Currently three species and one subspecies of Ribeiroia are recognized: R. ondatrae in North America, R. marini in the Caribbean, R. m. guadeloupensis on the Caribbean island of Guadeloupe, and R. congolensis in Africa ( Johnson et al.

Ribeiroia ondatrae has an indirect complex life cycle.

The key identifying characteristic of Ribeiroia ondatrae cercariae is the bifurcated esophagus ( although note that this trait can occur in some closely related genera such as Cladocystis trifolium.

Experimental exposure to Ribeiroia ondatrae cercariae has been shown to cause limb malformations in various frog, toad and salamander species, including Pseudacris regilla, Anaxyrus boreas, Lithobates pipiens, A. americanus, Ambystoma macrodactylum, L. clamitans and L. sylvatica.

Ribeiroia ondatrae is most often recovered from amphibians in lentic habitats, such as ponds, lakes, and wetlands, which support planorbid snails.

Nutrient enrichment leads to eutrophication, which has been linked with emergence of Ribeiroia ondatrae through direct and indirect effects on aquatic food webs ( Johnson and Chase 2004 ).

For Ribeiroia ondatrae, host species differences in susceptibility can influence infection patterns in multi-species communities ( Johnson et al.

In light of these data, and the increasing evidence that Ribeiroia infections are on the rise ( Johnson and McKenzie 2008 ), it is prudent to treat Ribeiroia ondatrae as a threat to amphibian populations and diversity, particularly in combination with other stressors.

* Ribeiroia ondatrae

Parasite ( Ribeiroia ondatrae ) infection linked to amphibian malformations in the western United States.

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.

Ribeiroia is a group of trematode parasites ( or flatworms ) that sequentially infect freshwater snails in the family Planorbidae ( ramshorn snails ) as first intermediate hosts, fish and larval amphibians as second intermediate hosts, and birds and mammals as definitive hosts ( see chapter Life Cycle ).

Ribeiroia is a genus of parasites in the class Trematoda, phylum Platyhelminthes.

The trematode Cercaria lileta is also closely related to Ribeiroia, and molecular sequence data indicates that it may actually be a species of Ribeiroia ( Johnson et al.

The factors determining variation in susceptibility among species remain poorly understood, but these observations suggest that the type of malformation alone is unlikely to be diagnostic of Ribeiroia exposure.

The role of Ribeiroia in explaining accounts of amphibian malformations in other regions is varied ; Ribeiroia has been associated with malformation ‘ hotspots ’ in the midwestern and northeastern USA, but it was not detected in malformation surveys from Vermont, Alaska, Bermuda, and Michigan.

Less is known about the distribution of Ribeiroia in Canada and Central America.

Although more research is necessary, these studies provide evidence that malformations, especially those linked to Ribeiroia infection, are emerging in some amphibian populations.

Ribeiroia infection is not responsible for Vermont amphibian deformities.

Ribeiroia infection has been linked to malformations in naturally occurring amphibian populations, especially in the western and midwestern USA.

In a large-scale study in the western USA, both the presence and abundance of Ribeiroia infection predicted higher-than-baseline ( e. g., > 5 %) frequencies of abnormalities in one or more amphibian species.

All species of Ribeiroia share the distinctive morphological characteristic of esophageal diverticula ( i. e., two short, dead-end branches that extend laterally from the esophagus ).

One pond in particular ( Jette Pond in western Montana ) showed increased prevalence of malformations in Pseudacris regila from 20 % in 1960 to 46 % in 2000, which was correlated with an increased intensity of Ribeiroia infection.

Other species of Ribeiroia occur in the Caribbean and South America ( R. marini and R. marini guadeloupensis ) and in Africa ( R. congolensis ).

For instance, in multiple species of frogs and toads, laboratory studies show that even low levels of Ribeiroia infection can induce 30-95 % mortality ( see Johnson et al.

Other genera closely related to Ribeiroia include Trifolium, Cathemasia, and Echinostoma ( Johnson et al.

Correspondingly, multi-year field studies show that in localities of high infection and malformations in metamorphosing frogs, < 2 % of amphibians returning to breed exhibit malformations, suggesting Ribeiroia infection and malformations have deleterious consequences for individual survival and fecundity ( Johnson et al.

The morphology and life history of Psilostomum ondatrae Price 1931 ( Trematoda: Psilostomatidae ).

The existence of a community is a state of mind -- a conviction that goals and values are widely shared, that effective communication is possible, that mutual trust is reasonably assured.

Of the handful of painters that Austria has produced in the 20th century, only one, Oskar Kokoschka, is widely known in the U.S..

What they should recognize is that children who have been placed in one of these groups on a narrow academic basis still differ widely in attributes that influence success, and that they still must be treated as individuals.

But to return to the main line of our inquiry, it is doubtful that Utopia is still widely read because More was medieval or even because he was a martyr -- indeed, it is likely that these days many who read Utopia with interest do not even know that its author was a martyr.

Utopia is still widely read because in a sense More stood on the margin of modernity.

Every few days, in the early morning, as the work progressed, twenty men would appear to push it ahead and to shift the plank foundation that distributed its weight widely on the Rotunda pavement, supported as it is by ancient brick vaulting.

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The suburban high school, it is worth noting, also is not a widely comprehensive high school because of the absence of vocational programs.

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There is nothing in the whole range of human experience more widely known and universally felt than spirit.

The English saints are widely venerated, quite naturally, and now there is great hope that the Forty Martyrs and Cardinal Newman will soon be canonized.

The average overall albedo of Earth, its planetary albedo, is 30 to 35 %, because of the covering by clouds, but varies widely locally across the surface, depending on the geological and environmental features.

Famous novelists of the 20th century include Mohammed Dib, Albert Camus, Kateb Yacine and Ahlam Mosteghanemi while Assia Djebar is widely translated.

Among the proposed etymologies is the Hurrian and Hittite divinity, Aplu, who was widely invoked during the " plague years ".

The most widely spoken Afroasiatic language is Arabic ( including all its colloquial varieties ), with 230 million native speakers, spoken mostly in the Middle East and North Africa.

The abacus was in use centuries before the adoption of the written modern numeral system and is still widely used by merchants, traders and clerks in Asia, Africa, and elsewhere.

The Brønsted-Lowry definition is the most widely used definition ; unless otherwise specified acid-base reactions are assumed to involve the transfer of a proton ( H < sup >+</ sup >) from an acid to a base.

This essay is widely held to be one of the greatest examples of sustained irony in the history of the English language.

Cyrillic is one of the most widely used modern alphabetic scripts, and is notable for its use in Slavic languages and also for other languages within the former Soviet Union.