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.
Gigantolaelaps mattogrossensis is a mite from the Americas. It has been found on the marsh rice rat, hispid cotton rat, black rat, brown rat, and white-footed mouse in the United States. In Venezuela, it has been recorded from Holochilus brasiliensis, Sigmodon hirsutus, and Marmosa robinsoni. In Argentina, it has been found on Scapteromys aquaticus, Oligoryzomys flavescens, and Holochilus brasiliensis. The North American form was first described as a separate species, Gigantolaelaps cricetidarum, and is still occasionally considered as such.
Amblyomma maculatum is a species of tick in the genus Amblyomma. Immatures usually infest small mammals and birds that dwell on the ground; cotton rats may be particularly favored hosts. Some recorded hosts include:
Androlaelaps fahrenholzi is a species of mite in the genus Androlaelaps of the family Laelapidae. It occurs throughout the contiguous United States, where it has been recorded on the following mammals:
Euschoengastia peromysci is a mite in the genus Euschoengastia of the family Trombiculidae. Recorded hosts include the cotton mouse and marsh rice rat in Georgia; the northern short-tailed shrew, northern red-backed vole, northern flying squirrel, rock vole, white-footed mouse, and deermouse in Tennessee; and northern red-backed vole, southern bog lemming, masked shrew, and eastern red squirrel in North Carolina, among others.
Euschoengastia setosa is a mite in the genus Euschoengastia of the family Trombiculidae that mostly parasitizes small rodents and lagomorphs. Recorded hosts include marsh rice rat in Georgia; the deermouse in Tennessee; and the eastern red squirrel in North Carolina, among others.
Eutrombicula batatas is a species of chigger.
Haemogamasus is a genus of mites in the family Haemogamasidae. In North America, they mostly infect rodents, in addition to other small mammals such as shrews, talpids, and Virginia opossums.
Ixodes brunneus is a species of tick in the genus Ixodes. It is normally a parasite of birds, but has also been recorded on the marsh rice rat.
Ixodes minor is a species of tick in the genus Ixodes. Some reported hosts are:
Ixodes texanus is a species of ticks in the genus Ixodes. It mainly infects raccoons, but has also been recorded on the marsh rice rat in Georgia.
Laelaps manguinhosi is a species of parasitic mite in the family Laelapidae. In the United States, it has been found on the marsh rice rat in Florida, Texas, and South Carolina. Other recorded hosts include the sigmodontine rodents Scapteromys aquaticus, Akodon azarae, Oligoryzomys flavescens, and Holochilus brasiliensis in Argentina and Oryzomys couesi and Handleyomys melanotis in Mexico. In Venezuela, it mainly infects the oryzomyines Holochilus sciureus and Nectomys, but it has also been recorded on a variety of other mammals and even on a bird. A separate subspecies, Laelaps manguinhosi calvescens, has been described from the ichthyomyine rodent Neusticomys venezuelae.
Listrophorus is a genus of parasitic mites in the family Listrophoridae. North American species with their hosts include:
Oryzomysia oryzomys is a parasitic mite in the genus Oryzomysia of the family Atopomelidae. It has been found on the marsh rice rat in Georgia. It was formerly known as Chirodiscoides oryzomys in the family Listrophoridae, but was later transferred to the atopomelid genus Oryzomysia.
Prolistrophorus bakeri is a parasitic mite in the genus Prolistrophorus. Together with the Argentine P. hirstianus, it forms the subgenus Beprolistrophorus. P. bakeri has been found on the hispid cotton rat, marsh rice rat, and cotton mouse in Georgia, South Carolina, Texas, and Florida and on Oryzomys couesi in Colima. It was formerly placed in the genus Listrophorus.
Prolistrophorus grassii is a parasitic mite in the genus Prolistrophorus. It was described as Listrophorus grassii in 1954 from the marsh rice rat in Georgia. In 1974, Fain and Hyland placed it in Prolistrophorus and in 1984, Fain and Lukoschus redescribed the species on the basis of collections from the marsh rice rat in Georgia, Alabama, and Florida and the southern bog lemming in Indiana, West Virginia, and Iowa.
Radfordia palustris is a species of mite in the subgenus Hesperomyobia of the genus Radfordia. It has been recorded on the marsh rice rat in Florida, Georgia, and South Carolina.
Eutrombicula splendens is a species of chigger. In Florida, it has been found on the marsh rice rat and hispid cotton rat.
Laelaps is a genus of common parasitic mites in the family Laelapidae. Species, with their hosts, include:
