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.

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.

scholarly journals Relative brain size and cognitive equivalence in fishes

2021 ◽  
Author(s):  
Zegni Triki ◽  
Mélisande Aellen ◽  
Carel van Schaik ◽  
Redouan Bshary
Keyword(s):  
Body Size ◽  
Cognitive Performance ◽  
Brain Size ◽  
Cognitive Tasks ◽  
Teleost Fishes ◽  
Vertebrate Species ◽  
Higher Taxa ◽  
Body Sizes ◽  
Mri Scans ◽  
Relative Brain Size

ABSTRACTThere are two well-established facts about vertebrate brains: brains are physiologically costly organs, and both absolute and relative brain size varies greatly between and within the major vertebrate clades. While the costs are relatively clear, scientists struggle to establish how larger brains translate into higher cognitive performance. Part of the challenge is that intuitively larger brains are needed to control larger bodies without any changes in cognitive performance. Therefore, body size needs to be controlled for in order to establish the slope of cognitive equivalence between animals of different sizes. Potentially, intraspecific slopes provide the best available estimate of how an increase in body size translates into an increase in brain size without changes in cognitive performance. Here, we provide slope estimates for brain-body sizes and for cognition-body in wild-caught “cleaner” fish Labroides dimidiatus. The cleaners’ cognitive performance was estimated from four different cognitive tasks that tested for learning, numerical, and inhibitory control abilities. The cognitive performance was found to be rather independent of body size, while brain-body slopes from two datasets gave the values of 0.58 (MRI scans data) and 0.47 (dissection data). These values can hence represent estimates of intraspecific cognitive equivalence for this species. Furthermore, another dataset of brain-body slopes estimated from 14 different fish species, gave a mean slope of 0.5, and hence rather similar to that of cleaners. This slope is very similar to the encephalisation quotients for ectotherm higher taxa, i.e. teleost fishes, amphibians and reptiles (∼ 0.5). The slope is much higher than what has been found in endotherm vertebrate species (∼ 0.3). Together, it suggests that endo- and ectotherm brain organisations and resulting cognitive performances are fundamentally different.

scholarly journals Feeding specialization and longer generation time are associated with relatively larger brains in bees

2020 ◽  
Vol 287 (1935) ◽  
pp. 20200762
Author(s):  
Ferran Sayol ◽  
Miguel Á. Collado ◽  
Joan Garcia-Porta ◽  
Marc A. Seid ◽  
Jason Gibbs ◽  
...  
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Phylogenetic Reconstruction ◽  
Brain Evolution ◽  
Insect Brain ◽  
Substantial Variation ◽  
Selective Pressures ◽  
Feeding Specialization ◽  
Relative Brain Size ◽  
Insect Group

Despite their miniature brains, insects exhibit substantial variation in brain size. Although the functional significance of this variation is increasingly recognized, research on whether differences in insect brain sizes are mainly the result of constraints or selective pressures has hardly been performed. Here, we address this gap by combining prospective and retrospective phylogenetic-based analyses of brain size for a major insect group, bees (superfamily Apoidea). Using a brain dataset of 93 species from North America and Europe, we found that body size was the single best predictor of brain size in bees. However, the analyses also revealed that substantial variation in brain size remained even when adjusting for body size. We consequently asked whether such variation in relative brain size might be explained by adaptive hypotheses. We found that ecologically specialized species with single generations have larger brains—relative to their body size—than generalist or multi-generation species, but we did not find an effect of sociality on relative brain size. Phylogenetic reconstruction further supported the existence of different adaptive optima for relative brain size in lineages differing in feeding specialization and reproductive strategy. Our findings shed new light on the evolution of the insect brain, highlighting the importance of ecological pressures over social factors and suggesting that these pressures are different from those previously found to influence brain evolution in other taxa.

scholarly journals Do Different Methods Yield Equivalent Estimations of Brain Size in Birds?

2020 ◽  
Vol 95 (2) ◽  
pp. 113-122
Author(s):  
Diego Ocampo ◽  
César Sánchez ◽  
Gilbert Barrantes
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Brain Mass ◽  
Wide Range ◽  
Evolutionary Studies ◽  
Relative Brain Size ◽  
Using Data ◽  
Endocranial Volume ◽  
The Brain ◽  
Size Estimates

The ratio of brain size to body size (relative brain size) is often used as a measure of relative investment in the brain in ecological and evolutionary studies on a wide range of animal groups. In birds, a variety of methods have been used to measure the brain size part of this ratio, including endocranial volume, fixed brain mass, and fresh brain mass. It is still unclear, however, whether these methods yield the same results. Using data obtained from fresh corpses and from published sources, this study shows that endocranial volume, mass of fixed brain tissue, and fresh mass provide equivalent estimations of brain size for 48 bird families, in 19 orders. We found, however, that the various methods yield significantly different brain size estimates for hummingbirds (Trochilidae). For hummingbirds, fixed brain mass tends to underestimate brain size due to reduced tissue density, whereas endocranial volume overestimates brain size because it includes a larger volume than that occupied by the brain.

scholarly journals Rethinking the Effects of Body Size on the Study of Brain Size Evolution

2019 ◽  
Vol 93 (4) ◽  
pp. 182-195 ◽  
Author(s):  
Enrique Font ◽  
Roberto García-Roa ◽  
Daniel Pincheira-Donoso ◽  
Pau Carazo
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Size Variation ◽  
Brain Evolution ◽  
Scaling Effects ◽  
Selection Pressures ◽  
Body Tissues ◽  
Relative Brain Size ◽  
Functional Components ◽  
The Brain

Body size correlates with most structural and functional components of an organism’s phenotype – brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. We address these problems by comparing brain-body relationships from across >1,000 species of birds and non-avian reptiles. Relative brain size in birds is often assumed to be 10 times larger than in reptiles of similar body size. We examine how differences in the specific gravity of body tissues and in body design (e.g., presence/absence of a tail or a dense shell) between these two groups can affect estimates of relative brain size. Using phylogenetic comparative analyses, we show that the gap in relative brain size between birds and reptiles has been grossly exaggerated. Our results highlight the need to take into account differences between taxa arising from selection pressures affecting body size and design, and call into question the widespread misconception that reptile brains are small and incapable of supporting sophisticated behavior and cognition.

scholarly journals Brain Changes during Phyletic Dwarfing in Elephants and Hippos

2018 ◽  
Vol 92 (3-4) ◽  
pp. 167-181 ◽  
Author(s):  
George A. Lyras
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Size Increase ◽  
Allometric Relationships ◽  
Scaling Models ◽  
Brain Changes ◽  
Relative Brain Size

Of all known insular mammals, hippos and elephants present the extremes of body size decrease, reducing to 4 and a mere 2% of their ancestral mainland size, respectively. Despite the numerous studies on these taxa, what happens to their relative brain size during phyletic dwarfing is not well known, and results are sometimes conflicting. For example, relative brain size increase has been noted in the Sicilian dwarf elephant, Palaeoloxodon falconeri, whereas relative brain size decrease has been postulated for Malagasy dwarf hippos. Here, I perform an analysis of brain, skull, and body size of 3 insular elephants (Palaeoloxodon “mnaidriensis,” P. tiliensis, and P. falconeri) and 3 insular hippos (Hippopotamus madagascariensis, H. lemerlei, and H. minor) to address this issue and to test whether relative brain size in phyletic dwarf species can be predicted. The results presented here show that the encephalization of all insular elephants and hippos is higher than that of their continental relatives. P. falconeri in particular has an enormous encephalization increase, which has so far not been reported in any other insular mammal. Insular brain size cannot be reliably predicted using either static allometric or ontogenetic scaling models. The results of this study indicate that insular dwarf species follow brain-body allometric relationships different from the expected patterns seen for their mainland relatives.

Animal intelligence as encephalization

1985 ◽  
Vol 308 (1135) ◽  
pp. 21-35 ◽  
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Great Apes ◽  
Processing Capacity ◽  
Scientific Question ◽  
Animal Intelligence ◽  
Neural Information ◽  
Neural Information Processing ◽  
Quantitative Analyses ◽  
Relative Brain Size

There is no consensus on the nature of animal intelligence despite a century of research, though recent work on cognitive capacities of dolphins and great apes seems to be on one right track. The most precise quantitative analyses have been of relative brain size, or structural encephalization, undertaken to find biological correlates of mind in animals. Encephalization and its evolution are remarkably orderly, and if the idea of intelligence were unknown it would have to be invented to explain encephalization. The scientific question is: what behaviour or dimensions of behaviour evolved when encephalization evolved? The answer: the relatively unusual behaviours that require increased neural information processing capacity, beyond that attributable to differences among species in body size. In this perspective, the different behaviours that depend on augmented processing capacity in different species are evidence of different intelligences (in the plural) that have evolved.

scholarly journals Nasonia Parasitic Wasps Escape from Haller's Rule by Diphasic, Partially Isometric Brain-Body Size Scaling and Selective Neuropil Adaptations

2017 ◽  
Vol 90 (3) ◽  
pp. 243-254 ◽  
Author(s):  
Jitte Groothuis ◽  
Hans M. Smid
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Parasitic Wasp ◽  
Volumetric Analysis ◽  
Relative Volume ◽  
Trichogramma Evanescens ◽  
Size Scaling ◽  
Relative Brain Size ◽  
Brain Architecture ◽  
Size Relation

Haller's rule states that brains scale allometrically with body size in all animals, meaning that relative brain size increases with decreasing body size. This rule applies both on inter- and intraspecific comparisons. Only 1 species, the extremely small parasitic wasp Trichogramma evanescens, is known as an exception and shows an isometric brain-body size relation in an intraspecific comparison between differently sized individuals. Here, we investigated if such an isometric brain-body size relationship also occurs in an intraspecific comparison with a slightly larger parasitic wasp, Nasonia vitripennis, a species that may vary 10-fold in body weight upon differences in levels of scramble competition during larval development. We show that Nasonia exhibits diphasic brain-body size scaling: larger wasps scale allometrically, following Haller's rule, whereas the smallest wasps show isometric scaling. Brains of smaller wasps are, therefore, smaller than expected and we hypothesized that this may lead to adaptations in brain architecture. Volumetric analysis of neuropil composition revealed that wasps of different sizes differed in relative volume of multiple neuropils. The optic lobes and mushroom bodies in particular were smaller in the smallest wasps. Furthermore, smaller brains had a relatively smaller total neuropil volume and larger cellular rind than large brains. These changes in relative brain size and brain architecture suggest that the energetic constraints on brain tissue outweigh specific cognitive requirements in small Nasonia wasps.

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.

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