| Rock pocket mouse | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Rodentia |
| Family: | Heteromyidae |
| Genus: | Chaetodipus |
| Species: | C. intermedius |
| Binomial name | |
| Chaetodipus intermedius (Merriam, 1889) | |
The rock pocket mouse (Chaetodipus intermedius) is one of 19 species of pocket mice in the genus Chaetodipus . It is sometimes grouped in the genus Perognathus . [2]
Found mainly in rocky outcrops in the deserts of the southwestern United States and Mexico, the rock pocket mouse is medium-sized (length ~18 cm, weight ~12–18g) and nocturnal. It eats mainly plant seeds and makes small burrows in soil close to or under rocks to evade owls, its main predator. The breeding season spans a few months, starting in February or March, and the litter size is typically between three and six. As with most pocket mice, the tail is longer than the body (~10 cm).
Historically, rock pocket mice have been subdivided into as many as ten subspecies (Benson 1933; Dice and Blossom 1937) based on geographical distribution and coat colour. Most rock pocket mouse populations have light, tawny fur consistent with the colour of the desert rocks on which they live. However, darker coloured rock pocket mice are found living amid black, basaltic rock formations.
In 2003, scientists sampled DNA from both light- and dark-coloured rock pocket mice from areas in Pinacate Peaks, Mexico and New Mexico, USA. In the Pinacate mice, they discovered a perfect association between different versions of the Melanocortin-1 receptor (Mc41r6) gene and coat colour. [3] Subsequent studies demonstrated that there is strong selective pressure maintaining Mc1r allele and coat colour frequencies across the short geographic distances between the light- and dark-coloured rock islands. [4]
Thus melanism in rock pocket mice is considered a fabulous example of adaptation by natural selection. Changes in the Mc1r gene sequence are not responsible for the colour difference in the mice sampled from New Mexico, however, leading the researchers to conclude that the almost identical dark coat colours developed multiple times in rock pocket mice, an example of convergent evolution. [5]
The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. The frequency of dark-coloured moths increased at that time, an example of industrial melanism. Later, when pollution was reduced, the light-coloured form again predominated. Industrial melanism in the peppered moth was an early test of Charles Darwin's natural selection in action, and it remains a classic example in the teaching of evolution. In 1978, Sewall Wright described it as "the clearest case in which a conspicuous evolutionary process has actually been observed."
Melanism is the congenital excess of melanin in an organism resulting in dark pigment.
Heteromyidae is a family of rodents consisting of kangaroo rats, kangaroo mice, pocket mice and spiny pocket mice. Most heteromyids live in complex burrows within the deserts and grasslands of western North America, though species within the genus Heteromys are also found in forests and their range extends as far south as northern South America. They feed mostly on seeds and other plant parts, which they carry in their fur-lined cheek pouches to their burrows.
Perognathinae is a subfamily of rodents consisting of two genera of pocket mice. Most species live in complex burrows within the deserts and grasslands of western North America, They feed mostly on seeds and other plant parts, which they carry in their fur-lined cheek pouches to their burrows.
Chaetodipus is a genus of pocket mice containing 17 species endemic to the United States and Mexico. Like other members of their family such as pocket mice in the genus Perognathus, they are more closely related to pocket gophers than to true mice.
Bailey's pocket mouse is a species of rodent of the subfamily Perognathinae, family Heteromyidae. It is found in Baja California, Sinaloa and Sonora in Mexico and in California, Arizona and New Mexico in the United States.
The California pocket mouse is a species of nocturnal and primarily solitary rodent in the family Heteromyidae.
Goldman's pocket mouse is a species of rodent in the family Heteromyidae. It is endemic to Mexico, where it is threatened by the increasing conversion of its dry, scrubby habitat into agricultural land. As a result, the International Union for Conservation of Nature has assessed its conservation status as being "near threatened".
The Sinaloan pocket mouse is one of 17 species of pocket mice in the genus Chaetodipus. Two subspecies of C. pernix are recognized, C. p. pernix and C. p. rostratus, all are endemic to Mexico.
The genetic basis of coat colour in the Labrador Retriever has been found to depend on several distinct genes. The interplay among these genes is used as an example of epistasis.
Pangaré is a coat trait found in some horses that features pale hair around the eyes, muzzle, and underside of the body. These pale areas can extend up to the flanks, throat and chest, behind the elbows, in front of the stifle, and up the buttock. Animals with the pangaré trait are sometimes called "mealy" or "light-pointed". The color of these lighter areas depends on the underlying color and ranges from off-white to light tan. This type of coloration is most often found in breeds such as the Fjord horse, Exmoor Pony, and Haflinger. Wild equids like the Przewalski's Horse, Onager, African Wild Ass, Kiang as well as the domestic donkey exhibit pangaré as a rule. Pangaré is thought to be a type of protective countershading. Horse foals are often born with "foal pangaré" or light points, especially over black haired areas, which they lose when they shed their foal coats.
Amelanism is a pigmentation abnormality characterized by the lack of pigments called melanins, commonly associated with a genetic loss of tyrosinase function. Amelanism can affect fish, amphibians, reptiles, birds, and mammals including humans. The appearance of an amelanistic animal depends on the remaining non-melanin pigments. The opposite of amelanism is melanism, a higher percentage of melanin.
The Chihuahuan pocket mouse is a species of heteromyid rodent found in the southwestern United States and Mexico. It was formerly considered a subspecies of the desert pocket mouse, but was determined to be a distinct species in 1996, following analysis of its mitochondrial DNA.
The melanocortin 1 receptor (MC1R), also known as melanocyte-stimulating hormone receptor (MSHR), melanin-activating peptide receptor, or melanotropin receptor, is a G protein–coupled receptor that binds to a class of pituitary peptide hormones known as the melanocortins, which include adrenocorticotropic hormone (ACTH) and the different forms of melanocyte-stimulating hormone (MSH). It is coupled to Gαs and upregulates levels of cAMP by activating adenylyl cyclase in cells expressing this receptor. It is normally expressed in skin and melanocytes, and to a lesser degree in periaqueductal gray matter, astrocytes and leukocytes. In skin cancer, MC1R is highly expressed in melanomas but not carcinomas.
Danielle "Hopi" Elisabeth Hoekstra is an evolutionary biologist working at Harvard University in Cambridge, Massachusetts, whete she is Dean of the Harvard Faculty of Arts and Sciences. Her lab uses natural populations of rodents to study the genetic basis of adaptation. She is the C.Y. Chan Professor of Arts and Sciences and the Xiaomeng Tong and Yu Chen Professor of Life Sciences in the Department of Organismic and Evolutionary Biology and the Department of Molecular and Cellular Biology at Harvard University. She is also the Curator of Mammals at the Museum of Comparative Zoology and a Harvard College Professor. In 2014, Hoekstra became a Howard Hughes Medical Institute Investigator. In 2016, she was elected to the National Academy of Sciences, and in 2017, she was elected to the American Academy of Arts and Sciences. Hoekstra became the Edgerley Family Dean of Harvard's Faculty of Arts and Sciences in August 2023.
The agouti gene, the Agouti-signaling protein (ASIP) is responsible for variations in color in many species. Agouti works with extension to regulate the color of melanin which is produced in hairs. The agouti protein causes red to yellow pheomelanin to be produced, while the competing molecule α-MSH signals production of brown to black eumelanin. In wildtype mice, alternating cycles of agouti and α-MSH production cause agouti coloration. Each hair has bands of yellow which grew during agouti production, and black which grew during α-MSH production. Wildtype mice also have light-colored bellies. The hairs there are a creamy color the whole length because the agouti protein was produced the whole time the hairs were growing.
