Fusion Parasitism

As Fusionsparasitismus refers to a special, only a few representatives of the Mucorales occurring type of parasitism .
Your hyphae have no or only a few transverse walls (septa) and therefore contain a large number of cell nuclei that are not spatially separated from one another .

The parasitic fungus attaches to its host with so-called sikyospores. It then dissolves its cell wall and that of its host and creates a cytoplasmic continuum with it. Shortly afterwards, it releases a large number of parasitic cell nuclei into the host's hyphae.

Compared to other forms of parasitism, the parasite has an extremely close connection with its host: it fuses with it at the cellular level and feeds directly from its cytoplasm . One therefore speaks of biotrophic fusion parasites.

Fusion parasitism probably arose from the Mucorales' own form of sexual reproduction. Fungi of the same species but different mating types recognize their potential sexual partner by means of chemical signal substances (trisporic acid and its derivatives ). The pairing takes place through the fusion of individual hyphae with subsequent fusion of numerous cell nuclei ( karyogamy ) and finally the formation of zygospores . Fusion parasites such as Parasitella parasitica or Chaetocladium brefeldii also recognize their potential host with the help of the trisporic acid signal system. Therefore, only mucorales that have such a signal system and at the same time belong to the other mating type can be parasitized.

The host does not usually die as a result, but often exhibits slowed growth and decreased spore production.