1
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Valadares L, Vieira BG, Santos do Nascimento F, Sandoz JC. Brain size and behavioral specialization in the jataí stingless bee (Tetragonisca angustula). J Comp Neurol 2022; 530:2304-2314. [PMID: 35513351 DOI: 10.1002/cne.25333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 04/11/2022] [Accepted: 04/13/2022] [Indexed: 11/08/2022]
Abstract
Social insects are instructive models for understanding the association between investment in brain size and behavioral variability because they show a relatively simple nervous system associated with a large set of complex behaviors. In the jataí stingless bee (Tetragonisca angustula), division of labor relies both on age and body size differences among workers. When young, both minors and soldiers engage in intranidal tasks and move to extranidal tasks as they age. Minors switch to foraging activities, while soldiers take over defensive roles. Nest defense performed by soldiers includes two different tasks: (1) hovering around the nest entrance for the detection and interception of heterospecific bees (a task relying mostly on vision) and (2) standing at the nest entrance tube for inspection of returning foragers and discrimination against conspecific non-nestmates based on olfactory cues. Here, using different-sized individuals (minors and soldiers) as well as same-sized individuals (hovering and standing soldiers) performing distinct tasks, we investigated the effects of both morphological and behavioral variability on brain size. We found a negative allometric growth between brain size and body size across jataí workers, meaning that minors had relatively larger brains than soldiers. Between soldier types, we found that hovering soldiers had larger brain compartments related to visual processing (the optic lobes) and learning (the mushroom bodies). Brain size differences between jataí soldiers thus correspond to behavioral specialization in defense (i.e., vision for hovering soldiers) and illustrate a functional neuroplasticity underpinning division of labor.
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Affiliation(s)
- Lohan Valadares
- Evolution, Genomes, Behavior, and Ecology (EGCE), Université Paris-Saclay, CNRS, IRD, Gif-sur-Yvette, France
| | - Bruno Gusmão Vieira
- Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Fabio Santos do Nascimento
- Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Jean-Christophe Sandoz
- Evolution, Genomes, Behavior, and Ecology (EGCE), Université Paris-Saclay, CNRS, IRD, Gif-sur-Yvette, France
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2
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Muratore IB, Fandozzi EM, Traniello JFA. Behavioral performance and division of labor influence brain mosaicism in the leafcutter ant Atta cephalotes. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2022; 208:325-344. [PMID: 35112161 DOI: 10.1007/s00359-021-01539-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 12/27/2021] [Accepted: 12/28/2021] [Indexed: 11/29/2022]
Abstract
Brain evolution is hypothesized to be driven by behavioral selection on neuroarchitecture. We developed a novel metric of relative neuroanatomical investments involved in performing tasks varying in sensorimotor and processing demands across polymorphic task-specialized workers of the leafcutter ant Atta cephalotes and quantified brain size and structure to examine their correlation with our computational approximations. Investment in multisensory and motor integration for task performance was estimated to be greatest for media workers, whose highly diverse repertoire includes leaf-quality discrimination and leaf-harvesting tasks that likely involve demanding sensory and motor processes. Confocal imaging revealed that absolute brain volume increased with worker size and functionally specialized compartmental scaling differed among workers. The mushroom bodies, centers of sensory integration and learning and memory, and the antennal lobes, olfactory input sites, were larger in medias than in minims (gardeners) and significantly larger than in majors ("soldiers"), both of which had lower scores for involvement of olfactory processing in the performance of their characteristic tasks. Minims had a proportionally larger central complex compared to other workers. These results support the hypothesis that variation in task performance influences selection for mosaic brain structure, the independent evolution of proportions of the brain composed of different neuropils.
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Affiliation(s)
- I B Muratore
- Department of Biology, Boston University, Boston, MA, 02215, USA.
| | - E M Fandozzi
- Department of Biology, Boston University, Boston, MA, 02215, USA
| | - J F A Traniello
- Department of Biology, Boston University, Boston, MA, 02215, USA.,Graduate Program in Neuroscience, Boston University, Boston, MA, 02215, USA
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3
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DeSilva JM, Traniello JFA, Claxton AG, Fannin LD. When and Why Did Human Brains Decrease in Size? A New Change-Point Analysis and Insights From Brain Evolution in Ants. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.742639] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Human brain size nearly quadrupled in the six million years since Homo last shared a common ancestor with chimpanzees, but human brains are thought to have decreased in volume since the end of the last Ice Age. The timing and reason for this decrease is enigmatic. Here we use change-point analysis to estimate the timing of changes in the rate of hominin brain evolution. We find that hominin brains experienced positive rate changes at 2.1 and 1.5 million years ago, coincident with the early evolution of Homo and technological innovations evident in the archeological record. But we also find that human brain size reduction was surprisingly recent, occurring in the last 3,000 years. Our dating does not support hypotheses concerning brain size reduction as a by-product of body size reduction, a result of a shift to an agricultural diet, or a consequence of self-domestication. We suggest our analysis supports the hypothesis that the recent decrease in brain size may instead result from the externalization of knowledge and advantages of group-level decision-making due in part to the advent of social systems of distributed cognition and the storage and sharing of information. Humans live in social groups in which multiple brains contribute to the emergence of collective intelligence. Although difficult to study in the deep history of Homo, the impacts of group size, social organization, collective intelligence and other potential selective forces on brain evolution can be elucidated using ants as models. The remarkable ecological diversity of ants and their species richness encompasses forms convergent in aspects of human sociality, including large group size, agrarian life histories, division of labor, and collective cognition. Ants provide a wide range of social systems to generate and test hypotheses concerning brain size enlargement or reduction and aid in interpreting patterns of brain evolution identified in humans. Although humans and ants represent very different routes in social and cognitive evolution, the insights ants offer can broadly inform us of the selective forces that influence brain size.
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4
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O'Donnell S, Bulova S, Barrett M. Experience-expectant brain plasticity corresponds to caste-specific abiotic challenges in dampwood termites (Zootermopsis angusticollis and Z. nevadensis). Naturwissenschaften 2021; 108:57. [PMID: 34665344 DOI: 10.1007/s00114-021-01763-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 09/21/2021] [Accepted: 09/22/2021] [Indexed: 02/03/2023]
Abstract
Hypotheses for adaptive brain investment predict associations between the relative sizes of functionally distinct brain regions and the sensory/cognitive demands animals confront. We measured developmental differences in the relative sizes of visual processing brain regions (optic lobes) among dampwood termite castes to test whether optic lobe investment matches caste differences in exposure to visually complex environments. The winged primary reproductives (Kings/Queens) on mating flights are the only caste to leave the dark nest cavities and as predicted, Kings/Queens showed greater relative investment in optic lobe tissue than nestbound (neotenic) reproductives and soldiers in two dampwood termite species (Zootermopsis angusticollis and Z. nevadensis). Relative optic lobe size spanned more than an order of magnitude among the castes we studied, suggesting the growth of the optic lobes incurs substantial tissue costs. Optic lobe growth was experience-expectant: the optic lobes of Z. angusticollis brachypterous nymphs, which typically develop into Kings/Queens, were relatively larger than the optic lobes of apterous nymphs, which precede neotenics and soldiers, and relative optic lobe size of nestbound brachypterous nymphs was statistically similar to that of Kings/Queens. Experience-expectant brain tissue growth is rarely documented in insects, likely because it entails high potential costs of tissue production and maintenance and relatively low immediate sensory/cognitive benefits. We develop hypotheses for the conditions under which experience-expectant growth in brain regions could be favored by natural selection.
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Affiliation(s)
- Sean O'Donnell
- Departments of Biodiversity Earth & Environmental Science and Biology, Drexel University, Philadelphia, PA, 19081, USA.
| | - Susan Bulova
- Departments of Biodiversity Earth & Environmental Science and Biology, Drexel University, Philadelphia, PA, 19081, USA
| | - Meghan Barrett
- Departments of Biodiversity Earth & Environmental Science and Biology, Drexel University, Philadelphia, PA, 19081, USA
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5
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Habenstein J, Amini E, Grübel K, el Jundi B, Rössler W. The brain of
Cataglyphis
ants: Neuronal organization and visual projections. J Comp Neurol 2020; 528:3479-3506. [DOI: 10.1002/cne.24934] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 04/15/2020] [Accepted: 04/20/2020] [Indexed: 12/25/2022]
Affiliation(s)
- Jens Habenstein
- Biocenter, Behavioral Physiology and Sociobiology (Zoology II) University of Würzburg Würzburg Germany
| | - Emad Amini
- Biocenter, Neurobiology and Genetics University of Würzburg Würzburg Germany
| | - Kornelia Grübel
- Biocenter, Behavioral Physiology and Sociobiology (Zoology II) University of Würzburg Würzburg Germany
| | - Basil el Jundi
- Biocenter, Behavioral Physiology and Sociobiology (Zoology II) University of Würzburg Würzburg Germany
| | - Wolfgang Rössler
- Biocenter, Behavioral Physiology and Sociobiology (Zoology II) University of Würzburg Würzburg Germany
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6
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Kamhi JF, Ilieş I, Traniello JFA. Social Complexity and Brain Evolution: Comparative Analysis of Modularity and Integration in Ant Brain Organization. BRAIN, BEHAVIOR AND EVOLUTION 2019; 93:4-18. [PMID: 30982030 DOI: 10.1159/000497267] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 01/27/2019] [Indexed: 11/19/2022]
Abstract
The behavioral demands of living in social groups have been linked to the evolution of brain size and structure, but how social organization shapes investment and connectivity within and among functionally specialized brain regions remains unclear. To understand the influence of sociality on brain evolution in ants, a premier clade of eusocial insects, we statistically analyzed patterns of brain region size covariation as a proxy for brain region connectivity. We investigated brain structure covariance in young and old workers of two formicine ants, the Australasian weaver ant Oecophylla smaragdina, a pinnacle of social complexity in insects, and its socially basic sister clade Formica subsericea. As previously identified in other ant species, we predicted that our analysis would recognize in both species an olfaction-related brain module underpinning social information processing in the brain, and a second neuroanatomical cluster involved in nonolfactory sensorimotor processes, thus reflecting conservation of compartmental connectivity. Furthermore, we hypothesized that covariance patterns would reflect divergence in social organization and life histories either within this species pair or compared to other ant species. Contrary to our predictions, our covariance analyses revealed a weakly defined visual, rather than olfactory, sensory processing cluster in both species. This pattern may be linked to the reliance on vision for worker behavioral performance outside of the nest and the correlated expansion of the optic lobes to meet navigational demands in both species. Additionally, we found that colony size and social organization, key measures of social complexity, were only weakly correlated with brain modularity in these formicine ants. Worker age also contributed to variance in brain organization, though in different ways in each species. These findings suggest that brain organization may be shaped by the divergent life histories of the two study species. We compare our findings with patterns of brain organization of other eusocial insects.
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Affiliation(s)
- J Frances Kamhi
- Graduate Program for Neuroscience, Boston University, Boston, Massachusetts, USA, .,Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia,
| | - Iulian Ilieş
- Healthcare Systems Engineering Institute, Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts, USA
| | - James F A Traniello
- Graduate Program for Neuroscience, Boston University, Boston, Massachusetts, USA.,Department of Biology, Boston University, Boston, Massachusetts, USA
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7
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Gordon DG, Zelaya A, Arganda-Carreras I, Arganda S, Traniello JFA. Division of labor and brain evolution in insect societies: Neurobiology of extreme specialization in the turtle ant Cephalotes varians. PLoS One 2019; 14:e0213618. [PMID: 30917163 PMCID: PMC6436684 DOI: 10.1371/journal.pone.0213618] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 02/25/2019] [Indexed: 12/29/2022] Open
Abstract
Strongly polyphenic social insects provide excellent models to examine the neurobiological basis of division of labor. Turtle ants, Cephalotes varians, have distinct minor worker, soldier, and reproductive (gyne/queen) morphologies associated with their behavioral profiles: small-bodied task-generalist minors lack the phragmotic shield-shaped heads of soldiers, which are specialized to block and guard the nest entrance. Gynes found new colonies and during early stages of colony growth overlap behaviorally with soldiers. Here we describe patterns of brain structure and synaptic organization associated with division of labor in C. varians minor workers, soldiers, and gynes. We quantified brain volumes, determined scaling relationships among brain regions, and quantified the density and size of microglomeruli, synaptic complexes in the mushroom body calyxes important to higher-order processing abilities that may underpin behavioral performance. We found that brain volume was significantly larger in gynes; minor workers and soldiers had similar brain sizes. Consistent with their larger behavioral repertoire, minors had disproportionately larger mushroom bodies than soldiers and gynes. Soldiers and gynes had larger optic lobes, which may be important for flight and navigation in gynes, but serve different functions in soldiers. Microglomeruli were larger and less dense in minor workers; soldiers and gynes did not differ. Correspondence in brain structure despite differences in soldiers and gyne behavior may reflect developmental integration, suggesting that neurobiological metrics not only advance our understanding of brain evolution in social insects, but may also help resolve questions of the origin of novel castes.
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Affiliation(s)
- Darcy Greer Gordon
- Department of Biology, Boston University, Boston, MA, United States of America
- * E-mail:
| | - Alejandra Zelaya
- Department of Biology, Boston University, Boston, MA, United States of America
| | - Ignacio Arganda-Carreras
- Ikerbasque, Basque Foundation for Science, Bilbao, Spain
- Department of Computer Science and Artificial Intelligence, Basque Country University, San Sebastian, Spain
- Donostia International Physics Center (DIPC), San Sebastian, Spain
| | - Sara Arganda
- Department of Biology, Boston University, Boston, MA, United States of America
- Departamento de Biología y Geología, Física y Química Inorgánica, Área de Biodiversidad y Conservación, Universidad Rey Juan Carlos, Madrid, Spain
| | - James F. A. Traniello
- Department of Biology, Boston University, Boston, MA, United States of America
- Graduate Program for Neuroscience, Boston University, Boston, MA, United States of America
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8
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Shilovsky GA, Putyatina TS, Ashapkin VV, Rozina AA, Lyubetsky VA, Minina EP, Bychkovskaia IB, Markov AV, Skulachev VP. Ants as Object of Gerontological Research. BIOCHEMISTRY (MOSCOW) 2019; 83:1489-1503. [PMID: 30878024 DOI: 10.1134/s0006297918120076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Social insects with identical genotype that form castes with radically different lifespans are a promising model system for studying the mechanisms underlying longevity. The main direction of progressive evolution of social insects, in particular, ants, is the development of the social way of life inextricably linked with the increase in the colony size. Only in a large colony, it is possible to have a developed polyethism, create large food reserves, and actively regulate the nest microclimate. The lifespan of ants hugely varies among genetically similar queens, workers (unproductive females), and males. The main advantage of studies on insects is the determinism of ontogenetic processes, with a single genome leading to completely different lifespans in different castes. This high degree of determinacy is precisely the reason why some researchers (incorrectly) call a colony of ants the "superorganism", emphasizing the fact that during the development, depending on the community needs, ants can switch their ontogenetic programs, which influences their social roles, ability to learn (i.e., the brain [mushroom-like body] plasticity), and, respectively, the spectrum of tasks performed by a given individual. It has been shown that in many types of food behavior, older ants surpass young ones in both performing the tasks and transferring the experience. The balance between the need to reduce the "cost" of non-breeding individuals (short lifespan and small size of workers) and the benefit from experienced long-lived workers possessing useful skills (large size and "non-aging") apparently determines the differences in the lifespan and aging rate of workers in different species of ants. A large spectrum of rigidly determined ontogenetic trajectories in different castes with identical genomes and the possibility of comparison between "evolutionarily advanced" and "primitive" subfamilies (e.g., Formicinae and Ponerinae) make ants an attractive object in the studies of both normal aging and effects of anti-aging drugs.
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Affiliation(s)
- G A Shilovsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia. .,Lomonosov Moscow State University, Faculty of Biology, Moscow, 119234, Russia.,Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, 127051, Russia
| | - T S Putyatina
- Lomonosov Moscow State University, Faculty of Biology, Moscow, 119234, Russia
| | - V V Ashapkin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - A A Rozina
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - V A Lyubetsky
- Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, 127051, Russia
| | - E P Minina
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - I B Bychkovskaia
- Nikiforov Center of Emergency and Radiation Medicine of the Russian Ministry of Emergency Control, St. Petersburg, 194044, Russia
| | - A V Markov
- Lomonosov Moscow State University, Faculty of Biology, Moscow, 119234, Russia
| | - V P Skulachev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
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9
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Wright CM, Lichtenstein JLL, Doering GN, Pretorius J, Meunier J, Pruitt JN. Collective personalities: present knowledge and new frontiers. Behav Ecol Sociobiol 2019. [DOI: 10.1007/s00265-019-2639-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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10
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Abstract
Nest choice in Temnothorax spp.; task allocation and the regulation of activity in Pheidole dentata, Pogonomyrmex barbatus, and Atta spp.; and trail networks in Monomorium pharaonis and Cephalotes goniodontus all provide examples of correspondences between the dynamics of the environment and the dynamics of collective behavior. Some important aspects of the dynamics of the environment include stability, the threat of rupture or disturbance, the ratio of inflow and outflow of resources or energy, and the distribution of resources. These correspond to the dynamics of collective behavior, including the extent of amplification, how feedback instigates and inhibits activity, and the extent to which the interactions that provide the information to regulate behavior are local or spatially centralized.
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Affiliation(s)
- Deborah M Gordon
- Department of Biology, Stanford University, Stanford, California 94305-5020, USA;
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11
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O’Donnell S, Bulova S, Barrett M, von Beeren C. Brain investment under colony-level selection: soldier specialization in Eciton army ants (Formicidae: Dorylinae). BMC ZOOL 2018. [DOI: 10.1186/s40850-018-0028-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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12
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Lillico-Ouachour A, Metscher B, Kaji T, Abouheif E. Internal head morphology of minor workers and soldiers in the hyperdiverse ant genus Pheidole. CAN J ZOOL 2018. [DOI: 10.1139/cjz-2017-0209] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the hyperdiverse ant genus Pheidole Westwood, 1839, the worker caste evolved into two morphologically distinct subcastes: minor workers and soldiers. The evolution of soldiers, which are larger in size than minor workers and have disproportionately larger heads, are thought to be key to Phediole’s success. Although many studies have focused on external anatomy, little is known about their internal anatomy. We therefore used microCT imaging and quantitative three-dimensional image analysis to reconstruct the major glands of the head, the musculature, nervous system, and digestive organ of minor workers and soldiers of four Pheidole species. We expected these tissues to scale isometrically and to be proportionally larger in soldiers relative to the minor workers. Surprisingly, we found that the nervous system, cephalic gland, and digestive organ volume are absolutely and relatively smaller in soldiers, whereas muscle volume is absolutely and relatively larger, than in minor workers. This may reflect individual-level trade-offs, where muscles grow at the expense of all other cephalic organs. Alternatively, this relationship may reflect the specialization of internal anatomy in each subcaste to enhance division of labour at the colony level. Future studies should test these alternative hypotheses across a larger number of Pheidole species.
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Affiliation(s)
- Angelica Lillico-Ouachour
- Department of Biology, McGill University, 1205, avenue Docteur Penfield, Montréal, QC H3A 1B1, Canada
| | - Brian Metscher
- Department of Theoretical Biology, Althanstraße 14, 1090 Vienna, Austria
| | - Tominari Kaji
- Bamfield Marine Sciences Centre, Bamfield, BC V0R 1B0, Canada
| | - Ehab Abouheif
- Department of Biology, McGill University, 1205, avenue Docteur Penfield, Montréal, QC H3A 1B1, Canada
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13
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Synaptic organization and division of labor in the exceptionally polymorphic ant Pheidole rhea. Neurosci Lett 2018; 676:46-50. [PMID: 29625207 DOI: 10.1016/j.neulet.2018.04.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Revised: 03/18/2018] [Accepted: 04/01/2018] [Indexed: 11/22/2022]
Abstract
Social insect polyphenisms provide models to examine the neural basis of division of labor and anatomy of the invertebrate social brain. Worker size-related behavior is hypothesized to enhance task performance, raising questions concerning the integration of morphology, behavior, and cellular neuroarchitecture, and how variation in sensory inputs and cognitive demands of behaviorally differentiated workers is reflected in higher-order processing ability. We used the highly polymorphic ant Pheidole rhea, which has three distinct worker size classes - minors, soldiers, and supersoldiers - to examine variation in synaptic circuitry across worker size and social role. We hypothesized that the density and size of synaptic complexes (microglomeruli, MG) would be positively associated with behavioral repertoire and the relative size of the mushroom bodies (MB). Supersoldiers had significantly larger and less dense MG in the lip (olfactory region) of the MB calyx (MBC), and larger MG in the collar (visual region) compared to minors. Soldiers were intermediate in synaptic phenotype: they did not differ significantly in MG density from minors and supersoldiers, had MG of similar size to minors in the lip, and did not differ from these two worker groups in MG size in the collar. Results suggest a complex relationship between MG density, size, behavior, and worker body size involving a conserved and plastic neurobiological development plan, although workers show strong variation in size and social role.
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14
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Kamhi JF, Gronenberg W, Robson SKA, Traniello JFA. Social complexity influences brain investment and neural operation costs in ants. Proc Biol Sci 2017; 283:rspb.2016.1949. [PMID: 27798312 DOI: 10.1098/rspb.2016.1949] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2016] [Accepted: 09/26/2016] [Indexed: 11/12/2022] Open
Abstract
The metabolic expense of producing and operating neural tissue required for adaptive behaviour is considered a significant selective force in brain evolution. In primates, brain size correlates positively with group size, presumably owing to the greater cognitive demands of complex social relationships in large societies. Social complexity in eusocial insects is also associated with large groups, as well as collective intelligence and division of labour among sterile workers. However, superorganism phenotypes may lower cognitive demands on behaviourally specialized workers resulting in selection for decreased brain size and/or energetic costs of brain metabolism. To test this hypothesis, we compared brain investment patterns and cytochrome oxidase (COX) activity, a proxy for ATP usage, in two ant species contrasting in social organization. Socially complex Oecophylla smaragdina workers had larger brain size and relative investment in the mushroom bodies (MBs)-higher order sensory processing compartments-than the more socially basic Formica subsericea workers. Oecophylla smaragdina workers, however, had reduced COX activity in the MBs. Our results suggest that as in primates, ant group size is associated with large brain size. The elevated costs of investment in metabolically expensive brain tissue in the socially complex O. smaragdina, however, appear to be offset by decreased energetic costs.
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Affiliation(s)
- J Frances Kamhi
- Department of Biology, Boston University, Boston, MA 02215, USA .,Graduate Program for Neuroscience, Boston University, Boston, MA 02215, USA
| | - Wulfila Gronenberg
- Department of Neuroscience, University of Arizona, Tucson, AZ 85721, USA
| | - Simon K A Robson
- Zoology and Ecology, James Cook University, Townsville, Queensland 4811, Australia
| | - James F A Traniello
- Department of Biology, Boston University, Boston, MA 02215, USA.,Graduate Program for Neuroscience, Boston University, Boston, MA 02215, USA
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15
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Behavior, brain, and morphology in a complex insect society: trait integration and social evolution in the exceptionally polymorphic ant Pheidole rhea. Behav Ecol Sociobiol 2017. [DOI: 10.1007/s00265-017-2396-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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16
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Kamhi JF, Arganda S, Moreau CS, Traniello JFA. Origins of Aminergic Regulation of Behavior in Complex Insect Social Systems. Front Syst Neurosci 2017; 11:74. [PMID: 29066958 PMCID: PMC5641352 DOI: 10.3389/fnsys.2017.00074] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 09/22/2017] [Indexed: 01/03/2023] Open
Abstract
Neuromodulators are conserved across insect taxa, but how biogenic amines and their receptors in ancestral solitary forms have been co-opted to control behaviors in derived socially complex species is largely unknown. Here we explore patterns associated with the functions of octopamine (OA), serotonin (5-HT) and dopamine (DA) in solitary ancestral insects and their derived functions in eusocial ants, bees, wasps and termites. Synthesizing current findings that reveal potential ancestral roles of monoamines in insects, we identify physiological processes and conserved behaviors under aminergic control, consider how biogenic amines may have evolved to modulate complex social behavior, and present focal research areas that warrant further study.
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Affiliation(s)
- J. Frances Kamhi
- Department of Biological Sciences, Macquarie University, Sydney, NSW, Australia
| | - Sara Arganda
- Department of Biology, Boston University, Boston, MA, United States
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Corrie S. Moreau
- Department of Science and Education, Field Museum of Natural History, Chicago, IL, United States
| | - James F. A. Traniello
- Department of Biology, Boston University, Boston, MA, United States
- Graduate Program for Neuroscience, Boston University, Boston, MA, United States
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Sarnat EM, Friedman NR, Fischer G, Lecroq-Bennet B, Economo EP. Rise of the spiny ants: diversification, ecology and function of extreme traits in the hyperdiverse genus Pheidole (Hymenoptera: Formicidae). Biol J Linn Soc Lond 2017. [DOI: 10.1093/biolinnean/blx081] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Giraldo YM, Kamhi JF, Fourcassié V, Moreau M, Robson SKA, Rusakov A, Wimberly L, Diloreto A, Kordek A, Traniello JFA. Lifespan behavioural and neural resilience in a social insect. Proc Biol Sci 2016; 283:rspb.2015.2603. [PMID: 26740614 DOI: 10.1098/rspb.2015.2603] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Analyses of senescence in social species are important to understanding how group living influences the evolution of ageing in society members. Social insects exhibit remarkable lifespan polyphenisms and division of labour, presenting excellent opportunities to test hypotheses concerning ageing and behaviour. Senescence patterns in other taxa suggest that behavioural performance in ageing workers would decrease in association with declining brain functions. Using the ant Pheidole dentata as a model, we found that 120-day-old minor workers, having completed 86% of their laboratory lifespan, showed no decrease in sensorimotor functions underscoring complex tasks such as alloparenting and foraging. Collaterally, we found no age-associated increases in apoptosis in functionally specialized brain compartments or decreases in synaptic densities in the mushroom bodies, regions associated with integrative processing. Furthermore, brain titres of serotonin and dopamine--neuromodulators that could negatively impact behaviour through age-related declines--increased in old workers. Unimpaired task performance appears to be based on the maintenance of brain functions supporting olfaction and motor coordination independent of age. Our study is the first to comprehensively assess lifespan task performance and its neurobiological correlates and identify constancy in behavioural performance and the absence of significant age-related neural declines.
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Affiliation(s)
| | - J Frances Kamhi
- Department of Biology, Boston University, Boston, MA 02215, USA
| | - Vincent Fourcassié
- Research Center on Animal Cognition, CNRS, Toulouse 31062 Cedex 9, France Research Center on Animal Cognition, Université de Toulouse, Toulouse 31062 Cedex 9, France
| | - Mathieu Moreau
- Research Center on Animal Cognition, CNRS, Toulouse 31062 Cedex 9, France Research Center on Animal Cognition, Université de Toulouse, Toulouse 31062 Cedex 9, France
| | - Simon K A Robson
- College of Marine and Environmental Science, James Cook University, Townsville 4811, Australia
| | - Adina Rusakov
- Department of Biology, Boston University, Boston, MA 02215, USA
| | | | | | - Adrianna Kordek
- Department of Biology, Boston University, Boston, MA 02215, USA
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Giraldo YM, Rusakov A, Diloreto A, Kordek A, Traniello JFA. Age, worksite location, neuromodulators, and task performance in the ant Pheidole dentata. Behav Ecol Sociobiol 2016; 70:1441-1455. [PMID: 28042198 DOI: 10.1007/s00265-016-2153-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Social insect workers modify task performance according to age-related schedules of behavioral development, and/or changing colony labor requirements based on flexible responses that may be independent of age. Using known-age minor workers of the ant Pheidole dentata throughout 68% of their 140-day laboratory lifespan, we asked whether workers found inside or outside the nest differed in task performance and if behaviors were correlated with and/or causally linked to changes in brain serotonin (5HT) and dopamine (DA). Our results suggest that task performance patterns of individually assayed minors collected at these two spatially different worksites were independent of age. Outside-nest minors displayed significantly higher levels of predatory behavior and greater activity than inside-nest minors, but these groups did not differ in brood care or phototaxis. We examined the relationship of 5HT and DA to these behaviors in known-age minors by quantifying individual brain titers. Both monoamines did not increase significantly from 20 to 95 days of age. DA did not appear to directly regulate worksite location, although titers were significantly higher in outside-nest than inside-nest workers. Pharmacological depletion of 5HT did not affect nursing, predation, phototaxis or activity. Our results suggest that worker task capabilities are independent of age beyond 20 days, and only predatory behavior can be consistently predicted by spatial location. This could reflect worker flexibility or variability in the behavior of individuals collected at each location, which could be influenced by complex interactions between age, worksite location, social interactions, neuromodulators, and other environmental and internal regulators of behavior.
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Affiliation(s)
| | - Adina Rusakov
- Department of Biology, Boston University, Boston, MA 02215, USA
| | | | - Adrianna Kordek
- Department of Biology, Boston University, Boston, MA 02215, USA
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Esteve-Altava B. In search of morphological modules: a systematic review. Biol Rev Camb Philos Soc 2016; 92:1332-1347. [DOI: 10.1111/brv.12284] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 05/06/2016] [Accepted: 05/10/2016] [Indexed: 12/25/2022]
Affiliation(s)
- Borja Esteve-Altava
- Department of Comparative Biomedical Sciences; Royal Veterinary College; Hawkshead Lane, North Mymms Hatfield Hertfordshire AL9 7TA UK
- Department of Anatomy; College of Medicine, Howard University; 520 W Street, NW, Numa Adams Building Washington DC 20059 USA
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Differential investment in visual and olfactory brain areas reflects behavioural choices in hawk moths. Sci Rep 2016; 6:26041. [PMID: 27185464 PMCID: PMC4869021 DOI: 10.1038/srep26041] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 04/26/2016] [Indexed: 11/08/2022] Open
Abstract
Nervous tissue is one of the most metabolically expensive animal tissues, thus evolutionary investments that result in enlarged brain regions should also result in improved behavioural performance. Indeed, large-scale comparative studies in vertebrates and invertebrates have successfully linked differences in brain anatomy to differences in ecology and behaviour, but their precision can be limited by the detail of the anatomical measurements, or by only measuring behaviour indirectly. Therefore, detailed case studies are valuable complements to these investigations, and have provided important evidence linking brain structure to function in a range of higher-order behavioural traits, such as foraging experience or aggressive behaviour. Here, we show that differences in the size of both lower and higher-order sensory brain areas reflect differences in the relative importance of these senses in the foraging choices of hawk moths, as suggested by previous anatomical work in Lepidopterans. To this end we combined anatomical and behavioural quantifications of the relative importance of vision and olfaction in two closely related hawk moth species. We conclude that differences in sensory brain volume in these hawk moths can indeed be interpreted as differences in the importance of these senses for the animal’s behaviour.
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Kamhi JF, Nunn K, Robson SKA, Traniello JFA. Polymorphism and division of labour in a socially complex ant: neuromodulation of aggression in the Australian weaver ant, Oecophylla smaragdina. Proc Biol Sci 2016; 282:rspb.2015.0704. [PMID: 26136448 DOI: 10.1098/rspb.2015.0704] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Complex social structure in eusocial insects can involve worker morphological and behavioural differentiation. Neuroanatomical variation may underscore worker division of labour, but the regulatory mechanisms of size-based task specialization in polymorphic species are unknown. The Australian weaver ant, Oecophylla smaragdina, exhibits worker polyphenism: larger major workers aggressively defend arboreal territories, whereas smaller minors nurse brood.Here, we demonstrate that octopamine (OA) modulates worker size-related aggression in O. smaragdina. We found that the brains of majors had significantly higher titres of OA than those of minors and that OA was positively and specifically correlated with the frequency of aggressive responses to non-nestmates, a key component of territorial defence. Pharmacological manipulations that effectively switched OA action in major and minor worker brains reversed levels of aggression characteristic of each worker size class. Results suggest that altering OA action is sufficient to produce differences in aggression characteristic of size-related social roles. Neuromodulators therefore may generate variation in responsiveness to task-related stimuli associated with worker size differentiation and collateral behavioural specializations, a significant component of division of labour in complex social systems.
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Into the black and back: the ecology of brain investment in Neotropical army ants (Formicidae: Dorylinae). THE SCIENCE OF NATURE - NATURWISSENSCHAFTEN 2016; 103:31. [DOI: 10.1007/s00114-016-1353-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 01/28/2016] [Accepted: 02/22/2016] [Indexed: 10/22/2022]
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Social complexity, diet, and brain evolution: modeling the effects of colony size, worker size, brain size, and foraging behavior on colony fitness in ants. Behav Ecol Sociobiol 2015. [DOI: 10.1007/s00265-015-2035-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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