Life

Protista

Protista knowledge

Together at all costs: the symbiosis

There are cases of symbiosis between animals and protozoa, in particular unicellular algae. The animals in which this phenomenon is most common are Radiolaria and Foraminifera (among protozoa), Coelenterata, Ctenophora, Platyhelminthes and molluscs (among Metazoa). In omnivore or herbivore species, such as, for instance, Radiolaria and Foraminifera, the algae adapt inside the cell by developing systems to resist the attack of some digestive enzymes of the host, especially cellulase. For instance, the zoochlorellae, even if they can also live on their own, can always be found in the Convoluta sp. Turbellaria (resembling a flat worm), where they get under the epidermis. They can invade the animal through the capsule of the egg, by which they are attracted. The Convoluta cannot live without these algae, because it needs the lipids they produce.