euglenoid

A euglenoid is a type of single-celled eukaryotic organism belonging to the phylum Euglenozoa. These organisms are characterized by their flexible pellicle, which allows them to change shape, and the presence of one or two flagella used for locomotion. Many euglenoids are photosynthetic, possessing chloroplasts similar to those found in plants, and can derive energy from sunlight. However, they also exhibit mixotrophy, meaning they can absorb nutrients from their environment when light is unavailable.

Euglenoids are found in a variety of aquatic habitats, including freshwater, brackish water, and marine environments, as well as in damp soil. Their reproduction is primarily asexual, typically through binary fission. A notable feature of many euglenoids is the presence of a stigma, or eyespot, which is sensitive to light and aids in phototaxis, allowing them to move towards optimal light conditions for photosynthesis.

While some euglenoids are exclusively photosynthetic, others are heterotrophic, meaning they consume other organisms or organic matter. The Euglenozoa phylum also includes kinetoplastids, which are exclusively heterotrophic and often parasitic, such as the genus Trypanosoma that causes sleeping sickness. However, the term "euglenoid" specifically refers to the photosynthetic or mixotrophic members with a distinct pellicle and flagellar arrangement. Their ecological roles vary, with photosynthetic species contributing to primary production in aquatic ecosystems.