''Dactylogyrus vastator'' is a species of monoic flatworms of class

Monogenea Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they have both male and female repro ...

. It is an ectoparasite of fish which infests the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s. It is problematic on fish farms. It is otherwise non-hazardous to humans.

Characteristics

''D. vastator'' is just over 1.25 millimeters long. It has two pairs of hooks known as hamuli, one on the lower surface of the worm, and a larger set at the rear. It has three pairs of sticky sacs and four eyespots.

Distribution

''D. vastator'' lives in the northern parts of North America, Europe, and Asia.

Significance

The flatworm causes mass mortality among fingerling carp in fish-rearing ponds. Abnormal multiplication of cells in the gill epithelium interferes with carp's respiratory functions. The parasite is especially significant in the former

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

, eastern and northern

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

, and Sri Lanka, where carp are bred for food.

Life cycle

''Dactylogyrus vastator'' has one host and no intermediate hosts. New hosts are located and infected by free-living larvae (

oncomiracidium An oncomiracidium is the ciliated and free-living larva of a monogenean, a type of parasitic flatworm commonly found on fish. It is similar to the miracidium of Trematoda, but has sclerotised Sclerotin is a component of the cuticle of various A ...

). ''D. vastator'' lives in the gills of carp species, including goldfish. The adult lays eggs on the gill filaments which are then washed out of the gill cavity and into the water. A

ciliated The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike project ...

oncomiracidium emerges from the egg in 3–5 days, depending on water temperature. In warmer temperatures the embryo develops more rapidly. The larva emerges, leaving the embryonic membrane inside the egg. The larva is drawn into the gill cavity of a host fish, where it attaches by its hooks. The larva can also swim actively and attach to the skin of the host and migrate to the gills. The larva reaches sexual maturity about ten days later.Animal Parasites Their Life Cycles and Ecology
/ref> Summer is the season of peak infestation, and by fall the worms are scarce. Eggs released late in the season enter

diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press I ...

, a period of inactivity. When the water warms the following spring the eggs develop. Young carp are more often infested, sometimes fatally when large numbers of worms attach to the gill filaments. Superinfection can occur during the summer when the worms are most abundant.

References

{{DEFAULTSORT:Dactylogyrus Vastator Dactylogyridae Animals described in 1924