WordNet

of or relating to cercaria
tadpole-shaped parasitic larva of a trematode worm; tail disappears in adult stage

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/09/03 01:07:23」(JST)

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Life-history stages of the trematode flatworm Fasciola hepatica from 1911 Encyclopædia Britannica

Trematodes or flukes are small parasitic flatworms that use vertebrates as their definitive host, and molluscs (usually freshwater snails or land snails) as their intermediate host. 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 cercarial larvae.^[1] The cercaria either infects vertebrates through the skin or is ingested. In its vertebrate host, the cercaria matures to an adult form, the fluke, and lays eggs that are discharged with the host feces or urine. In the presence of open water, the eggs hatch and the miracidium stage of life is reached again.

Typical life cycle stages

Metacercariae of Clinostomum phalacrocoracis in fish^[2]

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 life cycle stages are:

Egg

Discharged either in open water or in intestine of definitive host.

Miracidium (plural miracidia)

A free-living motile form, it is covered with cilia, and settles in the mollusc to become a sporocyst.^[3]

Sporocyst

An elongated sac, it produces either rediae or more sporocysts.^[4]

Redia (plural rediae)

A larval form with an oral sucker, it will produce either more rediae, or cercariae.^[4]

Cercaria (plural cercariae)

The larval form of the parasite, it develops within the germinal cells of the sporocyst or redia.^[4] A cercaria has a tapering head with large penetration glands.^[3] It may or may not have a long swimming "tail", depending on the species.^[4] 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, it is capable of sexual reproduction.

Deviations from the typical life cycle

Not all trematodes follow the typical sequence of eggs, miracidia, sporocysts, rediae, cercariae, and adults. In some species, the redial 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.^[3]

Representations of life cycles of several different trematode species

Life cycle stages of a digenean human parasite, Schistosoma japonicum

Life cycle stages of a digenean fish parasite, Bucephalus polymorphus

Life cycle stages of trematode species that cause "swimmer's itch"

References

^ "2. Fish Diseases (Cont'd.) 2.1.4 Parasitic Diseases". FAO of the UN Food and Agriculture Organization of the United Nations. Retrieved 18 February 2011.
^ Caffara, Monica; Davidovich, Nadav; Falk, Rama; Smirnov, Margarita; Ofek, Tamir; Cummings, David; Gustinelli, Andrea; Fioravanti, Maria L. (2014). "Redescription of Clinostomum phalacrocoracis metacercariae (Digenea: Clinostomidae) in cichlids from Lake Kinneret, Israel". Parasite. 21: 32. ISSN 1776-1042. PMC 4078730 . PMID 24986336. doi:10.1051/parasite/2014034.
^ ^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.

External links

Life cycle of Schistosoma mansoni

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English Journal

Discovery of molluscicidal and cercaricidal activities of 3-substituted quinazolinone derivatives by a scaffold hopping approach using a pseudo-ring based on the intramolecular hydrogen bond formation.

Guo W1, Zheng LY1, Li YD2, Wu RM1, Chen Q1, Yang DQ3, Fan XL4.
European journal of medicinal chemistry.Eur J Med Chem.2016 Jun 10;115:291-4. doi: 10.1016/j.ejmech.2016.03.037. Epub 2016 Mar 17.
Discovery of novel topological agents against Oncomelania hupensis snails and cercariae remains a significant challenge in current Schistosomiasis control. A pseudo-ring formed from salicylanilide by an intramolecular hydrogen bond led to the discovery of 3-substituted quinazolinone derivatives whic
PMID 27017555

Aptitude of Lymnaea palustris and L. stagnalis to Fasciola hepatica larval development through the infection of several successive generations of 4-mm-high snails.

Vignoles P1, Rondelaud D1, Dreyfuss G2.
Parasitology research.Parasitol Res.2016 Jun;115(6):2263-8. doi: 10.1007/s00436-016-4969-6. Epub 2016 Mar 5.
Bimiracidial infections of Lymnaea palustris and Lymnaea stagnalis (shell height at exposure, 4 mm) with Fasciola hepatica were carried out during six successive snail generations to determine if prevalence and intensity of snail infection increased over time through descendants issuing from eggs l
PMID 26944418

Saposin-like Proteins, a Multigene Family of Schistosoma Species, Are Biomarkers for the Immunodiagnosis of Schistosomiasis Japonica.

Liu S1, Zhou X1, Piao X1, Hou N1, Shen Y2, Zou Y3, Li S1, Cao J2, Chen Q4.
The Journal of infectious diseases.J Infect Dis.2016 May 10. pii: jiw188. [Epub ahead of print]
BACKGROUND: One major obstacle to schistosomiasis prevention and control is the lack of accurate and sensitive diagnostic approaches, which are essential for planning, targeting, and evaluating disease control efforts.METHODS: Based on bioinformatics analysis, we identified a multigene family
PMID 27190177

Japanese Journal

Analysis of the effectiveness of control measures against Schistosoma mekongi using an intra- and inter-village model in Champasak Province, Lao PDR

Fukuhara Kazuma,Phompida Samlane,Insisiengmay Sithat,Kirinoki Masashi,Chigusa Yuichi,Nakamura Satoshi,Matsuda Hajime,Ishikawa Hirofumi
Parasitology International 60(4), 452-459, 2011-12
… The chief characteristic of the present model is competence in dealing with the spread of infection among villages through the Mekong River in consideration of the reduction in longevity of cercariae and miracidia and their diffusion in the river. …
NAID 120004754293

Proteome approach for identification of schistosomiasis japonica vaccine candidate antigen.

ABDEL-HAFEEZ Ekhlas Hamed,KIKUCHI Mihoko,WATANABE Kanji,ITO Takashi,YU Chuanxin,CHEN Honggen,NARA Takeshi,ARAKAWA Takeshi,AOKI Yoshiki,HIRAYAMA Kenji
Parasitology international : official journal of the Japanese Society of Parasitology 58(1), 36-44, 2009-03-01
… Experimental vaccination with radiation-attenuated cercariae (RAC) confers possible practical levels of resistance to challenge infection by humoral and by cellular mechanism. … From the positive fractions we chose 17 of SEA and 10 of SWAP that had no reactivity with normal cercariae infected (NCI) sera and had single peak of 214 nm; …
NAID 10025329984

吸虫セルカリアに対する銅・亜鉛および塩素の毒性

児玉裕美子,浦部美佐子
水環境学会誌 = Journal of Japan Society on Water Environment 29(3), 157-162, 2006-03-10
… The toxicities of copper, zinc and chlorine to free-swimming cercariae of five trematode taxa were assayed. … magniovatus cercariae did not die during the experiment, but they ultimately did not metamorphose into metacercariae. …
NAID 10017312735