Description
I. multifiliis is one of the most prevalent protozoan parasites of fish and is an obligate parasite which means that the parasite cannot survive unless live fish are present. Adult organisms have an oval to round shape and measure 0.5 to 1.0 mm in size. The adult parasite is uniformly ciliated and contains a horseshoe-shaped nucleus which can be seen in older individuals. It is an important pathogen of ornamental and farm-raised food fish species when reared under intensive conditions. Wild fish populations are also susceptible and outbreaks are occasionally seen. There are few aquarists that have not met it on one or more occasions.
The ich protozoa goes though the following life stages:
- Feeding stage : The ich trophozoite (a protozoan in active stage of life) feeds in a nodule formed in the skin or gill epithelium.
- After it feeds within the skin or gills, the trophozoite falls off and enters an encapsulated dividing stage (tomont). The tomont adheres to plants, nets, gravel or other ornamental objects in the aquarium.
- The tomont divides up to 10 times by binary fission, producing infective theronts, thus dividing rapidly and attacking the fish.
This life cycle is highly dependent on water temperature, and the entire life cycle takes from approximately 7 days at 25 °C (77 °F) to 8 weeks at 6 °C (43 °F).
Marine ich is a similar disease caused by a different ciliate, Cryptocaryon irritans.
Read more about this topic: Ichthyophthirius Multifiliis
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