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Life-history stages of the trematode flatworm
Fasciola hepatica from 1911
Encyclopaedia Britannica
Trematodes are small parasitic flatworms that use vertebrates as their definitive host, and molluscs (usually freshwater snails or land snails) as their intermediate host. In order to accomplish this, they have several varied life cycle stages.
The life cycle of a typical digenean trematode can be thought to begin when its egg is immersed in water. Following this a miracidium hatches, which swims to find a mollusc host. The miracidia go through several stages in the mollusc host, eventually emerging as motile cercaria larvae.[1] The cercaria either infect vertebrates through the skin or are ingested. In its vertebrate host, the cercaria matures to an adult form, and lays eggs that are discharged with the host faeces or urine. In the presence of open water, the eggs will hatch and the miracidium stage of life is reached again.
Contents
- 1 Typical lifecyle stages
- 2 Deviations from the typical lifecycle
- 3 Representations of lifecycles of several different trematode species
- 4 References
- 5 See also
- 6 External links
Typical lifecyle stages
Bucephalid cercaria larva from Ernst Haeckel's Kunstformen der Natur (1904) The tail's furcae give the impression of horns, hence the genus name "
Bucephalus" meaning "ox head."
While the details vary with each species, the general lifecycle stages are as follows:
- Egg – discharged either in open water or in intestine of definitive host.
- Miracidium (plural Miracidia) – free-living motile form, covered with cilia, which settles in the mollusc to become a sporocyst.[2]
- Sporocyst – an elongated sac that produces either rediae or more sporocysts.[3]
- Redia (plural rediae) – a larval form with an oral sucker, it will produce either more rediae, or cercariae.[3]
- Cercaria (plural cercariae) – the larval form of the parasite, developed within the germinal cells of the sporocyst or redia.[3] A cercaria has a tapering head with large penetration glands.[2] It may or may not have a long swimming "tail", depending on the species.[3] The motile cercaria finds and settles in a host where it will become either an adult, or a mesocercaria, or a metacercaria, according to species.
- Mesocercaria – a cercaria little modified but resting.
- Metacercaria – a cercaria encysted and resting.
- Adult – the fully developed mature stage, capable of sexual reproduction.
Deviations from the typical lifecycle
The typical sequence (eggs, miracidia, sporocysts, rediae, cercariae, and adults) is by no means the rule for all trematode species. In some species the redia stage is omitted and sporocysts produce cercariae. In some species, the cercaria develops into an adult within the same host.
Many digenean trematodes require two hosts, one (typically a snail) where asexual reproduction occurs in sporocysts, the other a vertebrate (typically a fish) where the adult form engages in sexual reproduction to produce eggs. In some species (for example Ribeiroia) the cercaria encysts, and waits until the host is eaten by a third host, in whose gut it emerges and develops into an adult.
Most trematodes are hermaphroditic, but members of the family Schistosomatidae are dioecious. Males are shorter and stouter than the females.[2]
Representations of lifecycles of several different trematode species
Lifecycle stages of a digenean human parasite,
Schistosoma japonicum.
Lifecycle stages of a digenean fish parasite,
Bucephalus polymorphus.
Lifecycle stages of trematode species that cause "swimmer's itch".
References
- ^ "2. FISH DISEASES (Contd.) 2.1.4 Parasitic Diseases". FAO of the UN Food and Agriculture Organization of the United Nations. Retrieved 18 February 2011.
- ^ a b c "Schistosoma". Australian Society for Parasitology. Retrieved 19 February 2011.
- ^ a b c d "Glossary". VPTH 603 Veterinary Parasitology. University of Pennsylvania School of Veterinary Medicine.
See also
- Bucephalus polymorphus
- Trematode infection
- Apicomplexa lifecycle stages
External links
- Life cycle of Schistosoma mansoni
UpToDate Contents
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English Journal
- A multiplex PCR for the detection of Fasciola hepatica in the intermediate snail host Galba cubensis.
- Alba A1, Vázquez AA2, Hernández H1, Sánchez J2, Marcet R1, Figueredo M1, Sarracent J1, Fraga J3.
- Veterinary parasitology.Vet Parasitol.2015 Jul 30;211(3-4):195-200. doi: 10.1016/j.vetpar.2015.05.012. Epub 2015 May 15.
- Fasciolosis is a snail-borne trematode infection that has re-emerged as a human disease, and is considered a significant problem for veterinary medicine worldwide. The evaluation of the transmission risk of fasciolosis as well as the efficacy of the strategies for its control could be carried out th
- PMID 26012858
- Motility of Fasciola hepatica miracidia assessed with a computer-assisted sperm analyser.
- Villa-Mancera A1, Reynoso-Palomar A1, Olivares-Pérez J2, Ortega-Vargas S3, Cruz-Mendoza I3, Quiroz-Romero H3.
- Journal of helminthology.J Helminthol.2015 Jul;89(4):453-7. doi: 10.1017/S0022149X14000285.
- The motility parameters of Fasciola hepatica miracidia were assessed at different temperatures and times post-hatching using computer-assisted sperm analysis. Eggs were incubated at 22°C or 25°C for 14 days. Five motion parameters were evaluated at different incubation temperatures up to 10 h pos
- PMID 26017332
- [Expression profiling and immunofluorescence localization of the major egg antigen p40 of Schistosoma japonicum in the liver of infected New Zealand white rabbits].
- Xia D1, Deng GM, Teng PY, Xie Y, Li YM, Wang CM, Chen SJ, Chen MF, Mai RJ, Liao HY, Shi LY, Ou LY, Chen QW, Chen XG, Zhou XH.
- Nan fang yi ke da xue xue bao = Journal of Southern Medical University.Nan Fang Yi Ke Da Xue Xue Bao.2015 Jun 20;35(6):826-31.
- OBJECTIVE: To examine the expression profile and immunofluorescence localization of the major egg antigen p40 of Schistosoma japonicum (Sjp40) during granuloma formation in the liver of infected New Zealand white rabbits.METHODS: New Zealand white rabbits were infected with S. japonicum cercariae, a
- PMID 26111679
Japanese Journal
- B28 円山川中州菊屋島におけるクロベンケイガニの大平肺吸虫メタセルカリア寄生とハエ類のミラシジウム感染実験について(第62回日本衛生動物学会大会特集)
- The Effect of Praziquantel on Patterns of Schistosoma mansoni Eggshell Hatching Breaks
- Miura Mitsumasa,Katsumata Tatsuya,Mitsui Yoshinori,Fujimaki Yasunori,Sakamoto Makoto,Aoki Yoshiki
- 熱帯医学 Tropical medicine 34(1), 9-14, 1992-03-21
- … However, PZQ hatching produced smaller hatching orifices and the miracidium frequently failed to escape. …
- NAID 120000918075
- Scanning Electron Microscopic and Histochemical Observations on the Miracidium of Gigantobilharzia sturniae Tanabe,1948
Related Links
- Within the egg a miracidium develops and, when fully developed, hatches. The miracidium finds a suitable first intermediate host, a freshwater snail, and penetrates the foot. Here they hatch into a free-swimming ...
- mi·ra·cid·i·um noun \ ˌ mir-ə-ˈ si-dē-əm, ˌ mī-rə-\ plural mi·ra·cid·ia \-dē-ə\ Definition of MIRACIDIUM: the free-swimming ciliated first larva of a digenetic trematode that seeks out and penetrates a suitable snail intermediate host in ...
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- 英
- miracidium
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- ミラキジウム
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- 蠕虫、吸虫類、住血吸虫症
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- 英
- miracidium, (pl.)miracidia
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