Cycloid Scale

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cycloid scale

[′sī‚klȯid ‚skāl]
(vertebrate zoology)
A thin, acellular structure which is composed of a bonelike substance and shows annual growth rings; found in the skin of soft-rayed fishes.

Cycloid Scale


in teleost fishes (Salmonoidei, Clupeiformes, Cypriniformes, and others), a scale having a smooth, rounded margin. Each scale lies in a deep pocket of connective tissue and overlaps its neighbor. Cycloid scales consist of two layers of non-cellular bony tissue: homogeneous tegumentary tissue and fibrous basal tissue. The tegumentary layer proliferates along the periphery in concentric stripes known as sclerites. The periodicity of sclerite formation, shown by annual rings, makes it possible to determine the age and growth rate of the fish. Radial nutrient ducts, which in Osteoglossidae form a complex alveolar structure, depart from the center of the scale.

References in periodicals archive ?
4): cycloid scales tend to be more quadrangular or roundish (Fig.
The visceral side of cycloid scales is relatively smooth, with a knobby area in the middle of the scales (Fig.
The radii on ctenoid scales are much less numerous than those on cycloid scales (compare with Fig.
Cycloid scales, overgrowing ctenoid scales and overgrowing ctenoid tubercles, occur on the body of this species.
An example of cycloid scales of Platichthys flesus trachurus from the Baltic Sea is shown in Fig.
The new species differs from all other members of the genus, including the 15 species reported by Allen & Erdmann (2012) from the East Indian region in having a full complement of cycloid scales on the preoperculum as well as a small patch of three scales on the upper operculum.
31, n = 19), no scales on cheek or opercle (except in two specimens with one or two cycloid scales respectively on upper part of opercle); midline of predorsal usually scaleless, but with 6 scales in holotype, 4 in a 20.
37), cheek with 1-2 scales in upper row and 7-8 cycloid scales in main lower row, upper two-thirds of opercle covered with three longitudinal rows of 2, 2 and 1 cycloid scales respectively (the posterodorsal scale may occasionally be weakly ctenoid); 2 vertical rows of cycloid scales on pectoral base, with 3 scales in posterior row; 4 cycloid prepelvic scales in midline; 11-12 ([bar.
79), no scales in midline of predorsal, cheek or on opercle; pectoral base with 4-5 vertical rows of cycloid scales, outer row of 7-8-10 (n = 16) scales, anteriormost row largest, posteriormost smallest; 7-9 prepelvic cycloid scales in midline anterior to pelvic-fin base (2 specimens with 11, where scales extended anterior to ventral tips of cleithra on isthmus); 16-18 circumpeduncular - scales ([bar.
5 mm SL specimen); no scales on cheek; a single row of 3 cycloid or weakly ctenoid scales on opercle; 3-4 vertical rows of scales on pectoral fin base with 4-5 cycloid scales in posterior row; 5-8 ([bar.
Cheek naked or with one or two minute embedded cycloid scales; operculum naked or with 1-5 small embedded cycloid scales.
Operculum and cheek without scales, midline of nape usually naked, but sometimes with 1-5 rows across midline anteriorly, sides of nape scaled to point above posterior end of operculum to posterior end of eye; pectoral base covered with 6-9 cycloid scales in 2 vertical and 4 horizontal rows, posterodorsal 2 scales slightly enlarged, scales often missing in preserved specimens; prepelvic area largely scaled in 5-6 rows of cycloid scales.