Electron Microscopy on Sommerstorffia Spinosa, a Watermold Parasitic on Rotifers

ABSTRACT

Sommerstorffia spinosa Arnaudow (Saprolegniales, Oomycetes) infects loricate rotifers by both endoparasitic and predacious means, using sporelings and pegs, respectively. The sporeling is a lecythiform-shaped structure derived from the encysted, secondary zoospore, whereas the peg is a narrow terminal protuberance of a short, hyphal branch. In electron microscopy of thin sections, however, infective organs are very similar to each other, being packed with many, large (approx. 1.0 μm diam), electron-dense vesicles in their apical portion. When that portion is engulfed by rotifers, both infective organs secrete an amorphous, electron-dense, adhesive mass containing a number of bubbles.

Key Words:

• Sommerstorffia
• rotifer-parasitic watermold
• electron microscopy