Dactylogyrus

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Dactylogyrus
Dactylogyrus under the microscope. (a) four-eye points, (b) holding devices

Dactylogyrus under the microscope. (a) four-eye points, (b) holding devices

Systematics
Sub-stem : Neodermata
Class : Hook worms (Monogenea)
Subclass : Monopisthocotylea (gill worms)
Order : Dactylogyridea
Family : Dactylogyridae
Genre : Dactylogyrus
Scientific name
Dactylogyrus
Diesing , 1850

Dactylogyrus is a homoxene flatworm-kind from the class of monogenea (Monogenea) subclass gills worms . Dactylogyrus is an ectoparasite (external parasite) and mainly affects the gills of fish. Here it lives parasitically on mucus and blood particles from the gills. A gill worm infestation is also known as dactylogyrosis .

features

A characteristic feature are the holding devices at the rear end made of a complex construction (opisthaptor) of various hooks, teeth and brackets. By means of these holding devices it is possible for him to anchor himself in the skin or the gills of his host. At the front end of the head of Dactylogyrus is the four-lobed end with a mouth opening through which it ingests its food consisting of gills or blood particles. In Gyrodactylus , a related species of Dactylogyrus , this end is two-lobed. Dactylogyrus can be easily recognized by its four-eye pairs under the microscope . Gyrodactylus lacks these pairs of eyes.

Dactylogyrus is an egg-laying parasite and, depending on the species, can grow up to 2.3 mm in size. As a rule, most species reach a size of around 0.5 mm to 1.0 millimeters. It is thus one of the largest genera among the multicellular species. The most common species found in native fish is Gyrodactylus vastator, which primarily affects carp like the Koi . After the egg-laying process, adult gill worms die, their eggs sink to the bottom and after a maximum of 10 days, buoyant eyelash larvae hatch from these eggs, which have to find a new host within 24 hours. Larvae that have not found a host after 24 hours die. Adult gill worms perish after approx. 2 to 14 days without a host, depending on the species.

infection

Gill worms are transferred to the old population by aquatic plants on which there are eggs or new fish stock. Wild caught are almost always afflicted with gill worms. Gill worms of the species Monocoelium and Gyrodactylus are predominantly found in aquarium fish . Dactylogyrus can almost be regarded as a permanent visitor to fish, although some fish even form a real resistance to the most diverse parasites and the gill worm causes almost no damage here. Only through debilitating factors that have a stress-inducing effect does a mass occurrence occur. Stress factors are deteriorated water parameters, a lack or oversupply of oxygen , too high a content of ammonium , nitrite or carbon dioxide as well as unfavorable pH values , wrong water temperature, lack of hiding places, wrong choice of species or too strong currents. If left untreated, mass occurrences of Dactylogyrus will always be fatal. Poor housing conditions and poor hygiene are the main causes that favor an outbreak of Dactylogyrus .

Symptoms

In the case of Dactylogyrus infestation, the gills are changed. In addition to destruction, especially at the tip of the gill leaves, there are strong growths that often protrude in a thread-like manner. In the advanced stage, the host dies of a lack of oxygen due to its destroyed gills. This gill worm can be seen well under a microscope even at low magnification.

Typical symptoms of infected fish are:

External identifying features

  • extensive skin opacities
  • shredded mucous membrane detachments
  • Darkening
  • Gills strongly pink in color
  • Gills change color from yellowish-red to white-yellow
  • Gills turn pale
  • Protruding gill covers
  • a gill cover remains closed
  • Corneal opacities of the eye
  • limited, reddened areas

behavior

  • Choking movements
  • Fish rub against objects
  • more terrifying than usual
  • Isolate and stay hidden
  • apathy
  • Unwillingness to eat or refusal
  • Fish lies on the ground
  • Fish gasps for oxygen on the surface
  • Cachexia
  • Fin clamps, thereby tumbling
  • violent, heavy breathing
  • "Shoot" through the water

Inner features

  • Gill leaves mucus

treatment

Raising the temperature is not advisable for gill worms, as the fish already have difficulty absorbing oxygen and this procedure becomes even more difficult at higher temperatures.

Infested fish can be treated in a trypaflavin continuous bath. Dactylogyrus infestation can also be treated with the antihelminthic levamisole (e.g. Concurat®, Citarin®, Ripercol®) in the form of a bath solution or by feeding live food with the medication. Levamisole has a direct cholinergic effect, in higher doses it also has an inhibitory effect on acetylcholinesterase and leads to spastic paralysis of the parasite. The active ingredient also has immune-stimulating properties in the host. Levamisole should not be used for open wounds because glucose-containing drugs cause massive bacterial bloom, which then infect open wounds and B. cause an infectious ascites .

species

Web links

swell

  • Amlacher, E. 1992. Pocket book of fish diseases , 6th ed., Gustav Fischer Verlag, Jena Stuttgart
  • Journal Parasitology Research , Verlag Springer Berlin / Heidelberg, On the knowledge of the genus Dactylogyrus Diesing 1850 (Monogenoidea), Volume 25, Number 5 / September 1965
  • Journal Systematic Parasitology , New and known species of Dactylogyrus Diesing, 1850 (Monogenea, Dactylogyridae) from Iranian freshwater cyprinid fishes , Volume 25, Number 3 / July 1993
  • Heinz Mehlhorn, Encyclopedic Reference of Parasitology, Biology, Structure, Function, Verlag Springer Berlin Heidelberg, page 155, ISBN 978-3-540-66819-0
  • Rudolf Hoffmann: Fish diseases . 2005, ISBN 978-3-8252-8241-7
  • Rüdiger Spangenberg: Dactylogyroses. In: Claus Schaefer, Torsten Schröer (Hrsg.): The large lexicon of aquaristics. Eugen Ulmer, Stuttgart 2004, ISBN 3-8001-7497-9 , p. 318.