portrait

Description :

Portrait of the large nassulid ciliate Obertrumia aurea (Ehrenberg, 1833; Foissner 1987). Synonym of Nassula aurea. Obertrumia is distinguished by it's bipartite "hypostomial frange", linear arrays of ciliary tufts. A sigmoid ventrolateral frange runs anteriorly and to the left and is separated from a horizontal line of ciliary tufts that lies on the dorsal surface. This specimen is slightly compressed, the cell outline normally appearing as a more elongate ellipsoid. The cell appears brightly colored (orange, green or violet) due to multiple food vacuoles containing ingested cyanobacteria. The single spherical macronucleus is seen posteriorly. There is one large lateral contractile vacuole, which fills from smaller surrounding vacuoles rather than collecting canals (seen well here). There is a prominent cytopharyngeal basket (nasse) composed of stout nematodesmata at the base of a shallow oral introitus in the anterior 1/3 of the cell. Focal swellings of the nematodesmata give the appearance of a ring near the outer end of the nasse. Numerous small mucocysts give the cortex a roughly granular appearance. O. aurea feeds mainly on cyanobacteria. Collected from a freshwater pond near Boise, Idaho November 2003. DIC optics.