| Parasite | Unidentified turbellarian |
|---|---|
| Taxonomy | Plathyhelminthes, turbellaria |
| Hosts | Devil stinger (Inimicus japonicus), viviparous scorpionfish (Sebasticus marmoratus) |
| Infection site | Gill, skin, fin |
| Clinical sign | Diseased fish exhibit anorexia, clouded body and gill necrosis. |
| Parasitology | Many tubellarians (ca. 0.1-1.0 mm) parasitize the body surface and the gill (Fig. 1 and 2). A mature parasite detaches and produces 100-200 larvae. The longevity of swimming larvae is within 24 hours (Fukuda, 2006). It is possible that the detached adult can parasitize a new host again (Fukuda et al., 2006). Experimentally, this parasite can transmit also to viviparous scorpionfish. |
| Pathology | Diseased fish show the increased mucus secretion in the body surface. Heavily infested fish die due to the necrosis and destruction of the gill tissue. |
| Health hazard | Since this parasite is not infectious to human, it is harmless in food hygiene. |
| Diagnosis | Observe the morphology of the parasite in a flattened preparation. |
| Other information | Mass mortalities (cumulative mortality above 90 %) are observed in the devil stinger cultured in the flow-through pond from October to November (water temp. 20-22 C) (Fukuda, 2006). It is recommended to improve the water exchange in the bottom and move the fish to an offshore net-pen temporally because the parasite produces larvae in the bottom of pond. |
| References | Fukuda, Y. (2006):
Turbellarian disease in divil stinger Inimicus japonicas. Aqua
Culture Magazine, 546 (Dec.), p.41. (In Japanese) Fukuda, Y., Y. Miyoshi and K. Ogawa (2006): A turbellarian infection of cultured devil stinger Inimicus japonicas accompanied by mass mortality. Abstract of the meeting of the Japanese Society of Fish Pathology in 2006, p. 40. (In Japanese) |
Fig. 1. Turbellarians (arrows) attaching on the skin.
Fig. 2. Heavy infection of turbellarians (arrows) in the gill.
(Photos by Y. Fukuda)