scholarly journals Exceptionally Steep Brain-Body Evolutionary Allometry Underlies the Unique Encephalization of Osteoglossiformes

2021 ◽  
pp. 1-15
Author(s):  
Masahito Tsuboi
Keyword(s):  
Body Size ◽  
Brain Development ◽  
Teleost Fish ◽  
Brain Size ◽  
Genetic Constraints ◽  
Evolutionary Changes ◽  
Large Brain ◽  
Evolutionary Allometry ◽  
The Relationship ◽  
Static Allometry

Brain-body static allometry, which is the relationship between brain size and body size within species, is thought to reflect developmental and genetic constraints. Existing evidence suggests that the evolution of large brain size without accompanying changes in body size (that is, encephalization) may occur when this constraint is relaxed. Teleost fish species are generally characterized by having close-fitting brain-body static allometries, leading to strong allometric constraints and small relative brain sizes. However, one order of teleost, Osteoglossiformes, underwent extreme encephalization, and its mechanistic bases are unknown. Here, I used a dataset and phylogeny encompassing 859 teleost species to demonstrate that the encephalization of Osteoglossiformes occurred through an increase in the slope of evolutionary (among-species) brain-body allometry. The slope is virtually isometric (1.03 ± 0.09 SE), making it one of the steepest evolutionary brain-body allometric slopes reported to date, and it deviates significantly from the evolutionary brain-body allometric slopes of other clades of teleost. Examination of the relationship between static allometric parameters (intercepts and slopes) and evolutionary allometry revealed that the dramatic steepening of the evolutionary allometric slope in Osteoglossiformes was a combined result of evolution in the slopes and intercepts of static allometry. These results suggest that the evolution of static allometry, which likely has been driven by evolutionary changes in the rate and timing of brain development, has facilitated the unique encephalization of Osteoglossiformes.

scholarly journals Why are there so few smart mammals (but so many smart birds)?

2008 ◽  
Vol 5 (1) ◽  
pp. 125-129 ◽  
Author(s):  
Karin Isler ◽  
Carel P Van Schaik
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Population Increase ◽  
Large Brain ◽  
Cooperatively Breeding ◽  
Steep Decline ◽  
Relative Brain Size ◽  
Altricial Birds ◽  
Rates Of Growth ◽  
Very High

The expensive brain hypothesis predicts an interspecific link between relative brain size and life-history pace. Indeed, animals with relatively large brains have reduced rates of growth and reproduction. However, they also have increased total lifespan. Here we show that the reduction in production with increasing brain size is not fully compensated by the increase in lifespan. Consequently, the maximum rate of population increase ( r max ) is negatively correlated with brain mass. This result is not due to a confounding effect of body size, indicating that the well-known correlation between r max and body size is driven by brain size, at least among homeothermic vertebrates. Thus, each lineage faces a ‘grey ceiling’, i.e. a maximum viable brain size, beyond which r max is so low that the risk of local or species extinction is very high. We found that the steep decline in r max with brain size is absent in taxa with allomaternal offspring provisioning, such as cooperatively breeding mammals and most altricial birds. These taxa thus do not face a lineage-specific grey ceiling, which explains the far greater number of independent origins of large brain size in birds than mammals. We also predict that (absolute and relative) brain size is an important predictor of macroevolutionary extinction patterns.

The relationship between hunting methods and sex, age and body weight in a non-trophy animal, the red fox

2009 ◽  
Vol 36 (2) ◽  
pp. 106 ◽  
Author(s):  
Piotr Tryjanowski ◽  
Tim H. Sparks ◽  
Robert Kamieniarz ◽  
Marek Panek
Keyword(s):  
Body Weight ◽  
Body Size ◽  
Sex Ratio ◽  
Vulpes Vulpes ◽  
Red Fox ◽  
Seasonal Differences ◽  
Evolutionary Changes ◽  
Potential Sources ◽  
The Relationship ◽  
Game Animals

Recently, hunting has represented a major source of mortality in game animals, including red fox, Vulpes vulpes, populations. Data from hunting studies have been used to explain evolutionary changes (body size, dental structure) in fox populations; however, knowledge of potential sources of bias in these kinds of data is lacking. Moreover, nature and game managers as well as conservationists have recently been seeking methods to limit European fox populations, which are increasing. In the present study in Polish farmland, we show that three different hunting methods (individual – lying in wait, with dogs at dens, with beating undergrowth to flush out foxes) resulted in differences in the age, sex ratio and body size of shot foxes. Taking account of seasonal differences in hunting methods used, shooting assisted by beating gave a higher proportion of male foxes, whereas individual hunting resulted in smaller foxes in shot samples. Hunting with dogs resulted in heavier female foxes, with the results being skewed towards females. Thus, this method may help limit the breeding capacity of a population and is recommended to assist in the control of red fox populations, at least in farmland areas.

scholarly journals Some Remarks on Bird's Brain and Behavior under the Constraints of Domestication

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Julia Mehlhorn ◽  
Gerd Rehkämper
Keyword(s):  
New Species ◽  
Body Size ◽  
Brain Size ◽  
Evolutionary Process ◽  
Brain Morphology ◽  
Domestic Poultry ◽  
Brain And Behavior ◽  
And Behavior ◽  
The Relationship

The relationship between domestication and evolution is still a matter of discussion. In this review, we present some arguments for the assumption that domestication could be seen as an evolutionary process including the possibility that new species might evolve. In course of domestication, many breeds have been developed which show numerous alterations in different parameters such as body size, coloring, habitat, behavior, and brain size and composition. Here, we would like to give an overview particularly about alterations and varieties in (brain) morphology and behavior in domestic poultry and argue that these alterations could be seen as adaptations to the man-made environment.

scholarly journals Understanding primate brain evolution

2007 ◽  
Vol 362 (1480) ◽  
pp. 649-658 ◽  
Author(s):  
R.I.M Dunbar ◽  
Susanne Shultz
Keyword(s):  
Life History ◽  
Path Analysis ◽  
Group Size ◽  
Brain Size ◽  
Brain Evolution ◽  
Primate Brain ◽  
The Social ◽  
Large Brain ◽  
Brain Data ◽  
The Relationship

We present a detailed reanalysis of the comparative brain data for primates, and develop a model using path analysis that seeks to present the coevolution of primate brain (neocortex) and sociality within a broader ecological and life-history framework. We show that body size, basal metabolic rate and life history act as constraints on brain evolution and through this influence the coevolution of neocortex size and group size. However, they do not determine either of these variables, which appear to be locked in a tight coevolutionary system. We show that, within primates, this relationship is specific to the neocortex. Nonetheless, there are important constraints on brain evolution; we use path analysis to show that, in order to evolve a large neocortex, a species must first evolve a large brain to support that neocortex and this in turn requires adjustments in diet (to provide the energy needed) and life history (to allow sufficient time both for brain growth and for ‘software’ programming). We review a wider literature demonstrating a tight coevolutionary relationship between brain size and sociality in a range of mammalian taxa, but emphasize that the social brain hypothesis is not about the relationship between brain/neocortex size and group size per se ; rather, it is about social complexity and we adduce evidence to support this. Finally, we consider the wider issue of how mammalian (and primate) brains evolve in order to localize the social effects.

scholarly journals A Review of Effects of Environment on Brain Size in Insects

Insects ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 461
Author(s):  
Thomas Carle
Keyword(s):  
Body Size ◽  
Social Behaviour ◽  
Brain Size ◽  
Social Brain ◽  
Encephalization Quotient ◽  
The Social ◽  
Relative Brain Size ◽  
The Relationship ◽  
Development And Evolution

Brain size fascinates society as well as researchers since it is a measure often associated with intelligence and was used to define species with high “intellectual capabilities”. In general, brain size is correlated with body size. However, there are disparities in terms of relative brain size between species that may be explained by several factors such as the complexity of social behaviour, the ‘social brain hypothesis’, or learning and memory capabilities. These disparities are used to classify species according to an ‘encephalization quotient’. However, environment also has an important role on the development and evolution of brain size. In this review, I summarise the recent studies looking at the effects of environment on brain size in insects, and introduce the idea that the role of environment might be mediated through the relationship between olfaction and vision. I also discussed this idea with studies that contradict this way of thinking.

scholarly journals Brain size predicts learning abilities in bees

2020 ◽  
Author(s):  
Miguel Á. Collado ◽  
Cristina M. Montaner ◽  
Francisco P. Molina ◽  
Daniel Sol ◽  
Ignasi Bartomeus
Keyword(s):  
Body Size ◽  
Conditioned Stimulus ◽  
Distinctive Feature ◽  
Brain Size ◽  
Cognitive Tasks ◽  
Substantial Variation ◽  
Learning Abilities ◽  
Species Survival ◽  
Large Brain ◽  
Relative Brain Size

ABSTRACTA large brain is widely considered a distinctive feature of intelligence, a notion that mostly derives from studies in mammals. However, studies in insects demonstrates that cognitively sophisticated processes, such as social learning and tool use, are still possible with very small brains. Even after accounting for the allometric effect of body size, substantial variation in brain size still remains unexplained. A plausible advantage of a disproportionately larger brain might be an enhanced ability to learn new behaviors to cope with novel or complex challenges. While this hypothesis has received ample support from studies in birds and mammals, similar evidence is not available for small-brained animals like insects. Our objective is to compare the learning abilities of different bee species with their brain size investment. We conducted an experiment in which field-collected individuals had to associate an unconditioned stimulus (sucrose), with a conditioned stimulus (colored strip). We show that the probability of learning the reward-colour association was related to both absolute and relative brain size. This study shows that other bee species aside from the long studied honeybees and bumblebees, can be used in cognitive experiments and opens the door to explore the importance of relative brain sizes in cognitive tasks for insects and its consequences for species survival in a changing world.

Brain and Body Size Relations among Spotted Hyenas (Crocuta crocuta)

2018 ◽  
Vol 92 (1-2) ◽  
pp. 82-95
Author(s):  
Michael D. Mann ◽  
Lawrence G. Frank ◽  
Stephen E. Glickman ◽  
Arnold L. Towe
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Negative Relationship ◽  
Crocuta Crocuta ◽  
Spotted Hyena ◽  
Spotted Hyenas ◽  
Body Weights ◽  
Vertebrate Zoology ◽  
Males And Females ◽  
The Relationship

The relationship between brain size and body size across species “from mouse to elephant” is described by a function of positive slope. Almost uniformly, the relationship between brain size and body size within a species has a positive slope, though this is less steep than across species. The spotted hyena, Crocuta crocuta, differs from most other mammals in a number of ways including the fact that, on average, adult females weigh more than adult males and occasionally display greater body lengths. Brains of 5 female and 4 male hyenas were weighed in the field near Moyale in Northern Kenya, and body weights and body lengths were obtained from the same animals. When our analyses of brain/body relationships in these animals revealed an unanticipated negative relationship between brain size and body length, we extended our measurements to include intracranial volume in 19 skulls (8 females and 11 males) from the collection at the Museum of Vertebrate Zoology, University of California Berkeley; body weights and lengths were also available. A third dataset was formed by measuring intracranial volumes in 60 spotted hyena skulls (27 females and 33 males) in the Natural History Museum, London, UK; body lengths and intracranial volumes were available. Brain/body size slopes, in general, were not significantly different from zero except in 3 cases: brain weight/body length for Moyale males alone and males and females together, and cranial volume/body weight for Museum of Vertebrate Zoology males and females together. Although most of the slopes were not significantly different from zero, they were all negative, and a statistical test which combined probabilities from the 3 datasets supports the conclusion that there is a negative relationship between brain size and body size in spotted hyenas. Possible explanations for the negative slopes are discussed, including costs and benefits of large brains and large bodies and physiological mechanisms.

scholarly journals Variation in the strength of allometry drives rates of evolution in primate brain shape

2020 ◽  
Vol 287 (1930) ◽  
pp. 20200807 ◽  
Author(s):  
G. Sansalone ◽  
K. Allen ◽  
J. A. Ledogar ◽  
S. Ledogar ◽  
D. R. Mitchell ◽  
...  
Keyword(s):  
Brain Size ◽  
Three Dimensional ◽  
Shape Evolution ◽  
Evolutionary Time ◽  
Primate Brain ◽  
Rates Of Evolution ◽  
Evolutionary Allometry ◽  
The Relationship ◽  
The Brain ◽  
Brain Shape

Large brains are a defining feature of primates, as is a clear allometric trend between body mass and brain size. However, important questions on the macroevolution of brain shape in primates remain unanswered. Here we address two: (i), does the relationship between the brain size and its shape follow allometric trends and (ii), is this relationship consistent over evolutionary time? We employ three-dimensional geometric morphometrics and phylogenetic comparative methods to answer these questions, based on a large sample representing 151 species and most primate families. We found two distinct trends regarding the relationship between brain shape and brain size. Hominoidea and Cercopithecinae showed significant evolutionary allometry, whereas no allometric trends were discernible for Strepsirrhini, Colobinae or Platyrrhini. Furthermore, we found that in the taxa characterized by significant allometry, brain shape evolution accelerated, whereas for taxa in which such allometry was absent, the evolution of brain shape decelerated. We conclude that although primates in general are typically described as large-brained, strong allometric effects on brain shape are largely confined to the order's representatives that display more complex behavioural repertoires.

scholarly journals A Farewell to the Encephalization Quotient: A New Brain Size Measure for Comparative Primate Cognition

2021 ◽  
pp. 1-12
Author(s):  
Carel P. van Schaik ◽  
Zegni Triki ◽  
Redouan Bshary ◽  
Sandra A. Heldstab
Keyword(s):  
Body Size ◽  
Cognitive Abilities ◽  
Brain Size ◽  
Estimation Error ◽  
Primate Species ◽  
Mammal Species ◽  
Mean Values ◽  
Encephalization Quotient ◽  
Body Sizes ◽  
Size Measure

Both absolute and relative brain sizes vary greatly among and within the major vertebrate lineages. Scientists have long debated how larger brains in primates and hominins translate into greater cognitive performance, and in particular how to control for the relationship between the noncognitive functions of the brain and body size. One solution to this problem is to establish the slope of cognitive equivalence, i.e., the line connecting organisms with an identical bauplan but different body sizes. The original approach to estimate this slope through intraspecific regressions was abandoned after it became clear that it generated slopes that were too low by an unknown margin due to estimation error. Here, we revisit this method. We control for the error problem by focusing on highly dimorphic primate species with large sample sizes and fitting a line through the mean values for adult females and males. We obtain the best estimate for the slope of circa 0.27, a value much lower than those constructed using all mammal species and close to the value expected based on the genetic correlation between brain size and body size. We also find that the estimate of cognitive brain size based on cognitive equivalence fits empirical cognitive studies better than the encephalization quotient, which should therefore be avoided in future studies on primates and presumably mammals and birds in general. The use of residuals from the line of cognitive equivalence may change conclusions concerning the cognitive abilities of extant and extinct primate species, including hominins.

Leg Strength Is Related to Endurance Run Performance in Children and Adolescents with Mental Retardation

2000 ◽  
Vol 12 (3) ◽  
pp. 324-333 ◽  
Author(s):  
Bo Fernhall ◽  
Kenneth H. Pitetti
Keyword(s):  
Mental Retardation ◽  
Body Size ◽  
Children And Adolescents ◽  
Aerobic Capacity ◽  
Significant Influence ◽  
Moderate Mental Retardation ◽  
Leg Strength ◽  
And Gender ◽  
The Relationship ◽  
Shuttle Run

This study evaluated the relationship between leg strength and endurance run performance, independent of aerobic capacity (V̇O2peak), body size, and gender, in children and adolescents with mild or moderate mental retardation. Twenty-six individuals (15 boys and 11 girls) volunteered and underwent tests of V̇O2peak, isokinetic leg strength, and endurance run performance (600-yard ran/walk and 20-m shuttle run). Results showed that leg strength was significantly related to both types of run performance; however, when controlling for V̇O2peak, body size, and gender, leg strength was a more significant contributor to the 600-yard run/walk than to 20-m shuttle run performance. Gender did not influence these relationships. These data suggest that leg strength has a significant influence on endurance run performance in children and adolescents with mild or moderate mental retardation.

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