The oligotrichs are a group of

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

s, included among the

spirotrich The spirotrichs are a large and diverse group of ciliate protozoa. They typically have prominent oral cilia in the form of a series of polykinetids, called the adoral zone of membranelles, beginning anterior to the oral cavity and running down ...

s. They have prominent oral cilia, which are arranged as a collar and lapel, in contrast to the

choreotrich The choreotrichs are a group of small marine ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general sh ...

s where they form a complete circle. The body cilia are reduced to a girdle and ventral cilia. In ''Halteria'' and its relatives, they form bristles or cirri; however these forms may be closer relatives of the

stichotrich The stichotrichs were a proposed group of ciliates, in the class Spirotrich, Spirotrichea. In a classification system proposed by Eugene Small and Denis Lynn in 1985, Stichotrichia formed a subclass containing four orders: Stichotrichida, Urostyl ...

s than of other oligotrichs. These organisms are very common in plankton communities, especially in marine systems. Usually found in concentrations of about 1 per ml, they are the most important herbivores in the sea, the first link in the

food chain A food chain is a linear network of links in a food web starting from producer organisms (such as grass or algae which produce their own food via photosynthesis) and ending at an apex predator species (like grizzly bears or killer whales), de ...

. File:643 oligotrich-ciliate.jpg, Oligotrich ciliate, probably ''Strombidium'' File:Halteria.jpg, ''Halteria sp.''

References

Further reading