Anchor Worm
| The Anchor Worm, Lernaea is a parasitic crustacean that is usually seen on freshly purchased fishes, but can become a nuisance during the summer in a garden pond. Recently imported coldwater fishes, especially goldfish, are most likely to be affected. Heavy infestations of Anchor Worm can severely debilitate the host fish and make it more vulnerable to secondary bacterial and fungal infections. It is the female anchor worms which are commonly found parasitising fishes.
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 The Anchor Worm is commonly seen on freshly purchased fishes.
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Male Lernaea have a quite short life-span and die after mating.
The females appear as small whitish, stiff worms attached to various parts of the body of a fish. Sometimes they have a greenish appearance as they can become coated with algae. Females are characterised by two egg sacs, which appear at the posterior end of their body. The barbed heads of the Anchor Worm are embedded deeply into the muscle of the fish and a swelling or ulcer-like patch appears at this point.
The life-cycle of the Anchor Worm is fairly straightforward. The females that are embedded in the body of a fish, once mature, release eggs into the water from their egg sacs. The juvenile stage is free-swimming and must find a host fish within a few days if it is to survive. Subsequent stages are parasitic and moult, eventually turning into adults and mating. The life-cycle takes 25 days to complete at 20°C, the ideal temperature. Often at lower temperatures, especially below 18°C it may not be completed.
Adult anchor worms that are attached to fish must be removed carefully with a pair of tweezers. Hold the afflicted fish firmly in a damp soft cloth and then carefully withdraw each worm, gripping it near the point of attachment to its host. Treat the open wound with a suitable antiseptic. There are specific treatments, usually based upon metrifonate, which can be used in the water to destroy the free-swimming juvenile stage.
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