- The phenomenon was first described in a red alga and a green alga more than 30 years ago.
- The classical examples of symbiosis are the lichens, in which a fungus is associated with an alga or a cyanobacterium.
- That is, a simple alga like Volvox and a complex metazoan like an octopus both occupy the same sublevel.
- Most of the lichen is composed of fungal filaments, but living among the filaments are algal cells, usually from a green alga or a cyanobacterium.
- It is a blue-green alga, a primitive plant of the same class as seaweeds or the green slime seen on rocks and jetties when uncovered by the sea at low tide.