Nematode body filled with thalli and zoosporangia of Catenaria anguillulae
Catenaria produces uniflagellate zoospores. The zoospores are attracted by body secretions of the nematode and produce spherical cysts at the body orifices of the host (mouth, anus, etc). The cysts germinate and the germ tube pentrates the orifice into the body of the host where it produce a filamentous thallus (thallus is the name given to the vegetative body of a fungus). At maturity the thallus becomes septate and the individual segments(cells) produce zoosporangia. The zoosporangia produce exit tubes that penetrate the cuticle of the nematode to the exterior and produce an open pore at the mouth of the tube. Mature zoospores swim out through this mouth to seek out and attack more hosts. Very fine thread-like hyphae can be seen lacing through the nematode's body. These are rhizoids, arising from the filamentous hyphae for more effective absorption of body materials.