Parasitic on Japanese Halfbeak, Hyporhamphus Sajori, in the Central
RESEARCH ARTICLES Nature of Kagoshima Vol. 47 Mothocya parvostis (Isopoda: Cymothoidae) parasitic on Japanese halfbeak, Hyporhamphus sajori, in the central Seto Inland Sea, Japan, with a brief summary of the hosts, geographical distribution, and pathogenic effects of the isopod Kazuya Nagasawa1,2 1Graduate School of Integrated Sciences for Life, Hiroshima University, 1–4–4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739–8528, Japan 2Aquaparasitology Laboratory, 365–61 Kusanagi, Shizuoka 424–0886, Japan Abstract fish in Far East Asia (Nakabo, 2018), being commer- Two females and two males of the cymothoid iso- cially caught in coastal fisheries of Japan (Sadakata et pod Mothocya parvostis Bruce, 1986 were found on al., 1998; Tsuji and Sadakata, 2000). The male and fe- two of three individuals of Japanese halfbeak, Hyporh- male of the species grow up to 26–29 and 31–36 cm in amphus sajori (Temminck and Schlegel, 1846), from total length, respectively, and their life span is two the central Seto Inland Sea off Ikunoshima Island, Hi- years (Nakabo, 2018). roshima Prefecture, Japan. Each infected fish hosted a Since the 1930’s, a cymothoid infection has been female and a male of M. parvostis in the right and left recorded from Japanese halfbeak in Japan. The cy- branchial cavities, respectively. The female and the mothoid isopod from the fish had been identified as male of M. parvostis collected are briefly described. Irona melanosticta (Schioedte and Meinert, 1884) (Hi- To date, M. parvostis has been reported only from Ja- raiwa, 1934; Inouye, 1941; Shiino, 1951, 1965; Oga- pan, where the species occurs in the eastern East China wa, 1952; Hattori and Seki, 1956; Nunomura, 1981: Sea, the southern Sea of Japan, the Seto Inland Sea, 55) or Irona sp.
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