Ctenoid refers to a type of fish scale that has a comb-like or serrated edge. These scales are typically found in certain species of bony fish, such as perch and bass. Ctenoid scales provide protection and help reduce drag as the fish swims through water. Unlike cycloid scales, which are smooth and rounded, ctenoid scales have a more complex structure. This design allows for better flexibility and movement. The unique shape of ctenoid scales contributes to the overall adaptability and efficiency of the fish in its aquatic environment.