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Merchant A, Zhou X. Caste-biased patterns of brain investment in the subterranean termite Reticulitermes flavipes. iScience 2024; 27:110052. [PMID: 38883809 PMCID: PMC11176635 DOI: 10.1016/j.isci.2024.110052] [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: 01/01/2024] [Revised: 03/04/2024] [Accepted: 05/17/2024] [Indexed: 06/18/2024] Open
Abstract
Investment into neural tissue is expected to reflect the specific sensory and behavioral capabilities of a particular organism. Termites are eusocial insects that exhibit a caste system in which individuals can develop into one of several morphologically and behaviorally distinct castes. However, it is unclear to what extent these differences between castes are reflected in the anatomy of the brain. To address this question, we used deformation-based morphometry to conduct pairwise comparisons between the brains of different castes in the eastern subterranean termite, Reticulitermes flavipes. Workers exhibited enlargement in the antennal lobes and mushroom bodies, while reproductives showed increased investment into the optic lobes and central body. In addition, caste-specific enlargement was observed in regions that could not be mapped to distinct neuropils, most notably in soldiers. These findings demonstrate a significant influence of caste development on brain anatomy in termites alongside convergence with eusocial hymenopteran systems.
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Affiliation(s)
- Austin Merchant
- Department of Entomology, Martin-Gatton College of Agriculture, Food and Environment, University of Kentucky, Lexington, KY 40546, USA
| | - Xuguo Zhou
- Department of Entomology, School of Integrative Biology, College of Liberal Arts & Sciences, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
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2
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Li Y, Yin L, Guo R, Du Y, Wang B, Liu L, Li Z, Liu W, Zhang G, An S, Yin X, Su L. Juvenile Hormone Involved in the Defensive Behaviors of Soldiers in Termite Reticulitermes aculabialis. INSECTS 2024; 15:130. [PMID: 38392549 PMCID: PMC10889337 DOI: 10.3390/insects15020130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2023] [Revised: 02/08/2024] [Accepted: 02/09/2024] [Indexed: 02/24/2024]
Abstract
Eusocial insects have evolved specific defensive strategies to protect their colonies. In termite colonies, soldiers perform a colony-level defense by displaying mechanical biting, head-banging and mandible opening-closing behaviors. However, few studies have been reported on the factors modulating defensive behaviors in termites. Owing to JH (juvenile hormone) being involved in soldier differentiation, JH was speculated to affect defensive behaviors in termite soldiers. To determine the effect of JH on the defensive behaviors of termite soldiers, we performed a JHA-feeding and RaSsp1-silencing experiment and then tested the changes in defense-related behaviors, alarm pheromones and key JH signaling genes. The observed result was that after feeding workers with JHA, soldiers displayed the following: (1) decreased biting events and increased head-banging events; (2) a reduced expression of RaSsp1 and increased expression of Met (methoprene-tolerant, the nuclear receptor of JH) and Kr-h1 (the JH-inducible transcription factor Krüppel homolog 1); and (3) a decreased concentration of alarm pheromones, including α-pinene, β-pinene and limonene (+, -). Further study showed that soldiers silenced for RaSsp1 also exhibited (1) decreased biting events and increased head-banging events and (2) increased expression of Met and Kr-h1. In addition, soldiers stimulated by the alarm pheromone limonene displayed an increase in the frequency of mandible opening-closing and biting behavior. All of these results show that JHA influenced the defensive behaviors of termite soldiers, possibly via downregulating RaSsp1 expression, up-regulating Met and Kr-h1 and stimulating the secretion of alarm pheromones, suggesting that the JH pathway plays important roles in modulating social behaviors in termite colonies.
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Affiliation(s)
- Yiying Li
- College of Life Science, Henan Agricultural University, Zhengzhou 450002, China
| | - Letong Yin
- College of Life Science, Henan Agricultural University, Zhengzhou 450002, China
| | - Ruiyao Guo
- College of Life Science, Henan Agricultural University, Zhengzhou 450002, China
| | - Yunliang Du
- College of Life Science, Henan Agricultural University, Zhengzhou 450002, China
| | - Bo Wang
- College of Life Science, Henan Agricultural University, Zhengzhou 450002, China
| | - Long Liu
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, China
| | - Zhenya Li
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, China
| | - Wei Liu
- College of Life Science, Henan Agricultural University, Zhengzhou 450002, China
| | - Guozhi Zhang
- College of Life Science, Henan Agricultural University, Zhengzhou 450002, China
| | - Shiheng An
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, China
| | - Xinming Yin
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, China
| | - Lijuan Su
- College of Life Science, Henan Agricultural University, Zhengzhou 450002, China
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Valadares L, da Silva IB, Costa-Leonardo AM, Sandoz JC. Differentiation of workers into soldiers is associated with a size reduction of higher-order brain centers in the neotropical termite Procornitermes araujoi. Sci Rep 2023; 13:18279. [PMID: 37880273 PMCID: PMC10600217 DOI: 10.1038/s41598-023-45221-0] [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: 05/04/2023] [Accepted: 10/17/2023] [Indexed: 10/27/2023] Open
Abstract
Comparing the size of functionally distinct brain regions across individuals with remarkable differences in sensory processing and cognitive demands provides important insights into the selective forces shaping animal nervous systems. We took advantage of the complex system of worker-to-soldier differentiation in the termitid Procornitermes araujoi, to investigate how a profound modification of body morphology followed by an irreversible shift in task performance are translated in terms of brain structure and size. This behavioural shift is characterised by a reduction of the once wide and complex behavioural repertoire of workers to one exclusively dedicated to nest defence (soldiers). In accordance with soldier's reduced cognitive and sensory demands, we show here that differentiation of workers into soldiers is associated with a size reduction of the mushroom body (MB) compartments, higher-order brain regions responsible for multimodal processing and integration of sensory information, as well as learning, memory, and decision-making. Moreover, in soldiers, we found an apparent fusion of the medial and lateral MB calyces likely associated with its volume reduction. These results illustrate a functional neuroplasticity of the MB associated with division of labour, supporting the link between MB size and behavioural flexibility in social insect workers.
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Affiliation(s)
- Lohan Valadares
- Evolution, Genomes, Behavior, and Ecology (EGCE), Université Paris-Saclay, CNRS, IRD, Gif-Sur-Yvette, France.
| | - Iago Bueno da Silva
- Laboratório de Cupins, Departamento de Biologia Geral e Aplicada, Instituto de Biociências, Universidade Estadual Paulista (UNESP), Rio Claro, SP, Brazil
| | - Ana Maria Costa-Leonardo
- Laboratório de Cupins, Departamento de Biologia Geral e Aplicada, Instituto de Biociências, Universidade Estadual Paulista (UNESP), Rio Claro, SP, Brazil
| | - Jean-Christophe Sandoz
- Evolution, Genomes, Behavior, and Ecology (EGCE), Université Paris-Saclay, CNRS, IRD, Gif-Sur-Yvette, France
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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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Soldier Caste-Specific Protein 1 Is Involved in Soldier Differentiation in Termite Reticulitermes aculabialis. INSECTS 2022; 13:insects13060502. [PMID: 35735839 PMCID: PMC9224846 DOI: 10.3390/insects13060502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 05/22/2022] [Accepted: 05/23/2022] [Indexed: 01/27/2023]
Abstract
Termite soldiers are a unique caste among social insects, and their differentiation can be induced by Juvenile hormone (JH) from workers through two molts (worker–presoldier–soldier). However, the molecular mechanism underlying the worker-to-soldier transformation in termites is poorly understood. To explore the mechanism of soldier differentiation induced by JH, the gene soldier caste-specific protein 1 (RaSsp1, NCBI accession no: MT861054.1) in R. aculabialis was cloned, and its function was studied. This gene was highly expressed in the soldier caste, and the protein RsSsp1 was similar to the JHBP (JH-binding protein) domain-containing protein by Predict Protein online. In addition, JHIII could be anchored in the hydrophobic cage of RaSsp1 as the epoxide of the JHBP-bound JH according to the protein ligand molecular docking online tool AutoDock. The functional studies indicated that knocking down of the RaSsp1 shorted the presoldier’s head capsule, reduced mandible size, delayed molting time and decreased molting rate (from worker to presoldier) at the beginning of worker gut-purging. Furthermore, knocking down of the RaSsp1 had a more pronounced effect on soldier differentiation (from presoldier to soldier), and manifested in significantly shorter mandibles, rounder head capsules, and lower molting rate (from worker to presoldier) at the beginning of presoldier gut-purging. Correspondingly, the expressions of JH receptor Methoprene-tolerant (Met), the JH-inducible transcription factor Krüppel homolog1 (Kr-h1) and ecdysone signal genes Broad-complex (Br-C) were downregulated when knocking down the RaSsp1 at the above two stages. All these results that RaSsp1 may be involved in soldier differentiation from workers by binding and transporting JH.
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Miura T, Maekawa K. The making of the defensive caste: Physiology, development, and evolution of the soldier differentiation in termites. Evol Dev 2020; 22:425-437. [PMID: 32291940 DOI: 10.1111/ede.12335] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Revised: 02/11/2020] [Accepted: 03/08/2020] [Indexed: 12/29/2022]
Abstract
Termites (Blattodea, Termitoidea, or Isoptera) constitute one of the major lineages of eusocial insects. In termite societies, multiple types of functional individuals, that is, castes, perform divisions of labors to coordinate social behaviors. Among other castes, the soldier caste is distinctive since it is sterile and exclusively specialized into defensive behavior with largely modified morphological features. Therefore, many of the previous studies have been focused on soldiers, in terms of ecology, behavior, and evolution as well as developmental and physiological mechanisms. This article overviews the accumulation of studies especially focusing on the developmental and physiological mechanisms underlying the soldier differentiation in termites. Furthermore, the evolutionary trajectories that have led the acquisition of soldier caste and have diversified the soldier characteristics in association with the social evolution are discussed.
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Affiliation(s)
- Toru Miura
- Department of Biological Sciences, Misaki Marine Biological Station, School of Science, The University of Tokyo, Japan
| | - Kiyoto Maekawa
- Department of Biology, Faculty of Science, Academic Assembly, University of Toyama, Toyama, Japan
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Miura T. Juvenile hormone as a physiological regulator mediating phenotypic plasticity in pancrustaceans. Dev Growth Differ 2018; 61:85-96. [PMID: 30467834 DOI: 10.1111/dgd.12572] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 09/11/2018] [Accepted: 09/12/2018] [Indexed: 11/28/2022]
Abstract
Phenotypic plasticity and polyphenism, in which phenotypes can be changed depending on environmental conditions, are common in insects. Several studies focusing on physiological, developmental, and molecular processes underlying the plastic responses have revealed that similar endocrine mechanisms using juvenile hormone (JH) are used to coordinate the flexible developmental processes. This review discusses accumulated knowledge on the caste polyphenism in social insects (especially termites), the wing and the reproductive polyphenisms in aphids, and the nutritional polyphenism and sexual dimorphism in stag beetles. For the comparison with non-insect arthropods, extensive studies on the inducible defense (and reproductive polyphenism) in daphnids (crustacean) are also addressed. In all the cases, JH (and methyl farnesoate in daphnids) plays a central role in mediating environmental stimuli with morphogenetic processes. Since the synthetic pathways for juvenoids, i.e., the mevalonate pathway and downstream pathways to sesquiterpenoids, are conserved across pancrustacean lineages (crustaceans and hexapods including insects), the evolution of developmental regulation by juvenoids that control molting (ecdysis) and metamorphosis is suggested to have occurred in the ancestral arthropods. The discontinuous postembryonic development (i.e., molting) and the regulatory physiological factors (juvenoids) would have enabled plastic developmental systems observed in many arthropod lineages.
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Affiliation(s)
- Toru Miura
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Miura, Kanagawa, Japan
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Opachaloemphan C, Yan H, Leibholz A, Desplan C, Reinberg D. Recent Advances in Behavioral (Epi)Genetics in Eusocial Insects. Annu Rev Genet 2018; 52:489-510. [PMID: 30208294 DOI: 10.1146/annurev-genet-120116-024456] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Eusocial insects live in societies in which distinct family members serve specific roles in maintaining the colony and advancing the reproductive ability of a few select individuals. Given the genetic similarity of all colony members, the diversity of morphologies and behaviors is surprising. Social communication relies on pheromones and olfaction, as shown by mutants of orco, the universal odorant receptor coreceptor, and through electrophysiological analysis of neuronal responses to pheromones. Additionally, neurohormonal factors and epigenetic regulators play a key role in caste-specific behavior, such as foraging and caste switching. These studies start to allow an understanding of the molecular mechanisms underlying social behavior and provide a technological foundation for future studies of eusocial insects. In this review, we highlight recent findings in eusocial insects that advance our understanding of genetic and epigenetic regulations of social behavior and provide perspectives on future studies using cutting-edge technologies.
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Affiliation(s)
- Comzit Opachaloemphan
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA; ,
| | - Hua Yan
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA; , .,Department of Biology, University of Florida, Gainesville, Florida 32611, USA; .,Howard Hughes Medical Institute, New York University School of Medicine, New York, NY 10016, USA
| | | | - Claude Desplan
- Department of Biology, New York University, New York, NY 10003, USA; ,
| | - Danny Reinberg
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA; , .,Howard Hughes Medical Institute, New York University School of Medicine, New York, NY 10016, USA
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Kendroud S, Bohra AA, Kuert PA, Nguyen B, Guillermin O, Sprecher SG, Reichert H, VijayRaghavan K, Hartenstein V. Structure and development of the subesophageal zone of the Drosophila brain. II. Sensory compartments. J Comp Neurol 2018; 526:33-58. [PMID: 28875566 PMCID: PMC5971197 DOI: 10.1002/cne.24316] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 07/15/2017] [Accepted: 08/15/2017] [Indexed: 12/29/2022]
Abstract
The subesophageal zone (SEZ) of the Drosophila brain processes mechanosensory and gustatory sensory input from sensilla located on the head, mouth cavity and trunk. Motor output from the SEZ directly controls the movements involved in feeding behavior. In an accompanying paper (Hartenstein et al., ), we analyzed the systems of fiber tracts and secondary lineages to establish reliable criteria for defining boundaries between the four neuromeres of the SEZ, as well as discrete longitudinal neuropil domains within each SEZ neuromere. Here we use this anatomical framework to systematically map the sensory projections entering the SEZ throughout development. Our findings show continuity between larval and adult sensory neuropils. Gustatory axons from internal and external taste sensilla of the larva and adult form two closely related sensory projections, (a) the anterior central sensory center located deep in the ventromedial neuropil of the tritocerebrum and mandibular neuromere, and (b) the anterior ventral sensory center (AVSC), occupying a superficial layer within the ventromedial tritocerebrum. Additional, presumed mechanosensory terminal axons entering via the labial nerve define the ventromedial sensory center (VMSC) in the maxilla and labium. Mechanosensory afferents of the massive array of chordotonal organs (Johnston's organ) of the adult antenna project into the centrolateral neuropil column of the anterior SEZ, creating the antenno-mechanosensory and motor center (AMMC). Dendritic projections of dye back-filled motor neurons extend throughout a ventral layer of the SEZ, overlapping widely with the AVSC and VMSC. Our findings elucidate fundamental structural aspects of the developing sensory systems in Drosophila.
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Affiliation(s)
- Sarah Kendroud
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Ali Asgar Bohra
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, India
| | | | - Bao Nguyen
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Oriane Guillermin
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Simon G. Sprecher
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | | | | | - Volker Hartenstein
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
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Ishikawa Y, Aonuma H, Sasaki K, Miura T. Tyraminergic and Octopaminergic Modulation of Defensive Behavior in Termite Soldier. PLoS One 2016; 11:e0154230. [PMID: 27196303 PMCID: PMC4873212 DOI: 10.1371/journal.pone.0154230] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 04/11/2016] [Indexed: 11/18/2022] Open
Abstract
In termites, i.e. a major group of eusocial insects, the soldier caste exhibits specific morphological characteristics and extremely high aggression against predators. Although the genomic background is identical to the other non-aggressive castes, they acquire the soldier-specific behavioral character during the course of caste differentiation. The high aggressiveness and defensive behavior is essential for colony survival, but the neurophysiological bases are completely unknown. In the present study, using the damp-wood termite Hodotermopsis sjostedti, we focused on two biogenic amines, octopamine (OA) and tyramine (TA), as candidate neuromodulators for the defensive behavior in soldiers. High-performance liquid chromatographic analysis revealed that TA levels in the brain and suboesophageal ganglion (SOG) and the OA level in brain were increased in soldiers than in pseudergates (worker caste). Immunohistochemical analysis revealed that TA/OA neurons that innervate specific areas, including the mandibular muscles, antennal nerve, central complex, suboesophageal ganglion, and thoracic and/or abdominal ganglia, were enlarged in a soldier-specific manner. Together with the results that pharmacological application of TA promoted the defensive behavior in pseudergates, these findings suggest that the increased TA/OA levels induce the higher aggressiveness and defensive behavior in termite soldiers. The projection targets of these soldier-specific enlarged TA/OA neurons may have important roles in the higher aggressiveness and defensive behavior of the termite soldiers, inducing the neuronal transition that accompanies external morphological changes.
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Affiliation(s)
- Yuki Ishikawa
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, Japan
- Graduate School of Science, Nagoya University, Nagoya, Aichi, Japan
- * E-mail:
| | - Hitoshi Aonuma
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido, Japan
- Japan Science and Technology Agency CREST, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan
| | - Ken Sasaki
- Graduate School of Agriculture, Tamagawa University, Machida, Tokyo, Japan
| | - Toru Miura
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, Japan
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Kaji T, Keiler J, Bourguignon T, Miura T. Functional transformation series and the evolutionary origin of novel forms: evidence from a remarkable termite defensive organ. Evol Dev 2016; 18:78-88. [DOI: 10.1111/ede.12179] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tomonari Kaji
- Bamfield Marine Sciences Centre; 100 Pachena Rd Bamfield BC Canada V0R 1B0
| | - Jonas Keiler
- Allgemeine und Spezielle Zoologie; Institut für Biowissenschaften; Universität Rostock; Rostock Mecklenburg-Vorpommern Germany
| | - Thomas Bourguignon
- Department of Biological Sciences; National University of Singapore; 21 Lower Kent Ridge Rd Singapore
| | - Toru Miura
- Graduate School of Environmental Science; Hokkaido University; Sapporo Hokkaido Japan
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12
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Sugime Y, Ogawa K, Watanabe D, Shimoji H, Koshikawa S, Miura T. Expansion of presoldier cuticle contributes to head elongation during soldier differentiation in termites. Naturwissenschaften 2015; 102:71. [DOI: 10.1007/s00114-015-1322-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 10/29/2015] [Accepted: 10/31/2015] [Indexed: 11/28/2022]
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Masuoka Y, Yaguchi H, Suzuki R, Maekawa K. Knockdown of the juvenile hormone receptor gene inhibits soldier-specific morphogenesis in the damp-wood termite Zootermopsis nevadensis (Isoptera: Archotermopsidae). INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2015; 64:25-31. [PMID: 26188329 DOI: 10.1016/j.ibmb.2015.07.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 07/11/2015] [Accepted: 07/11/2015] [Indexed: 06/04/2023]
Abstract
The Methoprene-tolerant (Met) protein has been established as a juvenile hormone (JH) receptor. Knockdown of the Met gene caused precocious metamorphosis and suppression of ovarian development. However, the function of Met in caste development of social insects is unclear. In termites, JH acts as a central factor for caste development, especially for soldier differentiation, which involves two molts from workers via a presoldier stage. Increased JH titer in workers is needed for the presoldier molt, and the high JH titer is maintained throughout the presoldier period. Although presoldiers have the fundamental morphological features of soldiers, the nature of the cuticle is completely different from that of soldiers. We expected that JH signals via Met are involved in soldier-specific morphogenesis of the head and mandibles during soldier differentiation, especially in the presoldier period, in natural conditions. To test this hypothesis, we focused on soldier differentiation in an incipient colony of the damp-wood termite Zootermopsis nevadensis. Met homolog (ZnMet) expression in heads increased just after the presoldier molt. This high expression was reduced by ZnMet double stranded (dsRNA) injection before the presoldier molt. Although this treatment did not cause any morphological changes in presoldiers, it caused strong effects on soldiers, their mandibles being significantly shorter and head capsules smaller than those of control soldiers. Injection of ZnMet dsRNA throughout the presoldier stage did not affect the formation of soldier morphology, including cuticle formation. These results suggested that the rapid increase in ZnMet expression and subsequent activation of JH signaling just after the presoldier molt are needed for the formation of soldier-specific weapons. Therefore, besides its established role in insect metamorphosis, the JH receptor signaling also underlies soldier development in termites.
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Affiliation(s)
- Yudai Masuoka
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Hajime Yaguchi
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Ryutaro Suzuki
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Kiyoto Maekawa
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
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Hattori A, Sugime Y, Sasa C, Miyakawa H, Ishikawa Y, Miyazaki S, Okada Y, Cornette R, Lavine LC, Emlen DJ, Koshikawa S, Miura T. Soldier morphogenesis in the damp-wood termite is regulated by the insulin signaling pathway. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2013; 320:295-306. [PMID: 23703784 DOI: 10.1002/jez.b.22501] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 01/20/2013] [Accepted: 03/02/2013] [Indexed: 11/11/2022]
Abstract
Eusocial insects exhibit various morphological castes associated with the division of labor within a colony. Termite soldiers possess defensive traits including mandibles that are greatly exaggerated and enlarged, as compared to termite reproductives and workers. The enlarged mandibles of soldiers are known to result from dynamic morphogenesis during soldier differentiation that can be induced by juvenile hormone and its analogs. However, the detailed developmental mechanisms still remain unresolved. Because the insulin/insulin-like growth factor signaling (IIS) pathway has been shown to regulate the relative sizes of organs (i.e., allometry) in other insects, we examined the expression profiles of major IIS factors in the damp-wood termite Hodotermopsis sjostedti, during soldier differentiation. The relative expression patterns of orthologs for termite InR (HsjInR), PKB/Akt (HsjPKB/Akt), and FOXO (HsjFOXO) suggest that HsjInR and HsjPKB/Akt were up-regulated in the period of elongation of mandibles during soldier development. In situ hybridization showed that HsjInR was strongly expressed in the mandibular epithelial tissues, and RNA interference (RNAi) for HsjInR disrupted soldier-specific morphogenesis including mandibular elongation. These results suggest that signaling through the IIS pathway is required for soldier-specific morphogenesis. In addition, up-regulation of the IIS pathway in other body tissues occurred at earlier stages of development, indicating that there is tissue-specific IIS regulation. Because the IIS pathway is generally thought to act upstream of JH in insects, our results suggest the damp-wood termite may have evolved a novel feedback loop between JH and IIS that enables social interactions, rather than nutrition, to regulate caste determination.
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Affiliation(s)
- Akiko Hattori
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
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Cornette R, Hayashi Y, Koshikawa S, Miura T. Differential gene expression in response to juvenile hormone analog treatment in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Archotermopsidae). JOURNAL OF INSECT PHYSIOLOGY 2013; 59:509-518. [PMID: 23481672 DOI: 10.1016/j.jinsphys.2013.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 01/29/2013] [Accepted: 02/07/2013] [Indexed: 06/01/2023]
Abstract
Termite societies are characterized by a highly organized division of labor among conspicuous castes, groups of individuals with various morphological specializations. Termite caste differentiation is under control of juvenile hormone (JH), but the molecular mechanism underlying the response to JH and early events triggering caste differentiation are still poorly understood. In order to profile candidate gene expression during early soldier caste differentiation of the damp-wood termite, Hodotermopsis sjostedti, we treated pseudergates (workers) with a juvenile hormone analog (JHA) to induce soldier caste differentiation. We then used Suppressive Subtractive Hybridization to create two cDNA libraries enriched for transcripts that were either up- or downregulated at 24h after treatment. Finally, we used quantitative PCR to confirm temporal expression patterns. Hexamerins represent a large proportion of the genes upregulated following JHA treatment and have an expression pattern that shows roughly an inverse correlation to intrinsic JH titers. This data is consistent with the role of a JH "sink", which was demonstrated for hexamerins in another termite, Reticulitermes flavipes. A putative nuclear protein was also upregulated a few hours after JHA treatment, which suggests a role in the early response to JH and subsequent regulation of transcriptional events associated with soldier caste differentiation. Some digestive enzymes, such as endogenous beta-endoglucanase and chymotrypsin, as well as a protein associated to digestion were identified among genes downregulated after JHA treatment. This suggests that JH may directly influence the pseudergate-specific digestive system.
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Affiliation(s)
- Richard Cornette
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
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Muscedere ML, Traniello JFA. Division of labor in the hyperdiverse ant genus Pheidole is associated with distinct subcaste- and age-related patterns of worker brain organization. PLoS One 2012; 7:e31618. [PMID: 22363686 PMCID: PMC3281964 DOI: 10.1371/journal.pone.0031618] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 01/10/2012] [Indexed: 11/21/2022] Open
Abstract
The evolutionary success of ants and other social insects is considered to be intrinsically linked to division of labor among workers. The role of the brains of individual ants in generating division of labor, however, is poorly understood, as is the degree to which interspecific variation in worker social phenotypes is underscored by functional neurobiological differentiation. Here we demonstrate that dimorphic minor and major workers of different ages from three ecotypical species of the hyperdiverse ant genus Pheidole have distinct patterns of neuropil size variation. Brain subregions involved in sensory input (optic and antennal lobes), sensory integration, learning and memory (mushroom bodies), and motor functions (central body and subesophageal ganglion) vary significantly in relative size, reflecting differential investment in neuropils that likely regulate subcaste- and age-correlated task performance. Worker groups differ in brain size and display patterns of altered isometric and allometric subregion scaling that affect brain architecture independently of brain size variation. In particular, mushroom body size was positively correlated with task plasticity in the context of both age- and subcaste-related polyethism, providing strong, novel support that greater investment in this neuropil increases behavioral flexibility. Our findings reveal striking levels of developmental plasticity and evolutionary flexibility in Pheidole worker neuroanatomy, supporting the hypothesis that mosaic alterations of brain composition contribute to adaptive colony structure and interspecific variation in social organization.
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Affiliation(s)
- Mario L Muscedere
- Department of Biology, Boston University, Boston, Massachusetts, United States of America.
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Coming of age in an ant colony: cephalic muscle maturation accompanies behavioral development in Pheidole dentata. Naturwissenschaften 2011; 98:783-93. [DOI: 10.1007/s00114-011-0828-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 06/13/2011] [Accepted: 07/13/2011] [Indexed: 10/18/2022]
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Koshikawa S, Cornette R, Matsumoto T, Miura T. The homolog of Ciboulot in the termite (Hodotermopsis sjostedti): a multimeric beta-thymosin involved in soldier-specific morphogenesis. BMC DEVELOPMENTAL BIOLOGY 2010; 10:63. [PMID: 20529303 PMCID: PMC2896938 DOI: 10.1186/1471-213x-10-63] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Accepted: 06/08/2010] [Indexed: 11/23/2022]
Abstract
Background Caste differentiation in social insects is a type of polyphenism that enables division of labor among members of a colony. This elaborate social integration has attracted broad interest, although little is known about its regulatory mechanisms, especially in Isoptera (termites). In this study, we analyzed soldier differentiation in the damp-wood termite Hodotermopsis sjostedti, focusing on a possible effector gene for caste development. The gene for an actin-binding protein, HsjCib, which shows a high level of expression in developing mandibles during soldier differentiation, is characterized in detail. Results To examine the HsjCib gene, full-length cDNAs were obtained by rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR) and sequencing. Multiple isoforms were identified, and on the basis of the results of northern and Southern hybridization analyses, these isoforms were considered to be transcriptional variants from a single gene. On the basis of their sequence similarity to homologous genes of other organisms, functions in actin assembly were assumed to be different among isoforms. Expression analysis revealed high expression in the head during soldier differentiation, which was consistent with their allometric growth. Although isoform expression was observed in various tissues, different expression levels were observed among tissues, suggesting the possibility of tissue-specific morphogenetic regulation by HsjCib isoforms. Conclusion This study revealed the characteristics and dynamics of the HsjCib gene during soldier differentiation as a potential representative of downstream effector genes in caste-specific morphogenesis. From the expression patterns observed, this gene is considered to be involved in cephalic morphogenesis and neural reorganization, resulting in the establishment of caste-specific morphology and behavior.
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Affiliation(s)
- Shigeyuki Koshikawa
- Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan
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Ishikawa Y, Okada Y, Ishikawa A, Miyakawa H, Koshikawa S, Miura T. Gene expression changes during caste-specific neuronal development in the damp-wood termite Hodotermopsis sjostedti. BMC Genomics 2010; 11:314. [PMID: 20482890 PMCID: PMC2887416 DOI: 10.1186/1471-2164-11-314] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2009] [Accepted: 05/20/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND One of the key characters of social insects is the division of labor, in which different tasks are allocated to various castes. In termites, one of the representative groups of social insects, morphological differences as well as behavioral differences can be recognized among castes. However, very little is known about the neuronal and molecular bases of caste differentiation and caste-specific behavior. In almost all termite species, soldiers play defensive roles in their colonies, and their morphology and behavior are largely different from workers (or pseudergates). Therefore, we predicted that some genes linked to defensive behavior and/or those required for neuronal changes are differentially expressed between workers and soldiers, or during the soldier differentiation, respectively. RESULTS Using the brain and suboesophageal ganglion (SOG) of the damp-wood termite Hodotermopsis sjostedti, we first screened genes specifically expressed in soldiers or during soldier differentiation by the differential display method, followed by quantitative real-time polymerase chain reaction. No distinctive differences in expression patterns were detected between pseudergates and soldiers. In the course of soldier differentiation, however, five genes were found to be up-regulated in brain and/or SOG: 14-3-3 epsilon, fibrillin2, beta-tubulin, ciboulot, and a hypothetical protein containing a SAP motif. Some of these genes are thought to be associated with cytoskeletal structure or motor-associated proteins in neuronal tissues. CONCLUSION The identified five genes could be involved in soldier-specific neuronal modifications, resulting in defensive behaviors in termite soldiers. The temporal expression patterns of these genes were consistent with the neuronal changes during soldier differentiation, suggesting that molecular machineries, in which the identified factors would participate, play important roles in behavioral differentiation of termite soldiers.
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Affiliation(s)
- Yuki Ishikawa
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan
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