Description of Urotricha nais:
MUNOZ, TELLEZ,FERNANDEZ-GALIANO,1987.This small ciliate, oval in shape, varies in size from 16-34 um long by 12-32 um wide (measured from fixed specimens). The nuclear apparatus consists of a large oval macronucleus of 8-11 um in length and a spherical micronucleus. Silver impregnation demonstrates somatic kinetosomes distributed in 18 to 21 meridional kineties that run from the anterior pole close to the oral cavity and extend only part way down the cell leaving the posterior third of the cell barren of cilia with the exception of a single long caudal cilium. The number of kinetosomes in each kinety is very variable, even in the same specimen, and ranges from 5 to 11 kinetosomes per kinety. The somatic kinetosomes bear a kinetodesmal fiber at its right side that runs towards the anterior kinetosome. Associated with each somatic kinetosome is a single parasomal sac. One of the somatic kineties is shorter than the rest and leaves an anterior space that is occupied by the kinetosomes of the "brosse" or dorsal brush. The "brosse"consists two organelles similar appearance to the membranelles formed by obliquely oriented rows of kinetosomes around the oral aperture. The upper or first organelle is formed by two rows of four kinetosomes each, and the second one by two rows of two kinetosomes only. The kinetosomes of the organanelles do not bear kinetodesmal fibers. The oral infraciliature is represented by a circumoral corona of 9-10 pairs of kinetosomes surrounding the anterior oral cavity. This species has short rod-shaped extrusomes. The extrusomes are located between kinetosomes along the somatic kineties. The silverline system is composed of a regular rectangular mesh in the anterior 3/4 of the cell. In the unciliated posterior 1/4 the silverline system has an irregular polygonal configuration. Kinetosomes are located at the right side of each rectangle. The kinetosomes and extrusomes lie along the fine primary longitudinal meridians at the right side of each rectangle. The extrusomes are located at the intersection of the transverse lines and the primary meridians. Dense secondary longitudinal meridians lie to the right of each primary meridian.