YUKI KONDO

Behavioral & Reproductive Ecology
of Wild Medaka

Linking laboratory experiments and muddy field observations to uncover the reproductive ecology of Oryzias latipes.

Specially-appointed Assistant Professor · Osaka Metropolitan University
Behavioral Ecology · Reproductive Ecology · Sperm Allocation · Field Ethology

ABOUT

Yuki Kondo, Ph.D.

I am a behavioral ecologist working on the reproductive ecology of medaka fish (Oryzias latipes). My research combines aquarium-based experiments with field observations in Gifu, Japan, asking whether patterns discovered in the laboratory actually hold under natural conditions. Recent work has revealed that wild medaka begin courtship and spawning around midnight — overturning the long-held belief that they reproduce only at dawn — and that males flexibly adjust sperm allocation according to female quality, rival presence, and previous mating history.

Position: Specially-appointed Assistant Professor
Affiliation: Department of Biology, Graduate School of Science, Osaka Metropolitan University
Address: 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan

Email: youkikondou[at]omu.ac.jp · youkikondou[at]gmail.com
(Replace [at] with @)

ORCID 0000-0002-1481-6225 · Google Scholar · researchmap · X (@diary_of_yuki)

RESEARCH INTERESTS

From behaviour and reproduction to society

Keywords: Sperm allocation · Mate choice · Sexual conflict · Alternative reproductive tactics · Field ethology

My core question is how males and females resolve evolutionary conflicts over reproduction, and how these mechanisms scale up to social structure in fish. I use 24-hour video monitoring, automated pose tracking, and night-time field surveys to bridge the gap between controlled laboratory experiments and the messy reality of wild populations.

Three thematic lines currently run in parallel:

Sperm economics — how males allocate a finite ejaculate across mating opportunities, and how females respond.
Field-based reproductive ecology — when and where wild medaka actually spawn, often at odds with classical laboratory accounts.
Complex social relationships — individual recognition, shoaling, and territoriality (ongoing JSPS Early-Career project, 2025–2028).

SELECTED PUBLICATIONS

First-author papers

Kondo Y, Ito T, Awata S. Qualitative sperm depletion: successive mating reduces initial sperm velocity in medaka fish. Journal of Ethology. 2026 Apr. Peer-reviewed · Corresponding author
Kondo Y, Kobayashi R, Kobayashi Y, Koya Y, Awata S. Temporal shifts in ovulation between laboratory and semi-natural environments in the model fish medaka. Royal Society Open Science. 2026 Mar; 13(3). Peer-reviewed · Corresponding author
Kondo Y, Kobayashi R, Kobayashi Y, Awata S. Temporal dynamics of courtship and spawning in medaka under laboratory conditions revealed by 24 h video monitoring. Scientific Reports. 2025 Aug; 15(1). Peer-reviewed · Corresponding author
Kondo Y, Awata S. Courtship and spawning behaviour of medaka in a semi-outdoor environment initiating at midnight. Scientific Reports. 2025 May; 15(1). Peer-reviewed · Corresponding author
Kondo Y, Okamoto K, Kitamukai Y, Koya Y, Awata S. Medaka (Oryzias latipes) initiate courtship and spawning late at night: insights from field observations. PLOS ONE. 2025 Feb; 20(2): e0318358. Peer-reviewed · Corresponding author
Kondo Y, Kohda M, Awata S. Male medaka continue to mate with females despite sperm depletion. Royal Society Open Science. 2025 Jan; 12(1). Peer-reviewed · Corresponding author
Kondo Y, Kohda M, Koya Y, Awata S. Sperm allocation in relation to male-male aggression and courtship in an externally fertilizing fish, the medaka. Animal Behaviour. 2023 Aug; 202: 9–19. Peer-reviewed · Corresponding author
Kondo Y, Kohda M, Koya Y, Awata S. Sperm allocation strategies depending on female quality in medaka (Oryzias latipes). Zoological Science. 2020 May; 37(3): 203. Peer-reviewed · Corresponding author

Full publication list (Japanese) →

COAUTHORED

Coauthored papers

Hanya G, Otani Y, Hongo S, Honda T, Okamura H, Higo Y, Yamamoto H, Kurihara Y, Kondo Y, Tanji S, et al. Detection of vertebrate diversity using fly- and leech-derived iDNA. Ecological Research. 2026 Jan; 41(2): e70044.
Koya Y, Kodama M, Maruyama T, Kondo Y. Induction of male courtship behavior by chemical cues released from ovulating female in the medaka, Oryzias latipes. Journal of Experimental Zoology Part A. 2025 Jul; 343(9): 1049–1059.
Kobayashi Y, Kondo Y, Kohda M, Awata S. Active provisioning of food to host sea anemones by anemonefish. Scientific Reports. 2025 Feb; 15(1): 4115.
Hanya G, Yoshihiro S, Yamamoto H, Ueda Y, Kakuta F, Hiraki M, Otani Y, Kurihara Y, Kondo Y, et al. Two-decade changes in habitat and abundance of Japanese macaques in primary and logged forests in Yakushima: interim report. Forest Ecology and Management. 2023 Oct; 545: 121306.
Hanya G, Yoshihiro S, Yamamoto H, Ueda Y, Kakuta F, Hiraki M, Otani Y, Kurihara Y, Kondo Y, et al. Host selection of hematophagous leeches (Haemadipsa japonica): implications for iDNA studies. Ecological Research. 2019 Nov; 34(6): 842–855.

AWARDS

Honors

2025 — Research Award, Kinki Regional Conference, Ecological Society of Japan
2025 — Best Poster Award, 44th Annual Meeting of the Japan Ethological Society
2022 — Best Poster Award, 69th Annual Meeting of the Ecological Society of Japan
2020 — Best Poster Award, 39th Annual Meeting of the Japan Ethological Society

FUNDING

Active and past grants

2025–2028 — JSPS Grant-in-Aid for Early-Career Scientists (PI) — Formation processes of complex social relationships in animals using medaka as a model
2024–2027 — JSPS Grant-in-Aid for Scientific Research (C) (Co-investigator) — Chemical communication in medaka mating behaviour
2022–2024 — JSPS Grant-in-Aid for Research Activity Start-up (PI) — Sperm allocation strategies
2023, 2024 — Sasakawa Scientific Research Grant (PI)

View on KAKEN →

EDUCATION & CAREER

CV timeline

2022.03: Ph.D. in Science, Department of Biology and Geosciences, Graduate School of Science, Osaka City University
2018.04 – 2022.03: Doctoral Program, Graduate School of Science, Osaka City University
2018.03: M.S. in Education, Graduate School of Education, Gifu University
2016.04 – 2018.03: Master’s Program, Graduate School of Education, Gifu University
2016.03: B.S. in Education (School Teacher Training Course), Faculty of Education, Gifu University

Professional societies: Ecological Society of Japan · Japan Ethological Society · Ichthyological Society of Japan · International Society for Behavioral Ecology

Field experience: Yakushima Macaque Survey, NPO Yakushima Wildlife Conservancy (2012–2022) — long-term primate field censuses that shaped my field-oriented research style.

GET IN TOUCH

Open to collaboration

I welcome inquiries about collaborations, invited talks, interviews. The fastest response is by email.