4.2. Zoosporic hyperparasites
Zoosporic hyperparasites have been reported among Fungi in
Blastocladiomycota, Chytridiomycota, and Cryptomycota, and among
zoosporic fungus-like protists such as Hyphochytriomycota,
Labyrinthulomycota, and Oomycota (Gleason et al., 2014), all
three of which are now recognized as belonging to the Stramenopila
lineage of Eukaryotes (Keeling and Burki, 2019; Wijayawardene et
al., 2022). Zoosporic parasites can grow as epibionts on the surface of
their hosts by means of specialized structures such as rhizoids, or as
endobionts (i.e., intracellularly) being completely submerged within
their hosts (Held, 1973, 1974; Gleason et al., 2012; Karling,
1960). There is a third type of association, such as in hyphal-forming
zoosporic organisms, where interactions between hyphae of the
hyperparasite and the primary parasite can be observed (Gleason et
al., 2014). This is the case, for example, for the interactions of the
oomycete Pythium oligandrum and hyphae of its plant-parasitic
oomycete hosts, Pythium spp. and Phytophthora spp.
(Benhamou et al., 1999).