Gill Fluke/Dactylogyus
Image from Brunel Microscopes
There are 2,400 species of Monogenetic Trematodes (flat worms) of which just two are pathogenic to our fish. Monogenea are flukes, which are hermaphroditic - that is they are both of the male and female gender but do not need a mate to reproduce, the reason for rapid reproduction. Some are oviparous- egg layers, others are livebearers.
The two that are of particular interest to us are the Gill Fluke and the Skin or Body Fluke, both are pathogenic to our fish, simply they are capable of causing disease.
Dactylogyrus, more commonly known to the fish keeper, as the Gill Fluke is an egg-layer, despite its name can be found on other parts of the body as well as the gills. It is the more serious of the flukes, particularly at temperatures around 65 F - 70 F, this being the optimum temperature ranges for the eggs to hatch. At 68 F the eggs will hatch in just 4 days, this temperature is considered to be the height of their breeding cycle. Once the eggs have hatched, the free swimming larval stage has 6-8 hours to find a host or die. The males have only a short lifespan whereas the females can live up to 12 months on a host fish. At this time fish may be dying before this parasite is suspected.
A close relative of the Skin Fluke although approximately half the size this parasite has to be microscopically identified using a mucus scrape from around the gill area or under the gill cover. Extreme care must be taken when using this procedure, but it is the only way to achieve correct diagnosis. Identifying features of the Gill Fluke are the 4 eyespots on the head organ, on the Haptor (the posterior end) the array of hooks are set quite high. The juvenile parasite is much more transparent than the adult but the eyespots are still the recognising feature. One or two Flukes on a slide pose no real threat, particularly at low temperatures.
The Fluke uses the hooks (which look like grappling irons) to grasp the tissue of the fish while it browses around for food. The damage caused to the delicate lamella by these hooks is usually severe and has a lasting effect, if not fatal.
The gill function is vital to the survival of the fish and Dactylogyrus can be very destructive. Large areas become necrotic (diseased) and cease to carry out the primary function of oxygen diffusion, also secondary infection from bacteria and fungus is common. The filament may become hyperplastic, this is recognised by the filaments fusing together and becoming one.
In trying to clear the gill irritation (an action which looks like the fish is yawning) many eggs may be flushed into the pond. The eggs, being sticky may adhere to and infect other fish, but many perish.
There are very few outward signs of a Gill Fluke problem; the first may be a fatality. Some symptoms to look for, does the gill covers protrude abnormally, is the fish seeking oxygen enriched areas, is it lethargic or breathing very rapidly. Food may be refused but this is synonymous with most fish that are unwell.
By the time you realise there is a problem, swelling of the gill tissue may already have taken place due to bacterial infection, many eggs may be in the gills, add all these factors together and the fish is in serious trouble. Unable to diffuse sufficient oxygen from the water, it dies from asphyxiation.
For most fish keepers this parasite means that vigilance throughout the summer months is needed, for those with heated ponds close attention all year round is required.
Constant improvements in medication are made to eradicate this parasite, please contact us for treatments and correct use of dosage for your pond and Koi.
The two that are of particular interest to us are the Gill Fluke and the Skin or Body Fluke, both are pathogenic to our fish, simply they are capable of causing disease.
Dactylogyrus, more commonly known to the fish keeper, as the Gill Fluke is an egg-layer, despite its name can be found on other parts of the body as well as the gills. It is the more serious of the flukes, particularly at temperatures around 65 F - 70 F, this being the optimum temperature ranges for the eggs to hatch. At 68 F the eggs will hatch in just 4 days, this temperature is considered to be the height of their breeding cycle. Once the eggs have hatched, the free swimming larval stage has 6-8 hours to find a host or die. The males have only a short lifespan whereas the females can live up to 12 months on a host fish. At this time fish may be dying before this parasite is suspected.
A close relative of the Skin Fluke although approximately half the size this parasite has to be microscopically identified using a mucus scrape from around the gill area or under the gill cover. Extreme care must be taken when using this procedure, but it is the only way to achieve correct diagnosis. Identifying features of the Gill Fluke are the 4 eyespots on the head organ, on the Haptor (the posterior end) the array of hooks are set quite high. The juvenile parasite is much more transparent than the adult but the eyespots are still the recognising feature. One or two Flukes on a slide pose no real threat, particularly at low temperatures.
The Fluke uses the hooks (which look like grappling irons) to grasp the tissue of the fish while it browses around for food. The damage caused to the delicate lamella by these hooks is usually severe and has a lasting effect, if not fatal.
The gill function is vital to the survival of the fish and Dactylogyrus can be very destructive. Large areas become necrotic (diseased) and cease to carry out the primary function of oxygen diffusion, also secondary infection from bacteria and fungus is common. The filament may become hyperplastic, this is recognised by the filaments fusing together and becoming one.
In trying to clear the gill irritation (an action which looks like the fish is yawning) many eggs may be flushed into the pond. The eggs, being sticky may adhere to and infect other fish, but many perish.
There are very few outward signs of a Gill Fluke problem; the first may be a fatality. Some symptoms to look for, does the gill covers protrude abnormally, is the fish seeking oxygen enriched areas, is it lethargic or breathing very rapidly. Food may be refused but this is synonymous with most fish that are unwell.
By the time you realise there is a problem, swelling of the gill tissue may already have taken place due to bacterial infection, many eggs may be in the gills, add all these factors together and the fish is in serious trouble. Unable to diffuse sufficient oxygen from the water, it dies from asphyxiation.
For most fish keepers this parasite means that vigilance throughout the summer months is needed, for those with heated ponds close attention all year round is required.
Constant improvements in medication are made to eradicate this parasite, please contact us for treatments and correct use of dosage for your pond and Koi.