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Protozoa: Trichophyra piscium

Volume 4, Issue 6
June 2002

Trichophyra piscium belongs to a Phylum of protozoan organisms all of whom possess cilia (‘hairs”) during at least one stage of their lifecycle. Most species are free-living aquatic organisms that feed on bacteria, some are commensal organisms, living on but not harming the host, and cleaning bacteria off the host’s body.

Trichophyra piscium

Figure 1. Trichophyra piscium 400x phase contrast microscopy.

Several species of Trichophyra have been identified as commensal organisms living on the gills of freshwater fishes. Large numbers of Trichophyra may cause gill irritation, or may cause the fish to secrete excessive gill mucous decreasing it’s respiratory and osmoregulatory efficiency. Some Trichophyra have been found parasitizing blood from the fish’s gills.

In April 2002, 14-month old lake trout (S. namaycush) at the Maine Department of Inland Fisheries & Wildlife Enfield fish hatchery were acting as though they had gill parasites.

Fish with gill parasites will rub their heads, and bodies against hard surfaces presumably to dislodge the organisms. Upon examination of the affected fish, Trichophyra piscium was identified in large numbers infesting the fish’s gills. The fish were treated as directed by MDIF&W’s fish veterinarian, and the problem was resolved.


14-month old lake trout (salvelinus namaycush).

Figure 2. 14-month old lake trout (Salvelinus namaycush).

Trichophyra have a direct life cycle, reproducing on the host by simple cell division. The sessile forms are transmitted from fish to fish via motile dispersal forms that can either be produced by budding from the parent, or by detachment of the trophozoite and subsequent transformation into a motile form.

Special points of interest:


Fish with Trichophyra cannot transmit the disease to people.

Trichophyra is a bacteria-eating protozoan.

Trichophyra can be considered an ecto-commensal organism rather than a parasite.

For more information read: Hoffman 1999 Parasites of North American Freshwater Fishes.

Images were made possible by a grant from the Maine Outdoor Heritage Fund.