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.
Eimeria kinsellai is an apicomplexan parasite of the genus Eimeria that infects the marsh rice rat. It was discovered in 1970 at Paynes Prairie, Alachua County, Florida. A different Eimeria, Eimeria palustris, has been found in Alabama marsh rice rats. E. kinsellai differs from other Eimeria found in rice rats, such as Eimeria couesii, Eimeria oryzomysi, Eimeria ojastii, and E. palustris, in anatomical details. It was named after parasitologist John M. Kinsella.
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.
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.
Cladotaenia circi is a tapeworm of the genus Cladotaenia that has birds of prey as its definitive host, such as the western marsh harrier, hen harrier, and peregrine falcon in Europe. It has been found at low frequencies in small mammals, such as the bank vole and common vole in Hungary and the marsh rice rat in Florida.
Ascocotyle pindoramensis is a fluke in the genus Ascocotyle that occurs along the eastern coast of the Americas from Brazil to Nicaragua, Mexico, Louisiana, and Florida and doubtfully in Egypt. It occurs in the intestine of its definitive hosts. Hosts recorded in the wild include the least bittern, roseate spoonbill, great blue heron, striated heron, stripe-backed bittern, yellow-crowned night heron, black-crowned night heron, osprey, Neotropic cormorant, and marsh rice rat. In the marsh rice rat, it infected 9% of rats examined in a 1970–1972 study in the salt marsh at Cedar Key, Florida, but none in a freshwater marsh. A. pindoramensis has been experimentally introduced into the domestic duck, chicken, dog, house mouse, and golden hamster. It occurs in various body parts of its intermediate hosts—the poeciliid fish Phalloptychus januarius, Poecilia catemaconis, Poecilia mexicana, Poecilia mollienisicola, Poecilia vivipara, and a species of Xiphophorus and the cichlid Tilapia. It was first described as Pygidiopsis pindoramensis in 1928 and subsequently as Pseudoascocotyle mollienisicola in 1960. The latter species was moved to Ascocotyle in 1963, but only in 2006 it was recognized that the two represent the same species, which is now known as Ascocotyle pindoramensis. Other flukes from Argentina and Mexico that were identified as Pygidiopsis pindoramensis instead represent a different species of Pygidiopsis.
Brachylaima virginianum is a fluke of the genus Brachylaima that infects the Virginia opossum throughout its range. It has also been found in young black bears and in marsh rice rats, both from Florida., and from raccoons in Kentucky.
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.
Maritrema prosthometra is a parasitic fluke from North America. It was first described in 1969 from the intestine of the clapper rail in eastern North America. Later, it was also found in the small intestine of 5% of a sample of marsh rice rats collected in a salt marsh at Cedar Key, Florida, where it used the fiddler crab Uca pugilator as an intermediate host.
Maritrema is a genus of trematodes (flukes) in the family Microphallidae, although some have suggested its placement in the separate family Maritrematidae. It was first described by Nikoll in 1907 from birds in Britain. Species of the genus usually infect birds, but several have switched hosts and are found in mammals, such as the marsh rice rat. Several species use the fiddler crab Uca pugilator as an intermediate host.
Microphallus nicolli is a species of digenean parasite in the genus Microphallus. Recorded hosts include the marsh rice rat in a saltmarsh at Cedar Key, Florida, where the crab Eurytium limosum is an intermediate host, and the sea otter in central California. It was previously known as Spelotrema nicolli.
Urotrema scabridum is a fluke in the genus Urotrema of family Urotrematidae. Recorded hosts include:
Capillaria gastrica is a parasitic nematode in the genus Capillaria. Among the known host species are the marsh rice rat and deermouse.
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.
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.
