Dactylogyrus spp

From Fish
Unstained wet mount of monogenetic trematodes (Dactylogyrus) on the gills of a discus, 100X. Courtesy of Dr. Ruth Francis-Floyd

Dactylogyrus spp are a monogenean parasite of fish. Dactylogyrus lays eggs and is principally a parasite of the gills.

Monogenean trematodes, which have direct life cycles, are common, highly pathogenic, obligatory parasites of the skin and gills. They are ~0.1-0.8 mm long and are best seen microscopically[1]. So far, more than 70 species belong to the genus Dactylogyrus have been reported from wild and farmed freshwater fishes. Dactylogyrus is one of the largest genera of parasitic helminthes, approximately 95% of them are parasites of the gills of fishes in the family Cyprinidae. D. anchoratus and D. extensus need special attention due to their low host-specificity and high tolerance to a wide range of temperature and salinity. These characteristics make them the most successful among invading parasites of fishes[2].

This parasite attaches to the base of primary filaments where osmoregulating chloride cells are located. Therefore, infection with the parasite could be dangerous and harmful especially for the fries in hatcheries[3].

The worms can be identified by their characteristic hold-fast organ, the haptor, which is armed with large and small hooks. Aquarium and cultured fish are subject to a rapid buildup of parasites by continuous infection and worm transfer to other fish in the tank or pond. Although many species are host-specific, the more common types seen in aquaria are less selective[4].


  1. King, S. D. and D. K. Cone. (2009) Infections of Dactylogyrus pectenatus (Monogenea: Dactylogyridae) on Larvae of Pimephales promelas (Teleostei: Cyprinidae) in Scott Lake, Ontario, Canada. Comparative Parasitology 76:110–112
  2. Gibson, DI; Timofeeva, TA and Gerasev, PIA (1996) Catalogue of the nominal species of the monogenean genus Dactylogyrus Diesing, 1850 and their host genera. Syst Parasitol 35: 3-48
  3. Kollman, A (1972). Dactylogyrus vastator Nybelin, 1924 (Trematoda: Monogenoidea) as pathogens on gills of carp (Cyprinus carpio L). Z Wiss Zool 185:1-54
  4. Merck Veterinary Manual