Cryptocaryon irritans fischlexikon

Cryptocaryon irritans is a parasitosis often found in tropical marine fish occurrence. Cryptocaryon irritans is probably the most common parasitic disease in saltwater fishes.

Cryptocaryon irritans is a small ciliated protozoan and is found in all warmer oceans. This disease spreads rapidly in the aquarium. Can infect all fish species. Cryptocaryon irritans only attacks weakened fish.

The symptoms of this parasite (including shape and size) are similar to the symptoms of the freshwater parasite Ichthyophthirius multifiliis, which causes white spot disease in freshwater fish. However, the two parasites are not related and Cryptocaryon irritans is also controlled with other agents such as Ichthyophthirius multifiliis.

In the wild, many marine fish are infested with this parasite. However, it does not cause symptoms in healthy fish, but lives with them in a peaceful "coexistence".

Cryptocaryon irritans is always present in the aquarium. It belongs to the "weak parasites" and multiplies only in weakened fish (due to transport stress, too high stocking density, poor water values, wrong or infected food, etc.).) so strong that the fish gets sick.

Way of life, life cycle, infestation

The life cycle of this parasite includes several stages that are strongly linked to the ambient temperature. The theronts (swarmers) can survive without a host fish for a maximum of 1-2 days. The infected fish does not have to be visibly ill or show symptoms, however, this depends on its constitution. Only weakened fish become ill. Show the appropriate symptoms.

The life cycle includes three stages, all of which are ciliated and motile: Theront, Trophont and Tomont.

The hawkmoth form of Cryptocaryon irritans is called theront. The growth form of Cryptocaryon irritans (trophont) has thread-like appendages with which it clings to fish. Once attached, it penetrates the mucosa of the fish, anchors itself there and feeds on its cellular components.

At the end of its development (after ca. 4-6 days), the parasite leaves its host fish and forms a cyst (tomont). This tomont initially swims freely in the water and then attaches to aquatic plants or inorganic surfaces after about 1 hour by means of a transparent protein shell (mucocyst).

Symmetrical cell divisions take place in this sheath: a single mucocyst can reproduce up to 256 offspring by cell division.

The daughter cells develop into a flagellated dinoflagellate during the last division. One of these flagella protrudes from the cell surface. Serves the parasite for locomotion.

These dinospores, which swarm freely in the water, must now find a suitable host, otherwise they die off.


– small white dots (like grains of semolina) appear on the fins, skin and eyes – increased or accelerated breathing – fish rub themselves on the ground and objects, they produce more mucus – the fish often hide – the fish are hyperactive

Symptoms in the case of visible infestation (advanced stage):

– colors of the fish fade – extremely strong respiratory frequency – very heavily slimed gills – fish stay close to the water surface – fish stand near strong water movements – the affected fish take no or very little food and visibly lose weight – the fish fall ill with secondary bacterial infections (z.B. fin rot)


As Cryptocaryon irritans is a highly contagious fish disease, countermeasures should be taken immediately, otherwise the entire fish stock may be infected.

effective drug: z.B. Sera Costapur, Tetra Medica Contralck or Cyprinocur FMC. These medications all contain u.a. malachite green and must not be used in invertebrates.

Drugs containing copper have an extremely toxic effect on lower animals such as z.B. Snails, clams, crabs, shrimps, starfish, anemones, corals, etc.

Treatment with copper-containing drugs such as z.B. Sera Costapur should be given in a separate quarantine tank.

Fish with already visible infestation are unlikely to be cured. In any case, the advice of a knowledgeable veterinarian should be sought.

further measures

A good UV system is always recommended for control of parasites (theronts, hawkmoths) moving freely in the water. In addition, the fish can also be refreshed with multivitamin preparations. Strengthen garlic juice: to do this, simply mix these preparations with the feed, or. soak.

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