''Glaucoma'' is a genus of freshwater

ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

s in the

Oligohymenophorea The Oligohymenophorea are a large class of ciliates. There is typically a ventral groove containing the mouth and distinct oral cilia, separate from those of the body. These include a paroral membrane to the right of the mouth and membranelles ...

. Cells in this genus are between 30–150 μm long, and have three

membranelle Membranelles (also membranellae) are structures found around the mouth, or cytostome, in ciliates. They are typically arranged in series, to form an "adoral zone of membranelles", or AZM, on the left side of the buccal cavity (peristome). The membra ...

s (structures formed from multiple modified

cilia The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike proj ...

) that surround the oral cavity. Two of the membranelles are used to sweep water towards the mouth, while the third acts like a sieve to strain out food particles for ingestion. In contrast, many other

filter-feeding Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a specia ...

oligohymenophoreans use the paroral membrane, also known as an undulating membrane, for this purpose, but the paroral is not well-developed in ''Glaucoma''.

References

Oligohymenophorea Taxa named by Christian Gottfried Ehrenberg {{Ciliate-stub