Lernaea cyprinacea

From Fish
Anchor worm (arrow) parasitizing the goldfish.
Adult male of Lernaea cyprinacea

Lernaea cyprinacea (Anchor worm) is a copepod parasite that infects many freshwater fishes including common carp (Cyprinus carpio), goldfish (Carassius auratus), Japanese eel (Anguilla japonica) and oriental weatherfish (Misgurnus anguillicaudatus).

It parasitises the skin, buccal cavity wall (in Japanese eel and oriental weatherfish).

Life cycle

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). 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 host’s 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.

Clinical signs

Clinical signs are associated with stress due to infestation.

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[1].

Since this parasite is not infectious to human, it is harmless in food hygiene.


Diagnosis is based on observation of Lernaea copepods. Besides Lernaea cyprinacea, only L. parasiluri, a parasite of Amur catfish Silurus asotus, is reported in Japan[2].

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[3][4].


  1. 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
  2. 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
  3. Noga, E. J. (1996) ‘Fish Disease: Diagnosis and Treatment’, Mosby-Year Book, Inc., Missouri, p:367
  4. Piasecki, W., A. E. Goodwin, J. C. Eiras and B. F. Nowak (2004) Importance of copepoda in freshwater aquaculture. Zool Studies 43:193-205