Ultrastructure of filamentous microorganisms associated with zebra cyathostomes.

Filamentous microorganisms were observed colonizing the cuticle of cyathostomes (Nematoda: Strongylidae) collected from the large intestine of Burchell's zebra (Equus burchelli antiquorum). Scanning (SEM) and transmission (TEM) electron microscopy revealed three filamentous microorganisms, designated as segmented, continuous multicellular, and helical. The segmented and continuous multicellular morphotypes each revealed a process of segmentation in their developmental stages, and those of the segmented filaments are demonstrated in this report. In contrast, the helical types of filaments appeared to be complexes of spiraling rodshaped organisms. In addition to these filaments, the cyathostome cuticle was also colonized by other smaller microorganisms.