The marsh rice rat is a semiaquatic North American rodent in the family Cricetidae. It usually occurs in wetland habitats, such as swamps and salt marshes. It is found mostly in the eastern and southern United States, from New Jersey and Kansas south to Florida and northeasternmost Tamaulipas, Mexico; its range previously extended further west and north, where it may have been a commensal in corn-cultivating communities. Weighing about 40 to 80 g, the marsh rice rat is a medium-sized rodent that resembles the common black and brown rat. The upperparts are generally gray-brown, but are reddish in many Florida populations. The feet show several specializations for life in the water. The skull is large and flattened, and is short at the front.
Lyperosomum intermedium is a parasitic trematode belonging to the subclass Digenea that infects the marsh rice rat. The species was first described in 1972 by Denton and Kinsella, who wrote that it was closest to Lyperosomum sinuosum, known from birds and raccoons in the United States and Brazil. Three years later, Denton and Kissinger placed the two, together with a number of other species, in a new subgenus of Lyperosomum, Sinuosoides. Species of Lyperosomum mainly infect birds; L. intermedium is one of the few species to infect a mammal.
Notocotylus fosteri is a parasitic fluke that infects the marsh rice rat in Florida.
Maritrema heardi is a parasitic fluke that infects the marsh rice rat in a salt marsh at Cedar Key, Florida. It was first listed as Maritrema sp. II in 1988, then described as the only species of a new genus, Floridatrema heardi, in 1994, and eventually reassigned in 2003 to Maritrema as Maritrema heardi. Its intermediate host is the fiddler crab Uca pugilator and it lives in the intestine of the marsh rice rat, its definitive host. Together with two other species of Maritrema, it is very common in affected marsh rice rats; it infects 19% of studied rats at Cedar Key. According to Tkach and colleagues, M. heardi is probably primarily a parasite of birds that has secondarily infected the marsh rice rat. Floridatrema was distinguished from Maritrema on the basis of its possession of loops of the uterus that extend forward to the place where the intestine is forked or even to the pharynx. Genetically, M. heardi may be closest to the morphologically similar M. neomi, which infects Neomys water shrews in the Carpathians.
Aonchotheca forresteri is a parasitic nematode that infects the marsh rice rat in Florida. Occurring mainly in adults, it inhabits the stomach. It is much more common during the wet season, perhaps because its unknown intermediate host is an earthworm that only emerges when it rains. The worm was discovered in 1970 and formally described in 1987. Originally classified in the genus Capillaria, it was reclassified in Aonchotheca in 1999. A. forresteri is small and narrow-bodied, with a length of 13.8 to 19.4 mm in females and 6.8 to 9.2 mm in males. Similar species such as A. putorii differ in features of the alae and spicule, the size of the female, and the texture of the eggs.
Hassalstrongylus forresteri is a nematode worm of the genus Hassalstrongylus that infects the marsh rice rat in the United States. It was first described as Hassalstrongylus musculi by Marie-Claude Durette-Desset in 1972, but she later recognized it as a different species, H. forresteri. The females cannot be distinguished from those of the other species in the marsh rice rat, H. musculi and H. lichtenfelsi.
Hassalstrongylus musculi is a nematode worm of the genus Hassalstrongylus that infects the marsh rice rat and house mouse in the United States and Oryzomys couesi, Oligoryzomys fulvescens, and Handleyomys melanotis in San Luis Potosí, Mexico. It was first described as Longistriata musculi by Dikmans in 1935, but transferred to Hassalstrongylus in 1971 and 1972 by Marie-Claude Durette-Desset. She later renamed the material she had used to describe H. musculi in 1972 as H. forresteri. The females cannot be distinguished from those of the other species in the marsh rice rat, H. forresteri and H. lichtenfelsi.
Hassalstrongylus lichtenfelsi is a nematode worm of the genus Hassalstrongylus that infects the marsh rice rat in Florida. The females cannot be distinguished from those of the other species in the marsh rice rat, H. forresteri and H. musculi.
Fibricola lucida is a fluke that infects Virginia opossums, American minks, and marsh rice rats in North America. In a study in Florida, F. lucida was the only fluke of the marsh rice rat that occurred in both the freshwater marsh at Paynes Prairie and the saltwater marsh at Cedar Key. At the former locality, it infected 11% of rice rats and the number of worms per infected rat ranged from 1 to 65, averaging 17. At Cedar Key, 67% of rice rats were infected and the number of worms per infected rat ranged from 1 to 1975, averaging 143.
Gynaecotyla adunca is a fluke that normally infects birds. It has also been found in 15% of a sample of the marsh rice rat from a salt marsh at Cedar Key, Florida. It uses fiddler crabs such as Uca rapax as its intermediate host.
Litomosoides scotti is a parasitic nematode in the genus Litomosoides. First described in 1973, it infects the marsh rice rat and is known from a saltwater marsh at Cedar Key, Florida.
Mastophorus muris is a parasitic nematode in the genus Mastophorus. It infects animals such as the marsh rice rat, hispid cotton rat, and singing vole.
Parastrongylus schmidti is a species of parasitic nematode in the genus Parastrongylus. It was first described as Angiostrongylus schmidti in 1971 from the marsh rice rat in Florida, but later assigned to Parastrongylus.
Pterygodermatites ondatrae is a species of parasitic nematode in the genus Pterygodermatites. It has been recorded in the hispid cotton rat in Florida and Texas. In Florida, it has also been recorded on the marsh rice rat, together with an unnamed species of the same genus, the female of which cannot be distinguished from that of P. ondatrae.
Physaloptera hispida is a parasitic nematode in the genus Physaloptera. It has been found on the marsh rice rat, hispid cotton rat, Florida mouse, cotton mouse, and oldfield mouse in Florida.
Spiruridae is family of nematodes in the order Spirurida. An unidentified parasitic larval member of this family has been recorded in the marsh rice rat in a salt marsh at Cedar Key, Florida, and also in fiddler crabs (Uca) there; it is perhaps a bird parasite that does not reach maturity in the rice rat.
Syphacia oryzomyos is a nematode that infects the marsh rice rat in Florida. A similar species of Syphacia has been recorded from the rice rats Oligoryzomys fulvescens and Handleyomys melanotis in San Luis Potosí, but because only females were found, this worm could not be identified to species.
Trichostrongylus affinis is a species of parasitic nematode in the genus Trichostrongylus. It primarily infects cottontails (Sylvilagus), but has also been found in the hispid cotton rat and the marsh rice rat.
Trichostrongylus sigmodontis is a species of parasitic nematode in the genus Trichostrongylus. It primarily infects the hispid cotton rat, but has also been found in the marsh rice rat.
