methodology used to measure behavioural information affects the collected data to avoid systematic bias, which would invalidate data comparability and lead to misinterpreting the behaviour being measured.

Sign in / Sign up

Export Citation Format

Share Document