Ctenoid

Ctenoid scales are a type of fish scale found in the majority of bony fish belonging to the class Actinopterygii. These scales are characterized by their rough texture and comb-like edges, which distinguish them from other types of scales such as cycloid scales and ganoid scales.

Structure

Ctenoid scales are composed of a bony layer covered by a thin layer of skin. The posterior edge of the scale is serrated with tiny teeth-like projections called ctenii, which give the scale its name. These projections are thought to reduce drag and turbulence, aiding in the fish's swimming efficiency.

Types

There are three main types of ctenoid scales:

• Spinoid scales: These have spines that are continuous with the main body of the scale.
• Ctenoid scales proper: These have separate spines that are not continuous with the main body of the scale.
• Transforming scales: These scales can change from cycloid to ctenoid as the fish matures.

Function

Ctenoid scales serve multiple functions:

• Protection: They provide a protective barrier against predators, parasites, and physical injuries.
• Hydrodynamics: The ctenii reduce water resistance, making swimming more efficient.
• Sensory: The scales can also play a role in the sensory system of the fish, helping them detect changes in their environment.

Distribution

Ctenoid scales are predominantly found in teleost fish, which make up the largest group of bony fish. Examples of fish with ctenoid scales include perch, bass, and snapper.

Comparison with Other Scales

• Cycloid scales: These scales are smooth and lack the comb-like projections found in ctenoid scales.
• Ganoid scales: These are diamond-shaped and found in fish like gars and sturgeons.
• Placoid scales: Found in cartilaginous fish like sharks and rays, these scales are more tooth-like in structure.

Related Pages

• Fish anatomy
• Teleostei
• Actinopterygii
• Cycloid scales
• Ganoid scales
• Placoid scales