Fauna is a term generally referring to the animal life of a particular habitat, ecosystem or geographic region, as opposed to flora which refers to plant life.
Flora and fauna, along with other life forms such as fungi and microorganisms, together form the Biota.
In addition to being able to use these terms to refer to the organisms of a place, they can also be used to refer to the organisms of a period of time, usage that occurs especially in paleontology.
Both fauna and flora can be subdivided into categories or types to refer to more specific places or time periods. For example, cryofauna would be the fauna that lives on or near ice.
Likewise, the terms infauna and epifauna They also refer to groups of fauna depending on where they live, specifically groups of aquatic benthos fauna.
the benthos or benthic community is the community of living beings that inhabit the bottom and ground of aquatic ecosystems, both marine and freshwater. In this habitat it is possible to distinguish several areas with characteristic fauna in each of them:epifauna: formed by the group of organisms that live on the watery bottom. These organisms can live in sandy sediments or in hard rocky soil. Some live anchored to the ground, while others move on top of it. Examples of epifauna would be certain groups of bivalve molluscs and gastropods, some crustaceans or corals and starfish. infauna: the infauna, also called endofauna (both terms are synonymous, but infauna is more used and exact), is the community of benthic organisms that live buried in sediments of the aquatic bottom. Examples: many protozoa, bacteria and microalgae, some groups of molluscs, many types of annelids and flatworms, copepod crustaceans, etc.
The differentiation between epifauna and infauna, however, is not a strict and exclusive differentiation. The animals of the epifauna and the infauna exist exclusively or almost exclusively, but there are also many groups of animals that pass from one to the other continuously.
There are even animals that can swim freely in the water and that at the same time maintain a close relationship with the benthos where they spend long phases of their lives, for example to hunt, feed or reproduce.