The caatinga vesper mouse (''Calomys expulsus'') (also known as the caatinga laucha
or rejected vesper mouse
) is a
rodent
Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
in the family
Cricetidae
The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, muskrats, and New World rats and mice. At over 870 species, it is either the largest or second-largest family ...
from
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
.
It is endemic to eastern
Brazil
Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
, where it is found in open savanna (
cerrado
The Cerrado () is a vast ecoregion of Tropics, tropical savanna in central Brazil, being present in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Maranhão, Piauí, Bahia, Minas Gerais, São Paulo (state), São Paulo, Paraná ...
) and thorny scrub (
caatinga
Caatinga () is a type of semi-arid tropical vegetation, and an ecoregion characterized by this vegetation in interior northeastern Brazil. The name "Caatinga" comes from the Tupi word '' ka'atinga'', meaning "white forest" or "white vegetat ...
) habitats.
[ Its ]karyotype
A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is discerned by de ...
has 2n = 66 and FN = 68. It was formerly synonymized with '' C. callosus'', but the latter has 2n = 50 and FN = 66.[ Karyologic analysis of ''C. expulsus'' has shown that the ]X chromosome
The X chromosome is one of the two sex chromosomes in many organisms, including mammals, and is found in both males and females. It is a part of the XY sex-determination system and XO sex-determination system. The X chromosome was named for its u ...
is large and submetacentric
The centromere links a pair of sister chromatids together during cell division. This constricted region of chromosome connects the sister chromatids, creating a short arm (p) and a long arm (q) on the chromatids. During mitosis, spindle fibers ...
while the Y chromosome
The Y chromosome is one of two sex chromosomes in therian mammals and other organisms. Along with the X chromosome, it is part of the XY sex-determination system, in which the Y is the sex-determining chromosome because the presence of the ...
is either acrocentric
The centromere links a pair of sister chromatids together during cell division. This constricted region of chromosome connects the sister chromatids, creating a short arm (p) and a long arm (q) on the chromatids. During mitosis, spindle fibers ...
or submetacentric. Predators include the barn owl
The barn owls, owls in the genus '' Tyto'', are the most widely distributed genus of owls in the world. They are medium-sized owls with large heads and characteristic heart-shaped faces. They have long, strong legs with powerful talons. The ter ...
.
References
Calomys
Endemic mammals of Brazil
Fauna of the Caatinga
Rodents of Brazil
Mammals described in 1841
{{Calomys-stub