Anguillicola crassus
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| Anguillicola crassus Kuwahara, Niimi and Hagaki, 1974 |
Anguillicola crassus is a parasitic nematode worm that lives in the swimbladders of eels (Anguilla spp.) and appears to spread easily among eel populations after introduction to a body of water. It is considered to be one of the threats to the sustainability of populations of European eel (Anguilla anguilla). It was introduced to the European continent in the 1980s, where it was reported independently from Germany and Italy in 1982, having probably been introduced from Japan. It is thought to have reached England in 1987 from continental Europe. It is a natural parasite of the Japanese eel in its native range.
The life cycle of A. crassus begins when the adult nematode releases thousands of eggs in the eel's swimbladder. The eggs pass through the eel's digestive tract and the larvae emerge in the water and settle onto the substrate. They are ingested by their intermediate host, which is often a copepod or other crustacean but may also be a fish. The nematode larva reaches its infective stage within this intermediate host. The host is eaten by an eel, and the nematode finds its way from the eel's digestive tract to its swimbladder. An eel with an advanced parasite load shows symptoms such as bleeding lesions and swimbladder collapse. The eel becomes more susceptible to disease, its rate of growth slows, and if the infestation is severe enough, it may die. Since the swimbladder is the buoyant organ which allows the eel to swim, a severe parasite infestation can hamper its ability to reach its spawning grounds.
The state of being colonized by Anguillicola nematodes is termed anguillicolosis.
[edit] Further reading
- Kennedy, C.R. (1993). Introductions, spread and colonization of new localities by fish helminth and crustacean parasites in the British Isles: a perspective and appraisal. Journal of Fish Biology, 43: 287-301.
- Kennedy, C.R., & Fitch, D.J. (1990). Colonisation, larval survival, and epidemiology of the nematode Anguillicola crassus, parasite in the eel Anguilla anguilla in Britain. Journal of Fish Biology, 36: 117-131.
- Koops, H., & Hartmann, F. (1989). Anguillicola infestations in Germany and in German eel imports. Journal of Applied Ichthyology, 1: 41-45.
