Metamerism


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metamerism

[mə′tam·ə‚riz·əm]
(zoology)
The condition of an animal body characterized by the repetition of similar segments (metameres), exhibited especially by arthropods, annelids, and vertebrates in early embryonic stages and in certain specialized adult structures. Also known as segmentation.

Metamerism

 

(segmentation), in biology, division of the body in many bilaterally symmetrical animals into more or less similar repeating parts, or metameres (segments), arranged serially along the body’s longitudinal axis.

Metamerism in the form of strobilation is characteristic of parasitic tapeworms. The body of the parasite consists of proglottids, segments of identical structure that bud at the head (neck region) of the worm and form a chain, or strobila. Metamerism may be external only (pseudometamerism), or it may involve the internal organs as well (true metamerism). True metamerism can be complete, involving the entire organism, or incomplete, extending only to a few organ systems (for example, dermatomeres, or cutaneous metameres; myomeres, or muscular; scleromeres, or skeletal; and neuromeres, or neural).

A distinction is made between homonomous metamerism, where all of the metameres are structurally similar, perform identical functions, and bear identical extremities, and heteronomous metamerism, where the metameres, while retaining essentially a common structural plan, differentiate in different directions, become externally dissimilar, and bear different extremities or lose some. Complete metamerism is characteristic of annelids and arthropods, in which the metameres coalesce to form a head, thorax, and abdomen.

In chordates, metamerism is manifested in the structure of the skeleton, musculature, nervous system, cutaneous formations, circulatory system, and excretory organs. In most vertebrates, including man, metamerism is clearly expressed in the early stages of embryonic development. In the human adult, metameric features survive in the vertebral skeleton, cerebrospinal reflex centers, and roots of the spinal nerves and in the regular alternation of ribs, intercostal muscles, and nerves.

B. S. MATVEEV


Metamerism

 

in chemistry, a special case of isomerism relating to the position of a heterocyclic atom in a chain of aliphatic compounds. For example, methylpropyl ether CH3OCH2CH2CH3 and diethyl ether CH3CH2OCH2CH3 are metameric. The term “metamerism” was suggested by J. Berzelius in 1830. Today it is seldom used.

metamerism

(1) In colorimetry, the quality of some colors that causes them to appear different under various light sources. For example, two color samples might appear the same in natural light, but not in artificial light.

(2) In biology, repeating segments that appear the same but perform different functions. An earthworm is a common animal example.
References in periodicals archive ?
A measure of metamerism can be defined as the color difference between the match and standard under a reference illuminant/observer combination in which the pair match and a test illuminant/observer combination in which the degree of metamerism is evaluated.
A sampling of topics includes relations between color stimuli, light sources, metamerism and color constancy, RGB colorimetry, colorant mixtures, and models of color appearance for stimuli of different sizes.
With the growth of integral coloring, those materials' differences are no longer covered up with paint, so the probability of matching problems and metamerism issues is much higher.
Where there is a change in CCT, there is a corresponding hue shift and metamerism no longer exists.
Neurogenesis in the mossy chiton, Mopalia muscosa (Gould) (Polypla-cophora): evidence against molluscan metamerism.
Often there are very technical discussions such as the recent post about metamerism and the spectral response differences between a hard copy proof and a monitor.
Developers' efforts are made difficult by metamerism, a property that makes surface colors and metallic effects shift in appearance under different lighting or viewing conditions.
The visually resolved data is obviously affected by lighting, metamerism, and color perception.
Through an examination of the phenomena of approximate color constancy, metamerism, and simultaneous contrast, as well as the mechanisms that underlie them, the present paper argues that although Tye's candidate for surface color, spectral reflectance, satisfies (P2), it does not satisfy (P1).
According to the company, the Minimatcher produces five spectrally dissimilar sources of illumination, allowing for visual color assessment, comparison of color variations and the detection of metamerism.
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The approach to describing inflorescence morphology was in the context of metamerism, or of repeating units of plant growth.