| Parasite | Salmincola spp. |
|---|---|
| Taxonomy | Arthropoda, Crustacea, Copepoda, Siphonostomatoida |
| Hosts | Masu salmon (Oncorhynchus masou), Japanese char (Salvelinus pluvius), Japanese huchen (Hucho perryi) |
| Infection site | Bucal cavity wall, Branchial cavity wall |
| Clinical signs | White parasites are observed in the bucal cavity (Fig. 1). |
| Parasitology | Visually observed adults are females, which attach to the host’s tissues by a unique holdfast, known as the ‘bulla’ (Fig. 3), and possess a pair of long egg sacs at the posterior end (Fig. 2 and 4). Dwarf adult males which attach to the female, die after copulation. Hatched copepodid infects to the host and becomes chalimus followed by an adult stage. Salmincola californiensis infects to masu salmon and red-spotted masu salmon; Salmincola carpionis to Japanese char; Salmincola stellatus to Japanese huchen (Nagasawa and Urawa, 2002). |
| Pathology | Pathogenic effects to host are low in light infection, though the host tissues surrounding the bulla become hypertrophy. Salmincola californiensis gives a damage to the gill filaments since it parasitizes the branchial cavity (Nagasaw and Urawa, 2002; Nagasawa, 2006). Spawning activity of rainbow torut may be adversely affected (Gall et al., 1972). |
| Health hazard | Since this parasite is not infectious to human, it is harmless in food hygiene. |
| Diagnosis | Check adult parasites by the morphological observations. |
| Other information | The parasites are occasionally observed in salmonid fishes in aquaria and fish farms. Ivermectin and manual removal of parasites are useful for treatment of infected fishes (Roberts et al., 2004). |
| References | Gall, G. A. E., E. L. McClendon and W. E. Schafer (1972): Evidence on the influence of the copepod (Salmincola californiensis) on the reproductive performance of a domesticated strain of rainbow trout
(Salmo gairdneri). Trans. Am. Fish. Soc., 101, 345-346. Nagasawa, K. (2006): Salmincolosis. New atlas of fish diseases (Hatai K. and K. Ogawa), Midori Shobo, p. 45. (In Japanese) Nagasawa, K. and S. Urawa (2002): Infection of Salmincola californiensis (Copepoda: Lernaeopodidae) on juvenile masu salmon (Oncorhynchus masou) from a stream in Hokkaido. Bull. Natl. Salmon Resources Center, 5, 7-12. Roberts, R. J., K. A. Johnson and M. T. Casten (2004): Control of Salmincola californiensis (Copepoda: Lernaeapodidae) in rainbow trout, Oncorhynchus mykiss (Walbaum): a clinical and histopathological study. J. Fish Dis., 27, 73-79. |
(Photos by T. Awakura (1, 2, 3), S. Urawa (4))
Fig. 4.. S. californiensis from masu salmon
Fig. 1. S. stellatus (arrows) on Japanese huchen
Fig. 3. Bulla of S. stellatus
Fig. 2. Adults of S. stellatus from Japanese huchen
