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Takeuchi Yuichi

Faculty of Science　Biological Sciences　Behavioral NeuroethologyAssociate Professor
Research and Education Center for Brain ScienceAssociate Professor

「右利きと左利き」の仕組みと成り立ちについて、遺伝子からニューロン、行動、生態、進化まで、幅広いアプローチから研究を行っています。

Researcher basic information

■ Degree
  • 博士（理学）, 京都大学
■ URL
researchmap URLホームページURL■ Various IDs
Researcher number
  • 40508884
ORCID IDJ-Global ID■ Research Keywords and Fields
Research Keyword
  • Learning
  • Predation
  • Brain, neuron
  • Fish
  • Laterality
  • Cichlid
  • Behavioral ecology
  • Neuroethology
  • 包括脳ネットワーク
Research Field
  • Life Science, Ecology and environment
  • Life Science, Animal physiological chemistry, physiology and behavioral biology
  • Life Science, Genome biology
  • Life Science, Neuroscience-general, 神経行動学
■ Educational Organization

Career

■ Career
Career
  • Apr. 2023 - Present
    Hokkaido University, 准教授
  • Apr. 2013 - Mar. 2023
    Toyama University, 助教
  • Apr. 2010 - Mar. 2013
    名古屋大学 理学研究科, 日本学術振興会特別研究員-SPD
  • Apr. 2008 - Mar. 2010
    Kyoto University, Faculty of Science, gCOE研究員
Educational Background
  • Mar. 2008, 京都大学大学院, 理学研究科 博士課程修了
Committee Memberships
  • Jul. 2024 - Present
    日本動物学会, 国際交流委員, Society
  • Apr. 2021 - Present
    Frontiers in Behavioral Neuroscience, Editorial board members (Learning and Memory), Society
  • Apr. 2017 - Mar. 2020
    日本生態学会, 大会企画委員会 ポスター部会, Society

Research activity information

■ Awards
  • Sep. 2018, 日本動物学会, 日本動物学会奨励賞
    竹内 勇一
  • Sep. 2018, 日本動物学会, Zoological Science Award (論文賞)
    竹内 勇一
■ Papers
  • Understanding development of laterality through the scale-eating cichlid fish Perissodus microlepis in Lake Tanganyika
    Yuichi Takeuchi
    比較生理生化学, 42, 2, 103, 113, Sep. 2025, [Peer-reviewed], [Invited], [Lead author, Corresponding author], [Domestic magazines]
  • Dominant eye-dependent lateralized behavior in the scale-eating cichlid fish, Perissodus microlepis.
    Yuichi Takeuchi; Yuna Higuchi; Takaki Watanabe; Yoichi Oda
    Scientific reports, 15, 24725, 22 Jul. 2025, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
    English, Scientific journal, Visual lateralization, which is commonly observed in many animals, is believed to influence behavioral choices or lateral biases; however, the underlying mechanisms remain obscure. In the present study, we examined eye dominance in the scale-eating cichlid fish, Perissodus microlepis, and the role of the dominant eye in lateralized predation. P. microlepis responded to visual stimuli at a significantly higher rate when applied to the eye on the mouth-opening side than to the other eye, revealing visual lateralization. Impaired dominant eye vision with artificial cataracts reduced attacks from the dominant side, halved body flexion angle velocity, and significantly lowered predation success, demonstrating the role of the dominant eye in attack direction and performance. These findings reveal that P. microlepis has clear visual lateralization, which can be used effectively for side attacks during scale eating, probably with relatively high visual acuity or an efficient visual system, providing significant foraging advantages.
  • Phenotypic plasticity drives the development of laterality in the scale-eating cichlid fish Perissodus microlepis.
    Nanako Marubayashi; Masaki Yasugi; Yuichi Takeuchi
    Evolution, 97, 10, 2035, 2046, 04 Jul. 2025, [Peer-reviewed], [Last author, Corresponding author], [International Magazine]
    English, Scientific journal, Phenotypic plasticity, in which traits change in response to environmental conditions, is closely related to predator-prey interactions and speciation. The scale-eating cichlid fish Perissodus microlepis exhibits marked left-right differences in predatory behavior and mouth morphology. While phenotypic plasticity is hypothesized to contribute to the formation of laterality, direct evidence remains scarce. We examined how plasticity shapes laterality by analyzing the predatory behavior and mandibular changes under different foraging conditions: picking granulated feed (non-scale-eating) and tearing scales from prey fish. During the predation experiment, the number of attacks increased over time. Behavioral analysis revealed the mean inter-individual distance from scale-eater to prey gradually decreased, whereas mean swimming activity increased. Morphological analysis of the mandible showed elongation of the dentary bone along the anterior-posterior axis in the scale-eating groups compared to the non-scale-eating group. Furthermore, mandible height was significantly greater on the dominant side, with the degree of asymmetry increasing with scale-eating experience. This strongly suggests that phenotypic plasticity contributes to the enhancement of laterality and promotes disruptive selection of lateral morphs. This study advances our understanding of the unique adaptation in P. microlepis and highlights the importance of feeding experience in shaping adaptive traits within the cichlid lineage.
  • Preying on cyprinid snout warts (pearl organs) as a novel and peculiar habit in the Lake Malawi cichlid Docimodus evelynae.
    Yuichi Takeuchi; Hiroki Hata; Mizuki Sasaki; Andrew Mvula; Shinji Mizuhara; Bosco Rusuwa; Atsushi Maruyama
    Scientific reports, 14, 19300, 28 Aug. 2024, [Peer-reviewed], [Lead author, Corresponding author], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal, Cichlid fishes in the African Great Lakes have undergone explosive speciation, acquiring markedly varying ecologies and diets. There are multiple lineages of scale-eating cichlids, and their natural history and evolutionary ecology is only partially understood. We examined the feeding habit of Docimodus evelynae, a known scale eater, in Lake Malawi. The stomach contents of young individuals mainly consisted of unknown 1 mm hard, white warts (> 30%). To clarify the origin of these warts, we conducted an X-ray fluorometer analysis, and found they were rich in sulphur but low in silicon and calcium, suggesting they were epidermal tissues. Histological and morphological analyses revealed they were multicellular and cup-shaped. These characteristics matched only those of the pearl organs of the coexisting cyprinid Labeo cylindricus. DNA was extracted from the warts found in the stomach of five D. evelynae individuals, followed by PCR using primers targeting the partial COI gene of L. cylindricus. The resulting sequences exhibited 98% similarity to those of L. cylindricus. Pearl organs, never reported as a primary food for fish, could offer a substantial nutritional source based on calorific calculations. Understanding how this peculiar diet is foraged is essential for full comprehension of the food-web structure in this lake.
  • Developmental Process of a Pronounced Laterality in the Scale-eating Cichlid Fish Perissodus microlepis in Lake Tanganyika
    Yuichi Takeuchi
    Zoological Science, 40, 2, 160, 167, Zoological Society of Japan, 01 Apr. 2023, [Peer-reviewed], [Invited], [Lead author, Corresponding author], [International Magazine]
    Scientific journal
  • Experience-dependent learning of behavioral laterality in the scale-eating cichlid Perissodus microlepis occurs during the early developmental stage.
    Yuichi Takeuchi; Yuna Higuchi; Koki Ikeya; Masataka Tagami; Yoichi Oda
    Scientific reports, 12, 723, 14 Jan. 2022, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
    English, Scientific journal, Behavioral laterality-typically represented by human handedness-is widely observed among animals. However, how laterality is acquired during development remains largely unknown. Here, we examined the effect of behavioral experience on the acquisition of lateralized predation at different developmental stages of the scale-eating cichlid fish Perissodus microlepis. Naïve juvenile fish without previous scale-eating experience showed motivated attacks on prey goldfish and an innate attack side preference. Following short-term predation experience, naïve juveniles learned a pronounced lateralized attack using their slightly skewed mouth morphology, and improved the velocity and amplitude of body flexion to succeed in foraging scales during dominant-side attack. Naïve young fish, however, did not improve the dynamics of flexion movement, but progressively developed attack side preference and speed to approach the prey through predation experience. Thus, the cichlid learns different aspects of predation behavior at different developmental stages. In contrast, naïve adults lost the inherent laterality, and they neither developed the lateralized motions nor increased their success rate of predation, indicating that they missed appropriate learning opportunities for scale-eating skills. Therefore, we conclude that behavioral laterality of the cichlid fish requires the integration of genetic basis and behavioral experiences during early developmental stages, immediately after they start scale-eating.
  • Specialized movement and laterality of fin-biting behaviour in genyochromis mento in lake Malawi
    Takeuchi, Y.; Hata, H.; Maruyama, A.; Yamada, T.; Nishikawa, T.; Fukui, M.; Zatha, R.; Rusuwa, B.; Oda, Y.
    Journal of Experimental Biology, 222, 3, Feb. 2019, [Peer-reviewed], [Lead author, Corresponding author], ［Internationally co-authored］, [International Magazine]
    Scientific journal
  • Lateralized expression of left-right axis formation genes is shared by adult brains of lefty and righty scale-eating cichlids.
    Takeuchi Y; Ishikawa A; Oda Y; Kitano J
    Comparative biochemistry and physiology. Part D, Genomics & proteomics, 28, 99, 106, Jul. 2018, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
    English, Scientific journal, (Most downloaded article in the past 90 days)
  • Lateralized scale-eating behaviour of cichlid is acquired by learning to use the naturally stronger side
    Yuichi Takeuchi; Yoichi Oda
    SCIENTIFIC REPORTS, 7, 1, 8984, Aug. 2017, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
    English, Scientific journal
  • Laterality is Universal Among Fishes but Increasingly Cryptic Among Derived Groups
    Michio Hori; Mifuyu Nakajima; Hiroki Hata; Masaki Yasugi; Satoshi Takahashi; Masanori Nakae; Kosaku Yamaoka; Masanori Kohda; Jyun-ichi Kitamura; Masayoshi Maehata; Hirokazu Tanaka; Norihiro Okada; Yuichi Takeuchi
    ZOOLOGICAL SCIENCE, 34, 4, 267, 274, Aug. 2017, [Peer-reviewed], [Last author, Corresponding author], [International Magazine]
    English, Scientific journal
  • Organizing in-class and out-of-class learning: effects and problems inverted classrooms in human anatomy practice
    川口将史; 竹内勇一; 中村友也; 一條裕之
    Toyama medical journal, 28, 1, 6, 16, 2017, [Peer-reviewed], [Domestic magazines]
    Japanese, Research institution
  • An evolutionary hypothesis of binary opposition in functional incompatibility about habenular asymmetry in vertebrates
    Hiroyuki Ichijo; Tomoya Nakamura; Masahumi Kawaguchi; Yuichi Takeuchi
    Frontiers in Neuroscience, 10, 595, Frontiers Media S.A., 2017, [Peer-reviewed], [Last author], [International Magazine]
    English, Scientific journal
  • Active Lerning in Integrated Currisulum: Making the Use of Human Anatomy Practice
    Ichijo, H; Nakamura, T; Takeuchi U; Kawaguchi M
    Igaku Kyoiku / Medical Education (Japan), 47, 6, 343, 351, Japan Society for Medical Education, Oct. 2016, [Peer-reviewed], [Domestic magazines]
    Japanese, Scientific journal,

    Students always have many questions and problems during active participation. Here, we report an active learning course (AL) based on problems that medical students encountered in gross anatomy practice. This AL was implemented after the practice, consisting of a lecture, group discussions, resource hours, and presentation session to ensure exploratory learning. Based on a questionnaire survey, 75.1% of the students evaluated the AL as very valuable or valuable, indicating its usefulness. The AL not only complemented the anatomy course, but also directed the students toward other forms of basic and clinical learning. The results indicate that by making use of gross anatomy practice, the AL functions as a hub for horizontal and vertical integrations in medical education.

  • Acquisition of Lateralized Predation Behavior Associated with Development of Mouth Asymmetry in a Lake Tanganyika Scale-Eating Cichlid Fish
    Yuichi Takeuchi; Michio Hori; Shinya Tada; Yoichi Oda
    PLOS ONE, 11, 1, e0147476, Jan. 2016, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
    English, Scientific journal
  • Measuring and evaluating morphological asymmetry in fish: Distinct lateral dimorphism in the jaws of scale-eating cichlids
    Hiroki Hata; Masaki Yasugi; Yuichi Takeuchi; Satoshi Takahashi; Michio Hori
    Ecology and Evolution, 3, 14, 4641, 4647, 14, Nov. 2013, [Peer-reviewed], [International Magazine]
    English, Scientific journal
  • Relation Between Morphological Antisymmetry and Behavioral Laterality in a Poeciliid Fish
    Shoko Matsui; Yuichi Takeuchi; Michio Hori
    ZOOLOGICAL SCIENCE, 30, 8, 613, 618, Aug. 2013, [Peer-reviewed], [International Magazine]
    English, Scientific journal
  • Morphological asymmetry and behavioral laterality in the crayfish, Procambarus clarkii
    Shoko Tobo; Yuichi Takeuchi; Michio Hori
    ECOLOGICAL RESEARCH, 27, 1, 53, 59, Jan. 2012, [Peer-reviewed], [Corresponding author], [International Magazine]
    English, Scientific journal
  • Lateralized Kinematics of Predation Behavior in a Lake Tanganyika Scale-Eating Cichlid Fish
    Yuichi Takeuchi; Michio Hori; Yoichi Oda
    PLOS ONE, 7, 1, e29272, Jan. 2012, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
    English, Scientific journal
  • Nest site selection and nesting biology of Rock Ptarmigan Lagopus muta japonicus in Japan
    Yusuke Sawa; Yuichi Takeuchi; Hiroshi Nakamura
    BIRD STUDY, 58, 2, 200, 207, 2011, [Peer-reviewed], [International Magazine]
    English, Scientific journal
  • A 20-year census of a rocky littoral fish community in Lake Tanganyika
    Y. Takeuchi; H. Ochi; M. Kohda; D. Sinyinza; M. Hori
    ECOLOGY OF FRESHWATER FISH, 19, 2, 239, 248, Jun. 2010, [Peer-reviewed], [Lead author, Corresponding author], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Lateral bias of agonistic responses to mirror images and morphological asymmetry in the Siamese fighting fish (Betta splendens)
    Yuichi Takeuchi; Michicl Hori; Omar Myint; Masanori Kohda
    BEHAVIOURAL BRAIN RESEARCH, 208, 1, 106, 111, Mar. 2010, [Peer-reviewed], [Lead author, Corresponding author], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Behavioural laterality in the shrimp-eating cichlid fish Neolamprologus fasciatus in Lake Tanganyika
    Yuichi Takeuchi; Michio Hori
    ANIMAL BEHAVIOUR, 75, 1359, 1366, Apr. 2008, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
    English, Scientific journal
  • Morphological asymmetry of the abdomen and behavioral laterality in atyid shrimps
    Yuichi Takeuchi; Shoko Tobo; Michio Hori
    ZOOLOGICAL SCIENCE, 25, 4, 355, 363, Apr. 2008, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
    English, Scientific journal
  • Spatial density-dependent survival and development at different larval stages of the tiger beetle Cicindela japonica (Thunberg)
    Yuichi Takeuchi; Michio Hori
    POPULATION ECOLOGY, 49, 4, 305, 316, Oct. 2007, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
    English, Scientific journal
  • Color discrimination at the spatial resolution limit in a swallowtail butterfly, Papilio xuthus
    Yuichi Takeuchi; Kentaro Arikawa; Michiyo Kinoshita
    JOURNAL OF EXPERIMENTAL BIOLOGY, 209, 15, 2873, 2879, Aug. 2006, [Peer-reviewed], [Lead author], [International Magazine]
    English, Scientific journal
■ Other Activities and Achievements
■ Books and other publications
  • Behavioral Laterality in the Scale-Eating Cichlid Fish: Detailed Movement, Development, and Neuronal Mechanisms
    Behavioral Laterality in the Scale-Eating Cichlid Fish: Detailed Movement, Development, and Neuronal Mechanisms
    Springer, 24 Jul. 2022, 9811913404, 307, [Contributor]
  • スポーツが得意な子に育つ たのしいお話365
    竹内 勇一, 「利き手」はどうやって決まるの？
    誠文堂新光社, Feb. 2019, [Contributor]
  • 魚類学の百科事典
    竹内 勇一, 【6章】行動： 逃避行動
    丸善出版, Oct. 2018, [Contributor]
  • 調べる学習子ども年鑑2018
    竹内 勇一, 気になるニュース９月 課外活動
    岩崎書店, Mar. 2018, [Others]
  • 子供の科学 2018年2月号
    竹内 勇一, なぜ？なぜ？どうして？
    誠文堂新光社, Feb. 2018, [Others]
  • ブレインサイエンス・レビュー2015
    竹内 勇一, 右利きと左利きの脳内制御機構
    クバプロ, Feb. 2015, 9784878051401, [Contributor]
  • もっと！科学の宝箱
    竹内 勇一, "利き手"は進化の証!?
    講談社, Jul. 2014, 9784062183574, [Contributor]
  • 魚類行動生態学入門
    桑村 哲生; 安房田 智司
    東海大学出版会, 2013, 9784486020110, Japanese
■ Syllabus
  • 大学院共通授業科目（教育プログラム）：脳科学研究の展開, 2024年, 修士課程, 大学院共通科目
  • 行動システム制御科学特論, 2024年, 修士課程, 生命科学院
  • 科学・技術の世界（1単位）, 2024年, 学士課程, 全学教育
  • 行動神経生物学b, 2024年, 学士課程, 理学部
  • 行動神経生物学Ⅱ, 2024年, 学士課程, 理学部
  • ISP生物科学実習Ⅱ・a, 2024年, 学士課程, 理学部
  • ISP生物科学実習Ⅱ・b, 2024年, 学士課程, 理学部
  • 行動神経生物学実習, 2024年, 学士課程, 理学部
  • 行動神経生物学実習, 2024年, 学士課程, 理学部
  • 機能生物学Ⅱ, 2024年, 学士課程, 理学部
  • 生物学Ⅱ, 2024年, 学士課程, 全学教育
  • 脳と行動の進化, 2024年, 学士課程, 理学部
  • 行動神経生物学Ⅱc, 2024年, 学士課程, 理学部
  • 生物学特別講義Ⅲ, 2024年, 学士課程, 理学部
  • 生物学特別講義Ⅲ, 2024年, 学士課程, 理学部
■ Affiliated academic society
  • JAPAN ETHOLOGICAL SOCIETY
  • THE JAPAN NEUROSCIENCE SOCIETY
  • THE ZOOLOGICAL SOCIETY OF JAPAN
  • THE ECOLOGICAL SOCIETY OF JAPAN
■ Research Themes
  • 古代湖産魚類の多様な摂食行動と口部骨格の進化に対する力学的機能からの新解釈
    科学研究費助成事業
    27 Jun. 2025 - 31 Mar. 2028
    田原 大輔; 竹内 勇一; 丸山 敦
    日本学術振興会, 挑戦的研究(萌芽), 龍谷大学, 25K22495
  • Neural mechanisms of navigation that utilize the laterality in predation behavior
    Grants-in-Aid for Scientific Research
    01 Apr. 2024 - 31 Mar. 2026
    竹内 勇一
    Japan Society for the Promotion of Science, Grant-in-Aid for Transformative Research Areas (A), Hokkaido University, 24H01418
  • Ecomorphology driving adaptive radiation of cichlid fish in the three great ancient lakes of Africa
    Grants-in-Aid for Scientific Research
    08 Sep. 2023 - 31 Mar. 2026
    畑 啓生; 丸山 敦; 竹内 勇一; ZIADI Fabienne; 八杉 公基; 田原 大輔; 佐藤 駿
    Japan Society for the Promotion of Science, Fund for the Promotion of Joint International Research (International Collaborative Research), Ehime University, 23KK0131
  • Comprehensive elucidation of neural mechanisms controlling lefty and righty in scale-eating fish
    Grants-in-Aid for Scientific Research
    01 Apr. 2023 - 31 Mar. 2026
    竹内 勇一
    片眼の機能的優位性について、視覚刺激誘導性反応から検証した。鱗食魚１匹を入れた細長い水槽の両側にモニター２台を置き、片眼ごとにルーミング刺激を与えて逃避反応を記録した。その結果、左利き個体はランダムよりも右眼からの刺激に、右利き個体は左眼からの刺激により反応して、利き間では有意な違いがあった。すなわち、開口側の眼は視覚刺激に反応しやすいという、感覚機能の優位性をもつと考えられる。
    次に、捕食時に片眼を使えないようにするために、メタノールを眼球注射して人工的に白内障を促す処理（視覚阻害処理）をして、捕食実験を行った。開口側の眼（右利き個体の左眼、左利き個体の右眼）を阻害した場合、処理前には９割以上だった利き側からの襲撃が、処理後は５割にまで低下し、捕食成功率も大きく低下した。さらに運動解析から、利き側襲撃でみられる獲物に噛みつく胴の屈曲運動において、処理後では角速度と屈曲角度の変化量が大きく低下していた。開口側の視覚阻害により、襲撃の正確なタイミングがとれないと示唆される。一方で、開口側とは反対側の眼を阻害した場合は、処理前後で襲撃方向が変化した個体はおらず、処理後も開口側から９割以上襲い、捕食成功率も維持されていた。したがって、開口側の単眼視野が捕食行動にとって重要な利き眼であることが分かった。
    さらに、視覚阻害後に変化した捕食行動が捕食経験で変化するのかを明らかにするため、幼魚・若魚・成魚を用いて、数日おきに捕食実験を計5回行った。幼魚と若魚では、処理前には8割以上だった利き側からの襲撃が、処理直後は3割にまで低下し、捕食成功率も大きく低下した。一方、成魚では処理後においても本来の利き側から襲撃する傾向が残っていた。捕食実験を5回繰り返すと、幼魚は襲撃方向の好みが反転したが、成魚では経験による変化は見られなかった。以上より、発達依存的な可塑性の存在が示唆された。
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 23K05960
  • Brain mechanism controlling righty and lefty
    Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    01 Apr. 2020 - 31 Mar. 2023
    竹内 勇一
    利きの発達過程について大きな進展があり、原著論文１報を発表した。
    *Yuichi Takeuchi, Yuna Higuchi, Koki Ikeya, Masataka Tagami & Yoichi Oda. Experience-dependent learning of behavioral laterality in the scale-eating cichlid Perissodus microlepis occurs during the early developmental stage. Scientific Reports. 12: 723. 2022.


    私たちの利き手のように、数多くの動物たちにも、身体の左右一方をよく使う利き現象が見られる。利きは発達段階のいつ・どのように獲得されるのだろうか？一般に利きの確立過程を明らかにするには、長期にわたる追跡調査、遺伝要因の解析や生後発達における経験のコントロールが必要で、どのようなルールに基づいて利きが獲得されるのかは、長年の謎だった。
    利きのモデル動物画である鱗食魚は、鱗食経験に応じて襲撃方向の好み（利き）が強化される。では、学習する機会があればいつでも利きは確立できるのか、鱗食未経験の幼魚（4ヶ月齢）・若魚（8ヶ月齢）・成魚（12ヶ月齢）を用いて分析した。どの時期の魚も、初めは左右からランダムに獲物を襲ったが、幼魚は経験を重ねるごとに、生まれつきの顎の形に対応した側から襲撃するようになり、最終的に8割が利きを獲得し、若魚も5割は利きを獲得できた。一方、成魚は実験を繰り返してもランダムなままで、1匹も利きを獲得しなかった。つまり、利き獲得には発達初期における鱗食経験が必須、という利き獲得の感受性期を初めて実証した。
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), University of Toyama, 20K06851
  • Diversification of feeding strategies and coexistence of cichlid fishes in African ancient lakes
    Grants-in-Aid for Scientific Research Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))
    09 Oct. 2018 - 31 Mar. 2023
    丸山 敦; 畑 啓生; 竹内 勇一; ZIADI Fabienne; 八杉 公基
    群集レベルの研究では、タンガニイカ湖の沿岸岩礁帯で得られた群集動態データに対してEDM解析を行い、種間関係が抽出された (丸山ほか)。プロジェクト外の専門家も交えた研究会を繰り返して解析方法を精査し、投稿論文が仕上がりつつある。同源データに対しては微空間スケールでのGIS解析も行い、各種が選ぶ生息空間の詳細情報についても更新されつつある(畑ほか)。マイクロCT撮影と3Dモデル解析による食性と摂食形態の関係性についても、対象骨の内部微細構造や骨密度の算出など、プロジェクト外の専門家を交えた新しい解析が進展した(丸山ほか)。種ごとの食性と左右性の関係性についても分析データが蓄積されたが(竹内ほか)、Covid-19によって試料の追加収集は阻まれており、その影響は否定しきれない。
    個体レベルの研究では、左右性研究のモデル種であるタンガニイカ産鱗食魚を中心に、(Covid-19に最も大きな影響を受けつつ) マイクロCT撮影を活かした左右性指標の算出の標準化が進み、従来の測定法との比較に基づく新手法の利点の抽出も整理されつつある(Ziadiほか)。発達に伴う左右性強度の変化や要因を探る飼育実験や脳科学的アプローチも、プロジェクト外縁部の成果として公表された(竹内ほか)。3Dモデルの水中投影を活かした画期的飼育実験システムの提案は、当該種の3D撮影とモデル作成に成功したものの、行動の再現性を高める際の課題を埋める実験は、Covid-19対策としての人流抑制に阻まれた(八杉ほか)。マラウイ産鱗食魚の左右性に関する研究は、 胃内容物を確認するための現地調査がCovid-19に阻まれているものの、現地協力者を介した入手が奏功し、画期的な発見の兆しがある(竹内ほか)。
    以上の成果や課題は2022年3月2日・4日開催のオンライン拡大プロジェクト会議で共有され、今後の研究推進方策も話し合われた。
    Japan Society for the Promotion of Science, Fund for the Promotion of Joint International Research (Fostering Joint International Research (B)), Ryukoku University, 18KK0208
  • The brain mechanisms regulated righty and lefty in a scale-eating fish
    Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
    01 Apr. 2017 - 31 Mar. 2020
    Takeuchi Yuichi
    We investigated the neural elements, developmental processes, and genetic basis for laterality in the scale-eating fish, Perissodus microlepis, of Lake Tanganyika. Aiming at whether there is a laterality in scale-eating behavior (i.e., attack side preference) for the first time after birth, a predation experiment was carried out using naive juveniles raised only on artificial feed. The attack side preference of the first day of scale-eating was relatively weak but the strengthened by repeated predation. That is, this behavioral laterality is acquired based on the scale-eating experience. In addition, the brain genes related to the difference between lefty and righty fish and the two hemispheres were analyzed by RNA-seq. We identified a gene that is characteristic of the right or left hemisphere. Among them, genes involved in left-right axis determination in the early embryo were included, suggesting that they are involved in the maintenance of left-right difference in the adult brain.
    Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), University of Toyama, 17K14934
  • Ecological study on acquisition of lateralized behavior
    Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    01 Apr. 2015 - 31 Mar. 2018
    Oda Yoichi
    This study aimed to reveal the developmental process of laterality in morphology and feeding behavior of scale-eating cichlids, Perissodus microleps (P.m.) in Lake Tanganyika and Genyochromis mento (G.m.) in Lake Malawi. We collected these cichlids and analyzed the scales found inside the stomach and lower jaw morphology of them. Results indicated that both cichlids showed attack side preference corresponding to the left-right difference of mouth morphology. Further, we successfully bred P.m. in aquarium and found that P.m. had an innate kinematic laterality and that the attach side preference was gradually strengthened through scale-eating experience. We also succeeded in observing prey attach of G.m. in aquarium. The degree of attack side preference and the mouth asymmetry of G. m. was relatively weaker than that of P.m. Taken together, it is suggested that these cichlids develop, through experience, the lateralized hunting of prey fish by using their lateralized mouth.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Nagoya University, 15H05230
  • Component and mechanism of lefty/right in the scale-eating cichlid fish
    Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
    01 Apr. 2014 - 31 Mar. 2016
    Takeuchi Yuichi
    The scale-eating cichlid Perissodus microlepis with asymmetric mouth exhibit extreme behavioral laterality in predation: each adult robs scales from its prey fishes’ left or right flanks according to the direction in which its mouth is skewed. To clarify the neuronal mechanisms of behavioral laterality in predation, I examined the expression analysis of immediate early gene (Arc) after predation, and stomach contents and lower jaw-bone asymmetry of various-sized P. microlepis (22Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), University of Toyama, 26830009
  • 鱗食魚が示す顕著な左右性行動の神経基盤
    科学研究費助成事業 研究活動スタート支援
    30 Aug. 2013 - 31 Mar. 2015
    竹内 勇一
    様々な動物でみられる右利き・左利きはどのような要因によって決定されるのだろうか？利きの研究が最も進んでいるヒトの利き手ですら、優位性の決定機構の解明は十分でない。発達を通じて左右性がいつ・どのように現れるのかを明らかにすることは、その謎に対して有益な示唆を与えてくれるだろう。捕食行動に顕著な左右性を示す、タンガニイカ湖産鱗食魚（Perissodus microlepis）は、口部形態にも捕食行動と対応する左右非対称性をもち、種内に右利きと左利きが存在することで知られている。しかし、本種の左右性に関する研究は成魚に限られており、捕食行動の左右性と口部形態の左右差の発達過程は不明であった。
    そこで、我々は様々な発達段階の鱗食魚を野外で採集した。下顎骨の左右差を計測した結果、プランクトン食である稚魚期でも、その左右差の頻度分布は明瞭な左右二型を示すが、体長とともにその左右差は拡大し、成魚では稚魚期の約3倍に達した。また鱗食魚の胃から得られた鱗の形状を精査して鱗の由来する体側を割り出し、捕食行動の左右性を推定した。成魚では、口部形態の利きと合致した体側の鱗を専食していた。一方で、小さな鱗食魚では、それとは逆側の鱗も少し摂食していた。さらに、口部形態が偏っているほど、捕食行動の左右性が顕著で摂食鱗数が多いことが分かった。これは鱗食魚の口部形態の左右差が捕食において有利となるという仮説を初めて裏付けている。
    今回の結果から、口部形態の左右差が捕食行動の左右性の獲得前から発現していることが明らかとなり、遺伝的背景があることが示唆された。また、発育初期では両方の体側から襲うが、その過程で形態の利き側からの方が捕食成功率が高いことを学習し、捕食行動が利き側に偏っていくことが考えられた。一方で、環境要因（学習・経験）は、左右性の強さを変化させる可能性がある。
    日本学術振興会, 研究活動スタート支援, 富山大学, 25890006
  • Ecological and Physiological Basis underlying Acquisition of Behavioral Laterlity
    Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    01 Apr. 2012 - 31 Mar. 2015
    ODA Yoichi; HORI Michio; TAKEUCHI Yuichi
    The skewed-mouthed scale-eating cichlid Perissodus microlepis in Lake Tanganyika is an attractive model of behavioural laterality: each adult robs scales from its prey fishes’ left or right flanks according to the direction in which its mouth is skewed. To investigate the development of behavioural laterality and mouth asymmetry, we analysed stomach contents and lower jaw-bone asymmetry of various-sized P. microlepis sampled in the southern tip of the Lake. The shapes of the pored scales found in each specimen’s stomach indicated its attack side preference. Early-juveniles (SL <45mm) feeding on zooplankton exhibited slight mouth asymmetry. After scale-eating began, the attack side preference was gradually strengthened, as did mouth asymmetry. Our findings show that mouth asymmetry in P. microlepis precedes behavioural laterality, which is established in association with mouth development, and suggest that physical and behavioural lateralities confer a synergistic advantage.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Nagoya University, 24405001
  • 淘汰の基盤となる左右性行動の神経基盤
    科学研究費助成事業 特別研究員奨励費
    2010 - 2012
    竹内 勇一
    鱗食魚Perissodus microlepisの捕食行動の左右性の獲得過程を明らかにするために、野外採集された様々な発達段階の鱗食魚(稚魚期～若魚期～成魚)の胃内容分析を行い、摂食していた鱗の形状を精査して捕食行動の左右性を推定した。分析の結果、鱗を食べ始めてすぐから口部形態に合った体側由来の鱗を主に摂食していたので、捕食行動の左右性は遺伝的な影響を受けていると示唆された。また、稚魚期から若魚期の移行期では、口部形態と合わない鱗を摂食していた個体も見られたが、体長の増加とともに口部形態と合う体側の鱗を摂食していた比率が高まり、成魚ではほぼ一方向に偏ることを見出した。これは、成長過程における捕食行動の学習によって利きが発達する可能性を示す重要な結果であろう。
    また、捕食時にM細胞が活動しているかどうかを検証するために、神経活動に付随して発現する初期応答遺伝子の発現を検出する方法を確立した。これまでに、同じシクリッド科であるティラピアOreochromis niloticusのゲノムデータベースを用いて、M細胞を同定するためのChAT(コリン作動性ニューロンのマーカー)と、活動計測のための2種類の初期応答遺伝子c-fos,egr1のプローブを作成し、in situ hybridizationを行うに至った。現在、捕食させた個体とコントロール個体、右利き個体と左利き個体の間で、網羅的かつ詳細な解析を行っている。
    日本学術振興会, 特別研究員奨励費, 名古屋大学, 10J07689