various types of zooids found in obelia colony
Obelia The polyp colony reproduces asexually. During this stage of life, Obelia are confined to substrate surfaces. On this mature colony there are individual hydranths called gastrozooids, which can be found expanded or contracted, to aid in the growth of this organism by feeding; the reproductive polyp gonozooids has medusa buds. Other hydranths are specialized for defense. The main stalky body of the colony is composed of a coenosarc, which is covered by a protective perisarc.
Extremophile Most known extremophiles are microorganisms. The domain Archaea contains renowned examples, but extremophiles are present in numerous and diverse genetic lineages of bacteria and archaeans. Furthermore, it is erroneous to use the term extremophile to encompass all archaeans, as some are mesophilic. Neither are all extremophiles unicellular; protostome animals found in similar environments include the Pompeii worm, the psychrophilic Grylloblattidae (insects) and Antarctic krill (a crustacean). Many would also classify tardigrades (water bears) as extremophiles but while tardigrades can survive in extreme environments, they are not considered extremophiles because they are not adapted to live in these conditions. Their chances of dying increase the longer they are exposed to the extreme environment.