Cryptocaryon
Cryptocaryon irritans is a species of ciliate that parasitizes marine fish, causing marine white spot disease or marine ich. It is one of the most common causes of disease in marine aquaria.
Taxonomy
Cryptocaryon irritans was originally classified as Ichthyophthirius marinus, but it is not closely related to the other species. It belongs to the class Prostomatea, but beyond that its placement is still uncertain.Clinical
The symptoms and life-cycle are generally similar to those of Ichthyophthirius in freshwater fish, including white spots, on account of which Cryptocaryon is usually called marine ich. However, Cryptocaryon can spend a much longer time encysted. Fish that are infected with Cryptocaryon may present with small white spots, nodules, or patches on their skin, fins, or gills. In some cases the parasite may attach on the gills of the fish, making it much harder to see. They may also have ragged fins, cloudy eyes, pale gills, increased mucus production, or changes in skin color, and they may appear thin. Behavioural changes may be observed, such as scratching, abnormal swimming, lethargy, hanging at the surface or bottom of the tank, or breathing rapidly as if in distress.Life cycle
C. Irritans has a 4-stage lifecycle, consisting of a Trophon stage, a Protomont stage, a Tomont stage, and a Theront stage. The characteristic white spots occur in the Trophont stage, where C. irritans finds a host fish to attach to. This is where the paraste begins feeding on the host fish for 3-9 days. After this, C. irritans falls off the host and enters the Protomont stage. The free-swimming parasite now find substrate such as rocks or sand to attach to. Once it has achieved this, the parasite enters the Tomont stage and begins to reproduce asexually, this may last from 3 to 72 days. Lastly, the parasite enters the Theront stage, where it once again becomes free-swimming. Here, it searches for a new host to attach to and begins the cycle anew.Treatment
Due to this extensive life-cycle, Marine Ich can be difficult to treat. Especially as most available treatments are not safe for corals, snails and other invertebrates. This usually forces the aquarist to quarantine the infected fish in a separate tank for the duration of the treatment.Useful treatments of C. irritans include copper solutions, formalin solutions and quinine based drugs or hyposalinity..
Another treatment option called the Tank Transfer Method involves moving the affected fish to another tank at specific times in the parasite's lifecycle, intending for the parasite to "drop off" the fish in a separate, quarantined tank and moving the fish back to its original tank before the parasite is able to reattach.