Micrographs of CU428 and NP1 <i>T</i>. <i>thermophila</i> fed Congo Red dye at room temperature (RT) and 37°C.

<p>Micrographs taken at 20X magnification, 1.5X zoom. (A) CU428 at RT. (B) NP1 at RT. (C) 428 at 37°C. (D) NP1 at 37°C. The absence of dark vacuoles in NP1 at 37°C indicates a nonfunctional oral apparatus.</p> <p>(TIF)</p>