| Lernaea 
Photo used with the kind permission of Doc Johnson www.koivet.com
Lernaea, commonly known as anchor worm, is a large crustacean parasite. As these copepods have lost their articulated appearance and have elongated they now resemble a worm more than they do a crustacean. The name anchor worm comes from the way the females embed their anterior end in the host fishes flesh with the aid of a special organ known as the holdfast, thus anchoring it in place. Lernaea have a direct life cycle, needing no intermediate hosts. The female develops two distinctive egg sacs which gives her a Y or T shaped appearance. Male and female anchor worms pair up on the surface of the fish to mate but only the female is parasitic, the male dies soon after mating, the female after releasing her eggs, though she can go on to produce more egg sacs. The eggs are released into the water where they hatch and develop into young free swimming crustaceans, going through several free swimming and parasitic larval stages. During the copepodid stages (parasitic larval), the larvae generally settle on the fishes gills. It can take several months before the young anchor worms are noticeable. The eggs can also remain viable and undetected for quite some time, hatching out when conditions and water temperature are right. Anchor worms are most commonly found in pond fish though they are found in freshwater and marine aquaria on occasion. Eggs are often introduced via live food, water and on plants. There are several species of lernaea, the one most commonly encountered in tropical aquarium conditions is L.cyprinacea, this species is well adapted to tropical conditions and can parasitise a wide range of fish species. Females of this species can grow to appoximately 5-12 mm (excluding egg strings), males grow to approximately 0.8 mm. Symptoms - Lernaea often first appears as a length of fleshy cotton or heavy nylon fishing line attached to the surface of the host fish, the parasites can attach to any part of the body, they can also perforate the eyes or gills. Fish that are affected by only one or two anchor worms can be relatively free of symptoms, apart from the occasional scratching and flashing and sometimes mucus hyperproduction due to the irritation caused by the parasites. A reduction in appetite is also fairly common. Fatality in small fish and fry that are affected by a small number of parasites can occur as a result of blood loss, and secondary bacterial and fungal infections. The parasitic females cause deep puncture wounds which can cause acute haemorrhage's and ulcers, and can kill the host if a vital organ is penetrated. The site of penetration is also vulnerable to secondary infection with pathogenic bacteria and fungus which can cause fin damage, dropsy, loss of scales, sluggishness, weight loss etc. Large numbers of parasitic larvae can cause gill damage, leading to respiratory distress and sometimes death. Confirmation of an infestation of anchor worms is by visual detection of the parasites on the host fishes body. Correct diagnosis of the gill dwelling larval stages require microscopical examination of a gill scrape. Treatment - Fish infested with lernaea should be removed to a hospital tank to prevent any mature female worms from releasing their eggs into the main aquarium. Parasites can be carefully removed from fish that are large enough with the aid of forceps or tweezers, care must be taken to remove the whole parasite and the exposed wound needs to be treated with a topical antiseptic, large wounds can then be sealed with pharmacy grade petroleum jelly (e.g. Vaseline). The cream will act as a barrier while the wound heals and can also help reduce osmotic stress. There are several chemical bath treatments that target the larval stages of anchor worm, these include Trichlorfon which is an organophosphate compound. Effective at 0.2-0.3 mg/litre, repeated every seven days for four to six weeks (Trichlorfon is highly toxic to fish and invertebrates, use with extreme caution). Dipterex and Dylox are often cited in aquatic literature and on the web as an effective treatment, both of these chemicals are trade names for Trichlorfon so are in fact the same product. Salt baths (sodium chloride) at a concentration of 10-30 grammes per litre for 10-30 minutes is often stated as being effective against lernaea, however, this method of treatment is often cited in older aquatic literature, some fish health professionals say it works others say it doesn't. If I ever find out for sure I will update the page! The current treatment cited for lernaea is a product called Dimilin, which until recently wasn't licensed for use with fish. Doing a search on the internet for Dimilin will bring up a lot of pages that are slightly out of date. For more information on the product read here http://www.pondliner.com/Dimilin.htm Note - - Anchor worms can sometimes get coated with algae making them appear green.
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