DAO 122:13-19 (2016)  -  DOI: https://doi.org/10.3354/dao03064

Spatial variation in the parasitic isopod load of the Japanese halfbeak in western Japan

R. Kawanishi1,*, A. Sogabe2, R. Nishimoto3, H. Hata

1Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Japan
2Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan
3Faculty of Science, Ehime University, Matsuyama, Japan
4Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan
*Corresponding author:

ABSTRACT: Cymothoid isopods (family Cymothoidae) are commonly found parasitizing diverse fishes, including commercial species. However, the effects of these parasites on host body condition are still poorly known. Here we investigated the spatial variation of the effects of parasite infection on host body condition, using the parasitic load of the cymothoid Mothocya parvostis on the Japanese halfbeak Hyporhamphus sajori at 4 sampling sites in western Japan. M. parvostis prevalence at each site (41.6-74.4%) was higher than that known for other fish host-cymothoid systems (usually less than 30%). The number of isopods in infected hosts, the reproductive status of female isopods (i.e. ovigerous/non-ovigerous), and the body size of female and male isopods relative to the size of their hosts were not significantly different among sites. However, at the site where human activity was most intense, M. parvostis infection had a significantly negative effect on host body condition. These results suggest that the effect of cymothoid infection on host body condition might be benign under natural conditions but becomes detrimental in habitats that are unsuitable for the host, such as highly human-impacted areas.

KEY WORDS: Cymothoidae · Gill parasite · Isopod · Mothocya parvostis · Hyporhamphus sajori · Host body condition · Habitat heterogeneity

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Cite this article as: Kawanishi R, Sogabe A, Nishimoto R, Hata H (2016) Spatial variation in the parasitic isopod load of the Japanese halfbeak in western Japan. Dis Aquat Org 122:13-19. https://doi.org/10.3354/dao03064

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