Types of Metamorphic Changes

The process of metamorphosis includes reactivation of the morphogenetic processes. The morphogenetic changes also the mode of causation of these changes vary in different animal groups. The degrees of changes that take place during metamorphosis depend on the degree of difference between the larva and the adult forms. For instance, in urodele amphibians (newts) and hemimetabolous insects (cockroach), larva and adult show some differences. The metamorphic changes are comparatively less and metamorphosis is said to be gradual or incomplete. Conversely, in anuran amphibians (frogs) and holometabolous insects, where differences among the larva and adult are enormous, the changes during metamorphosis are extensive and drastic.

This kind of metamorphosis is called radical or complete metamorphosis. The changes throughout metamorphosis include those of structural, physiological and biochemical nature. These are marked through disintegration and atrophy of some structures, cellular death in some tissues, morphogenesis and differentiation of certain new structures and remodeling of some another. These alterations of metamorphosis in at least some groups of animals (insects, crustaceans, amphibians) are known to be controlled by hormones that serve as the causative agents of metamorphosis.