Katamorphosis

a direction of evolution characterized by the transition of a given group of organisms to simpler relations with the environment and resulting in general underdevelopment and simplification of structure.

The term “katamorphosis” was coined by the Soviet biologist I. I. Shmal’gauzen in 1939. Katamorphosis is usually associated with despecialization (loss of specific adaptations) and transition to a nonmotile or “hidden” mode of life (in cases, “little houses”). Examples of groups that underwent katamorphosis include the rotifers, bryozoans, aphids, coccids, tunicates, and underwater flowering plants. A special case of katamorphosis is hypomorphosis, that is, general underdevelopment of an organism (for example, permanent neoteny in Proteus anguinus and the axolotl). The word “catagenesis” is often used instead of katamorphosis.