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Noronha WS, Dos Santos Araújo R, Martins GF. Antennal sensilla variability among castes and sexes in the leaf-cutter ant Acromyrmex subterraneus subterraneus. PROTOPLASMA 2025; 262:609-618. [PMID: 39754610 DOI: 10.1007/s00709-024-02027-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2024] [Accepted: 12/19/2024] [Indexed: 01/06/2025]
Abstract
Insect antennae play a crucial role in communication, acting as receptors for both chemical and physical cues. This sensory reception is facilitated by specialized cuticular structures known as sensilla, which exhibit diverse morphologies and functions. In ants, caste polymorphism and sexual dimorphism manifest in antennal structure. This study characterized and compared the antennal sensilla across different castes (major and minor workers, and queens) and sexes of the leaf-cutter ant Acromyrmex subterraneus subterraneus, an important agricultural pest, using scanning electron microscopy. The lengths of the scape and pedicel were greater in major workers and queens compared to other classes of individuals (i.e., minor workers and males). Sensillum numbers were significantly higher for these two female classes than for minor workers and tended to be higher than for males. In addition, various types of sensilla were identified, including chaetic types I, II, and III, trichoid I and II, basiconic, ampullaceous, and coeloconic. Chaetic sensilla were found to be the most abundant in all classes of individuals studied. Overall, similar types of sensilla were found in females (major, minor, queen) and males. The differences in the presence, absence, and number of antennal sensilla were analyzed in relation to their functional roles across the studied groups.
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Affiliation(s)
- Weslane Silva Noronha
- Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG, 36570-900, Brazil
| | - Renan Dos Santos Araújo
- Instituto de Ciências Biológicas E da Saúde, Universidade Federal de Mato Grosso, Pontal Do Araguaia, MT, 78698-000, Brazil.
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Marty S, Couto A, Dawson EH, Brard N, d'Ettorre P, Montgomery SH, Sandoz JC. Ancestral complexity and constrained diversification of the ant olfactory system. Proc Biol Sci 2025; 292:20250662. [PMID: 40300630 PMCID: PMC12040470 DOI: 10.1098/rspb.2025.0662] [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: 03/07/2025] [Revised: 03/27/2025] [Accepted: 03/27/2025] [Indexed: 05/01/2025] Open
Abstract
Communication is a cornerstone of social living, allowing the exchange of information to align goals and synchronize behaviour. Ants, a group of highly successful social insects, have heightened olfactory abilities that are integral to their evolutionary success. Essential for colony cohesion and cooperation, a female-specific olfactory subsystem processes information about nestmate recognition cues (cuticular hydrocarbons), including basiconic sensilla on the antenna and a cluster of specific glomeruli in the antennal lobe. While it has often been linked to ants' social lifestyle, the evolutionary origins and phylogenetic distribution of this system remain unknown. We conducted a comparative exploration of the ant olfactory system across eight major subfamilies, integrating neuroanatomical, chemical and behavioural analyses. Our findings reveal that sophistication of the ant olfactory system has deep evolutionary roots. Moreover, antennal lobe investment is not associated with social traits such as colony size, polygyny or foraging strategies, but correlates with cuticular hydrocarbon profile complexity. Despite neuroanatomical differences, different ant species consistently excel in nestmate discrimination, indicating adaptation to chemical diversity while maintaining reliable social recognition. This suggests that cuticular hydrocarbon profile and neuronal investment in olfactory neuropil have co-evolved to sustain discrimination performance.
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Affiliation(s)
- Simon Marty
- IDEEV, Université Paris-Saclay, CNRS, IRD, Evolution Genomes Behaviour and Ecology, 91190 Gif-sur-Yvette, France
| | - Antoine Couto
- IDEEV, Université Paris-Saclay, CNRS, IRD, Evolution Genomes Behaviour and Ecology, 91190 Gif-sur-Yvette, France
| | - Erika H. Dawson
- Laboratory of Experimental and Comparative Ethology, Université Sorbonne Paris Nord, 93430 Villetaneuse, France
| | - Neven Brard
- Laboratory of Experimental and Comparative Ethology, Université Sorbonne Paris Nord, 93430 Villetaneuse, France
| | - Patrizia d'Ettorre
- Laboratory of Experimental and Comparative Ethology, Université Sorbonne Paris Nord, 93430 Villetaneuse, France
| | | | - Jean-Christophe Sandoz
- IDEEV, Université Paris-Saclay, CNRS, IRD, Evolution Genomes Behaviour and Ecology, 91190 Gif-sur-Yvette, France
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Hart T, Lopes LE, Frank DD, Kronauer DJC. Pheromone representation in the ant antennal lobe changes with age. Curr Biol 2024; 34:3233-3240.e4. [PMID: 38876103 PMCID: PMC11265976 DOI: 10.1016/j.cub.2024.05.031] [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: 01/22/2024] [Revised: 04/11/2024] [Accepted: 05/16/2024] [Indexed: 06/16/2024]
Abstract
While the neural basis of age-related decline has been extensively studied,1,2,3 less is known about changes in neural function during the pre-senescent stages of adulthood. Adult neural plasticity is likely a key factor in social insect age polyethism, where individuals perform different tasks as they age and divide labor in an age-dependent manner.4,5,6,7,8,9 Primarily, workers transition from nursing to foraging tasks,5,10 become more aggressive, and more readily display alarm behavior11,12,13,14,15,16 as they get older. While it is unknown how these behavioral dynamics are neurally regulated, they could partially be generated by altered salience of behaviorally relevant stimuli.4,6,7 Here, we investigated how odor coding in the antennal lobe (AL) changes with age in the context of alarm pheromone communication in the clonal raider ant (Ooceraea biroi).17 Similar to other social insects,11,12,16 older ants responded more rapidly to alarm pheromones, the chemical signals for danger. Using whole-AL calcium imaging,18 we then mapped odor representations for five general odorants and two alarm pheromones in young and old ants. Alarm pheromones were represented sparsely at all ages. However, alarm pheromone responses within individual glomeruli changed with age, either increasing or decreasing. Only two glomeruli became sensitized to alarm pheromones with age, while at the same time becoming desensitized to general odorants. Our results suggest that the heightened response to alarm pheromones in older ants occurs via increased sensitivity in these two core glomeruli, illustrating the importance of sensory modulation in social insect division of labor and age-associated behavioral plasticity.
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Affiliation(s)
- Taylor Hart
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
| | - Lindsey E Lopes
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Dominic D Frank
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Daniel J C Kronauer
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA; Howard Hughes Medical Institute, New York, NY 10065, USA.
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Taniguchi R, Grimaldi DA, Watanabe H, Iba Y. Sensory evidence for complex communication and advanced sociality in early ants. SCIENCE ADVANCES 2024; 10:eadp3623. [PMID: 38875342 PMCID: PMC11177930 DOI: 10.1126/sciadv.adp3623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Accepted: 05/13/2024] [Indexed: 06/16/2024]
Abstract
Advanced social behavior, or eusociality, has been evolutionarily profound, allowing colonies of ants, termites, social wasps, and bees to dominate competitively over solitary species throughout the Cenozoic. Advanced sociality requires not just nestmate cooperation and specialization but refined coordination and communication. Here, we provide independent evidence that 100-million-year-old Cretaceous ants in amber were social, based on chemosensory adaptations. Previous studies inferred fossil ant sociality from individual ants preserved adjacent to others. We analyzed several fossil ants for their antennal sensilla, using original rotation imaging of amber microinclusions, and found an array of antennal sensilla, specifically for alarm pheromone detection and nestmate recognition, sharing distinctive features with extant ants. Although Cretaceous ants were stem groups, the fossilized sensilla confirm hypotheses of their complex sociality.
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Affiliation(s)
- Ryo Taniguchi
- Department of Natural History Sciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - David A Grimaldi
- Division of Invertebrate Zoology, American Museum of Natural History, New York, NY 10024-5192, USA
| | - Hidehiro Watanabe
- Department of Earth System Science, Fukuoka University, Fukuoka, Fukuoka 814-0180 Japan
| | - Yasuhiro Iba
- Department of Earth and Planetary Sciences, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
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Hart T, Lopes LE, Frank DD, Kronauer DJ. Pheromone representation in the ant antennal lobe changes with age. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.13.580193. [PMID: 38405746 PMCID: PMC10888935 DOI: 10.1101/2024.02.13.580193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
While the neural basis of age-related decline has been extensively studied (1-3), less is known about changes in neural function during the pre-senescent stages of adulthood. Adult neural plasticity is likely a key factor in social insect age polyethism, where individuals perform different tasks as they age and divide labor in an age-dependent manner (4-9). Primarily, workers transition from nursing to foraging tasks (5, 10), become more aggressive, and more readily display alarm behavior (11-16) as they get older. While it is unknown how these behavioral dynamics are neurally regulated, they could partially be generated by altered salience of behaviorally relevant stimuli (4, 6, 7). Here, we investigated how odor coding in the antennal lobe (AL) changes with age in the context of alarm pheromone communication in the clonal raider ant (Ooceraea biroi) (17). Similar to other social insects (11, 12, 16), older ants responded more rapidly to alarm pheromones, the chemical signals for danger. Using whole-AL calcium imaging (18), we then mapped odor representations for five general odorants and two alarm pheromones in young and old ants. Alarm pheromones were represented sparsely at all ages. However, alarm pheromone responses within individual glomeruli changed with age, either increasing or decreasing. Only two glomeruli became sensitized to alarm pheromones with age, while at the same time becoming desensitized to general odorants. Our results suggest that the heightened response to alarm pheromones in older ants occurs via increased sensitivity in these two core glomeruli, illustrating the importance of sensory modulation in social insect division of labor and age-associated behavioral plasticity.
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Affiliation(s)
- Taylor Hart
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Lindsey E. Lopes
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Dominic D. Frank
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Daniel J.C. Kronauer
- Laboratory of Social Evolution and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
- Howard Hughes Medical Institute, New York, NY 10065, USA
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Couto A, Marty S, Dawson EH, d'Ettorre P, Sandoz JC, Montgomery SH. Evolution of the neuronal substrate for kin recognition in social Hymenoptera. Biol Rev Camb Philos Soc 2023; 98:2226-2242. [PMID: 37528574 DOI: 10.1111/brv.13003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 07/18/2023] [Accepted: 07/20/2023] [Indexed: 08/03/2023]
Abstract
In evolutionary terms, life is about reproduction. Yet, in some species, individuals forgo their own reproduction to support the reproductive efforts of others. Social insect colonies for example, can contain up to a million workers that actively cooperate in tasks such as foraging, brood care and nest defence, but do not produce offspring. In such societies the division of labour is pronounced, and reproduction is restricted to just one or a few individuals, most notably the queen(s). This extreme eusocial organisation exists in only a few mammals, crustaceans and insects, but strikingly, it evolved independently up to nine times in the order Hymenoptera (including ants, bees and wasps). Transitions from a solitary lifestyle to an organised society can occur through natural selection when helpers obtain a fitness benefit from cooperating with kin, owing to the indirect transmission of genes through siblings. However, this process, called kin selection, is vulnerable to parasitism and opportunistic behaviours from unrelated individuals. An ability to distinguish kin from non-kin, and to respond accordingly, could therefore critically facilitate the evolution of eusociality and the maintenance of non-reproductive workers. The question of how the hymenopteran brain has adapted to support this function is therefore a fundamental issue in evolutionary neuroethology. Early neuroanatomical investigations proposed that social Hymenoptera have expanded integrative brain areas due to selection for increased cognitive capabilities in the context of processing social information. Later studies challenged this assumption and instead pointed to an intimate link between higher social organisation and the existence of developed sensory structures involved in recognition and communication. In particular, chemical signalling of social identity, known to be mediated through cuticular hydrocarbons (CHCs), may have evolved hand in hand with a specialised chemosensory system in Hymenoptera. Here, we compile the current knowledge on this recognition system, from emitted identity signals, to the molecular and neuronal basis of chemical detection, with particular emphasis on its evolutionary history. Finally, we ask whether the evolution of social behaviour in Hymenoptera could have driven the expansion of their complex olfactory system, or whether the early origin and conservation of an olfactory subsystem dedicated to social recognition could explain the abundance of eusocial species in this insect order. Answering this question will require further comparative studies to provide a comprehensive view on lineage-specific adaptations in the olfactory pathway of Hymenoptera.
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Affiliation(s)
- Antoine Couto
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
- Evolution, Genomes, Behaviour and Ecology (UMR 9191), IDEEV, Université Paris-Saclay, CNRS, IRD, 12 route 128, Gif-sur-Yvette, 91190, France
| | - Simon Marty
- Evolution, Genomes, Behaviour and Ecology (UMR 9191), IDEEV, Université Paris-Saclay, CNRS, IRD, 12 route 128, Gif-sur-Yvette, 91190, France
| | - Erika H Dawson
- Laboratory of Experimental and Comparative Ethology, UR 4443 (LEEC), Université Sorbonne Paris Nord, 99 avenue J.-B. Clément, Villetaneuse, 93430, France
| | - Patrizia d'Ettorre
- Laboratory of Experimental and Comparative Ethology, UR 4443 (LEEC), Université Sorbonne Paris Nord, 99 avenue J.-B. Clément, Villetaneuse, 93430, France
- Institut Universitaire de France (IUF), 103 Boulevard Saint-Michel, Paris, 75005, France
| | - Jean-Christophe Sandoz
- Evolution, Genomes, Behaviour and Ecology (UMR 9191), IDEEV, Université Paris-Saclay, CNRS, IRD, 12 route 128, Gif-sur-Yvette, 91190, France
| | - Stephen H Montgomery
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
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