''Calomys cerqueirai'' is a

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), ...

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 ...

in the genus ''

Calomys Vesper mice are rodents belonging to the genus ''Calomys''. They are widely distributed in South America. Some species are notable as the Vector (epidemiology), vectors of Argentinian hemorrhagic fever and Bolivian hemorrhagic fever. The genus w ...

'' from southeastern

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 ...

. Distinct from other ''Calomys'' in 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 ...

and characters of the fur, it is known only from two places in

Minas Gerais Minas Gerais () is one of the 27 federative units of Brazil, being the fourth largest state by area and the second largest in number of inhabitants with a population of 20,539,989 according to the 2022 Brazilian census, 2022 census. Located in ...

. The karyotype was first described in 1996 and the species was formally named in 2010.

Taxonomy

In 1996, Geise and coworkers described a new karyotypic variant of ''Calomys'' from

Lagoa Santa, Minas Gerais Lagoa Santa (''Holy Lagoon'') is a Brazilian municipality and region in the state of Minas Gerais. It is located 37 km north-northeast from Belo Horizonte and belongs to the mesoregion Metropolitana de Belo Horizonte and to the microregion ...

with 36

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

s and a fundamental number of 66

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosome ...

arms ( 2n = 36, FNa = 66), and a 2007 genetic analysis confirmed that the new variant represents an evolutionary lineage separate from other ''Calomys'' species. In 2010, Bonvicino and others described another karyotypic variant from Capitão Andrade, also in Minas Gerais, with 2n = 38 and FNa = 66, and concluded that both karyotypic variants represented a single, previously undescribed species, which they named ''Calomys cerqueirai''. The specific name honors Brazilian mammalogist Rui Cerqueira. A single fusion or fission event is sufficient to derive one of the two karyotypes from the other. According to evidence from the

mitochondrial A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...

cytochrome ''b'' gene, ''Calomys cerqueirai'' is sister to a group of four other species within a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of large-bodied ''Calomys''.

Description

''Calomys cerqueirai'' is a relatively small member of the

Sigmodontinae 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 ...

, but is large for a ''Calomys''. The upperparts are yellowish brown, becoming lighter towards the sides; this coloration is sharply delineated from the whitish underparts. The external ears (pinnae) are small and rounded and have a patch of white hair behind them. The tail, which is dark above and white below, is relatively short. The feet are fairly long and narrow and are covered above by white hairs.Bonvicino et al., 2010, p. 28 In two specimens from Capitão Andrade, the head and body length is , the tail length is , the hindfoot length is , the ear length is , and the body mass is .Bonvicino et al., 2010, table 3 In the skull, the front region (

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

) is short and the

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, brain-pan, or brainbox, is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calv ...

is broadened. The incisive foramina are long, extending between the first molars. The

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...

itself is also long, extending beyond the third molars, and near the third molars is perforated by a pair of posterolateral palatal pits.Bonvicino et al., 2010, p. 29 The cutting faces of the upper

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s are inclined backwards ( opisthodont). The upper third molars are reduced in size.Bonvicino et al., 2010, p. 30 It differs from other ''Calomys'' by its karyotype and by characters of the fur.Bonvicino et al., 2010, pp. 31–32

Ecology and behavior

The species is known from two localities in Minas Gerais, southeastern Brazil, near the border of the Atlantic Forest and

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 ...

biomes.Bonvicino et al., 2010, p. 20 Both specimens from Capitão Andrade were caught in grass near a stream. The species is infected by species of '' Taenia'' and '' Hepsilon'' and unidentified

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

s.Bonvicino et al., 2010, p. 21

References

Literature cited

* Bonvicino, C.R., de Oliveira, J.A. and Gentile, R. 2010
A new species of ''Calomys'' (Rodentia: Sigmodontinae) from southeastern Brazil.
Zootaxa 2336:19–35. {{Taxonbar, from=Q5023152 cerqueirai Rodents of Brazil Endemic mammals of Brazil Mammals described in 2010