Pikkelyekre

Pikkelyekre, often translated as "scales," refers to small, overlapping plates that cover the bodies of many animals. These structures are primarily composed of keratin, a tough protein also found in hair and nails. Their distribution and appearance vary significantly across different animal groups.

In fish, pikkelyekre are a defining characteristic, providing protection and aiding in streamlining for efficient movement through water. Different types of fish scales exist, including cycloid, ctenoid, and placoid scales, each with a distinct structure and evolutionary origin. Reptiles, such as snakes, lizards, and crocodiles, also possess pikkelyekre, which form a protective armor and help prevent water loss in terrestrial environments. The arrangement and shape of these scales can be important for species identification.

In some mammals, modified pikkelyekre are found. Pangolins, for instance, are covered in large, keratinous scales that function as a defense mechanism, allowing them to roll into a ball when threatened. While birds are covered in feathers, the underlying structure of their scales on their legs and feet is homologous to the scales of reptiles. The term pikkelyekre can also be used metaphorically to describe thin, overlapping layers in other contexts, such as on certain plant structures or in geological formations.