portrait

Description :

Portrait of the metopid ciliate, Brachonella spiralis. The body is broadly conical anteriorly with a narrower obliquely truncate posterior. The long S-shaped peristome winds around the entire circumference of the cell terminating in the cytostome. This spiraling cytostome distinguishes Brachonella (Jankowski 1964) from similar genus Metopus in which the peristome runs obliquely from anterior to posterior but does not spiral around the long axis. The cytostome is paralleled on the right by a perizonal stripe of kineties. On the left is an adoral zone of membranelles. There are uniform longitudinal dorsal kineties with a tuft of longer caudal cilia. A distinctive aggregate of brownish refractile granules typical of most metopids is noted anteriorly. There is a spherical anterior macronucleus. The micronucleus is not seen here. There is a posterior terminal contractile vacuole. Brachonella is found in sapropelic habitats and contains methanogenic symbionts in the cytoplasm. From stagnant freshwater source with rotting vegetation near Boise, Idaho. DIC optics.