Monogenea
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Monogenea | |
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Echinoplectanum laeve | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Platyhelminthes |
Superclass: | Neodermata |
Class: | Monogenea Carus, 1863 |
Subgroups | |
Monogeneans, members of the class Monogenea, are a group of ectoparasitic
Some monogeneans are
Signs and symptoms
Freshwater fish that become infected with this parasite become lethargic and end up swimming towards the surface of the water. In addition, some may be seen rubbing the bottom or sides of their skin where the parasite is located. Infected skin where the parasite is attached may show areas of scale loss and may produce a pinkish fluid. Gills that are infected may appear swollen and pale. "Pipping", which is gulping for air at the water surface, could indicate severe respiratory distress.[2]
In salt water fish, Monogeneans can infect the skin and gills, resulting in irritations to the host. Heavy infections could result in erratic swimming behavior. Affected gills may become irritated and swollen.[2]
Characteristics
Monogenea are small parasitic flatworms mainly found on skin or gills of fish. They are rarely longer than about 2 cm. A few species infecting certain marine fish are larger, and marine forms are generally larger than those found on freshwater hosts. Monogenea are often capable of dramatically elongating and shortening as they move. Biologists need to ensure that specimens are completely relaxed before measurements are taken.[3]
Monogeneans lack respiratory, skeletal, and circulatory systems and have no or weakly developed oral suckers.[4] Like other flatworms, Monogenea have no true body cavity (coelom). They have a simple digestive system consisting of a mouth opening with a muscular pharynx and an intestine with no terminal opening (anus).
Monogenea are Platyhelminthes, so are among the lowest invertebrates to possess three embryonic germ layers—endoderm, mesoderm, and ectoderm. In addition, they have a head region that contains concentrated sense organs and nervous tissue (brain).
Like all ectoparasites, monogeneans have well-developed attachment structures. The anterior structures are collectively termed the prohaptor, while the posterior ones are collectively termed the opisthaptor, or simply haptor. The posterior opisthaptor with its hooks, anchors, clamps etc. is typically the major attachment organ.
Generally, monogeneans also are
Phylogeny
The following cladogram depicts the
Monogenea |
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Systematics and evolution
The ancestors of Monogenea were probably free-living flatworms similar to modern Turbellaria. According to the more widely accepted view, "rhabdocoel turbellarians gave rise to monogeneans; these, in turn, gave rise to
About 50 families and thousands of species are described[citation needed].
Some parasitologists divide the Monogenea into two (or three) subclasses based on the complexity of their haptor: the Monopisthocotylea have one main part to the haptor, often with hooks or a large attachment disc, whereas the Polyopisthocotylea have multiple parts to the haptor, typically clamps. These groups are also known as Polyonchoinea and Heteronchoinea, respectively. Polyopisthocotyleans are almost exclusively gill-dwelling blood feeders, whereas monopisthocotyleans may live on the gills, skin, and fins.
Monopisthocotylea include:
- Genus Gyrodactylus has no eyespots and is viviparous.
- Genus Dactylogyrus has four eyespots and is oviparous. This is one of the largest metazoan genera, with at least 970 species.
- Genus Neobenedenia much larger and lives on the skin of many tropical marine species, causing problematic infections in marine aquaria.
All of these can cause epizootics in freshwater fish when raised in aquaculture.
Polyopisthocotylea include:
- Genus marine fish and primitive freshwater fish such as sturgeons and paddlefish.
- Genus Protopolystoma is found in aquatic clawed toads (Xenopus species).
Ecology and lifecycle
Monogeneans possess the simplest lifecycle among the parasitic platyhelminths. They have no intermediate hosts and are ectoparasitic on fish (seldom in the
No known monogeneans infect
See also
Gastrocotylinae – Family of worms
References
- ^ a b c L.A. Tubbsa et al. (2005). "Effects of temperature on fecundity in vitro, egg hatching and reproductive development of Benedenia seriolae and Zeuxapta seriolae (Monogenea) parasitic on yellowtail kingfish Seriola lalandi". International Journal for Parasitology(35), 315–327.
- ^ a b Reed, Peggy et al. Monogenean Parasites of Fish. Institute of Food and Agricultural Sciences. . http://www.aces.edu/dept/fisheries/education/ras/publications/Update/Monogenean%20Parasites%20of%20Fish.pdf
- ^ Roberts, S. Larry & John Janovy, Jr. Foundations of Parasitology
- ^ flatworm :: Annotated classification - Britannica Online Encyclopedia
- , retrieved May 19, 2022
- ISBN 9780367397852.
External links
- Monogenea – ectoparasitic flukes (flatworms) - Clinical Sciences