The Adhesive Disk of Giardia
Scanning electron microscopy (SEM) reveals a concave structure, called the adhesive disk, that covers much of the ventral surface (Fig. A). Also evident are a pair of ventral flagella (VF) emerging into the ventral groove (VG) and a ventro-lateral flange (VLF). Transmission electron microscopy (TEM) reveals a close association between the adhesive disk and the brush border of the intestinal epithelium and the outer rim of the adhesive disk, called the lateral crest, is in direct contact with the microvilli (Fig. B). The adhesive disk has a striated appearance in cross-section and higher magnification (Fig. C) reveals structures called microribbons (mR) in close association with microtules (mT). These microribbons + microtubules are arranged in concentric rows that form a small circular spiral. (Note spiral shape of adhesive disk in Fig. A.) Trophozoite detachment leaves a dome-shaped imprint in the brush border (Fig. D) suggesting that contractile forces are involved in attachment.

Adhesive Disk

Massive numbers of trophozoites can cover the epithelial surface resulting in a cobblestone road like appearance (Fig. E).
Infected Epithelium

Acknowledgements. Figures A and C are from reference 1; figures D and E are from reference 2, and Figure B is from reference 3.

  1. Feely DE, Erlandsen SL and Chase DG (1984) Structure of the trophozoite and cyst. In: Giardia and Giardiasis (Erlandsen SL and Meyer EA, eds.). Plenum Press, New York, pp 3-31.
  2. Erlandsen SL and Feely DE (1984) Trophozoite motility and the mechanism of attachment. In: Giardia and Giardiasis (Erlandsen SL and Meyer EA, eds.). Plenum Press, New York, pp 33-63.
  3. Holberton DV (1973) Fine structure of the ventral disk apparatus and the mechanism of attachment in the flagellate Giardia muris. J. Cell Sci. 13, 11-41.

 

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