Cercaria


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cercaria

[sər′kar·ē·ə]
(invertebrate zoology)
The larval generation which terminates development of a digenetic trematode in the intermediate host.

Cercaria

 

the larva of parasitic worms of the class Trematoda. The body, which measures 0.3–1 mm in length, has an oral and a ventral sucker. Cercariae have a furcately branched intestine, a nervous system, sometimes ocelli, cephalic glands, and well-developed protonephridia. Typical of cercariae is the development of a tail, which is sometimes bifurcate (in furcocercariae) or equipped with lateral appendages.

The cercaria develops inside the preceding larval form, the sporocyst or redia, as a result of parthenogenesis. It leaves the body of the first intermediate host, a mollusk, and swims in water by means of its tail. It then penetrates the body of the second intermediate host, an invertebrate or frequently a fish, and becomes a metacercaria. The common liver fluke has no second intermediate host; the cercaria becomes encysted on coastal vegetation and is transformed into the next larval form, adolescarium.

References in periodicals archive ?
Koie (1973) rarely found tailed cercaria and considered tailless cercaria as metacercaria that do not encyst but are infective to the final host, as described by Lebour (1910).
According to Bartoli (1974), a gymnophallid cercaria can be identified by the following characteristics: Distome, pharyngeate larva, tegument spinose, eyespots absent, stylet lacking, excretory vesicle thin-walled V or Y shaped, furcated tail, developing in marine bivalves.
Hugghins (1954) described the life cycle of Hysteromorpha triloba (Rudolphi, 1819) whose cercaria is similar to Furcocercaria XIX in the morphology of the penetration gland cells, presence of three circles of spines surrounding the opening of the ventral sucker, number and position of sensory hairs on the body (one pair) and several pairs in the tail stem, resting position, size of the body (168-221/41-50 H.
Our study results, determined by using molecular techniques, confirmed that the cercaria stage of a digenetic trematode, P.
Para el establecimiento de esta parasitosis es necesaria la coincidencia de los hospedadores intermediarios y definitivos, temperaturas mayores de 10[grados]C, suelos con deficiente drenaje y/o humedad, caracteristicas indispensable para la sobrevivencia y multiplicacion de lymneidos [5,6], asi como para sobrevivencia y diseminacion de cercarias y metacercarias [7].
Similar observations were recorded by [61] in the snail Archachatina marginata that the digestive gland tubule becomes compressed thereby resulting reduced tubular lumen of the gland as observed by that more cercaria and rediae were found in between the hepatic tubules and tunica propria causing extension of the space between tubules.
An efficient method for the exposure of mice to cercaria of Schistosoma mansoni.
We cracked the shells of each live red-rim melania snail between the first and second body whorl, removed the digestive tract, and examined each for rediae and cercaria of trematodes with a dissecting microscope at 100x total magnification.
They are unique among digeneans by having a furcocystocercous cercaria that is macroscopic, progenetic, and actively swims, mimicking a fish prey item.
The life cycle of this digenean was first completed by Ostrowski de Nunez [6] in Argentina working with Pleurolophocercous cercaria released from the naturally infected Litoridina castellanosae (= Heleobia castellanosae (Gaillard, 1974) (Gastropoda: Hydrobiidae).
Description of redia and cercaria of Paragonimus peruvianus from experimentally infected Aroapyrgus colombiensis of Condebamba Valley, Peru.