mole

mole¹

/mohl/, n.

1. any of various small insectivorous mammals, esp. of the family Talpidae, living chiefly underground, and having velvety fur, very small eyes, and strong forefeet.

2. a spy who becomes part of and works from within the ranks of an enemy governmental staff or intelligence agency. Cf. double agent.

3. Mach. a large, powerful machine for boring through earth or rock, used in the construction of tunnels.

[1350-1400; ME molle; akin to MD, MLG mol]

mole²

/mohl/, n.

a small, congenital spot or blemish on the human skin, usually of a dark color, slightly elevated, and sometimes hairy; nevus.

[bef. 1000; ME; OE mal; c. OHG meil spot, Goth mail wrinkle]

mole³

/mohl/, n.

1. a massive structure, esp. of stone, set up in the water, as for a breakwater or a pier.

2. an anchorage or harbor protected by such a structure.

[1540-50; < L moles mass, dam, mole]

mole⁴

/mohl/, n. Chem.

the molecular weight of a substance expressed in grams; gram molecule.

Also, mol.

[1900-05; < G Mol, short for Molekül MOLECULE]

mole⁵

/mohl/, n. Pathol.

a fleshy mass in the uterus formed by a hemorrhagic dead ovum.

[1605-15; < NL mola, special use of mola millstone]

mole⁶

/moh"lay/; Sp. /maw"le/, n. Mexican Cookery.

a spicy sauce flavored with chocolate, usually served with turkey or chicken.

[1925-30; < MexSp < Nahuatl molli sauce; cf. GUACAMOLE]

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I

Any burrowing, often blind insectivore in the family Talpidae (including 42 species of true moles) or Chrysochloridae (18 species of golden moles).

Most species have short legs and tail, a pointed head, velvety grayish fur, no external ears, and a strong odour. They range from 3.5 to 8 in. (9 to 20 cm) long. The forelimbs are rotated outward like oars and have broad or pointed claws on the toes. Moles are active day and night, digging surface tunnels in search of earthworms, grubs, and other invertebrates and excavating deep (10 ft [3 m]), vented burrows (molehills) for occupancy. The star-nosed mole (Condylura cristata) of northeastern North America has 22 pink, tentacle-like touch organs radiating from its muzzle.

II

Pigmented flat or fleshy skin mark, made up mostly of cells that produce melanin, which gives moles their light to dark brown or black colour and, in the dermis, a bluish cast.

Thicker moles also contain nerve elements and connective tissue. Moles often begin in childhood, usually as flat spots between the dermis and epidermis. Those that remain there are more likely to become malignant. Most move into the dermis and become slightly raised. In children, moles may undergo changes resembling cancer but are benign. Malignant melanoma can begin in moles but almost never before puberty. During pregnancy, moles may enlarge and new ones may appear. Moles sometimes disappear with age. The term nevus refers to a congenital skin mark, whereas a mole may develop after birth. Epidermal nevi are usually the same colour as the surrounding skin.

III

or mol

Standard unit for measuring everyday quantities of such minute entities as atoms or molecules.

For any substance, the number of atoms or molecules in a mole is Avogadro's number (6.02 × 10²³) of particles. Defined exactly, it is the amount of pure substance containing the same number of chemical units that there are in exactly 12 g of carbon-12. For each substance, a mole is its atomic weight, molecular weight, or formula weight in grams. The number of moles of a solute in a litre of solution is its molarity (M); the number of moles of solute in 1,000 g of solvent is its molality (m). The two measures differ slightly and have different uses. See also stoichiometry.

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▪ chemistry

also spelled  mol 

      in chemistry, a standard scientific unit for measuring large quantities of very small entities such as atoms (atom), molecules (molecule), or other specified particles.

      The mole designates an extremely large number of units, 6.02214179 × 10²³, which is the number of atoms determined experimentally to be found in 12 grams of carbon-12. Carbon-12 was chosen arbitrarily to serve as the reference standard of the mole unit for the International System of Units (SI). The number of units in a mole also bears the name Avogadro's number, or Avogadro's constant, in honour of the Italian physicist Amedeo Avogadro (Avogadro, Amedeo) (1776–1856). Avogadro proposed that equal volumes of gases (gas) under the same conditions contain the same number of molecules, a hypothesis that proved useful in determining atomic and molecular weights and which led to the concept of the mole. (See Avogadro's law.)

      The number of atoms or other particles in a mole is the same for all substances. The mole is related to the atomic weight, or mass, of an element in the following way: one mole of carbon-12 atoms has 6.02214179 × 10²³ atoms and an atomic weight of 12 grams. In comparison, one mole of oxygen consists, by definition, of the same number of atoms as carbon-12, but it has an atomic weight of 16 grams. Oxygen, therefore, has a greater mass than carbon. This reasoning also can be applied to molecular or formula weights.

      The concept of the mole helps to put quantitative information about what happens in a chemical equation on a macroscopic level. The mole can be used to determine the simplest formula of a compound (chemical compound) and to calculate the quantities involved in chemical reactions (chemical reaction). When dealing with reactions that take place in solutions, the related concept of molarity is useful. Molarity (M) is defined as the number of moles of a solute in a litre of solution.

▪ insectivore

Introduction

  any of 42 species of insectivores (insectivore), most of which are adapted for aggressive burrowing and for living most of their lives underground. Burrowing moles have a cylindrical body with a short tail and short, stocky limbs. A long, nearly hairless, and highly mobile piglike muzzle extends beyond the upper lip. Most species lack external ears, and their tiny eyes are hidden in their fur. Many have a strong odour.

Natural history

      Moles have poor vision but acute senses of hearing and touch. The muzzle is tipped with thousands of microscopic tactile structures (Eimer's organs). Using these structures and sensory hairs along the muzzle and elsewhere on the body, moles detect and differentiate details of their environment and their prey. The powerful forelimbs of most species are rotated outward from the body, like oars protruding from a boat. The large circular hands are fringed with sensory hairs and have broad spadelike claws for digging; they also function as paddles for swimming.

      Moles are generally active all year and by day or night in cycles of activity and rest. Typical moles will only infrequently go to the surface to gather nest materials and seek water during drought. Terrestrial moles primarily eat earthworms, but they also consume other invertebrates, occasionally small mammals, succulent plant parts (roots, tubers, bulbs), seeds, and fungi. Amphibious moles eat aquatic invertebrates, fish, and amphibians. Some moles can consume more than their weight in food daily. There is one litter per year, usually of three to five young, born in a nest of dry vegetation; gestation lasts a month.

      Most species construct temporary tunnels through the soil with their front limbs, using a fore-and-aft motion similar to a human swimming the breaststroke. Permanent complex systems of galleries containing storage and nesting chambers are excavated up to 4.5 metres (15 feet) underground. The mole braces its body in the tunnel to shear soil from the tunnel face with first one forelimb and then the other and then turns around to push the loose soil with its forefeet through the tunnel onto the surface to form a small mound (molehill). The European mole (Talpa europaea) sometimes constructs a huge mound (fortress) of up to 750 kg (1,650 pounds) of soil, and it too contains tunnel networks and storage and nesting chambers. Moles have an acute sense of smell and mark their burrows with urine containing odorous substances produced by a pair of scent glands beneath the skin of the lower abdomen.

      In North America moles live throughout the eastern and western portions of the continent but not in the Great Plains or western deserts. In the Old World their range extends from Europe eastward to the Malayan Peninsula, Taiwan, and Japan. They primarily inhabit temperate regions, and in the Southeast Asian tropics they are restricted to temperate-like mountain habitats. They are found at elevations extending from sea level to 4,500 metres (14,800 feet). Moles dwell in moist lowland and alpine meadows, river floodplains, prairies, sagebrush-grass habitats, coniferous and deciduous forests, coastal sand dunes, cultivated fields and gardens, marshy areas, streams, lakes, and rivers.

Mole diversity

      The smallest mole is the American shrew mole (Neurotrichus gibbsii), which weighs only 7 to 11 grams (0.25 to 0.39 ounce) and has a body 3 to 4 cm (less than 2 inches) long and a slightly shorter tail. The largest is the Russian desman (Desmana moschata) of central Eurasia, which weighs 100 to 220 grams and has a body 18 to 22 cm long and a tail nearly as long. The nine species of Old World moles (genus Talpa), however, are typical, weighing 65 to 120 grams and having a body 9 to 18 cm long and a very short tail. The short, dense, velvety fur lies in any direction, providing no resistance to the mole as it moves forward or backward through burrows. The short-furred tail is also covered with longer sensitive bristles.

      Asian, Japanese, and American shrew moles (genera Uropsilus, Urotrichus, and Neurotrichus, respectively) differ from typical moles in that they resemble shrews (shrew) and are much less specialized for burrowing. Their tails are nearly as long as the body. The external ears are large and either extend beyond the fur (Uropsilus) or are hidden in it (Urotrichus). Hands and claws are small, resembling those of shrews, and the palms can be placed flat on the ground. Shrew moles spend much time aboveground and forage along subsurface tunnels resembling shallow troughs that run through leaf litter and the top layer of soft, moist soil. They also construct deeper, more complex burrows, but these extend no more than 30 cm belowground. The American shrew mole is an adept climber and swimmer and is the only North American mole to nest aboveground.

      The Russian and Pyrenean desmans (genera Desmana and Galemys, respectively) are amphibious, nesting in burrows and foraging underwater. They have webbed feet fringed with hair, water-repellent fur, and closable nostrils and ear openings. Desmans (desman) also have a long, vertically flattened tail fringed with stiff hairs. They propel themselves through the water with their broad hind feet and tail.

 The star-nosed mole (Condylura cristata) has the body form and anatomical specializations of typical moles but possesses a longer tail and slightly smaller forefeet. It is unique among mammals in having a muzzle tipped with 22 fleshy tentacles that are constantly moving. The tentacles are extremely sensitive not only to touch and ground vibrations but to electricity generated by the bodies of prey. This mole excavates deep tunnels, but it also forages along pathways on the surface and in water, where it is an expert swimmer and diver.

Classification and paleontology

      The 17 genera of “true” moles are classified in three subfamilies of the family Talpidae (order Soricimorpha), which belongs to a larger group of mammals referred to as insectivores. Their closest living relatives are shrews (family Soricidae). The evolutionary history of moles extends to the Eocene Epoch (54.8 to 33.7 million years ago) of Europe, the Oligocene Epoch (33.7 to 23.8 million years ago) of Asia and the Mediterranean region, and the Late Oligocene Epoch (28.5 to 23.8 million years ago) of North America. The closest relatives of moles belong to an extinct family (Proscalopidae) known from the Oligocene to the Miocene in North America.

Family Talpidae (“true” moles)

 42 species in 17 genera. 30 fossil genera have been identified from the Middle Eocene of Europe, the Oligocene in Asia and the Mediterranean region, and the Late Oligocene in North America.

      Subfamily Talpinae

 36 species in 14 genera from Asia and North America.

      Genus Talpa (Old World moles)

 9 species from Europe.

      Genus Mogera (East Asian moles)

 7 species from Asia.

      Genus Euroscaptor (Oriental moles)

 6 species from Southeast Asia and Japan.

      Genus Scapanus (western American moles)

 3 species from North America.

      Genus Urotrichus (Japanese shrew moles)

 2 species.

      Genus Condylura (star-nosed mole)

 1 species from Canada and the United States.

      Genus Nesoscaptor (Ryukyu, or Shenkaku, mole)

 1 species from Japan.

      Genus Neurotrichus (American shrew mole)

 1 species from western Canada and western United States.

      Genus Parascalops (hairy-tailed mole)

 1 species from Canada and the United States.

      Genus Parascaptor (white-tailed mole)

 1 species from Asia.

      Genus Scalopus (eastern mole)

 1 North American species.

      Genus Scapanulus (Gansu mole)

 1 species from central China.

      Genus Scaptochirus (short-faced mole)

 1 species from northeastern China.

      Genus Scaptonyx (long-tailed mole)

 1 species from southern China and Myanmar (Burma).

      Subfamily Uropsilinae

 

      Genus Uropsilus (Asiatic shrew moles)

 4 species from central China and Myanmar (Burma).

      Subfamily Desmaninae (desmans (desman))

 2 species in 2 genera from Europe and western Asia.

      Genus Desmana (Russian desman)

 1 species from Europe and western Asia.

      Genus Galemys (Pyrenean desman)

 1 European species.

Guy Musser

Additional Reading

Martyn L. Gorman and R. David Stone, The Natural History of Moles (1990), supplements biological and behavioral information with maps, drawings, and plates.

▪ skin disease

      in dermatology, pigmented, flat or fleshy skin lesion, composed for the most part of an aggregation of melanocytes, the cells of the skin that synthesize the pigment melanin. In thicker moles, nerve elements and connective tissue are also present. Moles vary in colour from light to dark brown or black; when deposition of melanin occurs in the dermis, the deeper layer of the skin located underneath the epidermis, the lesion has a bluish cast. Moles may be present at birth; more frequently, they appear and evolve in character during childhood.

      A new mole is usually flat and of the junctional type (junction nevus), so called because it is located between the dermis and the epidermis. It sometimes remains there, in which case the possibility of malignant development is increased. In most instances, however, the original mole evolves into a slightly raised lesion located in the dermis (intradermal nevus). Examination of the tissue of an actively changing mole in a child may show transformations resembling cancer, but actually such lesions are benign; malignant melanoma is almost never seen until after puberty.

      The following developments are indicative that a mole may be undergoing cancerous changes, giving rise to malignant melanoma: (1) development of a flat pigment zone around the base of the mole, (2) progressive enlargement of an existing mole in adults, (3) increase in pigmentation, or darkening, of a mole and, more frequently, a loss of evenness in pigmentation, with variations from very light to very dark (probably the single most significant sign of developing malignant melanoma), (4) loss of hair from a mole (hairy moles rarely undergo cancerous changes), and (5) advanced obvious symptoms, such as ulceration and bleeding. It should be noted that melanomas do not derive from pigmented moles only; approximately 25 percent of these tumours arise in normal skin. During pregnancy, existing moles may enlarge and new ones may appear. Moles will sometimes disappear with age. See also nevus.

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