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.
The metamer is defined as the internode, upper node, attached leaf, and axillary bud(s) (Barlow, 1989), and metamerism (White, 1984) is the serial repetition of metamers within or along an organism.
Utilizing the Photo Black, Matte Black, Gray, Dark Gray and Light Gray inks, photographers will experience smooth gradations, suppressed graininess and a reduction in the bronzing and metamerism phenomenon which shows a metallic luster such as iridescence due to the colors in reflected light.
GSX ink, delivering up to ten colors (a technology first for solvent printers), including an optional White and Silver Metallic and a first ever standard Light Black for improved grayscale and reduced metamerism.
It is also worth remembering that a metamerism cannot be resolved with a spectrophotometer alone.
This program's matching optimizer reportedly lets users customize formulations based on a variety of criteria including color differences for up to five illuminants, metamerism indices, curve fit, contrast ratio, and cost.
Attendees will learn to manage metamerism and process variables and also strength calculations and color matching.
Coverage of metamerism, hiding power, and colorant calibration has been expanded.
Comments: This is a unique, red shade copper phtalocyanine blue, epsilon crystal pigment which offers the opportunity to shade blues to a redder, cleaner hue with minimum risk of metamerism.
The new inks are also designed with an innovative polymer structure that results in greater scratch resistance and protection from color fading, while also reducing bronzing and metamerism ensuring durable, stable output.
The new Epson UltraChrome GSX ink is available on the SureColor S70670 and delivers up to ten colors, including an optional White, Silver Metallic and standard Light Black, for improved grayscale and reduced metamerism to deliver a level of image quality and color gamut previously unattainable in a solvent printer.
The colorimeter is ideal for routine comparisons of similar colours and the spectrophotometer is ideal for colour formulation and the measurement of Metamerism, and would be typically found in the research and development and quality control laboratory.