''Dactylogyrus'' is a genus of
monogenea
Monogeneans, members of the class Monogenea, 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 ...
ns in the
Dactylogyridae family.
Like other monogeneans, species of ''Dactylogyrus'' only have one host required to complete their life cycle.
Introduction
Members of ''Dactylogyrus'' (common name: Gill Fluke) are oviparous (egg-laying) monogeneans trematodes that have two pairs of anchors. These anchors can be used to latch onto the gills of a host, particularly freshwater fish such as carp. In heavily infected fish, ''Dactylogyrus'' can also be found on the buccal cavity, and at times fins and skin of the freshwater fish.
Species
''Dactylogyrus'' is one of the most speciose genus of helminths, with more than 900 species described,
[ ][ ][ ] such as ''
Dactylogyrus vastator''. Consequently, in 1996, it was estimated that the taxonomy was "in a state of considerable confusion".
Anatomy
Other characteristics of ''Dactylogyrus'' species include the appearance of four eye-spots, 14 marginal hooks (7 pairs), one to two connective bars and two needle-like structures and spindle-shaped dactylogyrid-type seminal vesicles.
[Woo, P.T.K, David W. Bruno, L. H. Susan Lim. Diseases and Disorders of Finfish in Cage Culture. Malaysia: CABI, 2002.] ''Dactylogyrus'' has an adult structure that is up to 2 mm in length.
Life cycle
The life cycle of ''Dactylogyrus'' species is direct, having no intermediate host. The hermaphroditic adults are oviparous and produce eggs into the water which hatch prior to attaching to the gills of a fish host and developing into an
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
Trematoda is a class of flatworms known as trematodes, and commonly as ...
.
Adult ''Dactylogyrus'' lay about 4-10 eggs per day. After the eggs hatch, water currents aid the free-swimming ciliated larva in reaching its host. Once eggs are released into the water and have hatched within 4 days time period at 20 °C, the free-swimming ciliated larvae then is required to find their host within a 6–8 hours time frame in order to survive.
[Karen Paul."Flukes(Gyrodactylus and Dactylogyrus)." pond-life.me.uk. Pond Life: Fish Health. 2007-2017 ] The time required for egg maturation into the adult form is temperature dependent. Water temperatures of 72–75 °F allow life cycle completion in a few days, whereas temperatures of 34–36 °F extend the generation time to five or six months.
[Reed, Peggy A., Ruth Francis-Floyd, and Ruthellen C. Klinger. "FA28/FA033: Monogenean Parasites of Fish." EDIS - Electronic Data Information Source - UF/IFAS Extension. University of Florida. 17 May 2009 ]
Prevalence
''Dactylogyrus'' species are monogenean parasites that are usually found on the gills of cyprinid fishes. The prevalence of ''Dactylogyrus'' infection on fish differ depending on the seasons. It was found that ''Dactylogyrus'' infections are at their greatest during late autumn or early winter. Correlation has also been found between the temperature of the water and the intensity of ''Dactylogyrus'' infection.
[Hanzelová, V. & Žitnan, R. (1985) Epizootiologic importance of the concurrent monogenean invasion in carp. J. Helminthologia 22: 277–283.]
It is also generally accepted that fish are exposed to increased ''Dactylogyrus'' infections during their spawning period.
[
]
Symptoms
Cyprinid fish that are infected by ''Dactylogyrus'' species may have symptoms that include inflamed gills, excessive mucous secretions and accelerated respiration. Also increased movement of the gills due to damage (fibrosis
Fibrosis, also known as fibrotic scarring, is the development of fibrous connective tissue in response to an injury. Fibrosis can be a normal connective tissue deposition or excessive tissue deposition caused by a disease.
Repeated injuries, ch ...
) the fluke is causing to the tissues.[Dawes, John. Complete Encyclopedia of the Freshwater Aquarium. Firefly Books, 2001.]
In severe infections, ''Dactylogyrus'' species can cause hemorrhaging and metaplasia
Metaplasia () is the transformation of a cell type to another cell type. The change from one type of cell to another may be part of a normal maturation process, or caused by some sort of abnormal stimulus. In simplistic terms, it is as if the ...
of the gills which can lead to secondary bacterial infections and death. Heavily infected fish are also anorexic and can be found gasping for air and exhibiting abnormal behavior such as jumping out of the water.[
]
Treatment
A primary method for control of ''Dactylogyrus'' species is the application of chemicals. Treatments include Praziquantel
Praziquantel, sold under the brandname Biltricide among others, is a medication used to treat a number of types of parasitic worm infections in mammals, birds, amphibians, reptiles, and fish. In humans specifically, it is used to treat schist ...
, salt baths, formalin or organophosphates, fenbendazole, albendazole, Bromex-50 and potassium permanganate.[
]
Ecology and evolution
Species of ''Dactylogyrus'' are studied by a variety of methods, including classical morphology, staining
Staining is a technique used to enhance contrast in samples, generally at the Microscope, microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissue (biology), tissues), in cytology (microscopic ...
with various dyes, scanning electron microscopy
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that ...
of sclerotised parts, and molecular methods.ecology
Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...
and evolution
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
of host-parasite associations of monogeneans, and of parasites in general; dozens of scientific publications have been published on these subjects.host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
* Host Island, in the Wilhelm Archipelago, Antarctica
People
* ...
levels, microhabitat
In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
specificity expressed by restricted positions on fish gills, and the link between microhabitat preference and morphological adaptation.
These studies on species of ''Dactylogyrus'' have also shown that host-specific congeneric monogeneans could reveal historical intercontinental and intracontinental contacts between freshwater fish.hybrid
Hybrid may refer to:
Science
* Hybrid (biology), an offspring resulting from cross-breeding
** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species
** Hybridity, the property of a hybrid plant which is a union of two diff ...
fish, was also studied on species of ''Dactylogyrus''.[ ]
References
External links
{{Taxonbar, from=Q174912
Dactylogyridae
Monogenea genera