The capybara or greater capybara (Hydrochoerus hydrochaeris) is the largest living rodent, native to South America. It is a member of the genus Hydrochoerus. Its close relatives includeguinea pigs and rock cavies, and it is more distantly related to the agouti, the chinchilla, and the nutria. The capybara inhabits savannas and dense forests, and lives near bodies of water. It is a highly social species and can be found in groups as large as one hundred individuals, but usually live in groups of 10–20 individuals. The capybara is hunted for its meat and hide and also for grease from its thick fatty skin.
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In this Dossier
Agouti in the context of Tijuca Forest
The Tijuca National Park (Portuguese: Parque Nacional da Tijuca) is an urban national park in the mountains of the city of Rio de Janeiro, Brazil. The park is part of the Atlantic Forest Biosphere Preserve, and is administered by the Chico Mendes Institute for Biodiversity Conservation (ICMBio).
The area is composed of secondary vegetation, as it is the result of reforestation carried out during the Second Empire, when it became clear that deforestation caused by coffee farms was harming the drinking water supply of the then capital of the Empire. More than 230 species of animals and birds live in the park, including capuchin monkeys, coatis, agoutis, wild dogs, marmosets, hummingbirds and thrushes.
Agouti in the context of Agouti gene
Agouti-signaling protein is a protein that in humans is encoded by the ASIP gene. It is responsible for the distribution of melanin pigment in mammals. Agouti interacts with the melanocortin 1 receptor to determine whether the melanocyte (pigment cell) produces phaeomelanin (a red to yellow pigment), or eumelanin (a brown to black pigment). This interaction is responsible for making distinct light and dark bands in the hairs of animals such as the agouti, which the gene is named after. In other species such as horses, agouti signalling is responsible for determining which parts of the body will be red or black. Mice with wildtype agouti will be grey-brown, with each hair being partly yellow and partly black. Loss of function mutations in mice and other species cause black fur coloration, while mutations causing expression throughout the whole body in mice cause yellow fur and obesity.
The agouti-signaling protein (ASIP) is a competitive antagonist with alpha-Melanocyte-stimulating hormone (α-MSH) to bind with melanocortin 1 receptor (MC1R) proteins. Activation by α-MSH causes production of the darker eumelanin, while activation by ASIP causes production of the redder phaeomelanin. This means where and while agouti is being expressed, the part of the hair that is growing will come out yellow rather than black.