The placoid scales of cartilaginous fishes are also called dermal denticles and are structurally homologous with vertebrate teeth. Most fish are also covered in a layer of mucus or slime which can protect against pathogens such as bacteria, fungi, and viruses, and reduce surface resistance when the fish swims.

Does fish have scale?

Fish scales are smooth to help them glide through the water, and some reflect light to help camouflage them underwater. Unlike reptiles, the scales of bony fish are made of enamel and dentine (like teeth) and they can be detached individually from the skin.

Which fish does not have scales?

Fishes that don't have scales include the clingfish, catfish and shark family, among others. Instead of scales, they have other layers of material over their skin. They can have bony plates that are also covered by another layer or tiny, teeth-like protrusions covering their skin.