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Ishibashi T, Waliullah ASM, Aramaki S, Kamiya M, Kahyo T, Nakamura K, Tasaki E, Takata M, Setou M, Matsuura K. Plastic brain structure changes associated with the division of labor and aging in termites. Dev Growth Differ 2023; 65:374-383. [PMID: 37357446 DOI: 10.1111/dgd.12873] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 05/29/2023] [Accepted: 06/13/2023] [Indexed: 06/27/2023]
Abstract
Division of labor is a prominent feature of social insect societies, where different castes engage in different specialized tasks. As brain differences are associated with behavioral differences, brain anatomy may be linked to caste polymorphism. Here, we show that termite brain morphology changes markedly with caste differentiation and age in the termite, Reticulitermes speratus. Brain morphology was shown to be associated with reproductive division of labor, with reproductive individuals (alates and neotenic reproductives) having larger brains than nonreproductives (workers and soldiers). Micro-computed tomography (CT) imaging and dissection observations showed that the king's brain morphology changed markedly with shrinkage of the optic lobes during their long life in the dark. Behavioral experiments showed that mature primary kings lose visual function as a result of optic lobe shrinkage. These results suggested that termites restructure their nervous systems to perform necessary tasks as they undergo caste differentiation, and that they also show flexible changes in brain morphology even after the final molt. This study showed that brain morphology in social insects is linked to caste and aging, and that the evolution of the division of labor is underpinned by the development of diverse neural systems for specialized tasks.
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Affiliation(s)
- Tomoki Ishibashi
- Laboratory of Insect Ecology, Kyoto University, Kyoto, Japan
- Laboratory for Physical Biology, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - A S M Waliullah
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Shuhei Aramaki
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Shizuoka, Japan
- International Mass Imaging Center, Hamamatsu University School of Medicine, Shizuoka, Japan
- Department of Radiology, Hamamatsu University Hospital, Shizuoka, Japan
| | - Masaki Kamiya
- Department of Radiology, Hamamatsu University Hospital, Shizuoka, Japan
| | - Tomoaki Kahyo
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Shizuoka, Japan
- International Mass Imaging Center, Hamamatsu University School of Medicine, Shizuoka, Japan
| | | | - Eisuke Tasaki
- Laboratory of Insect Ecology, Kyoto University, Kyoto, Japan
| | - Mamoru Takata
- Laboratory of Insect Ecology, Kyoto University, Kyoto, Japan
| | - Mitsutoshi Setou
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Shizuoka, Japan
- International Mass Imaging Center, Hamamatsu University School of Medicine, Shizuoka, Japan
- Department of Systems Molecular Anatomy, Institute for Medical Photonics Research, Preeminent Medical Photonics Education and Research Center, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Kenji Matsuura
- Laboratory of Insect Ecology, Kyoto University, Kyoto, Japan
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Lucon-Xiccato T, Montalbano G, Bertolucci C. Adaptive phenotypic plasticity induces individual variability along a cognitive trade-off. Proc Biol Sci 2023; 290:20230350. [PMID: 37357854 PMCID: PMC10291716 DOI: 10.1098/rspb.2023.0350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 06/02/2023] [Indexed: 06/27/2023] Open
Abstract
Animal species, including humans, display patterns of individual variability in cognition that are difficult to explain. For instance, some individuals perform well in certain cognitive tasks but show difficulties in others. We experimentally analysed the contribution of cognitive plasticity to such variability. Theory suggests that diametrically opposed cognitive phenotypes increase individuals' fitness in environments with different conditions such as resource predictability. Therefore, if selection has generated plasticity that matches individuals' cognitive phenotypes to the environment, this might produce remarkable cognitive variability. We found that guppies, Poecilia reticulata, exposed to an environment with high resource predictability (i.e. food available at the same time and in the same location) developed enhanced learning abilities. Conversely, guppies exposed to an environment with low resource predictability (i.e. food available at a random time and location) developed enhanced cognitive flexibility and inhibitory control. These cognitive differences align along a trade-off between functions that favour the acquisition of regularities such as learning and functions that adjust behaviour to changing conditions (cognitive flexibility and inhibitory control). Therefore, adaptive cognitive plasticity in response to resource predictability (and potentially similar factors) is a key determinant of cognitive individual differences.
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Affiliation(s)
- Tyrone Lucon-Xiccato
- Department of Life Sciences and Biotechnology, University of Ferrara, Via L. Borsari 46, 44121 Ferrara, Italy
| | - Giulia Montalbano
- Department of Life Sciences and Biotechnology, University of Ferrara, Via L. Borsari 46, 44121 Ferrara, Italy
| | - Cristiano Bertolucci
- Department of Life Sciences and Biotechnology, University of Ferrara, Via L. Borsari 46, 44121 Ferrara, Italy
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Kruuk LEB, Brosnan SF, Neiman M. Despite COVID: showcasing new research in evolutionary biology from academic care-givers in the middle of a pandemic. Proc Biol Sci 2022; 289:20222131. [PMID: 36475441 PMCID: PMC9727660 DOI: 10.1098/rspb.2022.2131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Loeske E. B. Kruuk
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Sarah F. Brosnan
- Departments of Psychology and Philosophy, Neuroscience Institute, Center for Behavioral Neuroscience, Georgia State University, PO Box 5010, Atlanta, GA 30302-5010, USA
| | - Maurine Neiman
- Department of Biology and Department of Gender, Women's, and Sexuality Studies, Provost Faculty Fellow for Diversity, Equity, and Inclusion, University of Iowa, Iowa City, IA 52242, USA
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Cunha F, Stingo-Hirmas D, Cardoso RF, Wright D, Henriksen R. Neuronal and non-neuronal scaling across brain regions within an intercross of domestic and wild chickens. Front Neuroanat 2022; 16:1048261. [PMID: 36506870 PMCID: PMC9732670 DOI: 10.3389/fnana.2022.1048261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 11/11/2022] [Indexed: 11/26/2022] Open
Abstract
The allometric scaling of the brain size and neuron number across species has been extensively studied in recent years. With the exception of primates, parrots, and songbirds, larger brains have more neurons but relatively lower neuronal densities than smaller brains. Conversely, when considering within-population variability, it has been shown that mice with larger brains do not necessarily have more neurons but rather more neurons in the brain reflect higher neuronal density. To what extent this intraspecific allometric scaling pattern of the brain applies to individuals from other species remains to be explored. Here, we investigate the allometric relationships among the sizes of the body, brain, telencephalon, cerebellum, and optic tectum, and the numbers of neurons and non-neuronal cells of the telencephalon, cerebellum, and optic tectum across 66 individuals originated from an intercross between wild and domestic chickens. Our intercross of chickens generates a population with high variation in brain size, making it an excellent model to determine the allometric scaling of the brain within population. Our results show that larger chickens have larger brains with moderately more neurons and non-neuronal cells. Yet, absolute number of neurons and non-neuronal cells correlated strongly and positively with the density of neurons and non-neuronal cells, respectively. As previously shown in mice, this scaling pattern is in stark contrast with what has been found across different species. Our findings suggest that neuronal scaling rules across species are not a simple extension of the neuronal scaling rules that apply within a species, with important implications for the evolutionary developmental origins of brain diversity.
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Reyes AS, Bittar A, Ávila LC, Botia C, Esmeral NP, Bloch NI. Divergence in brain size and brain region volumes across wild guppy populations. Proc Biol Sci 2022; 289:20212784. [PMID: 36000235 PMCID: PMC9399710 DOI: 10.1098/rspb.2021.2784] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Complex evolutionary dynamics have produced extensive variation in brain anatomy in the animal world. In guppies, Poecilia reticulata, brain size and anatomy have been extensively studied in the laboratory contributing to our understanding of brain evolution and the cognitive advantages that arise with brain anatomical variation. However, it is unclear whether these laboratory results can be translated to natural populations. Here, we study brain neuroanatomy and its relationship with sexual traits across 18 wild guppy populations in diverse environments. We found extensive variation in female and male relative brain size and brain region volumes across populations in different environment types and with varying degrees of predation risk. In contrast with laboratory studies, we found differences in allometric scaling of brain regions, leading to variation in brain region proportions across populations. Finally, we found an association between sexual traits, mainly the area of black patches and tail length, and brain size. Our results suggest differences in ecological conditions and sexual traits are associated with differences in brain size and brain regions volumes in the wild, as well as sexual dimorphisms in the brain's neuroanatomy.
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Affiliation(s)
- Angie S. Reyes
- Department of Biomedical Engineering, University of Los Andes, Bogota, Colombia
| | - Amaury Bittar
- Department of Biomedical Engineering, University of Los Andes, Bogota, Colombia
| | - Laura C. Ávila
- Department of Biomedical Engineering, University of Los Andes, Bogota, Colombia
| | - Catalina Botia
- Department of Biomedical Engineering, University of Los Andes, Bogota, Colombia
| | - Natalia P. Esmeral
- Department of Biomedical Engineering, University of Los Andes, Bogota, Colombia
| | - Natasha I. Bloch
- Department of Biomedical Engineering, University of Los Andes, Bogota, Colombia
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