Here's why:
* Composition: Fish scales are primarily made of collagen and other proteins. These molecules have polar groups (like -OH and -NH2) that can form hydrogen bonds with water molecules.
* Function: The hydrophilic nature of scales helps them to stay moist and prevents them from drying out. This is important for fish who live in water and are constantly exposed to it.
* Evolution: Over time, fish scales have evolved to have this hydrophilic property to support their survival in aquatic environments.
While the scales themselves are hydrophilic, the outer layer of some fish scales can be covered in a thin layer of mucus, which is hydrophobic. This mucus helps reduce friction as the fish swims through water.