| Tawny-bellied cotton rat | |
|---|---|
 | |
| S. fulviventer in Janos, Chihuahua, Mexico | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Rodentia |
| Family: | Cricetidae |
| Subfamily: | Sigmodontinae |
| Genus: | Sigmodon |
| Species: | S. fulviventer |
| Binomial name | |
| Sigmodon fulviventer J.A. Allen, 1889 | |
The tawny-bellied cotton rat (Sigmodon fulviventer) is a species of rodent in the family Cricetidae. It is found in Mexico and in the US states of Arizona and New Mexico. [1]
Sexual dimorphism is not present, but the adult male weighs slightly more than the female at 222 grams (7.8 oz) compared to 206 grams (7.3 oz). The tail has small scales and is covered in hair which distinguishes it from the larger scales of the closely related hispid cotton rat (Sigmodon hispidus). [2] Another characteristic distinguishing it from S. hispidus is a short and broad rather than elongated skull. The dentition is marked by well-developed maxillary incisors and high-crowned molars. [3]
The fur is tawny on the belly (the origin of the species' common name), and black and tan speckled on the back. The fur body contains three types of hair: guard-awl hair, guard hair, and under hair. The guard hair is the longest with the guard-awl and under hair following in decreasing length. [2] Whiskers are located on the face and have been observed to play a role in maintaining body position while swimming. [4]
The species inhabits the grasslands of central Mexico, expanding north to the central and southwestern parts of New Mexico and southeastern parts of Arizona. [2] It prefers areas with dense grass, in which it makes navigational trails called runways that resemble a tunnel with a grass covering. It feeds on grasses, specifically bunchgrass, which they also use in nest-building. [5] Its range in central New Mexico is expanding westward due to an increase in precipitation and in temperature from climate change. [5]
The tawny-bellied cotton rat occurs in the same area as the closely related hispid cotton rat, with the former occupying the moister areas and the latter the more arid areas. [5] When living in adjacent habitats, one species tends to become more numerous while the other maintains a smaller population. Even though both species seem to avoid one another, there is a passive, indirect competition between the species. In Durango, Mexico, S. fulviventer was found to be dominant, probably due to being a specialist compared to the generalist S. hispidus. [6]
The tawny-bellied cotton rat is used as a model organism to develop and test human pathogen treatments. [6] It is affected by many of the same viral and bacterial infections that humans are susceptible to, which helps create vaccines and therapeutic treatments. Other factors that make the species a desirable test subject are the existence of inbred strains, ease of handling, and inexpensive upkeep. [7] Some of the diseases tested on the cotton rat are respiratory syncytial virus, [8] and pulmonary tuberculosis, [9] and HIV type-1. [7]
In the case of HIV type-1, finding an animal with similar antibody response to the virus as humans can prove difficult. A study conducted in 1998 found that the tawny-bellied cotton rat can be infected by low-level HIV-1. [7] A similar immune response to humans is activated on infection. The degree of infection may be increased by altering the co-receptors on the animal's cells, which would improve the reliability of the test subject. [7]
The species was found to undergo an equivalent infection to pulmonary tuberculosis as humans. [9] This is an upgrade over the previous animal models of other small rodents and rabbits. Cotton rats combine the best traits of human-like lung granuloma formation (trait of rabbits) and inexpensive care (trait of other small rodents) to provide a suitable host for this type of study. Future research is underway to use the cotton rat for studying pulmonary tuberculosis complicated by HIV-1 due to similarities with humans in both diseases. [9]
The rodent subfamily Sigmodontinae includes New World rats and mice, with at least 376 species. Many authorities include the Neotominae and Tylomyinae as part of a larger definition of Sigmodontinae. When those genera are included, the species count numbers at least 508. Their distribution includes much of the New World, but the genera are predominantly South American, such as brucies. They invaded South America from Central America as part of the Great American Interchange near the end of the Miocene, about 5 million years ago. Sigmodontines proceeded to diversify explosively in the formerly isolated continent. They inhabit many of the same ecological niches that the Murinae occupy in the Old World.
A cotton rat is any member of the rodent genus Sigmodon. Their name derives from their damaging effects on cotton as well as other plantation crops, such as sugarcane, corn, peanut and rice. Cotton rats have small ears and dark coats, and are found in North and South America. Members of this genus are distributed in the Southwestern United States, Mexico, Central America, and South American countries of: Venezuela, Ecuador, Colombia, Peru, Brazil, Guyana, and Suriname. Many of the species are found in Mexico.
Gregory Antone Prince is an American pathology researcher, businessman, author, social critic, and historian of the Latter Day Saint movement.
The hispid cotton rat is a rodent species long thought to occur in parts of South America, Central America, and southern North America. However, recent taxonomic revisions, based on mitochondrial DNA sequence data, have split this widely distributed species into three separate species. The distribution of S. hispidus ranges from Arizona in the west to Virginia to the east and from the Platte River in Nebraska in the north to, likely, the Rio Grande in the south, where it meets the northern edge of the distribution of S. toltecus. Adult size is total length 202–340 mm (8.0–13.4 in); tail 87–122 mm (3.4–4.8 in), frequently broken or stubbed; hind foot 29–35 mm (1.1–1.4 in); ear 16–20 mm (0.63–0.79 in); mass 50–250 g (1.8–8.8 oz). They have been used as laboratory animals.
The Jaliscan cotton rat or Mexican cotton rat is a species of rodent in the family Cricetidae. It is found only in Mexico. They commonly have brown fur with white fur on the belly. They are ground-dwelling and prefer open habitats.
The Toltec cotton rat is a rodent species in the family Cricetidae. It is found in eastern Mexico from the Rio Grande to the Yucatán Peninsula, as well as in Belize and northern Guatemala. It prefers moist grassland habitat. While long thought to be a subspecies of S. hispidus, recent taxonomic revisions, based on mitochondrial DNA sequence data, have split the extensive former species range into three separate species. Carroll et al. (2004) indicate that the southern edge of the S. hispidus distribution is likely near the Rio Grande where it meets the northern distribution of S. toltecus. The range of S. toltecus extends from northern Mexico south into Chiapas where it occurs in sympatry with S. hirsutus . Rats from this species group have been used as laboratory animals.
The southern cotton rat is a rodent species in the family Cricetidae. It is found from southern Chiapas in Mexico through Central America, except for Belize, and as far east as northern Colombia and Venezuela. It lives in tropical rainforest, dry forest and savanna, as well as in cultivated areas. The species is terrestrial and primarily diurnal. It was long thought to be a subspecies of S. hispidus. However, recent taxonomic revisions, based on mitochondrial DNA sequence data, have split the extensive former species range into three separate species. Carroll et al. (2004) indicate that the southern edge of the S. hispidus distribution is likely near the Rio Grande where it meets the northern distribution of S. toltecus. The range of S. toltecus extends from northern Mexico south into Chiapas where it occurs in sympatry with S. hirsutus . Rats from this species group have been used as laboratory animals.
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.
Taenia rileyi is a tapeworm of the genus Taenia from the United States. Adults infect bobcats and feral domestic cats, but larvae have been found in rodents such as the cotton mouse, the marsh rice rat in Florida, and the hispid cotton rat in Florida and Georgia. These rodents may serve as intermediate hosts.
Taenia mustelae is a tapeworm of the genus Taenia from the United States. Adults infect carnivorans such as weasels, skunks, and martens, but larvae have been found in rodents such as the Florida mouse and the marsh rice rat in Florida and the hispid cotton rat in Florida and Georgia. These rodents may serve as intermediate hosts.
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:
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.
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.
Playa de Oro virus (OROV) is a probable species of orthohantavirus found in the rodents Oryzomys couesi and Sigmodon mascotensis in the Mexican state of Colima. The former is thought to be the main host. The sequences of parts of the virus's RNA-based genome have been determined; they differ by 7–10% in amino acid composition and 22–24% in nucleotide composition from closely related viruses.
Black Creek Canal orthohantavirus (BCCV) is a single-stranded, negative sense RNA virus species of New World Orthohantavirus. It was first isolated in cotton rats found in the Black Creek Canal area of Dade County, Florida in 1995. The discovery followed from an isolated case of Hantavirus pulmonary syndrome diagnosed in a Dade County resident.
Hantavirus pulmonary syndrome (HPS) is one of two potentially fatal syndromes of zoonotic origin caused by species of hantavirus. These include Black Creek Canal virus (BCCV), New York orthohantavirus (NYV), Monongahela virus (MGLV), Sin Nombre orthohantavirus (SNV), and certain other members of hantavirus genera that are native to the United States and Canada.
