This type of overlapping scale demonstrates added flexibility and grows larger as the fish grows. In some species, cycloid scales possess annual growth rings. Scales, divided into several categories on the basis of composition and structure, provide protection from the environment and predators and are found on almost all fish. Other types of scales include bony, spiny projections with an enamel-like covering termed placoid scales. Another group of scales is similar to placoid scales, but are covered with an enamel-like substance called ganolin.
Many scientists believe that teeth evolved from placoid scales.
Cycloid scales are found on advanced fish species such as trout, herring, and carp. All Rights Reserved . No images, graphics, scripts, or applets may be reproduced or used in any manner without permission from the copyright holders.