The Floating Bell – Perhaps the most famous type of animal within the phylum known for its stinging cells, jellyfish species are remarkable animals. It is easy to remember the things that jellyfish are commonly known for, pelagic drifting animals with often extremely long tentacles with powerful stings on them. Jellyfish are single animals that are responsible for huge booms in populations, often resulting in dead zones, yet they are also some of the worlds most unique habitats. Many species of jellyfish, both in life and death, host small schools of fish within the spaces of its body. This commensal relationship offers protection for the fish, often juveniles, from predators due to the stinging cells that adorn the tentacles of the jelly. The jellyfish gains little by hosting these fish, and since many of the fish species have mucous based coatings to protect them from the stings, the jellyfish cannot feed on them.
Though population numbers are seen to be growing out of control, it must be remembered that they remain and important food source for many animals such as sea turtles, butterfly fish and various species of shark. Numbers of predators of jellyfish have reduced over the years due to anthropogenic causes so, much like the Crown of Thorns sea star discussed earlier, without natural predators and intervention, the ecosystem cannot be balanced and population growth can excel unchecked.