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(1) In biology, aphagia is the absence of feeding (that is, obtaining food from without) in some animals in various developmental phases. The most widespread form of aphagia is the development in an egg of an embryo that obtains its requirements mostly from the yolk, which is particularly large in species with a long development (for example, birds). Aphagia is also peculiar to the adult stages of some insects and fish—for example, Pacific Ocean salmon, which reproduce once a lifetime, do not feed during spawning, and die after spawning. In insects, aphagia is characteristic of the adult stage in cases where it performs only the function of dispersal and reproduction (such as mayflies and some moths). The stage characterized by aphagia usually lasts only a few days or even hours (in mayflies). Aphagia is sometimes peculiar to one sex (for example, females of some click beetles and cockchafers, and males of the Coccidae family and many mosquitoes). The digestive system usually degenerates in the nonfeeding stages, large quantities of reserve substances are stored, and the locomotive organs become stronger (enabling individuals of both sexes to meet more easily).
N. P. NAUMOV
(2) In medicine, aphagia is the impairment of normal feeding (through the mouth) resulting in man from the inability to swallow. It is observed in lesions of the medulla oblongata or nerves involved in swallowing, spasm of the pharyngeal muscles, some mental disorders, and so on.