For example, amphibians of species Pseudacris regilla, Rana aurora and Taricha torosa were found to physically display a higher frequency in the number of abnormalities.

R. ondatrae is a digenetic trematode that occurs in lentic aquatic environments and has a complex life cycle that requires the infection of three different host species.

For second intermediate hosts, the free-swimming cercariae will begin to locate a suitable area for encystment where cercarial bodies will enclose themselves within cyst walls (metacercariae).

Since herbicides and pesticides affect the prevalence of R. ondatrae in frogs, they tend to increase mortality and pathology due to extra or missing limbs.

[4] The birds that eat the crippled amphibians act as a tertiary host in which the flatworm reproduces, and by which it is spread over larger distances.

Like Trifolium spp., the defining morphological structure of R. ondatrae is the appearance of two laterally projecting esophageal diverticula, which are located halfway along the length of the esophagus.

Another feature is the presence of a rose-colored organ or pink colored tissue that resides between the oral sucker and pharynx of freshly shed living specimens.

Studies show that when frogs or toads are affected with R. ondatrae it seems that the most common spot for any deformity is on the hind limbs.