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a physical malformation in plants and animals. Hereditary monstrosities occur as a result of mutations that cause developmental anomalies, while nonhereditary monstrosities occur only in organisms directly affected by changes in their course of development.
Monstrosities may be causally related to polyploidy, aneuploi-dy, haploidy, chimerism, heterosis, apomixis, inbreeding, and distant hybridization. They are sometimes linked with cytoplasmic sterility, which may result from chemical and physical teratogenetic and mutagenic factors, excessively high or low temperature, changes in the photoperiod, and excess or lack of water, trace elements, and macronutrients. The comparative study of monstrosity in plants and animals elucidates the most common causes, conditions, and courses of development of monstrosities and clarifies the role of monstrosities in the historical development of groups of organisms and in the development of tissues and organs.
In higher plants, monstrosities occur in roots, leaves, buds, shoots, flowers, inflorescences, fruits, aggregate fruits, and seeds. Most often the size, shape, and configuration of organs are affected. Pathological changes are observed in the number of fruits and the number of anatomical elements in individual fruits. Deviations in the periods and rates of formation of component elements also occur.
Monstrosities are caused by disturbances in the rhythm, frequency, and duration of cell divisions and by the protraction and differentiation of cells. Various physical functions are affected in the development of monstrosities, which explains the great variety of monstrosities encountered. The most common plant monstrosities are dwarfism and gigantism of organs and entire plants, doubleness of flowers, fasciation, proliferation, witches’-brooms, and vivipary. Monstrosities also occur in tissues, such as xylem and phloem; in cellular apparatus, such as the stomata; and in cellular organelles, such as nuclei and mitochondria. Because monstrosities result from so many varied causes, a need arose to establish principles of teratological variability in plant organisms. Teratological variability is subject to the law of homologous series formulated by the Soviet scientist N. I. Vavilov.
Monstrosities of plants may be harmful, such as loose corn smut and doubleness of currants. On the other hand, dwarfism of wheat, gigantism of root vegetables, and many other monstrosities are beneficial. In order to develop valuable forms of cultivable plants, it is important to employ various forms of monstrosities in the selection process. It is desirable to develop giant and fast-growing tree varieties and to establish measures to prevent the development of harmful monstrosities, which lower the economic value of plants and threaten plant associations. General biological principles should be investigated to increase the productivity of irregularly formed plants used in the national economy. Plant monstrosities are also useful as indicators of the presence of mineral deposits.
In animals, monstrosities may develop in representatives of all taxonomic groups and in one or more organs. Common monstrosities in tapeworms, for example, include the disappearance and decrease or increase in the number of suckers, doubling of the scolex and bifurcation of the strobilae. In annelid worms bifurcation of the body is observed, while in insects the following are encountered: fusion of body segments, diminution of antennae, formation of extremities at the site of the eyes, and multiple monstrosities due to intersexuality. Other well-known monstrosities include acephalia in reptiles, multiple extremities in amphibians, anophthalmia and microphthalmia in various mammals, and bifurcation of the trunk in cows. A number of monstrosities have been described in humans (seeANOMALIES, DEVELOPMENTAL; XIPHOPAGUS; PYGOPAGUS).
Monstrosities may occur when embryonic development is hampered by unusually high or low temperature, ionizing radiation, toxic substances, and various pollutants, including lead and arsenic compounds and phenols. They may also result from oxygen deficiency; disturbance of osmotic pressure; the effects of certain medicinal preparations; infestation by viruses, helminths, and other parasites; hybridization; traumatism; and anomalies of sex chromosomes. Monstrosities may also arise as a result of hereditary mutations.
The study of monstrosities in laboratory test animals is especially important, as it indicates potential dangers for humans that are presented by various physical conditions and chemical substances, including medicines. It may also lead to the discovery of methods for treating such hereditary afflictions of man as hydrocephalus, anophthalmia, coloboma of the retina, polydactyly, and syndactyly.
The study of monstrosities is called teratology.
REFERENCESKanaev, I.I. Bliznetsy. Moscow-Leningrad, 1959.
Martynenko, N. A. Dvoini u korov. Kiev, 1965.
Koniukhov, B. V. Biologicheskoe modelirovanie nasledstvennykh boleznei cheloveka. Moscow, 1969.
Chernukh, A. M., and P. N. Aleksandrov. O teratogennom deistvii khimiche kikh (lekarstvennykh) veshchestv. Moscow, 1969.
Kalmykov, P. G. Vliianie ioniziruiushchikh izluchenii na nasekomykh. Moscow, 1970.
Stroeva, O. G. Morfogenez i vrozhdennye anomalii glaza mlekopitaiushchikh. Moscow, 1971.
Schwalbe, E., Die Morphologie der Missbildungen des Menschen und der Tiere, vol. 1. Jena, 1906.
For works on plant monstrosities, see references under TERATOLOGY.
E. I. SLEPIAN