Mice

MICE, small rodents forming together with rats the subfamily Murinae. Mus musculus, the house mouse, is a cosmopolitan species that has spread worldwide with man. It lives in houses and outbuildings; it can inhabit gardens and shrubbery located near settlements. Mus musculus hortulanus, the steppe or mound-building mouse; the underside of the body is whitish with an ochreous tinge, the upper side is grayish-brown or reddish-gray. The paws are white with dark claw bases. Length of the body with the head is up to 7.4 cm, tail 5.7 cm. It lives in steppes, where it accumulates food supplies for the winter in specially constructed mounds. For the winter, it can also climb into ricks and houses. Mus agrarius, the striped field mouse, is reddish-brown on top and white underneath; a black stripe runs along the middle line of the back. Body length with head is 8–10.5 cm, and tail 5–6 cm. It inhabits fields, forest edges, and floodplains. It can move into the immediate vicinity of man and climb not only into ricks, but also into dwellings. Mus flavicollis (Mus silvaticus), the yellow-necked field mouse, is reddish-brown above; a rust-colored spot often stands out on the white coloration of the throat. It lives in forests and bushes. The house mouse has albinos, known as white mice, which find wide application as laboratory animals (see). Certain anatomical features of mice boil down to the following: the right lung is divided into four lobes, the left is solid. The apex of the heart lies in the fourth left intercostal space near the sternum. The intestine exceeds body length threefold, reaching 20–25 cm in length. Taeniae and constrictions on the cecum are absent. The liver is generally four-lobed; its four excretory ducts merge into a common ductus hepaticus near the duodenal wall. This duct, together with the artery, runs along the edge of the hepatoduodenal ligament. The gallbladder is present. The pancreas adjoins the greater curvature of the stomach. The spleen is suspended immediately near the stomach on a short gastrosplenic ligament. The stomach is simple. The testes rise from under the skin into the abdominal cavity or return back in connection with the mating period. The uterus is bipartite (uterus bipartitus). The placenta is disc-shaped. The domestic mouse lives on average 2–3 years, but can reach seven years of age. Sexual maturity occurs in the second month of life. Mating occurs five to six times a year. Pregnancy lasts 22–24 days; the female litters 4–6 hairless young, whose eyes open on the 13th day. Feeding of the young by the female lasts about 16 days. Over the course of a year, a female produces up to 30 direct descendants. A mutation of the house mouse known as "dancing mice" is interesting; they have a congenital defect of the equilibrium apparatus, and they run very rapidly in a circle or spin for a long time in one place. Some domestic mice emit sounds, which is why they are called singing or chirping mice. The significance of mice is great. Being rodents that inhabit human dwellings, mice spoil provisions and supplies; very great harm can be caused by them gnawing valuable objects (rare and expensive books, manuscripts, wooden objects, collections, and many others). The economic harmfulness of mice inhabiting fields and steppes is quite great. Mice move into ricks, where they make passages and eat out the grain in folded ears. It happens that practically only chaff remains in a rick. It has been noted that in some years mice multiplied in untold numbers and filled entire provinces, causing enormous damage by the destruction of grain. Mice can infect man with various parasites, maintaining the existence of the latter in the environment surrounding man. Mice and human diseases. Mus flavicollis can be infected with rabies. Mus musculus is susceptible to plague. Diplococcus pneumoniae and Spirella morsus muris (=Spirillum minus) (sodoku) can be found in mice; mice can be a reservoir of Leptospira ictero-haemorrhagiae. The fungus Sabouraudites quinckeanus (Achorion quinckeanum) can pass from mice to man. Parasites of mice. — I. Protozoa: A. Sarcodina. Entamoeba muris, closely resembling Entamoeba coli (intestine). B. Flagellates: Spiromonas angusta (Toxobodo Sangiorgii), Oicomonas termo (intestine); Cryptococcus muris and Toxoplasma musculi (spleen); Trypanosoma lewisi (blood); Trypanosoma duttoni (the same); Trichomonas muris (intestine); Hexamita muris (intestine); Giardia muris (intestine). C. Sporozoa. Microsporidia: Encephalitozoon cuniculi (brain); Coccidiomorpha: Cryptosporidium muris (stomach), Eimeria falciformis (stomach, intestine), Piroplasma muris (erythrocytes), Toxoplasma musculi (endothelial cells, leukocytes), Grahamella musculi (erythrocytes), Bartonella muris (erythrocytes), Klossiella muris (kidneys), Hepatozoon musculi (intestine, liver, blood). — II. Parasitic worms. A. Tapeworms. Catenotaenia pusilla, Hymenolepis contracta, Hymenolepis crassa, Hymenolepis diminuta (the latter can be a host-parasite of man), Hymenolepis fraterna, Hymenolepis microsoma, Hymenolepis relicta, Mesocestoides lineatus, Taenia imbricata, Taenia umbonata. In addition, bladder worms may occur in Mus musculus: Echinococcus (liver), Cysticercus pisiformis (liver, viscera), Cysticercus fasciolaris (tapeworm form of Taenia taeniaeformis = Taenia crassicollis in the liver). — B. Nematodes. Capillaria bacillata, Capillaria muris-musculi, Trichinella spiralis (in muscles); Haemonchus contortus, pinworms Aspiculuris tetraptera and Syphacia obvelata (can be a host-parasite in man); Protospirura muris, Gongylonema problematicum, Gongylonema musculi, Physaloptera massino, Agamospirura sp. — III. Arthropods. Mites: Liponyssus (fam. Parasitidae); various Ixodoidea in different stages of metamorphosis. — Lice: Polyplax serratus, Hoplopleura acanthopus, Hoplopleura hesperomydis, Polyplax affinis (Mus silvaticus). — Fleas: Ctenopsylla segnis (=Leptopsylla musculi), Ctenopsylla taschenbergi (Mus musculus hortulanus), Ctenops. silvatica, Ctenops. sexdentata (Mus musculus wagneri), Pectinoctenus lautus (Mus musculus wagneri), Ceratophyllus londiniensis, Ceratophyllus fasciatus, Ceratophyllus consimilis, Ceratophyllus mokrzeckyi (both on Mus musculus hortulanus); Frontopsylla macrophthalma (Mus musculus wagneri); Neopsylla acanthina; Stenoponia tripectinata; Mesopsylla hebes (Mus musculus wagneri); Ctenophthalmus agyrtes celticus, Ct. orientalis (Mus musculus hortulanus); Xenopsylla mycerini (Mus musculus wagneri).

E. Pavlovsky. The Mouse in Genetic Regards. The genetics of the mouse at the present moment is sufficiently well developed. A large number of genes, their interrelationships in determining traits, and the phenomenon of multiple allelomorphism have been studied; finally, a recent work by Snell (Snell, 1931) provides extensive material on the establishment of linkage groups in mice. Mice were one of the classical objects on which the full applicability of Mendelism (see) to animals was proven. The French author Cuenot established a number of remarkable inheritance forms in mice that became a contribution to general genetics. Cuenot was the first to propose the use of hereditary formulas, which, in a somewhat modified form, now have enormous distribution and significance. Cuenot was the first zoologist to apply Mendel's teachings to the experimental study of heredity in animals. - 1. Genetics of mouse coat color. The coloration proper to the wild mouse (gray) is called agouti. The gene for this color is denoted by the symbol A (agouti). Gene A, in a series of mutations, gave several different genes that form a series of multiple allelomorphs of the agouti gene. A^y (yellow) causes a reduction of black and brown pigment in the heterozygous state, as a result of which the mouse is colored yellow. Gene A^y dominates over all members of the agouti gene series. In addition to yellow coloration, it causes a tendency toward obesity and sterility. Homozygotes for the gene A^y cannot be obtained, because it is recessively lethal. Gene A^w (white-bellied-agouti) is white-bellied agouti. Gene A^w is recessive relative to gene A^y, but dominant relative to other members of the A series. Gene a^t (black-and-tan) causes a light belly in a black-colored mouse. In terms of dominance, the action of this gene falls into two parts: with respect to the black color of the body, it is recessive to all members of the A series, while with respect to the color of the belly, on the contrary, it is dominant. Gene a (non-agouti) determines the black color of the entire mouse. Thus, the series of allelomorphs of gene A (agouti) contains 5 members, and the order of dominance in it is as follows: A^y > A^w > A > a^t > a. - Another series of multiple allelomorphs is given by the main color gene C (colour). In the presence of gene C, the mouse turns out to be fully colored. Gene c^ch (chinchilla) causes a weakening of the coloration (chinchilla color). Gene c^d (extreme dilution) already very strongly weakens the coloration, turning the mouse (in the homozygous state) practically completely white. Only with age does a brown stripe outline on the back. The eyes also lighten, and only the ears and scrotum are colored. Gene c causes complete albinism (see). In the order of dominance, the C gene series is arranged in the following order: C > c^ch > c^d > c. The remaining mouse coat color genes are single. - Gene p (pink-eye) - pink-eyed *. Eyes are like an albino's, but (according to Durham's data; 1911) traces of pigment are present in the retina and iris. The body color is lighter (from black to lilac, from gray to grayish-yellow). - Gene b causes a brown color in mice. This gene shows a remarkable interaction with gene s^l (see below). Gene d (dilution) causes a general lightening of the color. Gene s (piebald) - white-spotted. Incompletely recessive, because white spots on the belly are noticeable in the heterozygote. Gene W (black-and-white) causes a mild degree of spotting in the heterozygote. In the homozygous state, it is lethal. Death ensues from anemia before or shortly after birth. It received its name because, in combination with gene s (see above), it can produce a white mouse with black eyes. Gene s^l (silver) - silver coloration. However, apparently, the silver coloration is determined by a number of equivalent factors, among which the main gene s^l also acts. All these mouse coat color genes are inherited quite correctly according to Mendel's laws, and their combinations can form a huge number of colored breeds of mice (see table). Formulas of some mouse coat colors: GABD - gray (agouti); CaBD - black; CabD - brown; CABd - brownish-gray; CaBd - blue; Cabd - light brown; cABD - albino.

Figure 1. Male mouse, homozygous for the hairless gene (h^rh^r).

Figure 2.

Figure 3.

Figure 2. Female mouse heterozygous for the gene nacked (Nn). Figure 3. Male mouse heterozygous for the hairless and nacked genes (H^rh^rNn). nacked (see below). Gene v (waltzing) determines the peculiar ability of "waltzing" in so-called Japanese mice (degeneration of the stria vascularis, and behind it the Corti's organ); mice are deaf, smaller in size, and with weakened viability. - Gene r (rodless) - blind mice due to a defect in the retinal region (rods are absent). Gene N (nacked) - in the homozygous state, mice are almost completely naked at birth. In the heterozygote (Figs. 2 and 3), they resemble mouse v in the early stages of hair loss. - Gene h (hemorrhagic head) - a semilethal factor with strongly varying manifestation (obtained by the action of X-rays; Little and Bagg, 1924). - Gene T (tailless) - absence of the tail, lethal in the homozygous state. - Gene d^w (dwarf) - dwarf mice (Fig. 4); size reaches only ¹/₄ of normal; sterile, viability reduced. - In addition to the cited mouse genes, their symbols and linkage, [Table data omitted in translation text stream as per formatting rules]

female, homozygous for the dwarf gene (d^wd^w). Both mice at the age of 2 months.

of genes, a number of hereditary structural changes of inheritance have been described that are not yet well studied (lethal genes linked to sex, ectromelus, polydactyly, etc.). Of physiological traits (true, a number of the described structural traits were at the same time physiological), the following is known: gene W (hyperglycemia) - a recessive gene determining an increased concentration of sugar in the blood. The susceptibility of mice to cancerous diseases is determined by a dominant gene (possibly several equivalent ones). The predisposition to staphylococcus infection is a dominant trait. 3. Linkage groups in mice. The chromosome number in mice is 20 pairs. Of the possible 20 linkage groups, 9 are known at present. Crossing-over in mice turns out to be different in males and females; in the former, it is lower than in the latter. The attached table gives an idea of all mouse genes, their symbols, as well as the number of linkage groups (see the chromosome column) and the magnitude of crossing-over between individual genes (see the column for the percentage of crossing-over in females and males). N. Dubinin. Mice as laboratory animals - see Laboratory animals.