1
|
Young FJ, Alcalde Anton A, Melo-Flórez L, Couto A, Foley J, Monllor M, McMillan WO, Montgomery SH. Enhanced long-term memory and increased mushroom body plasticity in Heliconius butterflies. iScience 2024; 27:108949. [PMID: 38357666 PMCID: PMC10864207 DOI: 10.1016/j.isci.2024.108949] [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: 07/21/2023] [Revised: 11/27/2023] [Accepted: 01/15/2024] [Indexed: 02/16/2024] Open
Abstract
Heliconius butterflies exhibit expanded mushroom bodies, a key brain region for learning and memory in insects, and a novel foraging strategy unique among Lepidoptera - traplining for pollen. We tested visual long-term memory across six Heliconius and outgroup Heliconiini species. Heliconius species exhibited greater fidelity to learned colors after eight days without reinforcement, with further evidence of recall at 13 days. We also measured the plastic response of the mushroom body calyces over this time period, finding substantial post-eclosion expansion and synaptic pruning in the calyx of Heliconius erato, but not in the outgroup Heliconiini Dryas iulia. In Heliconius erato, visual associative learning experience specifically was associated with a greater retention of synapses and recall accuracy was positively correlated with synapse number. These results suggest that increases in the size of specific brain regions and changes in their plastic response to experience may coevolve to support novel behaviors.
Collapse
Affiliation(s)
- Fletcher J. Young
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
- Smithsonian Tropical Research Institute, Gamboa, Panama
- School of Biological Science, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Amaia Alcalde Anton
- School of Biological Science, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | | | - Antoine Couto
- School of Biological Science, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Jessica Foley
- Smithsonian Tropical Research Institute, Gamboa, Panama
- School of Biological Science, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | | | | | - Stephen H. Montgomery
- Smithsonian Tropical Research Institute, Gamboa, Panama
- School of Biological Science, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| |
Collapse
|
2
|
Azorsa F, Muscedere ML, Traniello JFA. Socioecology and Evolutionary Neurobiology of Predatory Ants. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2021.804200] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
3
|
Coto ZN, Traniello JFA. Brain Size, Metabolism, and Social Evolution. Front Physiol 2021; 12:612865. [PMID: 33708134 PMCID: PMC7940180 DOI: 10.3389/fphys.2021.612865] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 02/01/2021] [Indexed: 12/24/2022] Open
Affiliation(s)
- Zach N Coto
- Department of Biology, Boston University, Boston, MA, United States
| | - James F A Traniello
- Department of Biology, Boston University, Boston, MA, United States.,Graduate Program in Neuroscience, Boston University, Boston, MA, United States
| |
Collapse
|
4
|
Kraft N, Spaethe J, Rössler W, Groh C. Neuronal Plasticity in the Mushroom-Body Calyx of Bumble Bee Workers During Early Adult Development. Dev Neurobiol 2019; 79:287-302. [PMID: 30963700 DOI: 10.1002/dneu.22678] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 03/01/2019] [Accepted: 03/25/2019] [Indexed: 12/17/2022]
Abstract
Division of labor among workers is a key feature of social insects and frequently characterized by an age-related transition between tasks, which is accompanied by considerable structural changes in higher brain centers. Bumble bees (Bombus terrestris), in contrast, exhibit a size-related rather than an age-related task allocation, and thus workers may already start foraging at two days of age. We ask how this early behavioral maturation and distinct size variation are represented at the neuronal level and focused our analysis on the mushroom bodies (MBs), brain centers associated with sensory integration, learning and memory. To test for structural neuronal changes related to age, light exposure, and body size, whole-mount brains of age-marked workers were dissected for synapsin immunolabeling. MB calyx volumes, densities, and absolute numbers of olfactory and visual projection neuron (PN) boutons were determined by confocal laser scanning microscopy and three-dimensional image analyses. Dark-reared bumble bee workers showed an early age-related volume increase in olfactory and visual calyx subcompartments together with a decrease in PN-bouton density during the first three days of adult life. A 12:12 h light-dark cycle did not affect structural organization of the MB calyces compared to dark-reared individuals. MB calyx volumes and bouton numbers positively correlated with body size, whereas bouton density was lower in larger workers. We conclude that, in comparison to the closely related honey bees, neuronal maturation in bumble bees is completed at a much earlier stage, suggesting a strong correlation between neuronal maturation time and lifestyle in both species.
Collapse
Affiliation(s)
- Nadine Kraft
- Behavioral Physiology and Sociobiology (Zoology II), University of Würzburg, Biozentrum, Würzburg, 97074, Germany
| | - Johannes Spaethe
- Behavioral Physiology and Sociobiology (Zoology II), University of Würzburg, Biozentrum, Würzburg, 97074, Germany
| | - Wolfgang Rössler
- Behavioral Physiology and Sociobiology (Zoology II), University of Würzburg, Biozentrum, Würzburg, 97074, Germany
| | - Claudia Groh
- Behavioral Physiology and Sociobiology (Zoology II), University of Würzburg, Biozentrum, Würzburg, 97074, Germany
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
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.
Collapse
|