Stentor (protozoa)
Stentor, sometimes called trumpet animalcules, are a genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of filter-feeding, heterotroph
A heterotroph is an organism that cannot fix carbon and uses organic carbon for growth. This contrasts with autotrophs, such as plants and algae, which can use energy from sunlight or inorganic compounds to produce organic compounds such as carbohydrates, fats, and proteins from inorganic carbon...

ic ciliate
The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella...

Protists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...

s, representative of the heterotrich
The heterotrichs are a class of ciliates. They typically have a prominent adoral zone of membranelles circling the mouth, used in locomotion and feeding, and shorter cilia on the rest of the body. Many species are highly contractile, and are typically compressed or conical in form...

s. They are usually horn-shaped, and reaching lengths of 2 millimeters, they are among the biggest known unicellular organisms.
The body, or cortex
Cortex may refer to:-Sciences:* Cortex , the outer portion of the stem or root of a plant...

, is generally horn-shaped, hence the association with the Greek herald
In Greek mythology, Stentor was a herald of the Greek forces during the Trojan War. Although he is mentioned only briefly in Homer's Iliad, in which Hera takes Stentor's character to encourage the Greeks to fight, his name has been living in the term "stentorian" voice, meaning loud-voiced, for...

 and the former name "trumpet animalcule", with a ring of prominent cilia around the anterior "bell" that sweep in food and aid in swimming.