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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
4): cycloid scales tend to be more quadrangular or roundish (Fig.
Cycloid scales. The scale plate edge is smooth posteriorly and laterally, but uneven anteriorly to varying degrees.
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.
Diagnosis: Bollmannia can be distinguished from other Gobiosomatini genera by the following combination of characters, not listed in order of taxonomic importance: first dorsal of most species with black spot or blotch on posterior portion of fin; second dorsal I,11-15; anal I,10-15; pelvic fins with well-developed frenum supported with collagenous thickenings, frenum with scalloped posterior margin; caudal fin lanceolate; trunk scales ctenoid; predorsal region, cheek, pectoral fin base and breast with cycloid scales; predorsal scales 7-10.
Scales: trunk completely covered with ctenoid scales, ctenii becoming larger posteriorly; predorsal region, cheek, operculum, pectoral fin base and pelvic fin base with scattered cycloid scales; lateral scale rows 27-31; transverse scale rows 7; predorsal scales 9-10, scales extending anteriorly to vertical behind eye; caudal peduncle scales 11-13; no modified basicaudal scales present.
Lateral scales 23; anterior transverse scales 7-8-8.5 ([bar.x] = 8.1, SD = 0.37); posterior transverse scales 7-8-8.5 ([bar.x] = 7.5, SD = 0.41); predorsal scales 8-9 ([bar.x] = 8.2, SD = 0.39); no scales on cheek; opercle with single row of 2-3 usually ctenoid scales; pectoral base with usually 3 vertical rows of scales and 4 cycloid scales in posterior row; 5-7-8 ([bar.x] = 6.4, SD = 0.79) cycloid prepelvic scales (in midline anterior to basal membrane); 11-12 ([bar.x] = 11.9, SD = 0.3) circumpeduncular scales; body scales ctenoid except for cycloid scales on anterior belly midline and on, beneath and just posterior to pectoral fin base; body scales extending anteriorly to just behind eye.
papayum in meristic values and in general shape, but adults have 2-3 cycloid scales on the cheek.
Cheek naked or with one or two minute embedded cycloid scales; operculum naked or with 1-5 small embedded cycloid scales.
Body covered with cycloid scales. Head largely naked, midline of nape with scales extending to above preoperculum, operculum and preoperculum naked or with a few small embedded scales.
Cheek posteriorly with 2 (1), 3 (8), 4 (1) rows of small cycloid scales, anteriorly naked; posterior to orbit one row of ctenoid 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.
Suboperculum fully covered with cycloid scales; interoperculum fully covered by one row of cycloid scales; cheeks fully scaled; postorbital squamation with two rows of different-sized scales; size of occipital scales not significantly smaller than dorsal scales; predorsal squamation pattern irregular; cycloid and weakly ctenoid scales on dorsum rostrally, more strongly ctenoid scales increasing caudally; flanks with strongly ctenoid scales (Fig.