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Helmbrecht H, Lin TJ, Janakiraman S, Decker K, Nance E. Prevalence and practices of immunofluorescent cell image processing: a systematic review. Front Cell Neurosci 2023; 17:1188858. [PMID: 37545881 PMCID: PMC10400723 DOI: 10.3389/fncel.2023.1188858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 07/06/2023] [Indexed: 08/08/2023] Open
Abstract
Background We performed a systematic review that identified at least 9,000 scientific papers on PubMed that include immunofluorescent images of cells from the central nervous system (CNS). These CNS papers contain tens of thousands of immunofluorescent neural images supporting the findings of over 50,000 associated researchers. While many existing reviews discuss different aspects of immunofluorescent microscopy, such as image acquisition and staining protocols, few papers discuss immunofluorescent imaging from an image-processing perspective. We analyzed the literature to determine the image processing methods that were commonly published alongside the associated CNS cell, microscopy technique, and animal model, and highlight gaps in image processing documentation and reporting in the CNS research field. Methods We completed a comprehensive search of PubMed publications using Medical Subject Headings (MeSH) terms and other general search terms for CNS cells and common fluorescent microscopy techniques. Publications were found on PubMed using a combination of column description terms and row description terms. We manually tagged the comma-separated values file (CSV) metadata of each publication with the following categories: animal or cell model, quantified features, threshold techniques, segmentation techniques, and image processing software. Results Of the almost 9,000 immunofluorescent imaging papers identified in our search, only 856 explicitly include image processing information. Moreover, hundreds of the 856 papers are missing thresholding, segmentation, and morphological feature details necessary for explainable, unbiased, and reproducible results. In our assessment of the literature, we visualized current image processing practices, compiled the image processing options from the top twelve software programs, and designed a road map to enhance image processing. We determined that thresholding and segmentation methods were often left out of publications and underreported or underutilized for quantifying CNS cell research. Discussion Less than 10% of papers with immunofluorescent images include image processing in their methods. A few authors are implementing advanced methods in image analysis to quantify over 40 different CNS cell features, which can provide quantitative insights in CNS cell features that will advance CNS research. However, our review puts forward that image analysis methods will remain limited in rigor and reproducibility without more rigorous and detailed reporting of image processing methods. Conclusion Image processing is a critical part of CNS research that must be improved to increase scientific insight, explainability, reproducibility, and rigor.
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Affiliation(s)
- Hawley Helmbrecht
- Department of Chemical Engineering, University of Washington, Seattle, WA, United States
| | - Teng-Jui Lin
- Department of Chemical Engineering, University of Washington, Seattle, WA, United States
| | - Sanjana Janakiraman
- Paul G. Allen School of Computer Science & Engineering, Seattle, WA, United States
| | - Kaleb Decker
- Department of Chemical Engineering, University of Washington, Seattle, WA, United States
| | - Elizabeth Nance
- Department of Chemical Engineering, University of Washington, Seattle, WA, United States
- Department of Bioengineering, University of Washington, Seattle, WA, United States
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2
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Azorsa F, Muscedere ML, Traniello JFA. Socioecology and Evolutionary Neurobiology of Predatory Ants. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2021.804200] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Muratore IB, Fandozzi EM, Traniello JFA. Behavioral performance and division of labor influence brain mosaicism in the leafcutter ant Atta cephalotes. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2022; 208:325-344. [PMID: 35112161 DOI: 10.1007/s00359-021-01539-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 12/27/2021] [Accepted: 12/28/2021] [Indexed: 11/29/2022]
Abstract
Brain evolution is hypothesized to be driven by behavioral selection on neuroarchitecture. We developed a novel metric of relative neuroanatomical investments involved in performing tasks varying in sensorimotor and processing demands across polymorphic task-specialized workers of the leafcutter ant Atta cephalotes and quantified brain size and structure to examine their correlation with our computational approximations. Investment in multisensory and motor integration for task performance was estimated to be greatest for media workers, whose highly diverse repertoire includes leaf-quality discrimination and leaf-harvesting tasks that likely involve demanding sensory and motor processes. Confocal imaging revealed that absolute brain volume increased with worker size and functionally specialized compartmental scaling differed among workers. The mushroom bodies, centers of sensory integration and learning and memory, and the antennal lobes, olfactory input sites, were larger in medias than in minims (gardeners) and significantly larger than in majors ("soldiers"), both of which had lower scores for involvement of olfactory processing in the performance of their characteristic tasks. Minims had a proportionally larger central complex compared to other workers. These results support the hypothesis that variation in task performance influences selection for mosaic brain structure, the independent evolution of proportions of the brain composed of different neuropils.
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Affiliation(s)
- I B Muratore
- Department of Biology, Boston University, Boston, MA, 02215, USA.
| | - E M Fandozzi
- Department of Biology, Boston University, Boston, MA, 02215, USA
| | - J F A Traniello
- Department of Biology, Boston University, Boston, MA, 02215, USA.,Graduate Program in Neuroscience, Boston University, Boston, MA, 02215, USA
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Couto A, Arnold G, Ai H, Sandoz JC. Interspecific variation of antennal lobe composition among four hornet species. Sci Rep 2021; 11:20883. [PMID: 34686710 PMCID: PMC8536693 DOI: 10.1038/s41598-021-00280-z] [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: 07/08/2021] [Accepted: 09/27/2021] [Indexed: 11/09/2022] Open
Abstract
Olfaction is a crucial sensory modality underlying foraging, social and mating behaviors in many insects. Since the olfactory system is at the interface between the animal and its environment, it receives strong evolutionary pressures that promote neuronal adaptations and phenotypic variations across species. Hornets are large eusocial predatory wasps with a highly developed olfactory system, critical for foraging and intra-specific communication. In their natural range, hornet species display contrasting ecologies and olfactory-based behaviors, which might match to adaptive shifts in their olfactory system. The first olfactory processing center of the insect brain, the antennal lobe, is made of morphological and functional units called glomeruli. Using fluorescent staining, confocal microscopy and 3D reconstructions, we compared antennal lobe structure, glomerular numbers and volumes in four hornet species (Vespa crabro, Vespa velutina, Vespa mandarinia and Vespa orientalis) with marked differences in nesting site preferences and predatory behaviors. Despite a conserved organization of their antennal lobe compartments, glomeruli numbers varied strongly between species, including in a subsystem thought to process intraspecific cuticular signals. Moreover, specific adaptations involving enlarged glomeruli appeared in two species, V. crabro and V. mandarinia, but not in the others. We discuss the possible function of these adaptations based on species-specific behavioral differences.
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Affiliation(s)
- Antoine Couto
- Laboratory Evolution Genomes Behavior and Ecology, CNRS, University Paris-Sud, IRD, Université Paris Saclay, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France.,School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - Gérard Arnold
- Laboratory Evolution Genomes Behavior and Ecology, CNRS, University Paris-Sud, IRD, Université Paris Saclay, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France
| | - Hiroyuki Ai
- Department of Earth System Science, Fukuoka University, Fukuoka, 814-0180, Japan
| | - Jean-Christophe Sandoz
- Laboratory Evolution Genomes Behavior and Ecology, CNRS, University Paris-Sud, IRD, Université Paris Saclay, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France.
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Haverkamp A, Smid HM. A neuronal arms race: the role of learning in parasitoid-host interactions. CURRENT OPINION IN INSECT SCIENCE 2020; 42:47-54. [PMID: 32947014 DOI: 10.1016/j.cois.2020.09.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 08/21/2020] [Accepted: 09/07/2020] [Indexed: 06/11/2023]
Abstract
Parasitic wasps and their larval hosts are intimately connected by an array of behavioral adaptations and counter-adaptations. This co-evolution has led to highly specific, natural variation in learning rates and memory consolidation in parasitoid wasps. Similarly, the hosts of the parasitoids show specific sensory adaptations as well as non-associative learning strategies for parasitoid avoidance. However, these neuronal and behavioral adaptations of both hosts and wasps have so far been studied largely apart from each other. Here we argue that a parallel investigation of the nervous system in wasps and their hosts might lead to novel insights into the evolution of insect behavior and the neurobiology of learning and memory.
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Affiliation(s)
- Alexander Haverkamp
- Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
| | - Hans M Smid
- Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
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Diakova AV, Polilov AA. Sensation of the tiniest kind: the antennal sensilla of the smallest free-living insect Scydosella musawasensis (Coleoptera: Ptiliidae). PeerJ 2020; 8:e10401. [PMID: 33282562 PMCID: PMC7690297 DOI: 10.7717/peerj.10401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 10/29/2020] [Indexed: 11/29/2022] Open
Abstract
Miniaturization is a major evolutionary trend prominent in insects, which has resulted in the existence of insects comparable in size to some unicellular protists. The adaptation of the complex antennal multisensory systems to extreme miniaturization is a fascinating problem, which remains almost unexplored. We studied the antennal sensilla of Scydosella musawasensis Hall, 1999 (Coleoptera: Ptiliidae), the smallest free-living insect, using scanning electron microscopy. The antenna of S. musawasensis bears 131 sensilla; no intraspecific variation in the number or position of the sensilla has been revealed. Nine different morphological types of sensilla are described according to their external morphological features and distribution: four types of sensilla trichodea, one type of sensilla chaetica, two types of sensilla styloconica, and two types of sensilla basiconica. Morphometric analysis of the sensilla of S. musawasensis, based on measurements of the lengths and diameters of sensilla and their location and number, showed the absence of significant differences between females and males. Comparative allometric analysis of S. musawasensis and larger Coleoptera showed that the number of sensilla and the size of sensilla chaetica decrease with decreasing body size. However, the number of the types of sensilla and the length and diameter of the multiporous sensilla basiconica revealed no correlation with the body size. Comparison of the acquired data with the results of our earlier study of the antennal sensilla of some of the smallest parasitic wasps is used to put forward hypotheses on the common principles of miniaturization of the antennal sensory systems of insects.
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Affiliation(s)
- Anna V. Diakova
- Department of Entomology, Faculty of Biology, Moscow State University, Moscow, Russian Federation
| | - Alexey A. Polilov
- Department of Entomology, Faculty of Biology, Moscow State University, Moscow, Russian Federation
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van der Woude E, Groothuis J, Smid HM. No gains for bigger brains: Functional and neuroanatomical consequences of relative brain size in a parasitic wasp. J Evol Biol 2019; 32:694-705. [PMID: 30929291 PMCID: PMC6850633 DOI: 10.1111/jeb.13450] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Revised: 10/25/2018] [Accepted: 03/26/2019] [Indexed: 11/28/2022]
Abstract
Heritable genetic variation in relative brain size can underlie the relationship between brain performance and the relative size of the brain. We used bidirectional artificial selection to study the consequences of genetic variation in relative brain size on brain morphology, cognition and longevity in Nasonia vitripennis parasitoid wasps. Our results show a robust change in relative brain size after 26 generations of selection and six generations of relaxation. Total average neuropil volume of the brain was 16% larger in wasps selected for relatively large brains than in wasps selected for relatively small brains, whereas the body length of the large‐brained wasps was smaller. Furthermore, the relative volume of the antennal lobes was larger in wasps with relatively large brains. Relative brain size did not influence olfactory memory retention, whereas wasps that were selected for larger relative brain size had a shorter longevity, which was even further reduced after a learning experience. These effects of genetic variation on neuropil composition and memory retention are different from previously described effects of phenotypic plasticity in absolute brain size. In conclusion, having relatively large brains may be costly for N. vitripennis, whereas no cognitive benefits were recorded.
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Affiliation(s)
- Emma van der Woude
- Laboratory of Entomology, Wageningen University, Wageningen, The Netherlands
| | - Jitte Groothuis
- Laboratory of Entomology, Wageningen University, Wageningen, The Netherlands
| | - Hans M Smid
- Laboratory of Entomology, Wageningen University, Wageningen, The Netherlands
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Diakova AV, Makarova AA, Polilov AA. Between extreme simplification and ideal optimization: antennal sensilla morphology of miniaturized Megaphragma wasps (Hymenoptera: Trichogrammatidae). PeerJ 2018; 6:e6005. [PMID: 30533303 PMCID: PMC6276593 DOI: 10.7717/peerj.6005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 10/26/2018] [Indexed: 12/28/2022] Open
Abstract
One of the major trends in the evolution of parasitoid wasps is miniaturization, which has produced the smallest known insects. Megaphragma spp. (Hymenoptera: Trichogrammatidae) are smaller than some unicellular organisms, with an adult body length of the smallest only 170 µm. Their parasitoid lifestyle depends on retention of a high level of sensory reception comparable to that in parasitoid wasps that may have antennae hundreds of times larger. Antennal sensilla of males and females of Megaphragma amalphitanum and M. caribea and females of the parthenogenetic M. mymaripenne are described, including sensillum size, external morphology, and distribution. Eight different morphological types of sensilla were discovered, two of them appearing exclusively on female antennae. Two of the types, sensilla styloconica and aporous placoid sensilla, have not been described previously. Regression analyses were performed to detect and evaluate possible miniaturization trends by comparing available data for species of larger parasitoid wasps. The number of antennal sensilla was found to decrease with the body size; M. amalphitanum males have only 39 sensilla per antenna. The number of antennal sensilla types and sizes of the sensilla, however, show little to no correlation with the body size. Our findings on the effects of miniaturization on the antennal sensilla of Megaphragma provide material for discussion on the limits to the reduction of insect antenna.
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Affiliation(s)
- Anna V Diakova
- Department of Entomology, Biological Faculty, Moscow State University, Moscow, Russia
| | - Anastasia A Makarova
- Department of Entomology, Biological Faculty, Moscow State University, Moscow, Russia
| | - Alexey A Polilov
- Department of Entomology, Biological Faculty, Moscow State University, Moscow, Russia
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10
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Liefting M, Hoedjes KM, Le Lann C, Smid HM, Ellers J. Selection for associative learning of color stimuli reveals correlated evolution of this learning ability across multiple stimuli and rewards. Evolution 2018; 72:1449-1459. [PMID: 29768649 PMCID: PMC6099215 DOI: 10.1111/evo.13498] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 04/15/2018] [Indexed: 01/19/2023]
Abstract
We are only starting to understand how variation in cognitive ability can result from local adaptations to environmental conditions. A major question in this regard is to what extent selection on cognitive ability in a specific context affects that ability in general through correlated evolution. To address this question, we performed artificial selection on visual associative learning in female Nasonia vitripennis wasps. Using appetitive conditioning in which a visual stimulus was offered in association with a host reward, the ability to learn visual associations was enhanced within 10 generations of selection. To test for correlated evolution affecting this form of learning, the ability to readily form learned associations in females was also tested using an olfactory instead of a visual stimulus in the appetitive conditioning. Additionally, we assessed whether the improved associative learning ability was expressed across sexes by color-conditioning males with a mating reward. Both females and males from the selected lines consistently demonstrated an increased associative learning ability compared to the control lines, independent of learning context or conditioned stimulus. No difference in relative volume of brain neuropils was detected between the selected and control lines.
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Affiliation(s)
- Maartje Liefting
- Animal EcologyVrije Universiteit AmsterdamAmsterdam1081 HVthe Netherlands
- Applied Zoology/Animal EcologyFreie Universität BerlinBerlinD‐12163Germany
| | - Katja M. Hoedjes
- Laboratory of EntomologyWageningen UniversityWageningen6700 AAthe Netherlands
- Department of Ecology and EvolutionUniversity of LausanneLausanneCH‐1015Switzerland
| | - Cécile Le Lann
- Animal EcologyVrije Universiteit AmsterdamAmsterdam1081 HVthe Netherlands
- CNRS, ECOBIO (Ecosystèmes, Biodiversité, Evolution)UMR 6553, Université de RennesRennesF‐35000France
| | - Hans M. Smid
- Laboratory of EntomologyWageningen UniversityWageningen6700 AAthe Netherlands
| | - Jacintha Ellers
- Animal EcologyVrije Universiteit AmsterdamAmsterdam1081 HVthe Netherlands
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Groothuis J, Smid HM. Nasonia Parasitic Wasps Escape from Haller's Rule by Diphasic, Partially Isometric Brain-Body Size Scaling and Selective Neuropil Adaptations. BRAIN, BEHAVIOR AND EVOLUTION 2017; 90:243-254. [PMID: 29059675 DOI: 10.1159/000480421] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 08/16/2017] [Indexed: 11/19/2022]
Abstract
Haller's rule states that brains scale allometrically with body size in all animals, meaning that relative brain size increases with decreasing body size. This rule applies both on inter- and intraspecific comparisons. Only 1 species, the extremely small parasitic wasp Trichogramma evanescens, is known as an exception and shows an isometric brain-body size relation in an intraspecific comparison between differently sized individuals. Here, we investigated if such an isometric brain-body size relationship also occurs in an intraspecific comparison with a slightly larger parasitic wasp, Nasonia vitripennis, a species that may vary 10-fold in body weight upon differences in levels of scramble competition during larval development. We show that Nasonia exhibits diphasic brain-body size scaling: larger wasps scale allometrically, following Haller's rule, whereas the smallest wasps show isometric scaling. Brains of smaller wasps are, therefore, smaller than expected and we hypothesized that this may lead to adaptations in brain architecture. Volumetric analysis of neuropil composition revealed that wasps of different sizes differed in relative volume of multiple neuropils. The optic lobes and mushroom bodies in particular were smaller in the smallest wasps. Furthermore, smaller brains had a relatively smaller total neuropil volume and larger cellular rind than large brains. These changes in relative brain size and brain architecture suggest that the energetic constraints on brain tissue outweigh specific cognitive requirements in small Nasonia wasps.
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Affiliation(s)
- Jitte Groothuis
- Laboratory of Entomology, Wageningen University, Wageningen, The Netherlands
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12
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Ramirez-Esquivel F, Leitner NE, Zeil J, Narendra A. The sensory arrays of the ant, Temnothorax rugatulus. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:552-563. [PMID: 28347859 DOI: 10.1016/j.asd.2017.03.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 03/22/2017] [Accepted: 03/22/2017] [Indexed: 06/06/2023]
Abstract
Individual differences in response thresholds to task-related stimuli may be one mechanism driving task allocation among social insect workers. These differences may arise at various stages in the nervous system. We investigate variability in the peripheral nervous system as a simple mechanism that can introduce inter-individual differences in sensory information. In this study we describe size-dependent variation of the compound eyes and the antennae in the ant Temnothorax rugatulus. Head width in T. rugatulus varies between 0.4 and 0.7 mm (2.6-3.8 mm body length). But despite this limited range of worker sizes we find sensory array variability. We find that the number of ommatidia and of some, but not all, antennal sensilla types vary with head width. The antennal array of T. rugatulus displays the full complement of sensillum types observed in other species of ants, although at much lower quantities than other, larger, studied species. In addition, we describe what we believe to be a new type of sensillum in hymenoptera that occurs on the antennae and on all body segments. T. rugatulus has apposition compound eyes with 45-76 facets per eye, depending on head width, with average lens diameters of 16.5 μm, rhabdom diameters of 5.7 μm and inter-ommatidial angles of 16.8°. The optical system of T. rugatulus ommatidia is severely under focussed, but the absolute sensitivity of the eyes is unusually high. We discuss the functional significance of these findings and the extent to which the variability of sensory arrays may correlate with task allocation.
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Affiliation(s)
| | - Nicole E Leitner
- Department of Ecology and Evolutionary Biology, University of Arizona, PO Box 210088, Tucson, AZ 85721-0088, USA.
| | - Jochen Zeil
- Research School of Biology, The Australian National University, Canberra, ACT 2601, Australia.
| | - Ajay Narendra
- Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
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Makarova AA, Polilov AA. Peculiarities of the brain organization and fine structure in small insects related to miniaturization. 4. Thrips (Thysanoptera, Thripidae). ACTA ACUST UNITED AC 2017. [DOI: 10.1134/s0013873817030046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Maximized complexity in miniaturized brains: morphology and distribution of octopaminergic, dopaminergic and serotonergic neurons in the parasitic wasp, Trichogramma evanescens. Cell Tissue Res 2017; 369:477-496. [PMID: 28597098 PMCID: PMC5579201 DOI: 10.1007/s00441-017-2642-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 05/02/2017] [Indexed: 11/13/2022]
Abstract
The parasitic wasp, Trichogramma evanescens, is an extremely small insect, with a body length as small as 0.3 mm. To facilitate this miniaturization, their brains may have evolved to contain smaller neural components and/or reduced neural complexity than larger insects. Here, we study whether the size and number of neurons are reduced in the miniaturized brain of T. evanescens, focusing on neurons that express serotonin (5HT), octopamine (OA) and dopamine (DA). We provide the first description of the distribution, projection patterns and number of 5HT-, OA- and DA-like immunoreactive cell bodies in T. evanescens and compare our observations with descriptions of much larger insects. The brains of T. evanescens contain comparable numbers of monoaminergic neurons to those of larger insects. Serotonergic neurons appear to be especially conserved; most of the clusters contain a similar number of neurons to those described in Apis mellifera and Drosophila melanogaster. This maintained complexity may have been facilitated by miniaturization of neuron size. However, many dopaminergic and some octopaminergic neuron clusters in T. evanescens contain fewer neurons than in larger insects. Modification of the complexity of these monoaminergic systems may have been necessary to maintain neuron functionality during brain miniaturization in T. evanescens. Our results reveal some of the evolutionary adaptations that may enable behavioural and cognitive complexity with respect to miniaturized brains.
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van der Woude E, Smid HM. Effects of Isometric Brain-Body Size Scaling on the Complexity of Monoaminergic Neurons in a Minute Parasitic Wasp. BRAIN, BEHAVIOR AND EVOLUTION 2017; 89:185-194. [PMID: 28478445 DOI: 10.1159/000468974] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 03/07/2017] [Indexed: 01/24/2023]
Abstract
Trichogramma evanescens parasitic wasps show large phenotypic plasticity in brain and body size, resulting in a 5-fold difference in brain volume among genetically identical sister wasps. Brain volume scales linearly with body volume in these wasps. This isometric brain scaling forms an exception to Haller's rule, which states that small animals have relatively larger brains than large animals. The large plasticity in brain size may be facilitated by plasticity in neuron size, in the number of neurons, or both. Here, we investigated whether brain isometry requires plasticity in the number and size of monoaminergic neurons that express serotonin (5HT), octopamine (OA), and dopamine (DA). Genetically identical small and large T. evanescens appear to have the same number of 5HT-, OA-, and DA-like immunoreactive cell bodies in their brains, but these cell bodies differ in diameter. This indicates that brain isometry can be facilitated by plasticity in the size of monoaminergic neurons, rather than plasticity in numbers of monoaminergic neurons. Selection pressures on body miniaturization may have resulted in the evolution of miniaturized neural pathways that allow even the smallest wasps to find suitable hosts. Plasticity in the size of neural components may be among the mechanisms that underlie isometric brain scaling while maintaining cognitive abilities in the smallest individuals.
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Affiliation(s)
- Emma van der Woude
- Laboratory of Entomology, Wageningen University, Wageningen, The Netherlands
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