A mycophycobiosis (composed of myco-, from the Ancient Greek: μύκης (mukês , "mushroom"), phyco-, from Ancient Greek: φῦκος, (phûkos, fucus, used for algae), and -biose, from ancient Greek: βιόω (bióô, "to spend one's life") is a symbiotic organism made up of a multicellular algae and an ascomycete fungus housed inside the algae (in the thallus for example). The algae and fungus involved in this association are called mycophycobionts.
The essential role of the algae is to carry out photosynthesis, while that of the fungus is less obvious, but it could be linked to the transfer of minerals within the thallus, to a repellent effect on herbivores and, above all, to resistance to desiccation of this living organism in the intertidal zone.[1]
Such symbioses have been reported in a few green algae (Prasiola, Blidingia) and red algae (Apophlaea), both in seawater and in freshwater.