Scales
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<fishfyi-glossary slug="scales"></fishfyi-glossary>Définition
Thin, overlapping plates covering the skin of most fish, providing protection from predators and parasites. Types include cycloid, ctenoid, ganoid, and placoid.
Explication détaillée
Cycloid scales (smooth-edged, salmon, herring) and ctenoid scales (comb-toothed rear margin, perch, bass) both form from dermal papillae and grow by adding concentric rings (circuli). Annual growth check marks (annuli) allow age determination by scale reading, analogous to tree rings. Ganoid scales (bichirs, gars) are thick, rhomboidal, and covered in ganoin (a hard enamel-like coating), providing armor-like protection. Placoid scales (shark denticles) are structurally equivalent to teeth and give shark skin its hydrodynamically functional roughness.