Sessile animal
Sessile animals ( Latin sessilis , `` fixed '', `` suitable for sitting '') are all animals that do not have the ability to change their location or have lost this ability in the course of their development ( ontogenesis ) or evolution ( phylogenesis ). All sessile animals, with the exception of the tube eel , are invertebrates ; they are known practically exclusively from the sea and limnic habitats.
The sessile animals closest to the vertebrates are the so-called tunicates , which in their youth stage, also known as the tadpole larva, have a notochord . Often the larval stages of sessile animals, as with tunicates, are freely mobile or live planktonically .
The most famous sessile animals are the reef-building hard corals . Other examples are sponges , bog animals and arm pods .
Many parasites also attach themselves as larvae to their host animals and transform into sessile forms. You are then no longer able to leave the host. As an example, you can see the Whale louse from the family of amphipods (amphipods) call, as ectoparasites on the skin of whales live.
Hemisessile animals
A semi-sessile or hemisessile is the term used to refer to stuck species that are still able to move, but only rarely or very slowly operate it under extreme circumstances. Many species of mussels and sea anemones are semi-sessile.
Vagile animals
Organisms that do not live in a sessile manner, i.e. those that actively move about, are referred to as living vagilely .