| Parasite | Eudiplozoon nipponicum |
|---|---|
| Taxonomy | Plathyhelminthes, Monogenea, Polypisthocotylea |
| Hosts | Cyprinid freshwater fishes including common carp (Cyprinus carpio) and crucian carp (Carassius auratus). |
| Infection site | Gill |
| Clincal signs | The gills become pale in heavily infected fish. |
| Parasitology | The hermaphroditic adults are permanently fused together, forming a characteristic X-shape. They share the reproductive and digestive systems (Kamegai, 1976). A hatched oncomiracidium larva settles on the gill of a host fish, followed by the transformation into a diporpa larva. The ventral sucker is formed after 3 days and pairing of 2 diporpae occurs after 4 days at 25 C. (Hirose et al., 1987). The parasite attaches by 4 pairs of clamps at the posterior end of the body and feeds on host's blood. |
| Pathology | Infected fish exhibits hypochromic microcytic anaemia characterized by increase of immature erythrocytes (Kawatsu, 1978). In Tribolodon sp., hyperplasia of the gill epithelia and dilation of the gill lamellae were observed around the parasite (Shindo, 1997). |
| Health hazard | Since this parasite is not infectious to human, it is harmless in food hygiene. |
| Diagnosis | Confirm the X-shaped parasite in the gill under a stereomicroscope. |
| Other information | This parasite is the logo of Meguro Parasitological Museum (MPM), because Dr. Satoru Kamegai, the primal curator of MPM, studied on this parasite as his life work. There is a hypothesis that this parasite is the first organism which develops male and female. |
| References |
Hirose, H., H. Akamatsu
and T. Hibiya (1987): On the development of clamps and pairing of diporpae in Diplozoon nipponicum (Monogenea). Bull. Japan. Soc. Sci. Fish., 53, 953-957. Kamegai, S. (1976):
Studies on Diplozoon NORDMANN, 1832.
Proc. Jpn. Soc. Syst. Zool., 49,
1-9. |
Fig. 1. Fused worm of E. nipponicum.
(Photo by K. Ogawa)