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Ikenaga T, Kobayashi A, Takeuchi A, Uesugi K, Maezawa T, Shibata N, Sakamoto T, Sakamoto H. Volume X-Ray Micro-Computed Tomography Analysis of the Early Cephalized Central Nervous System in a Marine Flatworm, Stylochoplana pusilla. Zoolog Sci 2024; 41:281-289. [PMID: 38809867 DOI: 10.2108/zs230082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 12/29/2023] [Indexed: 05/31/2024]
Abstract
Platyhelminthes are a phylum of simple bilaterian invertebrates with prototypic body systems. Compared with non-bilaterians such as cnidarians, the bilaterians are likely to exhibit integrated free-moving behaviors, which require a concentrated nervous system "brain" rather than the distributed nervous system of radiatans. Marine flatworms have an early cephalized 'central' nervous system compared not only with non-bilaterians but also with parasitic flatworms or freshwater planarians. In this study, we used the marine flatworm Stylochoplana pusilla as an excellent model organism in Platyhelminthes because of the early cephalized central nervous system. Here, we investigated the three-dimensional structures of the flatworm central nervous system by the use of X-ray micro-computed tomography (micro-CT) in a synchrotron radiation facility. We found that the obtained tomographic images were sufficient to discriminate some characteristic structures of the nervous system, including nerve cords around the cephalic ganglion, mushroom body-like structures, and putative optic nerves forming an optic commissure-like structure. Through the micro-CT imaging, we could obtain undistorted serial section images, permitting us to visualize precise spatial relationships of neuronal subpopulations and nerve tracts. 3-D micro-CT is very effective in the volume analysis of the nervous system at the cellular level; the methodology is straightforward and could be applied to many other non-model organisms.
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Affiliation(s)
- Takanori Ikenaga
- Graduate School of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japan
| | - Aoshi Kobayashi
- Ushimado Marine Institute (UMI), Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Ushimado, Setouchi, Okayama 701-4303, Japan
| | - Akihisa Takeuchi
- Japan Synchrotron Radiation Research Institute/SPring-8, Hyogo 679-5198, Japan
| | - Kentaro Uesugi
- Japan Synchrotron Radiation Research Institute/SPring-8, Hyogo 679-5198, Japan
| | - Takanobu Maezawa
- Department of Integrated Science and Technology, National Institute of Technology, Tsuyama College, Tsuyama, Okayama 708-8509, Japan
| | - Norito Shibata
- Department of Integrated Science and Technology, National Institute of Technology, Tsuyama College, Tsuyama, Okayama 708-8509, Japan
| | - Tatsuya Sakamoto
- Ushimado Marine Institute (UMI), Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Ushimado, Setouchi, Okayama 701-4303, Japan
| | - Hirotaka Sakamoto
- Ushimado Marine Institute (UMI), Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Ushimado, Setouchi, Okayama 701-4303, Japan,
- Department of Biology, Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Kita-ku, Tsushimanaka, Okayama 700-8530, Japan
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Fu SJ, Yang EC. Neuroplasticity in honey bee brains: An enhanced micro-computed tomography protocol for precise mushroom body volume measurement. J Neurosci Methods 2024; 403:110040. [PMID: 38135123 DOI: 10.1016/j.jneumeth.2023.110040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/31/2023] [Accepted: 12/17/2023] [Indexed: 12/24/2023]
Abstract
BACKGROUND In insect brains, mushroom bodies are associated with memory and learning behavior. It has been demonstrated that the volume of the mushroom bodies in the brain of a worker honey bee changes during the adult stage. Changes in mushroom body volume imply high neuroplasticity in the brains and may be related to the age polyethism of honey bees. A suitable volume measurement method is needed to understand the correlation between behavioral changes and mushroom body volume changes in honey bees. NEW METHOD We developed a new protocol for insect micro-computed tomography by modifying a previously reported method. Permount™ mounting medium was used as the embedding medium for micro-computed tomography scanning. RESULTS This protocol can generate images with high contrast inside the brain and reduce the marked shape changes during specimen processing. From the resulting high-contrast images, we used freeware to generate a three-dimensional model and calculate the volumes of the mushroom bodies in honey bees. The measured volumes of the mushroom bodies were larger than the values reported in most previous studies. There was no significant difference between the left and right mushroom body volumes, but the volumes of honey bee mushroom bodies significantly increased with age. COMPARISON WITH EXISTING METHODS Previous protocols for micro-computed tomography using dried samples would cause brain shrinkage; protocols using ethanol-preserved or resin-embedded samples generated images with lower contrast. CONCLUSIONS The embedding protocol for micro-computed tomography is suitable for calculating volume of the mushroom bodies in honey bee brains.
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Affiliation(s)
- Shang-Jui Fu
- Department of Entomology, National Taiwan University, Taiwan
| | - En-Cheng Yang
- Department of Entomology, National Taiwan University, Taiwan.
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Steinhoff POM, Harzsch S, Uhl G. Comparative neuroanatomy of the central nervous system in web-building and cursorial hunting spiders. J Comp Neurol 2023; 532:e25554. [PMID: 37948052 DOI: 10.1002/cne.25554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 09/01/2023] [Accepted: 10/17/2023] [Indexed: 11/12/2023]
Abstract
Spiders (Araneae) include cursorial species that stalk their prey and more stationary species that use webs for prey capture. While many cursorial hunting spiders rely on visual cues, web-building spiders use vibratory cues (mechanosensation) for prey capture. We predicted that the differences in primary sensory input between the species are mirrored by differences in the morphology/architecture of the central nervous system (CNS). Here, we investigated the CNS anatomy of four spider species, two cursorial hunters Pardosa amentata (Lycosidae) and Marpissa muscosa (Salticidae), and two web-building hunters Argiope bruennichi (Araneidae) and Parasteatoda tepidariorum (Theridiidae). Their CNS was analyzed using Bodian silver impregnations, immunohistochemistry, and microCT analysis. We found that there are major differences between species in the secondary eye pathway of the brain that pertain to first-order, second-order, and higher order brain centers (mushroom bodies [MB]). While P. amentata and M. muscosa have prominent visual neuropils and MB, these are much reduced in the two web-building species. Argiope bruennichi lacks second-order visual neuropils but has specialized photoreceptors that project into two distinct visual neuropils, and P. tepidariorum lacks MB, suggesting that motion vision might be absent in this species. Interestingly, the differences in the ventral nerve cord are much less pronounced, but the web-building spiders have proportionally larger leg neuropils than the cursorial spiders. Our findings suggest that the importance of visual information is much reduced in web-building spiders, compared to cursorial spiders, while processing of mechanosensory information requires the same major circuits in both web-building and cursorial hunting spiders.
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Affiliation(s)
- Philip O M Steinhoff
- Zoological Institute and Museum, General and Systematic Zoology, University of Greifswald, Greifswald, Germany
| | - Steffen Harzsch
- Zoological Institute and Museum, Cytology and Evolutionary Biology, University of Greifswald, Greifswald, Germany
| | - Gabriele Uhl
- Zoological Institute and Museum, General and Systematic Zoology, University of Greifswald, Greifswald, Germany
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