| Parasite | Lernaea cyprinacea (anchor worm) |
|---|---|
| Taxonomy | Arthropoda, Crustacea, Copopoda, Cyclopoida |
| Hosts | Many freshwater fishes including common carp (Cyprinus carpio), goldfish (Carassius auratus), Japanese eel (Anguilla japonica), oriental weatherfish (Misgurnus anguillicaudatus). |
| Disease name | Lernaeosis, anchor worm disease |
| Infection site | Skin, buccal cavity wall (in Japanese eel and oriental weatherfish). |
| Clinical signs | Anchor worm is observed on the skin (Fig. 1). |
| Parasitology | Lernaea cyprinacea is an ectoparasitic crustacean. The head is equipped with horns that anchor the parasite in the subdermal tissues of the host fish. Only females are visually seen (length ca. 10-12 mm) (Fig. 2). A hatched nauplius grows to the first copepodid which settles on a host fish (Kasahara, 1962). Males detach from the host after the copulation. The parasite feeds on hostfs body fluid with its mouth located in the head. It reproduces at >15 C., stops the reproduction and overwinters at <12 C. after 4-5 generation changes. |
| Pathology | Tissues adjacent to the head part of worm become inflamed, which are susceptible to secondary infections of bacteria. In Japanese eel, many Lernaea cyprinacea infect the buccal cavity, impairing the feeding activity of the host fish. |
| Health hazard | Since this parasite is not infectious to human, it is harmless in food hygiene. |
| Diagnosis | Observe the morphology of the adult female. Besides Lernaea cyprinacea, only L. parasiluri, a parasite of Amur catfish Silurus asotus, is reported in Japan (Ogawa, 2004). |
| Other information | Though this parasite gave a serious damage to Japanese eel culture during the early period of aquaculture, few outbreaks have been reported recently since a prevention method using the organophosphorous agent was developed. However, even now, the disease is occasionally found in cultured freshwater fishes and ornamental fishes ( Noga, 1996; Piasecki et al., 2004). |
| References | Noga, E. J. (1996): eFish Disease: Diagnosis and Treatmentf, Mosby-Year
Book, Inc., Missouri, 367 p.
Piasecki, W., A. E. Goodwin, J. C. Eiras and B. F. Nowak (2004): Importance of copepoda in freshwater aquaculture. Zool. Studies, 43, 193-205. Kasahara, S. (1962): Studies on the biology of the parasitic copepod Lernaea cyprinacea LINNAEUS and the methods for controlling this parasite in fish-culture ponds. Contributions of the Fisheries Laboratory Faculty of Agriculture University of Tokyo, 3, 103-196. (In Japanese) Ogawa, K. (2004): Metazoan diseases. Infectious and parasitic diseases of fish and shellfish. (ed. by Wakabayashi, H. and K. Muroga), Koseisha Koseikaku, pp. 381-405. (In Japanese) |
Fig. 2. Adult male of Lernaea cyprinacea.
(Photo by K. Ogawa)
Fig. 1. Anchor worm (arrow) parasitizing the goldfish.