PhD Environmental Science, Hokkaido University (Japan), 2024
MSc Environmental Science, Hokkaido University (Japan), 2021
BSc Fisheries, Hokkaido University (Japan), 2019
Email: ryotahase344922@gmail.com
Evolutionary and Ecological Parasitology Research Group
Research interests
- Ecology and Taxonomy of parasitic copepods
- Ecology of freshwater fish (mainly salmonids)
- Association between fish body condition and parasite infections
- Parasite community assembly
I’m a parasite ecologist mainly working on host-parasite relationships between salmonid fishes and parasitic copepods of the genus Salmincola, which infects the mouth and gill cavities of their hosts. My focus has been on how copepod infections alter host behaviour, body condition, and survival. Then, my interest shifted to parasite-parasite interactions within individual hosts and their consequences on host ecology. Here in Dunedin, I’m currently working on whether priority effects contribute to creating trematode communities in amphipod hosts and their consequences for host fitness and ecosystem functioning.
Current postdoctoral project
Priority effects in parasite community assembly and its consequences on amphipod host fitness and ecosystem functioning
(JSPS Overseas Research Fellow; Japanese Society of Proportion of Science)
Publications
Hasegawa, R., & Koizumi, I. (2024). Consistent negative correlations between parasite infection and host body condition across seasons suggest potential harmful impacts of Salmincola markewitschi on wild white-spotted charr, Salvelinus leucomaenis. Zoological Science, 41, 192–200. doi: 10.2108/zs230028
Hasegawa, R., & Koizumi, I. (2023). Parasites either reduce or increase host vulnerability to fishing: a case study of a parasitic copepod and its salmonid host. The Science of Nature 110, 10. doi: 10.1007/s00114-023-01836-x
Hasegawa, R., Katahira, H., & Koizumi, I. (2022). Salmincola markewitschi (Copepoda: Lernaeopodidae) or S. carpionis ? taxonomic confusion due to high morphological variations and a requirement for revising their taxonomic status. Folia Parasitologica 62, 025. doi: 10.14411/fp.2022.025
Hasegawa, R., & Nitta, M. (2022). Rediscovery of Lernaeenicus ramosus Kirtisinghe, 1956 (Copepoda: Pennellidae) parasitizing the type host, comet grouper Epinephelus morrhua (Perciformes: Serranidae) from the Japanese coast, with a note on its underdeveloped head.
Biogeography 24, 17–23. doi: 10.11358/biogeo.24.25
Hasegawa, R., Ayer, C. G., Umatani, Y., Miura, K., Ukumura, M., Katahira, H., & Koizumi, I. (2022). Potential negative effects and heterogeneous distribution of a parasitic copepod Salmincola edwardsii (Copepoda: Lernaeopodidae) on Southern Asian Dolly Varden Salvelinus curilus in Hokkaido, Japan. Parasitology International, 87, 102529. doi: 10.1016/j.parint.2021.102529
Hasegawa, R., & Koizumi, I. (2021). Relative importance of host dependent vs. physical environmental characteristics affecting the distribution of an ectoparasitic copepod infecting the mouth cavity of stream salmonid. Ecological Research, 36, 1015–1027. doi: 10.1111/1440-1703.12262
Hasegawa, R., Yamada, H., Ishihara, C., & Wada, S. (2020). Personality differences in white-spotted char fry evident between habitats.
Japanese Journal of Ichthyology, 67, 11–24. 2020. doi: 10.11369/jji.19-021 (In Japanese with English Abstract.)