Sessility (zoology)

Have sessile animals (Latin sessilis, tightly ', suitable for seats ') are all animals that do not possess the ability to change their place of residence, or this ability over the course of their development ( ontogeny ) and evolution ( phylogeny ) lost. All sessile animals are invertebrates, they are practically known only from the sea and freshwater habitats.

The vertebrates are closest sessile animals are the so-called tunicates, which have in their juvenile stage, which is also known as Kaulquappenlarve a notochord. Often the larval stages of sessile animals such as the tunicates, freely or live plankton.

The best known sessile animals are the reef-building corals. Other examples are sponges, bryozoans and brachiopods.

Many parasites attach themselves as larvae on their host animals and transform into sessile forms. They are no longer able to leave the host. As an example, the Walläuse from the family of amphipods ( Amphipoda ) call, who live as ectoparasites on the skin of whales.

Hemisessile Animals

As halbsessil or hemisessil is called sessile species that are still to the local change in the situation, but these only operate under extreme circumstances, rare or very slow. Many species of mussels and sea anemones are halbsessil.

Vagile animals

As Vagil living organisms is called the non- living sessile, ie those undertaking active locomotion.