1
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Jernigan CM, Uy FM. Impact of the social environment in insect sensory systems. CURRENT OPINION IN INSECT SCIENCE 2023; 59:101083. [PMID: 37423425 DOI: 10.1016/j.cois.2023.101083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 06/26/2023] [Accepted: 07/04/2023] [Indexed: 07/11/2023]
Abstract
The social environment has a direct impact on sensory systems and unquestionable consequences on allocation of neural tissue. Although neuroplasticity is adaptive, responses to different social contexts may be mediated by energetic constraints and/or trade-offs between sensory modalities. However, general patterns of sensory plasticity remain elusive due to variability in experimental approaches. Here, we highlight recent studies in social Hymenoptera showing effects of the social environment on sensory systems. Further, we propose to identify a core set of socially mediated mechanisms that drive sensory plasticity. We hope this approach is widely adopted in different insect clades under a phylogenetic framework, which will allow for a more direct integration of the how and why questions exploring sensory plasticity evolution.
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Affiliation(s)
- Christopher M Jernigan
- Laboratory for Animal Social Evolution and Recognition, Department of Neurobiology and Behavior, Cornell University, NY, USA.
| | - Floria Mk Uy
- Department of Biology, University of Rochester, Rochester, NY, USA.
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2
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Sasaki K, Yoshimura H, Nishimura M. Caste-specific storage of dopamine-related substances in the brains of four Polistes paper wasp species. PLoS One 2023; 18:e0280881. [PMID: 36701284 PMCID: PMC9879392 DOI: 10.1371/journal.pone.0280881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Accepted: 01/10/2023] [Indexed: 01/27/2023] Open
Abstract
How the role of dopamine differs according to the evolution of eusociality and how it is required in the flexible society of Polistes paper wasps need further clarification. In the present study, we compared the storage and usage of dopamine-related substances in brains between the castes of paper wasps. The head widths, lipid stores in the abdomen, and levels of biogenic amines in the brains were measured in newly emerged females before male emergence (workers) and after male emergence (gynes) in four Polistes species. The head widths and the lipid stores were significantly larger in gynes than workers in P. snelleni, P. rothneyi, and P. jokahamae, whereas they did not differ between castes in P. chinensis. The levels of dopamine precursors in the brains were significantly higher in gynes than workers in P. snelleni, P. chinensis, and P. rothneyi, whereas those of dopamine and its metabolites did not differ between castes in these species. In P. jokahamae, the levels of dopamine precursors and dopamine in the brains did not differ between castes, but those of a dopamine metabolite were significantly higher in gynes than workers. Thus, the caste differences in the levels of dopamine-related substances did not always match body sizes and nutritional reserves. Foundresses in P. rothneyi had significantly lower levels of dopamine precursors and higher levels of dopamine and its metabolite than newly emerged gynes. These results suggested that in several Polistes species, dopamine precursors were stored in the brain without dopamine biosynthesis at emergence, and then converted into dopamine in foundresses during colony founding. These neuroendocrinal states in Polistes species largely differed from those in eusocial bees.
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Affiliation(s)
- Ken Sasaki
- Graduate School of Agriculture, Tamagawa University, Machida, Tokyo, Japan
- Honeybee Science Research Center, Tamagawa University, Machida, Tokyo, Japan
- * E-mail:
| | - Hideto Yoshimura
- Division of Agro-Environment Research, Tohoku Agricultural Research Center, NARO, Morioka, Iwate, Japan
| | - Masakazu Nishimura
- Honeybee Science Research Center, Tamagawa University, Machida, Tokyo, Japan
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3
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Jaumann S, Rehan SM, Schwartz K, Smith AR. Reduced neural investment in post-reproductive females of the bee Ceratina calcarta. Sci Rep 2022; 12:8256. [PMID: 35585164 PMCID: PMC9117229 DOI: 10.1038/s41598-022-12281-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 04/27/2022] [Indexed: 11/09/2022] Open
Abstract
Many insects show plasticity in the area of the brain called the mushroom bodies (MB) with foraging and social experience. MBs are paired neuropils associated with learning and memory. MB volume is typically greater in mature foragers relative to young and/or inexperienced individuals. Long-term studies show that extended experience may further increase MB volume, but long-term studies have only been performed on non-reproductive social insect workers. Here we use the subsocial bee Ceratina calcarata to test the effect of extended foraging experience on MB volume among reproductive females. Ceratina calcarata females forage to provision their immature offspring in the spring, and then again to provision their adult daughters in the late summer. We measured the volume of the MB calyces and peduncle, antennal lobes (AL), optic lobes (OL), central complex (CX), and whole brains of three groups of bees: newly emerged females, reproductive females in spring (foundresses), and post-reproductive mothers feeding their adult daughters in late summer. Post-reproductive late summer mothers had smaller MB calyces and ALs than foundresses. Moreover, among late mothers (but not other bees), wing wear, which is a measure of foraging experience, negatively correlated with both MB and OL volume. This is contrary to previously studied non-reproductive social insect workers in which foraging experience correlates postiviely with MB volume, and suggests that post-reproductive bees may reduce neural investment near the end of their lives.
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Affiliation(s)
- Sarah Jaumann
- Department of Biological Sciences, George Washington University, 800 22nd St. NW, Washington, DC, 20052, USA
| | - Sandra M Rehan
- Department of Biology, York University, Toronto, ON, Canada
| | - Kayla Schwartz
- Department of Biological Sciences, George Washington University, 800 22nd St. NW, Washington, DC, 20052, USA
| | - Adam R Smith
- Department of Biological Sciences, George Washington University, 800 22nd St. NW, Washington, DC, 20052, USA.
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4
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Gandia KM, Cappa F, Baracchi D, Hauber ME, Beani L, Uy FMK. Caste, Sex, and Parasitism Influence Brain Plasticity in a Social Wasp. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.803437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Brain plasticity is widespread in nature, as it enables adaptive responses to sensory demands associated with novel stimuli, environmental changes and social conditions. Social Hymenoptera are particularly well-suited to study neuroplasticity, because the division of labor amongst females and the different life histories of males and females are associated with specific sensory needs. Here, we take advantage of the social wasp Polistes dominula to explore if brain plasticity is influenced by caste and sex, and the exploitation by the strepsipteran parasite Xenos vesparum. Within sexes, male wasps had proportionally larger optic lobes, while females had larger antennal lobes, which is consistent with the sensory needs of sex-specific life histories. Within castes, reproductive females had larger mushroom body calyces, as predicted by their sensory needs for extensive within-colony interactions and winter aggregations, than workers who frequently forage for nest material and prey. Parasites had different effects on female and male hosts. Contrary to our predictions, female workers were castrated and behaviorally manipulated by female or male parasites, but only showed moderate differences in brain tissue allocation compared to non-parasitized workers. Parasitized males maintained their reproductive apparatus and sexual behavior. However, they had smaller brains and larger sensory brain regions than non-parasitized males. Our findings confirm that caste and sex mediate brain plasticity in P. dominula, and that parasitic manipulation drives differential allocation of brain regions depending on host sex.
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5
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Rozanski AN, Cini A, Lopreto TE, Gandia KM, Hauber ME, Cervo R, Uy FMK. Differential investment in visual and olfactory brain regions is linked to the sensory needs of a wasp social parasite and its host. J Comp Neurol 2021; 530:756-767. [PMID: 34473851 DOI: 10.1002/cne.25242] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 08/03/2021] [Accepted: 08/31/2021] [Indexed: 01/30/2023]
Abstract
Obligate insect social parasites evolve traits to effectively locate and then exploit their hosts, whereas hosts have complex social behavioral repertoires, which include sensory recognition to reject potential conspecific intruders and heterospecific parasites. While social parasites and host behaviors have been studied extensively, less is known about how their sensory systems function to meet their specific selective pressures. Here, we compare investment in visual and olfactory brain regions in the paper wasp Polistes dominula, and its obligate social parasite P. sulcifer, to explore the links among sensory systems,brain and behavior. Our results show significant relative volumetric differences between these two closely related species, consistent with their very different life histories. Social parasites show proportionally larger optic lobes and central complex to likely navigate long-distance migrations and unfamiliar landscapes to locate the specific species of hosts they usurp. Contrastingly, hosts have larger antennal lobes and calyces of the mushroom bodies compared with social parasites, as predicted by their sensory means to maintain social cohesion via olfactory signals, allocate colony tasks, forage, and recognize conspecific and heterospecific intruders. Our work suggests how this tradeoff between visual and olfactory brain regions may facilitate different sensory adaptations needed to perform social and foraging tasks by the host, including recognition of parasites, or to fly long distances and successful host localizing by the social parasite.
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Affiliation(s)
| | - Alessandro Cini
- Department of Biology, University of Florence, Sesto Fiorentino, Firenze, Italy.,Centre for Biodiversity and Environment Research, University College London, London, UK
| | - Taylor E Lopreto
- Department of Biology, University of Miami, Coral Gables, Florida, USA
| | - Kristine M Gandia
- Department of Biology, University of Miami, Coral Gables, Florida, USA
| | - Mark E Hauber
- Department of Evolution, Ecology and Behavior, School of Integrative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Rita Cervo
- Department of Biology, University of Florence, Sesto Fiorentino, Firenze, Italy
| | - Floria M K Uy
- Department of Biology, University of Miami, Coral Gables, Florida, USA.,Department of Biology, University of Rochester, Rochester, New York, USA
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6
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Pahlke S, Seid MA, Jaumann S, Smith A. The Loss of Sociality Is Accompanied by Reduced Neural Investment in Mushroom Body Volume in the Sweat Bee Augochlora Pura (Hymenoptera: Halictidae). ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA 2021; 114:637-642. [PMID: 34512860 PMCID: PMC8423109 DOI: 10.1093/aesa/saaa019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Indexed: 05/04/2023]
Abstract
Social behavior has been predicted to select for increased neural investment (the social brain hypothesis) and also to select for decreased neural investment (the distributed cognition hypothesis). Here, we use two related bees, the social Augochlorella aurata (Smith) (Hymenoptera: Halictidae) and the related Augochlora pura (Say), which has lost social behavior, to test the contrasting predictions of these two hypotheses in these taxa. We measured the volumes of the mushroom body (MB) calyces, a brain area shown to be important for cognition in previous studies, as well as the optic lobes and antennal lobes. We compared females at the nest foundress stage when both species are solitary so that brain development would not be influenced by social interactions. We show that the loss of sociality was accompanied by a loss in relative neural investment in the MB calyces. This is consistent with the predictions of the social brain hypothesis. Ovary size did not correlate with MB calyx volume. This is the first study to demonstrate changes in mosaic brain evolution in response to the loss of sociality.
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Affiliation(s)
- Sarah Pahlke
- Department of Biological Sciences, George Washington University, Washington, DC
| | - Marc A Seid
- Department of Biology and Program in Neurobiology, University of Scranton, Scranton, PA
| | - Sarah Jaumann
- Department of Biological Sciences, George Washington University, Washington, DC
| | - Adam Smith
- Department of Biological Sciences, George Washington University, Washington, DC
- Corresponding author, e-mail:
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7
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Hagadorn MA, Eck K, Del Grosso M, Haemmerle X, Wcislo WT, Kapheim KM. Age-related mushroom body expansion in male sweat bees and bumble bees. Sci Rep 2021; 11:17039. [PMID: 34426595 PMCID: PMC8382693 DOI: 10.1038/s41598-021-96268-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 08/04/2021] [Indexed: 01/20/2023] Open
Abstract
A well-documented phenomenon among social insects is that brain changes occur prior to or at the onset of certain experiences, potentially serving to prime the brain for specific tasks. This insight comes almost exclusively from studies considering developmental maturation in females. As a result, it is unclear whether age-related brain plasticity is consistent across sexes, and to what extent developmental patterns differ. Using confocal microscopy and volumetric analyses, we investigated age-related brain changes coinciding with sexual maturation in the males of the facultatively eusocial sweat bee, Megalopta genalis, and the obligately eusocial bumble bee, Bombus impatiens. We compared volumetric measurements between newly eclosed and reproductively mature males kept isolated in the lab. We found expansion of the mushroom bodies-brain regions associated with learning and memory-with maturation, which were consistent across both species. This age-related plasticity may, therefore, play a functionally-relevant role in preparing male bees for mating, and suggests that developmentally-driven neural restructuring can occur in males, even in species where it is absent in females.
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Affiliation(s)
- Mallory A Hagadorn
- Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT, 84322, USA.
| | - Karlee Eck
- Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT, 84322, USA
| | - Matthew Del Grosso
- Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT, 84322, USA
| | - Xavier Haemmerle
- Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT, 84322, USA
| | - William T Wcislo
- Smithsonian Tropical Research Institute, 0843-03092, Panama City, Republic of Panama
| | - Karen M Kapheim
- Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT, 84322, USA.
- Smithsonian Tropical Research Institute, 0843-03092, Panama City, Republic of Panama.
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8
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Muth F. Intra-specific differences in cognition: bumblebee queens learn better than workers. Biol Lett 2021; 17:20210280. [PMID: 34376073 DOI: 10.1098/rsbl.2021.0280] [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] [Indexed: 11/12/2022] Open
Abstract
Species' cognitive traits are shaped by their ecology, and even within a species, cognition can reflect the behavioural requirements of individuals with different roles. Social insects have a number of discrete roles (castes) within a colony and thus offer a useful system to determine how ecological requirements shape cognition. Bumblebee queens are a critical point in the lifecycle of their colony, since its future success is reliant on a single individual's ability to learn about floral stimuli while finding a suitable nest site; thus, one might expect particularly adept learning capabilities at this stage. I compared wild Bombus vosnesenskii queens and workers on their ability to learn a colour association and found that queens performed better than workers. In addition, queens of another species, B. insularis, a cuckoo species with a different lifecycle but similar requirements at this stage, performed equally well as the non-parasitic queens. To control for differences in foraging experience, I then repeated this comparison with laboratory-based B. impatiens and found that unmated queens performed better than workers. These results add to the body of work on how ecology shapes cognition and opens the door to further research in comparative cognition using wild bees.
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Affiliation(s)
- Felicity Muth
- Departmnet of Integrative Biology, University of Texas at Austin, TX, USA
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9
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Jernigan CM, Zaba NC, Sheehan MJ. Age and social experience induced plasticity across brain regions of the paper wasp Polistes fuscatus. Biol Lett 2021; 17:20210073. [PMID: 33849349 PMCID: PMC8086938 DOI: 10.1098/rsbl.2021.0073] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 03/15/2021] [Indexed: 12/18/2022] Open
Abstract
Developmental studies of brain volumes can reveal which portions of neural circuits are sensitive to environmental inputs. In social insects, differences in relative investment across brain regions emerge as behavioural repertoires change during ontogeny or as a result of experience. Here, we test the effects of maturation and social experience on morphological brain development in Polistes fuscatus paper wasps, focusing on brain regions involved in visual and olfactory processing. We find that mature wasps regardless of social experience have relatively larger brains than newly emerged wasps and this difference is driven by changes to mushroom body calyx and visual regions but not olfactory processing neuropils. Notably, social wasps invest more in the anterior optic tubercle (AOT), a visual glomerulus involved in colour and object processing in other taxa, relative to other visual integration centres the mushroom body calyces compared with aged socially naive wasps. Differences in developmental plasticity between visual and olfactory neuropil volumes are discussed in light of behavioural maturation in paper wasps, especially as it relates to social recognition. Previous research has shown that P. fuscatus need social experience to develop specialized visual processing of faces, which is used to individually recognize conspecifics. The present study suggests that the AOT is a candidate brain region that could mediate facial processing in this species.
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Affiliation(s)
| | - Natalie C. Zaba
- Department of Neurobiology and Behaviour, Cornell University, Ithaca, NY 14853, USA
| | - Michael J. Sheehan
- Department of Neurobiology and Behaviour, Cornell University, Ithaca, NY 14853, USA
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10
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Hagadorn MA, Johnson MM, Smith AR, Seid MA, Kapheim KM. Experience, but not age, is associated with volumetric mushroom body expansion in solitary alkali bees. J Exp Biol 2021; 224:jeb.238899. [DOI: 10.1242/jeb.238899] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 02/09/2021] [Indexed: 01/03/2023]
Abstract
ABSTRACT
In social insects, changes in behavior are often accompanied by structural changes in the brain. This neuroplasticity may come with experience (experience-dependent) or age (experience-expectant). Yet, the evolutionary relationship between neuroplasticity and sociality is unclear, because we know little about neuroplasticity in the solitary relatives of social species. We used confocal microscopy to measure brain changes in response to age and experience in a solitary halictid bee (Nomia melanderi). First, we compared the volume of individual brain regions among newly emerged females, laboratory females deprived of reproductive and foraging experience, and free-flying, nesting females. Experience, but not age, led to significant expansion of the mushroom bodies – higher-order processing centers associated with learning and memory. Next, we investigated how social experience influences neuroplasticity by comparing the brains of females kept in the laboratory either alone or paired with another female. Paired females had significantly larger olfactory regions of the mushroom bodies. Together, these experimental results indicate that experience-dependent neuroplasticity is common to both solitary and social taxa, whereas experience-expectant neuroplasticity may be an adaptation to life in a social colony. Further, neuroplasticity in response to social chemical signals may have facilitated the evolution of sociality.
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Affiliation(s)
- Mallory A. Hagadorn
- Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA
| | - Makenna M. Johnson
- Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA
| | - Adam R. Smith
- Department of Biological Sciences, George Washington University, 800 22nd St NW, Washington, DC 20052, USA
| | - Marc A. Seid
- Biology Department, University of Scranton, 800 Linden St, Scranton, PA 18510, USA
| | - Karen M. Kapheim
- Department of Biology, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA
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11
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Strausfeld N, Sayre ME. Shore crabs reveal novel evolutionary attributes of the mushroom body. eLife 2021; 10:65167. [PMID: 33559601 PMCID: PMC7872517 DOI: 10.7554/elife.65167] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 01/14/2021] [Indexed: 11/13/2022] Open
Abstract
Neural organization of mushroom bodies is largely consistent across insects, whereas the ancestral ground pattern diverges broadly across crustacean lineages resulting in successive loss of columns and the acquisition of domed centers retaining ancestral Hebbian-like networks and aminergic connections. We demonstrate here a major departure from this evolutionary trend in Brachyura, the most recent malacostracan lineage. In the shore crab Hemigrapsus nudus, instead of occupying the rostral surface of the lateral protocerebrum, mushroom body calyces are buried deep within it with their columns extending outwards to an expansive system of gyri on the brain’s surface. The organization amongst mushroom body neurons reaches extreme elaboration throughout its constituent neuropils. The calyces, columns, and especially the gyri show DC0 immunoreactivity, an indicator of extensive circuits involved in learning and memory.
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Affiliation(s)
| | - Marcel E Sayre
- Lund Vision Group, Department of Biology, Lund University, Lund, Sweden.,Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia
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12
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Adden A, Wibrand S, Pfeiffer K, Warrant E, Heinze S. The brain of a nocturnal migratory insect, the Australian Bogong moth. J Comp Neurol 2020; 528:1942-1963. [PMID: 31994724 DOI: 10.1002/cne.24866] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 01/16/2020] [Accepted: 01/18/2020] [Indexed: 12/12/2022]
Abstract
Every year, millions of Australian Bogong moths (Agrotis infusa) complete an astonishing journey: In Spring, they migrate over 1,000 km from their breeding grounds to the alpine regions of the Snowy Mountains, where they endure the hot summer in the cool climate of alpine caves. In autumn, the moths return to their breeding grounds, where they mate, lay eggs and die. These moths can use visual cues in combination with the geomagnetic field to guide their flight, but how these cues are processed and integrated into the brain to drive migratory behavior is unknown. To generate an access point for functional studies, we provide a detailed description of the Bogong moth's brain. Based on immunohistochemical stainings against synapsin and serotonin (5HT), we describe the overall layout as well as the fine structure of all major neuropils, including the regions that have previously been implicated in compass-based navigation. The resulting average brain atlas consists of 3D reconstructions of 25 separate neuropils, comprising the most detailed account of a moth brain to date. Our results show that the Bogong moth brain follows the typical lepidopteran ground pattern, with no major specializations that can be attributed to their spectacular migratory lifestyle. These findings suggest that migratory behavior does not require widespread modifications of brain structure, but might be achievable via small adjustments of neural circuitry in key brain areas. Locating these subtle changes will be a challenging task for the future, for which our study provides an essential anatomical framework.
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Affiliation(s)
- Andrea Adden
- Lund Vision Group, Department of Biology, Lund University, Lund, Sweden
| | - Sara Wibrand
- Lund Vision Group, Department of Biology, Lund University, Lund, Sweden
| | | | - Eric Warrant
- Lund Vision Group, Department of Biology, Lund University, Lund, Sweden
| | - Stanley Heinze
- Lund Vision Group, Department of Biology, Lund University, Lund, Sweden.,NanoLund, Department of Biology, Lund University, Lund, Sweden
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13
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Pahlke S, Jaumann S, Seid MA, Smith AR. Brain differences between social castes precede group formation in a primitively eusocial bee. Naturwissenschaften 2019; 106:49. [DOI: 10.1007/s00114-019-1644-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/20/2019] [Accepted: 08/05/2019] [Indexed: 02/03/2023]
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14
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Eriksson M, Nylin S, Carlsson MA. Insect brain plasticity: effects of olfactory input on neuropil size. ROYAL SOCIETY OPEN SCIENCE 2019; 6:190875. [PMID: 31598254 PMCID: PMC6731737 DOI: 10.1098/rsos.190875] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 07/23/2019] [Indexed: 06/10/2023]
Abstract
Insect brains are known to express a high degree of experience-dependent structural plasticity. One brain structure in particular, the mushroom body (MB), has been attended to in numerous studies as it is implicated in complex cognitive processes such as olfactory learning and memory. It is, however, poorly understood to what extent sensory input per se affects the plasticity of the mushroom bodies. By performing unilateral blocking of olfactory input on immobilized butterflies, we were able to measure the effect of passive sensory input on the volumes of antennal lobes (ALs) and MB calyces. We showed that the primary and secondary olfactory neuropils respond in different ways to olfactory input. ALs show absolute experience-dependency and increase in volume only if receiving direct olfactory input from ipsilateral antennae, while MB calyx volumes were unaffected by the treatment and instead show absolute age-dependency in this regard. We therefore propose that cognitive processes related to behavioural expressions are needed in order for the calyx to show experience-dependent volumetric expansions. Our results indicate that such experience-dependent volumetric expansions of calyces observed in other studies may have been caused by cognitive processes rather than by sensory input, bringing some causative clarity to a complex neural phenomenon.
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15
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Jaumann S, Seid MA, Simons M, Smith AR. Queen Dominance May Reduce Worker Mushroom Body Size in a Social Bee. Dev Neurobiol 2019; 79:596-607. [PMID: 31207130 DOI: 10.1002/dneu.22705] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 01/20/2023]
Abstract
The mushroom body (MB) is an area of the insect brain involved in learning, memory, and sensory integration. Here, we used the sweat bee Megalopta genalis (Halictidae) to test for differences between queens and workers in the volume of the MB calyces. We used confocal microscopy to measure the volume of the whole brain, MB calyces, optic lobes, and antennal lobes of queens and workers. Queens had larger brains, larger MB calyces, and a larger MB calyces:whole brain ratio than workers, suggesting an effect of social dominance in brain development. This could result from social interactions leading to smaller worker MBs, or larger queen MBs. It could also result from other factors, such as differences in age or sensory experience. To test these explanations, we next compared queens and workers to other groups. We compared newly emerged bees, bees reared in isolation for 10 days, bees initiating new observation nests, and bees initiating new natural nests collected from the field to queens and workers. Queens did not differ from these other groups. We suggest that the effects of queen dominance over workers, rather than differences in age, experience, or reproductive status, are responsible for the queen-worker differences we observed. Worker MB development may be affected by queen aggression directly and/or manipulation of larval nutrition, which is provisioned by the queen. We found no consistent differences in the size of antennal lobes or optic lobes associated with differences in age, experience, reproductive status, or social caste.
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Affiliation(s)
- Sarah Jaumann
- Department of Biological Sciences, George Washington University, Washington, District of Columbia
| | - Marc A Seid
- Biology Department, University of Scranton, Scranton, Pennsylvania
| | - Meagan Simons
- Department of Biological Sciences, George Washington University, Washington, District of Columbia
| | - Adam R Smith
- Department of Biological Sciences, George Washington University, Washington, District of Columbia
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16
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Brain evolution in social insects: advocating for the comparative approach. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2019; 205:13-32. [DOI: 10.1007/s00359-019-01315-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 01/09/2019] [Accepted: 01/11/2019] [Indexed: 10/27/2022]
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17
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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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18
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O'Donnell S, Bulova S. Development and evolution of brain allometry in wasps (Vespidae): size, ecology and sociality. CURRENT OPINION IN INSECT SCIENCE 2017; 22:54-61. [PMID: 28805639 DOI: 10.1016/j.cois.2017.05.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 04/25/2017] [Accepted: 05/11/2017] [Indexed: 06/07/2023]
Abstract
We review research on brain development and brain evolution in the wasp family Vespidae. Basic vespid neuroanatomy and some aspects of functional neural circuitry are well-characterized, and genomic tools for exploring brain plasticity are being developed. Although relatively modest in terms of species richness, the Vespidae include species spanning much of the known range of animal social complexity, from solitary nesters to highly eusocial species with some of the largest known colonies and multiple reproductives. Eusocial species differ in behavior and ecology including variation in queen/worker caste differentiation and in diurnal/nocturnal activity. Species differences in overall brain size are strongly associated with brain allometry; relative sizes of visual processing tissues increase at faster rates than antennal processing tissues. The lower relative size of the central-processing mushroom bodies (MB) in eusocial species compared to solitary relatives suggests sociality may relax demands on individual cognitive abilities. However, queens have greater relative MB volumes than their workers, and MB development is positively associated with social dominance status in some species. Fruitful areas for future investigations of adaptive brain investment in the clade include sampling of key overlooked taxa with diverse social structures, and the analysis of neural correlations with ecological divergence in foraging resources and diel activity patterns.
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Affiliation(s)
- Sean O'Donnell
- Department of Biodiversity Earth & Environmental Science, Drexel University, Philadelphia, PA, USA.
| | - Susan Bulova
- Department of Biodiversity Earth & Environmental Science, Drexel University, Philadelphia, PA, USA
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19
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Caste differences in the mushroom bodies of swarm-founding paper wasps: implications for brain plasticity and brain evolution (Vespidae, Epiponini). Behav Ecol Sociobiol 2017. [DOI: 10.1007/s00265-017-2344-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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20
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Kamhi JF, Sandridge-Gresko A, Walker C, Robson SKA, Traniello JFA. Worker brain development and colony organization in ants: Does division of labor influence neuroplasticity? Dev Neurobiol 2017; 77:1072-1085. [PMID: 28276652 DOI: 10.1002/dneu.22496] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 02/24/2017] [Accepted: 02/25/2017] [Indexed: 01/09/2023]
Abstract
Brain compartment size allometries may adaptively reflect cognitive needs associated with behavioral development and ecology. Ants provide an informative system to study the relationship of neural architecture and development because worker tasks and sensory inputs may change with age. Additionally, tasks may be divided among morphologically and behaviorally differentiated worker groups (subcastes), reducing repertoire size through specialization and aligning brain structure with task-specific cognitive requirements. We hypothesized that division of labor may decrease developmental neuroplasticity in workers due to the apparently limited behavioral flexibility associated with task specialization. To test this hypothesis, we compared macroscopic and cellular neuroanatomy in two ant sister clades with striking contrasts in worker morphological differentiation and colony-level social organization: Oecophylla smaragdina, a socially complex species with large colonies and behaviorally distinct dimorphic workers, and Formica subsericea, a socially basic species with small colonies containing monomorphic workers. We quantified volumes of functionally distinct brain compartments in newly eclosed and mature workers and measured the effects of visual experience on synaptic complex (microglomeruli) organization in the mushroom bodies-regions of higher-order sensory integration-to determine the extent of experience-dependent neuroplasticity. We demonstrate that, contrary to our hypothesis, O. smaragdina workers have significant age-related volume increases and synaptic reorganization in the mushroom bodies, whereas F. subsericea workers have reduced age-related neuroplasticity. We also found no visual experience-dependent synaptic reorganization in either species. Our findings thus suggest that changes in the mushroom body with age are associated with division of labor, and therefore social complexity, in ants. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1072-1085, 2017.
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Affiliation(s)
- J Frances Kamhi
- Department of Biology, Boston University, Boston, Massachusetts, 02215.,Graduate Program for Neuroscience, Boston University, Boston, Massachusetts, 02215
| | - Aynsley Sandridge-Gresko
- Department of Natural Sciences and Mathematics, Lesley University, Cambridge, Massachusetts, 02138
| | - Christina Walker
- Department of Biology, Boston University, Boston, Massachusetts, 02215
| | - Simon K A Robson
- Zoology and Ecology, James Cook University, Townsville, Queensland, 4811, Australia
| | - James F A Traniello
- Department of Biology, Boston University, Boston, Massachusetts, 02215.,Graduate Program for Neuroscience, Boston University, Boston, Massachusetts, 02215
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21
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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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22
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Couto A, Lapeyre B, Thiéry D, Sandoz JC. Olfactory pathway of the hornet Vespa velutina
: New insights into the evolution of the hymenopteran antennal lobe. J Comp Neurol 2016; 524:2335-59. [DOI: 10.1002/cne.23975] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 01/20/2016] [Accepted: 01/29/2016] [Indexed: 01/16/2023]
Affiliation(s)
- Antoine Couto
- Laboratory Evolution Genome Behavior and Ecology, CNRS, Université Paris-Sud, IRD, Université Paris Saclay; F-91198 Gif-sur-Yvette France
| | - Benoit Lapeyre
- Laboratory Evolution Genome Behavior and Ecology, CNRS, Université Paris-Sud, IRD, Université Paris Saclay; F-91198 Gif-sur-Yvette France
| | - Denis Thiéry
- UMR 1065 Santé et Agroécologie du Vignoble, INRA; F-33883 Villenave d'Ornon France
- Université de Bordeaux, ISVV, UMR 1065 Santé et Agroécologie du Vignoble, Bordeaux Sciences Agro; F-33883 Villenave d'Ornon France
| | - Jean-Christophe Sandoz
- Laboratory Evolution Genome Behavior and Ecology, CNRS, Université Paris-Sud, IRD, Université Paris Saclay; F-91198 Gif-sur-Yvette France
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The genetic basis of natural variation in mushroom body size in Drosophila melanogaster. Nat Commun 2015; 6:10115. [PMID: 26656654 PMCID: PMC4682101 DOI: 10.1038/ncomms10115] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 11/04/2015] [Indexed: 11/30/2022] Open
Abstract
Genetic variation in brain size may provide the basis for the evolution of the brain and complex behaviours. The genetic substrate and the selective pressures acting on brain size are poorly understood. Here we use the Drosophila Genetic Reference Panel to map polymorphic variants affecting natural variation in mushroom body morphology. We identify 139 genes and 39 transcription factors and confirm effects on development and adult plasticity. We show correlations between morphology and aggression, sleep and lifespan. We propose that natural variation in adult brain size is controlled by interaction of the environment with gene networks controlling development and plasticity. The mushroom bodies (MBs) in an insect brain integrate and process sensory information. Using fully sequenced/inbred lines of the Drosophila Genetic Reference Panel, this study performs genome wide association analyses and identifies candidate genes affecting MB size, and uses RNAi to functionally validate the identified loci.
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Rehan SM, Bulova SJ, O''Donnell S. Cumulative Effects of Foraging Behavior and Social Dominance on Brain Development in a Facultatively Social Bee (Ceratina australensis). BRAIN, BEHAVIOR AND EVOLUTION 2015; 85:117-24. [DOI: 10.1159/000381414] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 12/30/2014] [Indexed: 11/19/2022]
Abstract
In social insects, both task performance (foraging) and dominance are associated with increased brain investment, particularly in the mushroom bodies. Whether and how these factors interact is unknown. Here we present data on a system where task performance and social behavior can be analyzed simultaneously: the small carpenter bee Ceratina australensis. We show that foraging and dominance have separate and combined cumulative effects on mushroom body calyx investment. Female C. australensis nest solitarily and socially in the same populations at the same time. Social colonies comprise two sisters: the social primary, which monopolizes foraging and reproduction, and the social secondary, which is neither a forager nor reproductive but rather remains at the nest as a guard. We compare the brains of solitary females that forage and reproduce but do not engage in social interactions with those of social individuals while controlling for age, reproductive status, and foraging experience. Mushroom body calyx volume was positively correlated with wing wear, a proxy for foraging experience. We also found that, although total brain volume did not vary among reproductive strategies (solitary vs. social nesters), socially dominant primaries had larger mushroom body calyx volumes (corrected for both brain and body size variation) than solitary females; socially subordinate secondaries (that are neither dominant nor foragers) had the least-developed mushroom body calyces. These data demonstrate that sociality itself does not explain mushroom body volume; however, achieving and maintaining dominance status in a group was associated with mushroom body calyx enlargement. Dominance and foraging effects were cumulative; dominant social primary foragers had larger mushroom body volumes than solitary foragers, and solitary foragers had larger mushroom body volumes than nonforaging social secondary guards. This is the first evidence for cumulative effects on brain development by dominance and task performance.
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25
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The trap of sex in social insects: From the female to the male perspective. Neurosci Biobehav Rev 2014; 46 Pt 4:519-33. [DOI: 10.1016/j.neubiorev.2014.09.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 09/14/2014] [Accepted: 09/22/2014] [Indexed: 01/27/2023]
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26
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Chachua T, Goletiani C, Maglakelidze G, Sidyelyeva G, Daniel M, Morris E, Miller J, Shang E, Wolgemuth DJ, Greenberg DA, Velíšková J, Velíšek L. Sex-specific behavioral traits in the Brd2 mouse model of juvenile myoclonic epilepsy. GENES BRAIN AND BEHAVIOR 2014; 13:702-12. [PMID: 25130458 DOI: 10.1111/gbb.12160] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 07/31/2014] [Accepted: 08/04/2014] [Indexed: 12/23/2022]
Abstract
Idiopathic generalized epilepsy represents about 30-35% of all epilepsies in humans. The bromodomain BRD2 gene has been repeatedly associated with the subsyndrome of juvenile myoclonic epilepsy (JME). Our previous work determined that mice haploinsufficient in Brd2 (Brd2+/-) have increased susceptibility to provoked seizures, develop spontaneous seizures and have significantly decreased gamma-aminobutyric acid (GABA) markers in the direct basal ganglia pathway as well as in the neocortex and superior colliculus. Here, we tested male and female Brd2+/- and wild-type littermate mice in a battery of behavioral tests (open field, tube dominance test, elevated plus maze, Morris water maze and Barnes maze) to identify whether Brd2 haploinsufficiency is associated with the human behavioral patterns, the so-called JME personality. Brd2+/- females but not males consistently displayed decreased anxiety. Furthermore, we found a highly significant dominance trait (aggression) in the Brd2+/- mice compared with the wild type, more pronounced in females. Brd2+/- mice of either sex did not differ from wild-type mice in spatial learning and memory tests. Compared with wild-type littermates, we found decreased numbers of GABA neurons in the basolateral amygdala, which is consistent with the increase in aggressive behavior. Our results indicate that Brd2+/- haploinsufficient mice show no cognitive impairment but have behavioral traits similar to those found in patients with JME (recklessness, aggression). This suggests that either the BRD2 gene is directly responsible for influencing many traits of JME or it controls upstream regulators of individual phenotypes.
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Affiliation(s)
- T Chachua
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, NY, USA
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27
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Muscedere ML, Gronenberg W, Moreau CS, Traniello JFA. Investment in higher order central processing regions is not constrained by brain size in social insects. Proc Biol Sci 2014; 281:20140217. [PMID: 24741016 DOI: 10.1098/rspb.2014.0217] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The extent to which size constrains the evolution of brain organization and the genesis of complex behaviour is a central, unanswered question in evolutionary neuroscience. Advanced cognition has long been linked to the expansion of specific brain compartments, such as the neocortex in vertebrates and the mushroom bodies in insects. Scaling constraints that limit the size of these brain regions in small animals may therefore be particularly significant to behavioural evolution. Recent findings from studies of paper wasps suggest miniaturization constrains the size of central sensory processing brain centres (mushroom body calyces) in favour of peripheral, sensory input centres (antennal and optic lobes). We tested the generality of this hypothesis in diverse eusocial hymenopteran species (ants, bees and wasps) exhibiting striking variation in body size and thus brain size. Combining multiple neuroanatomical datasets from these three taxa, we found no universal size constraint on brain organization within or among species. In fact, small-bodied ants with miniscule brains had mushroom body calyces proportionally as large as or larger than those of wasps and bees with brains orders of magnitude larger. Our comparative analyses suggest that brain organization in ants is shaped more by natural selection imposed by visual demands than intrinsic design limitations.
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Affiliation(s)
- Mario L Muscedere
- Undergraduate Program in Neuroscience, Boston University, , 2 Cummington Mall, Boston, MA 02215, USA, Department of Neuroscience, University of Arizona, , 611 Gould-Simpson Science Building, Tucson, AZ 85721, USA, Department of Science and Education, Field Museum of Natural History, , 1400 South Lake Shore Drive, Chicago, IL 60605, USA, Department of Biology, Boston University, , 5 Cummington Mall, Boston, MA 02215, USA
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28
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Jones BM, Leonard AS, Papaj DR, Gronenberg W. Plasticity of the worker bumblebee brain in relation to age and rearing environment. BRAIN, BEHAVIOR AND EVOLUTION 2013; 82:250-61. [PMID: 24281415 DOI: 10.1159/000355845] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 09/18/2013] [Indexed: 02/03/2023]
Abstract
The environment experienced during development can dramatically affect the brain, with possible implications for sensory processing, learning, and memory. Although the effects of single sensory modalities on brain development have been repeatedly explored, the additive or interactive effects of multiple modalities have been less thoroughly investigated. We asked how experience with multisensory stimuli affected brain development in the bumblebee Bombus impatiens. First, to establish the timeline of brain development during early adulthood, we estimated regional brain volumes across a range of ages. We discovered significant age-related volume changes in nearly every region of the brain. Next, to determine whether these changes were dependent upon certain environmental stimuli, we manipulated the visual and olfactory stimuli available to newly emerged bumblebee workers in a factorial manner. Newly emerged bumblebees were maintained in the presence or absence of supplemental visual and/or olfactory stimuli for 7 days, after which the volumes of several brain regions were estimated. We found that the volumes of the mushroom body lobes and calyces were larger in the absence of visual stimuli. Additionally, visual deprivation was associated with the expression of larger antennal lobes, the primary olfactory processing regions of the brain. In contrast, exposure to plant-derived olfactory stimuli did not have a significant effect on brain region volumes. This study is the first to explore the separate and interactive effects of visual and olfactory stimuli on bee brain development. Assessing the timing and sensitivity of brain development is a first step toward understanding how different rearing environments differentially affect regional brain volumes in this species. Our findings suggest that environmental factors experienced during the first week of adulthood can modify bumblebee brain development in many subtle ways.
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Affiliation(s)
- Beryl M Jones
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Ariz., USA
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29
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Biogenic amines are associated with worker task but not patriline in the leaf-cutting ant Acromyrmex echinatior. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2013; 199:1117-27. [PMID: 24072064 DOI: 10.1007/s00359-013-0854-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 08/31/2013] [Accepted: 09/02/2013] [Indexed: 10/26/2022]
Abstract
Division of labor among eusocial insect workers is a hallmark of advanced social organization, but its underlying neural mechanisms are not well understood. We investigated whether differences in whole-brain levels of the biogenic amines dopamine (DA), serotonin (5HT), and octopamine (OA) are associated with task specialization and genotype in similarly sized and aged workers of the leaf-cutting ant Acromyrmex echinatior, a polyandrous species in which genotype correlates with worker task specialization. We compared amine levels of foragers and waste management workers to test for an association with worker task, and young in-nest workers across patrilines to test for a genetic influence on brain amine levels. Foragers had higher levels of DA and OA and a higher OA:5HT ratio than waste management workers. Patrilines did not significantly differ in amine levels or their ratios, although patriline affected worker body size, which correlated with amine levels despite the small size range sampled. Levels of all three amines were correlated within individuals in both studies. Among patrilines, mean levels of DA and OA, and OA and 5HT were also correlated. Our results suggest that differences in biogenic amines could regulate worker task specialization, but may be not be significantly affected by genotype.
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30
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Wilson DE, Velarde RA, Fahrbach SE, Mommaerts V, Smagghe G. Use of primary cultures of Kenyon cells from bumblebee brains to assess pesticide side effects. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2013; 84:43-56. [PMID: 23922293 DOI: 10.1002/arch.21112] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Bumblebees are important pollinators in natural and agricultural ecosystems. The latter results in the frequent exposure of bumblebees to pesticides. We report here on a new bioassay that uses primary cultures of neurons derived from adult bumblebee workers to evaluate possible side-effects of the neonicotinoid pesticide imidacloprid. Mushroom bodies (MBs) from the brains of bumblebee workers were dissected and dissociated to produce cultures of Kenyon cells (KCs). Cultured KCs typically extend branched, dendrite-like processes called neurites, with substantial growth evident 24-48 h after culture initiation. Exposure of cultured KCs obtained from newly eclosed adult workers to 2.5 parts per billion (ppb) imidacloprid, an environmentally relevant concentration of pesticide, did not have a detectable effect on neurite outgrowth. By contrast, in cultures prepared from newly eclosed adult bumblebees, inhibitory effects of imidacloprid were evident when the medium contained 25 ppb imidacloprid, and no growth was observed at 2,500 ppb. The KCs of older workers (13-day-old nurses and foragers) appeared to be more sensitive to imidacloprid than newly eclosed adults, as strong effects on KCs obtained from older nurses and foragers were also evident at 2.5 ppb imidacloprid. In conclusion, primary cultures using KCs of bumblebee worker brains offer a tool to assess sublethal effects of neurotoxic pesticides in vitro. Such studies also have the potential to contribute to the understanding of mechanisms of plasticity in the adult bumblebee brain.
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Affiliation(s)
- Daniel E Wilson
- Department of Biology, Wake Forest University, Winston-Salem, NC, USA
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31
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Lihoreau M, Latty T, Chittka L. An exploration of the social brain hypothesis in insects. Front Physiol 2012; 3:442. [PMID: 23205013 PMCID: PMC3506958 DOI: 10.3389/fphys.2012.00442] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 11/05/2012] [Indexed: 11/25/2022] Open
Abstract
The "social brain hypothesis" posits that the cognitive demands of sociality have driven the evolution of substantially enlarged brains in primates and some other mammals. Whether such reasoning can apply to all social animals is an open question. Here we examine the evolutionary relationships between sociality, cognition, and brain size in insects, a taxonomic group characterized by an extreme sophistication of social behaviors and relatively simple nervous systems. We discuss the application of the social brain hypothesis in this group, based on comparative studies of brain volumes across species exhibiting various levels of social complexity. We illustrate how some of the major behavioral innovations of social insects may in fact require little information-processing and minor adjustments of neural circuitry, thus potentially selecting for more specialized rather than bigger brains. We argue that future work aiming to understand how animal behavior, cognition, and brains are shaped by the environment (including social interactions) should focus on brain functions and identify neural circuitry correlates of social tasks, not only brain sizes.
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Affiliation(s)
- Mathieu Lihoreau
- School of Biological Sciences, The University of SydneySydney, NSW, Australia
- The Charles Perkins Centre, The University of SydneySydney, NSW, Australia
| | - Tanya Latty
- School of Biological Sciences, The University of SydneySydney, NSW, Australia
| | - Lars Chittka
- Psychology Division, School of Biological and Chemical Sciences, Queen Mary University of LondonLondon, UK
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32
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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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Abstract
Aggressive behavior is widely present throughout the animal kingdom and is crucial to ensure survival and reproduction. Aggressive actions serve to acquire territory, food, or mates and in defense against predators or rivals; while in some species these behaviors are involved in establishing a social hierarchy. Aggression is a complex behavior, influenced by a broad range of genetic and environmental factors. Recent studies in Drosophila provide insight into the genetic basis and control of aggression. The state of the art on aggression in Drosophila and the many opportunities provided by this model organism to unravel the genetic and neurobiological basis of aggression are reviewed.
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Affiliation(s)
- Liesbeth Zwarts
- Laboratory of Behavioral and Developmental Genetics, K.U. Leuven Center for Human Genetics, VIB Center for the Biology of Disease, Leuven, Belgium
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34
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Comparative analysis of constraints and caste differences in brain investment among social paper wasps. Proc Natl Acad Sci U S A 2011; 108:7107-12. [PMID: 21482775 DOI: 10.1073/pnas.1017566108] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We compared species mean data on the size of functionally distinct brain regions to test the relative rates at which investment in higher-order cognitive processing (mushroom body calyces) versus peripheral sensory processing (optic and antennal lobes) increased with increasing brain size. Subjects were eusocial paper wasps from queen and worker castes of 10 species from different genera. Relative investment in central processing tissue increased with brain size at a higher rate than peripheral structure investment, demonstrating that tissue devoted to higher-order cognitive processing is more constrained by brain size. This pattern held for raw data and for phylogenetically independent contrasts. These findings suggest that there is a minimum necessary investment in peripheral sensory processing brain tissue, with little to gain from additional investment. In contrast, increased brain size provides opportunities to invest in additional higher-order cognitive processing tissue. Reproductive castes differed within species in brain tissue investment, with higher central-to-peripheral brain tissue ratios in queens than in workers. Coupled with previous findings that paper wasp queen, but not worker, brain architecture corresponds to ecological and social variation, queen brain evolution appears to be most strongly shaped by cognitive demands, such as social interactions. These evolutionary patterns of neural investment echo findings in other animal lineages and have important implications, given that a greater investment in higher-order processing has been shown to increase the prevalence of complex and flexible behaviors across the animal kingdom.
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Badisco L, Huybrechts J, Simonet G, Verlinden H, Marchal E, Huybrechts R, Schoofs L, De Loof A, Vanden Broeck J. Transcriptome analysis of the desert locust central nervous system: production and annotation of a Schistocerca gregaria EST database. PLoS One 2011; 6:e17274. [PMID: 21445293 PMCID: PMC3061863 DOI: 10.1371/journal.pone.0017274] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 01/28/2011] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND The desert locust (Schistocerca gregaria) displays a fascinating type of phenotypic plasticity, designated as 'phase polyphenism'. Depending on environmental conditions, one genome can be translated into two highly divergent phenotypes, termed the solitarious and gregarious (swarming) phase. Although many of the underlying molecular events remain elusive, the central nervous system (CNS) is expected to play a crucial role in the phase transition process. Locusts have also proven to be interesting model organisms in a physiological and neurobiological research context. However, molecular studies in locusts are hampered by the fact that genome/transcriptome sequence information available for this branch of insects is still limited. METHODOLOGY We have generated 34,672 raw expressed sequence tags (EST) from the CNS of desert locusts in both phases. These ESTs were assembled in 12,709 unique transcript sequences and nearly 4,000 sequences were functionally annotated. Moreover, the obtained S. gregaria EST information is highly complementary to the existing orthopteran transcriptomic data. Since many novel transcripts encode neuronal signaling and signal transduction components, this paper includes an overview of these sequences. Furthermore, several transcripts being differentially represented in solitarious and gregarious locusts were retrieved from this EST database. The findings highlight the involvement of the CNS in the phase transition process and indicate that this novel annotated database may also add to the emerging knowledge of concomitant neuronal signaling and neuroplasticity events. CONCLUSIONS In summary, we met the need for novel sequence data from desert locust CNS. To our knowledge, we hereby also present the first insect EST database that is derived from the complete CNS. The obtained S. gregaria EST data constitute an important new source of information that will be instrumental in further unraveling the molecular principles of phase polyphenism, in further establishing locusts as valuable research model organisms and in molecular evolutionary and comparative entomology.
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Affiliation(s)
- Liesbeth Badisco
- Department of Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Jurgen Huybrechts
- Department of Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Gert Simonet
- Department of Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Heleen Verlinden
- Department of Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Elisabeth Marchal
- Department of Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Roger Huybrechts
- Department of Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Liliane Schoofs
- Department of Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Arnold De Loof
- Department of Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Jozef Vanden Broeck
- Department of Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Leuven, Belgium
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Farris SM, Schulmeister S. Parasitoidism, not sociality, is associated with the evolution of elaborate mushroom bodies in the brains of hymenopteran insects. Proc Biol Sci 2010; 278:940-51. [PMID: 21068044 DOI: 10.1098/rspb.2010.2161] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The social brain hypothesis posits that the cognitive demands of social behaviour have driven evolutionary expansions in brain size in some vertebrate lineages. In insects, higher brain centres called mushroom bodies are enlarged and morphologically elaborate (having doubled, invaginated and subcompartmentalized calyces that receive visual input) in social species such as the ants, bees and wasps of the aculeate Hymenoptera, suggesting that the social brain hypothesis may also apply to invertebrate animals. In a quantitative and qualitative survey of mushroom body morphology across the Hymenoptera, we demonstrate that large, elaborate mushroom bodies arose concurrent with the acquisition of a parasitoid mode of life at the base of the Euhymenopteran (Orussioidea + Apocrita) lineage, approximately 90 Myr before the evolution of sociality in the Aculeata. Thus, sociality could not have driven mushroom body elaboration in the Hymenoptera. Rather, we propose that the cognitive demands of host-finding behaviour in parasitoids, particularly the capacity for associative and spatial learning, drove the acquisition of this evolutionarily novel mushroom body architecture. These neurobehavioural modifications may have served as pre-adaptations for central place foraging, a spatial learning-intensive behaviour that is widespread across the Aculeata and may have contributed to the multiple acquisitions of sociality in this taxon.
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Affiliation(s)
- Sarah M Farris
- Department of Biology, West Virginia University, Morgantown, WV 26505, USA.
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Ott SR, Rogers SM. Gregarious desert locusts have substantially larger brains with altered proportions compared with the solitarious phase. Proc Biol Sci 2010; 277:3087-96. [PMID: 20507896 PMCID: PMC2982065 DOI: 10.1098/rspb.2010.0694] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Accepted: 05/06/2010] [Indexed: 11/12/2022] Open
Abstract
The behavioural demands of group living and foraging have been implicated in both evolutionary and plastic changes in brain size. Desert locusts show extreme phenotypic plasticity, allowing brain morphology to be related to very different lifestyles in one species. At low population densities, locusts occur in a solitarious phase that avoids other locusts and is cryptic in appearance and behaviour. Crowding triggers the transformation into the highly active gregarious phase, which aggregates into dense migratory swarms. We found that the brains of gregarious locusts have very different proportions and are also 30 per cent larger overall than in solitarious locusts. To address whether brain proportions change with size through nonlinear scaling (allometry), we conducted the first comprehensive major axis regression analysis of scaling relations in an insect brain. This revealed that phase differences in brain proportions arise from a combination of allometric effects and deviations from the allometric expectation (grade shifts). In consequence, gregarious locusts had a larger midbrainoptic lobe ratio, a larger central complex and a 50 per cent larger ratio of the olfactory primary calyx to the first olfactory neuropile. Solitarious locusts invest more in low-level sensory processing, having disproportionally larger primary visual and olfactory neuropiles, possibly to gain sensitivity. The larger brains of gregarious locusts prioritize higher integration, which may support the behavioural demands of generalist foraging and living in dense and highly mobile swarms dominated by intense intraspecific competition.
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Affiliation(s)
- Swidbert R Ott
- Department of Zoology, University of Cambridge, Cambridge, UK.
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Smith AR, Seid MA, Jiménez LC, Wcislo WT. Socially induced brain development in a facultatively eusocial sweat bee Megalopta genalis (Halictidae). Proc Biol Sci 2010; 277:2157-63. [PMID: 20335213 DOI: 10.1098/rspb.2010.0269] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Changes in the relative size of brain regions are often dependent on experience and environmental stimulation, which includes an animal's social environment. Some studies suggest that social interactions are cognitively demanding, and have examined predictions that the evolution of sociality led to the evolution of larger brains. Previous studies have compared species with different social organizations or different groups within obligately social species. Here, we report the first intraspecific study to examine how social experience shapes brain volume using a species with facultatively eusocial or solitary behaviour, the sweat bee Megalopta genalis. Serial histological sections were used to reconstruct and measure the volume of brain areas of bees behaving as social reproductives, social workers, solitary reproductives or 1-day-old bees that are undifferentiated with respect to the social phenotype. Social reproductives showed increased development of the mushroom body (an area of the insect brain associated with sensory integration and learning) relative to social workers and solitary reproductives. The gross neuroanatomy of young bees is developmentally similar to the advanced eusocial species previously studied, despite vast differences in colony size and social organization. Our results suggest that the transition from solitary to social behaviour is associated with modified brain development, and that maintaining dominance, rather than sociality per se, leads to increased mushroom body development, even in the smallest social groups possible (i.e. groups with two bees). Such results suggest that capabilities to navigate the complexities of social life may be a factor shaping brain evolution in some social insects, as for some vertebrates.
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Affiliation(s)
- Adam R Smith
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Republic of Panama.
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Dreyer D, Vitt H, Dippel S, Goetz B, El Jundi B, Kollmann M, Huetteroth W, Schachtner J. 3D Standard Brain of the Red Flour Beetle Tribolium Castaneum: A Tool to Study Metamorphic Development and Adult Plasticity. Front Syst Neurosci 2010; 4:3. [PMID: 20339482 PMCID: PMC2845059 DOI: 10.3389/neuro.06.003.2010] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2009] [Accepted: 01/18/2010] [Indexed: 12/21/2022] Open
Abstract
The red flour beetle Tribolium castaneum is emerging as a further standard insect model beside Drosophila. Its genome is fully sequenced and it is susceptible for genetic manipulations including RNA-interference. We use this beetle to study adult brain development and plasticity primarily with respect to the olfactory system. In the current study, we provide 3D standard brain atlases of freshly eclosed adult female and male beetles (A0). The atlases include eight paired and three unpaired neuropils including antennal lobes (ALs), optic lobe neuropils, mushroom body calyces and pedunculi, and central complex. For each of the two standard brains, we averaged brain areas of 20 individual brains. Additionally, we characterized eight selected olfactory glomeruli from 10 A0 female and male beetles respectively, which we could unequivocally recognize from individual to individual owing to their size and typical position in the ALs. In summary, comparison of the averaged neuropil volumes revealed no sexual dimorphism in any of the reconstructed neuropils in A0 Tribolium brains. Both, the female and male 3D standard brain are also used for interspecies comparisons, and, importantly, will serve as future volumetric references after genetical manipulation especially regarding metamorphic development and adult plasticity.
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Affiliation(s)
- David Dreyer
- Department of Biology, Animal Physiology, Philipps-University Marburg Marburg, Germany
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El Jundi B, Huetteroth W, Kurylas AE, Schachtner J. Anisometric brain dimorphism revisited: Implementation of a volumetric 3D standard brain in Manduca sexta. J Comp Neurol 2009; 517:210-25. [PMID: 19731336 DOI: 10.1002/cne.22150] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Lepidopterans like the giant sphinx moth Manduca sexta are known for their conspicuous sexual dimorphism in the olfactory system, which is especially pronounced in the antennae and in the antennal lobe, the primary integration center of odor information. Even minute scents of female pheromone are detected by male moths, facilitated by a huge array of pheromone receptors on their antennae. The associated neuropilar areas in the antennal lobe, the glomeruli, are enlarged in males and organized in the form of the so-called macroglomerular complex (MGC). In this study we searched for anatomical sexual dimorphism more downstream in the olfactory pathway and in other neuropil areas in the central brain. Based on freshly eclosed animals, we created a volumetric female and male standard brain and compared 30 separate neuropilar regions. Additionally, we labeled 10 female glomeruli that were homologous to previously quantitatively described male glomeruli including the MGC. In summary, the neuropil volumes reveal an isometric sexual dimorphism in M. sexta brains. This proportional size difference between male and female brain neuropils masks an anisometric or disproportional dimorphism, which is restricted to the sex-related glomeruli of the antennal lobes and neither mirrored in other normal glomeruli nor in higher brain centers like the calyces of the mushroom bodies. Both the female and male 3D standard brain are also used for interspecies comparisons, and may serve as future volumetric reference in pharmacological and behavioral experiments especially regarding development and adult plasticity. J. Comp. Neurol. 517:210-225, 2009. (c) 2009 Wiley-Liss, Inc.
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Affiliation(s)
- Basil El Jundi
- Department of Biology, Animal Physiology, Philipps-University, Marburg, Germany
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Molina Y, Harris RM, O'Donnell S. Brain organization mirrors caste differences, colony founding and nest architecture in paper wasps (Hymenoptera: Vespidae). Proc Biol Sci 2009; 276:3345-51. [PMID: 19553252 DOI: 10.1098/rspb.2009.0817] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The cognitive challenges that social animals face depend on species differences in social organization and may affect mosaic brain evolution. We asked whether the relative size of functionally distinct brain regions corresponds to species differences in social behaviour among paper wasps (Hymenoptera: Vespidae). We measured the volumes of targeted brain regions in eight species of paper wasps. We found species variation in functionally distinct brain regions, which was especially strong in queens. Queens from species with open-comb nests had larger central processing regions dedicated to vision (mushroom body (MB) calyx collars) than those with enclosed nests. Queens from advanced eusocial species (swarm founders), who rely on pheromones in several contexts, had larger antennal lobes than primitively eusocial independent founders. Queens from species with morphologically distinct castes had augmented central processing regions dedicated to antennal input (MB lips) relative to caste monomorphic species. Intraspecific caste differences also varied with mode of colony founding. Independent-founding queens had larger MB collars than their workers. Conversely, workers in swarm-founding species with decentralized colony regulation had larger MB calyx collars and optic lobes than their queens. Our results suggest that brain organization is affected by evolutionary transitions in social interactions and is related to the environmental stimuli group members face.
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Affiliation(s)
- Y Molina
- Animal Behavior Program, Department of Psychology, University of Washington, Seattle, WA 98195, USA.
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Jones TA, Donlan NA, O'Donnell S. Growth and pruning of mushroom body Kenyon cell dendrites during worker behavioral development in the paper wasp, Polybia aequatorialis (Hymenoptera: Vespidae). Neurobiol Learn Mem 2009; 92:485-95. [PMID: 19539772 DOI: 10.1016/j.nlm.2009.06.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Revised: 06/03/2009] [Accepted: 06/11/2009] [Indexed: 12/01/2022]
Abstract
Adult workers of some social insect species show dramatic behavioral changes as they pass through a sequence of task specializations. In the paper wasp, Polybia aequatorialis, female workers begin adult life within the nest tending brood, progress to maintaining and defending the nest exterior, and ultimately leave the nest to forage. The mushroom body (MB) calyx neuropil increases in volume as workers progress from in-nest to foraging tasks. In other social Hymenoptera (bees and ants), MB Kenyon cell dendrites, axons and synapses change with the transition to foraging, but these neuronal effects had not been studied in wasps. Furthermore, the on-nest worker of Polybia wasps, an intermediate task specialization not identified in bees or ants, provides the opportunity to study pre-foraging worker class transitions. We asked whether Kenyon cell dendritic arborization varies with the task specialization of Polybia workers observed in the field near Monteverde, Costa Rica. Golgi-impregnated arbors in the lip and collar calyces, which receive a predominance of olfactory and visual input, respectively, were quantified using Sholl's concentric circles and a novel application of virtual spherical probes. Arbors of the lip varied in a manner reminiscent of honeybees, with foragers having the largest and in-nest workers having the smallest arbors. In contrast, arbors of the collar were largest in foragers but smallest in on-nest workers. Thus, progression through task specializations in P. aequatorialis involves subregion specific dendritic growth and regression in the MB neuropil. These results may reflect the sensitivity of Kenyon cell dendritic structure to specialization dependent social and sensory experience.
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Affiliation(s)
- Theresa A Jones
- Psychology Department and Institute for Neuroscience, University of Texas at Austin, Austin, TX 78746, USA.
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Seid MA, Wehner R. Delayed axonal pruning in the ant brain: A study of developmental trajectories. Dev Neurobiol 2009; 69:350-64. [DOI: 10.1002/dneu.20709] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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