ABSTRACT
Zoosporic fungi are found in two different kingdoms of eukaryotic organisms: the kingdom Fungi and the recently named kingdom Stramenopila (or Straminipila) (Dick, 2001). One of the most basal branches of the kingdom Fungi is the phylum Chytridiomycota, all of which are zoosporic fungi. The more familiar (but not zoosporic) Ascomycota, Basidiomycota, and Glomeromycota are also in the kingdom Fungi. The phylum Zygomycota (Chapter 10) is currently being revised, and students should be aware that several clades (Mucormycotina, Kickxellomycotina, Zoopagomycotina, and Entomophthoromycotina) are being used in place of the phylum until relationships can be fully resolved (Hibbett et al., 2007). The zoosporic fungi in the kingdom Stramenopila include hyphochytrids, labyrinthulids, and oomycetes. This kingdom represents an extremely diverse group of organisms, which also includes photosynthetic organisms such as brown algae, chrysophyte algae, and diatoms. Organisms classified in the phylum Chytridiomycota produce zoospores that usually have a single, posteriorly directed, and smooth agellum, whereas organisms classified in the kingdom Stramenopila (stramenopiles) are characterized by the production of zoospores that usually have two flagella (biflagellate), but always with tripartite tubular hairs on the anterior flagellum (Dick, 2001; Figure 9.1). A flagellum that possesses two rows of tripartite tubular hairs is also referred to as a heterokont or tinsel flagellum
Concept Box
(Kirk et al., 2001). While the flagella exhibited by zoospores in each group can be seen by light microscopy, details such as the tripartite hairs and diagnostic internal features must be viewed using an electron microscope, which can unfortunately limit proper identification.
