Monogeneans: Monogenea

Physical characteristics: Worms in the species Dactylogyrus vastator (abbreviated as D. vastator) are a little more than one–thirty-second of an inch (1.25 millimeters) long. They have two pairs of hooks. A set on the bottom surface of the worm is smaller than the set at the rear. These worms have three pairs of sticky sacs and four eyespots.

Geographic range: D. vastator lives in the northern parts of North America, Europe, and Asia.

Habitat: D. vastator lives in the gills of carp and goldfish, which live in freshwater.

Diet: D. vastator feeds on gill cells.

Behavior and reproduction: D. vastator worms attach themselves to their hosts with their hooks. The eggs are washed out of the host's gills and sink to the bottom of the water. Larvae emerge in three to Dactylogyrus vastator live in the gills of carp and goldfish. (Illustration by Barbara Duperron. Reproduced by permission.) five days, depending on water temperature. Larvae drawn into the gill cavity by the water current attach themselves to another host's gills. Some larvae may first attach to a host's skin and then migrate to the gills.

Dactylogyrus vastator and people: D. vastator kills young carp in fish-farming ponds. This problem is significant in areas where carp is bred for food.

Conservation status: D. vastator is not threatened or endangered. ∎