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.
Highlights
Dis Aquat Org 122: 13–19, 2016Infection with cymothoid isopods can cause skin lecymothoid species of the genus Mothocya (M. parsions and anemia, and it can increase the cost of vostis Bruce, 1986 and M. sajori Bruce, 1986)
Among the 161 Japanese halfbeak individuals collected from the 4 sites, 87 were parasitized by Mothocya parvostis (Table 1): 17 fish carried 1 isopod and 69 fish carried 2 isopods in the gill cavities
The present study revealed that the effect of Mothocya parvostis infection on host body condition varied among sampling sites and was only negative in Mitsuhama, where infected fish showed lower relative weight than uninfected fish
Summary
Infection with cymothoid isopods can cause skin lecymothoid species of the genus Mothocya (M. parsions and anemia, and it can increase the cost of vostis Bruce, 1986 and M. sajori Bruce, 1986). The aim of the present study fection does not influence the growth and body condiwas to determine the spatial variation in cymothoid tion of hosts For this purpose, Japanese halfbeak individuals were studies have found that cymothoid infection significollected from 4 sites in western Japan, presenting cantly deteriorates host condition The 34° 20’ N effect of cymothoid isopods on fish might show spatial variation across Yoshimi host and parasite distributional ranges This issue has received little attention in Kanmon most fish−cymothoid systems studied, Seto Inland Sea. Straits Sala-Bozano et al (2012) discussed possible spatial variation in cyJapan. Geographic location of fish sampling sites (open circles) in western
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