Figure 4.

Modern spirochetes. Hollandina pterotermitidis from the wood-eating cockroach (Cryptocercus punctulatus; bar = 0.25 μm) and a termite spirochete Hollandina (Hollandina cryptotermitidis; Lower Left Inset; bar = 0.20 μm) transverse section, compared with the putative fossil termite spirochete (Upper Right Inset, bar = 0.15 μm). Longitudinal section of spirochete formerly attached to wood fiber (Upper Left Inset; x = xylem, bar = 7.5 μm). PC, protoplasmic cylinder; om, outer membrane; w, wood; fb, fibers; f, flagella; po, polar organelle; s, sillon. These spirochetes belong to the family Pillotinaceae. Cryptocercus is considered an ancestral group to the termites (1, 14, 15). Images were produced by transmission electron microscopy.