Ampullofolliculina[1] Ascobius[1] Bickella[1] Diafolliculina[1] Eufolliculina[1] Folliculina[1] Folliculinopsis[1] Freia (genus)[1] Halofolliculina[1] Lagotia[1] Metafolliculina[1] Mirofolliculina[1] Orthofolliculina[1] Parafolliculina[1] Pseudofolliculina[1] The Folliculinidae are a family of ciliates in the class Heterotrichea, with the common name "bottle-animalcule".

Folliculinids are called "bottle-animalcules" because mature individuals are sessile and live inside a bottle-shaped lorica (shell).

[2] The cell body has two wing-shaped protrusions, called peristomal wings, which carry the ciliary structures which are part of the oral apparatus, by which they feed.

[6] Most of these bacteria are methanotrophs, which can use methane coming from the hydrothermal vents as a source of carbon and energy.

[8] The folliculinid species Halofolliculina corallasia are argued by some to cause a disease in corals called Skeletal Eroding Band (SEB) syndrome.