Ciliada

Ciliada (often referred to by the alternative names Ciliata or Ciliophora) is a grouping of single-celled eukaryotic organisms known collectively as ciliates. Characterized by the presence of numerous hair-like organelles called cilia, ciliates use these structures for locomotion, feeding, and sensory functions. They occur in a wide range of aquatic and moist terrestrial habitats, including freshwater, marine, and soil environments.

Ciliates display complex cellular organization for single-celled organisms, commonly possessing differentiated structures such as an oral region or cytostome for ingesting food, contractile vacuoles for osmoregulation, and specialized extrusomes (e.g., trichocysts) for defense or prey capture. Many ciliates have two types of nuclei — a typically larger macronucleus that controls everyday metabolic functions and one or more micronuclei involved in genetic exchange.

Reproduction in ciliates occurs asexually by binary fission and sexually through conjugation, a process of nuclear exchange that increases genetic diversity. Some species can form cysts to survive unfavorable conditions. Taxonomically, ciliates are placed within the Alveolata, a major eukaryotic clade that also includes dinoflagellates and apicomplexans.

Ecologically, ciliates play important roles as predators of bacteria and other microorganisms, contributing to nutrient cycling and microbial food webs. Several species are used as model organisms in research and as indicators of environmental quality. The name derives from the Latin cilium, meaning eyelash, a reference to the hair-like cilia.