Euglenoids are a group of protists that contain a whip-like structure called flagella, used for locomotion. Although most species feed absorbing the nutrients dissolved in the water, some euglenoids are autotrophs, which means they can synthesize their own food through photosynthesis, like plants. Peranema and Euglena are euglenoids often found in pond water with high levels of organic nutrients.
Ameboids feed through phagocytosis by surrounding and engulfing food particles with their body. Some species, such as Entamoeba histolytica, are animal human parasites. Only pond waters contaminated with feces can contain this species, which causes a intestinal infection called Amoebiasis. Harmless ameboids often found in pond water include Amoeba proteus and members of the genera Chaos and Dictyostelium.
Although most species of dinoflagellates live in marine environments, some species are also found in pond water. Like euglenoids, dinoflagelates also feature two flagella, which are used for locomotion. Ceratium, Entzia, Peridinium and Thompsodinium are some freshwater species found in ponds. Dinoflagellates species were found in fossil records from the Triassic period, from about 250 million years ago. About half of dinoflagellates perform photosynthesis.
Like other protists, cilliates also feature hair-like structures involved in their locomotion. All cilliates have many short cillia around their unicellular body. The group contains the most evolved and largest of all protists, some reaching 2 mm. Cilliates found in pond water include members of the genera Paramecium, Vorticella, Colpoda, Tetrahymena and Childonella.