portrait

Description:

Portrait of Didinium nasutum (Mueller,1773) Stein, 1859, a barrel-shape haptorid ciliate with a conical anterior snout containing prominent extrusomes (seen well in this image). Two ciliary girdles. Oral aperture forms anteriorly at the apex of the snout. Two ciliary girdles, one circumoral and the other equatorial (not well-seen in this image). Posterior contractile vacuole. Macronucleus C-shaped or oblong. Fast swimmer. Fixes prey (often Paramecium or Frontonia) with nontoxic extrusomes called pexicysts and kills them with toxicysts before engulfing them whole through enormously extensible oral aperture.Didinium may be confused with early dividing individuals of Monodinium. From freshwater pond with abundant Frontonia near Boise, Idaho. DIC.