Calomys cerqueirai
Encyclopedia
Calomys cerqueirai is a species
of rodent
in the genus Calomys from southeastern Brazil. Distinct from other Calomys in its karyotype
and characters of the fur, it is known only from two places in Minas Gerais
. The karyotype was first described in 1996 and the species was formally named in 2010.
variant of Calomys from Lagoa Santa
, Minas Gerais
with 36 chromosome
s and a fundamental number of 66 autosomal
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
cytochrome b
gene, Calomys cerqueirai is sister to a group of four other species within a clade
of large-bodied Calomys.
, 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. In two specimens from Capitão Andrade, the head and body length is 86 millimetre, the tail length is 75 millimetre, the hindfoot length is 86 to 112 mm (3.4 to 4.4 in), the tail length is 75 to 85 mm (3.0 to 3.3 in), the hindfoot length is 21 to 22 mm (0.83 to 0.87 in), the ear length is 16 to 18 mm (0.63 to 0.71 in), and the body mass is 25 to 35 g (0.9 to 1.2 oz).
In the skull, the front region (rostrum
) is short and the braincase is broadened. The incisive foramina
are long, extending between the first molars. The palate
itself is also long, extending beyond the third molars, and near the third molars is perforated by a pair of posterolateral palatal pits
. The cutting faces of the upper incisor
s are inclined backwards (opisthodont). The upper third molars are reduced in size.
It differs from other Calomys by its karyotype and by characters of the fur.
biomes. 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
s.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
in the genus Calomys from southeastern Brazil. Distinct from other Calomys in its karyotype
Karyotype
A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
and characters of the fur, it is known only from two places in Minas Gerais
Minas Gerais
Minas Gerais is one of the 26 states of Brazil, of which it is the second most populous, the third richest, and the fourth largest in area. Minas Gerais is the Brazilian state with the largest number of Presidents of Brazil, the current one, Dilma Rousseff, being one of them. The capital is the...
. The karyotype was first described in 1996 and the species was formally named in 2010.
Taxonomy
In 1996, Geise and coworkers described a new karyotypicKaryotype
A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
variant of Calomys from Lagoa Santa
Lagoa Santa
For Lagoa Santa, a municipality in Goiás see Lagoa Santa, GoiásLagoa Santa is a municipality and region in the state of Minas Gerais, Brazil...
, Minas Gerais
Minas Gerais
Minas Gerais is one of the 26 states of Brazil, of which it is the second most populous, the third richest, and the fourth largest in area. Minas Gerais is the Brazilian state with the largest number of Presidents of Brazil, the current one, Dilma Rousseff, being one of them. The capital is the...
with 36 chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s and a fundamental number of 66 autosomal
Autosome
An autosome is a chromosome that is not a sex chromosome, or allosome; that is to say, there is an equal number of copies of the chromosome in males and females. For example, in humans, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, to be specific: X and Y...
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
Capitão Andrade
Capitão Andrade is a town and municipality in the state of Minas Gerais in the Southeast region of Brazil. The most Important root family that actually started the city was The Rodrigues family, popular known as Pio's family ....
, 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
Mammalogy
In zoology, mammalogy is the study of mammals – a class of vertebrates with characteristics such as homeothermic metabolism, fur, four-chambered hearts, and complex nervous systems...
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
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
cytochrome b
Cytochrome b
Cytochrome b/b6 is the main subunit of transmembrane cytochrome bc1 and b6f complexes. In addition, it commonly refers to a region of mtDNA used for population genetics and phylogenetics.- Function :...
gene, Calomys cerqueirai is sister to a group of four other species within a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of large-bodied Calomys.
Description
Calomys cerqueirai is a relatively small member of the SigmodontinaeSigmodontinae
The subfamily Sigmodontinae is one of the most diverse groups of mammals. It 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...
, 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. In two specimens from Capitão Andrade, the head and body length is 86 millimetre, the tail length is 75 millimetre, the hindfoot length is 86 to 112 mm (3.4 to 4.4 in), the tail length is 75 to 85 mm (3.0 to 3.3 in), the hindfoot length is 21 to 22 mm (0.83 to 0.87 in), the ear length is 16 to 18 mm (0.63 to 0.71 in), and the body mass is 25 to 35 g (0.9 to 1.2 oz).
In the skull, the front region (rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
) is short and the braincase is broadened. The incisive foramina
Incisive foramen
The fossa incisiva is an opening in the bone of the oral hard palate where blood vessels and nerves may pass. There are four of these openings in the incisive fossa.-Formation:...
are long, extending between the first molars. The palate
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 separate. The palate is divided into two parts, the anterior...
itself is also long, extending beyond the third molars, and near the third molars is perforated by a pair of posterolateral palatal pits
Posterolateral palatal pits
In anatomy, posterolateral palatal pits are gaps at the sides of the back of the bony palate, near the last molars. Posterolateral palatal pits are present, in various degrees of development, in several members of the rodent family Cricetidae...
. The cutting faces of the upper incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s are inclined backwards (opisthodont). The upper third molars are reduced in size.
It differs from other Calomys by its karyotype and by characters of the fur.
Ecology and behavior
The species is known from two localities in Minas Gerais, southeastern Brazil, near the border of the Atlantic Forest and CerradoCerrado
The Cerrado, is a vast tropical savanna ecoregion of Brazil, particularly in the states of Gioas and Minas Gerais...
biomes. Both specimens from Capitão Andrade were caught in grass near a stream. The species is infected by species of Taenia
Taenia (tapeworm)
Taenia is a genus of tapeworm that includes some important parasites of livestock. Members of the genus are responsible for taeniasis and cysticercosis in humans. There are more than 100 species recorded...
and Hepsilon and unidentified nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s.
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.