''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, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

) 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 a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

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