Urotricha agilis

(Stokes 1886) Kahl 1930

Most likely ID: n.a.


Synonym: n.a.


Sampling location: Ulmisried, Bussensried, Simmelried, Purren pond, Pond of the convent Hegne, Mainau pond, Mühlweiher Litzelstetten


Phylogenetic tree: Urotricha agilis



  • body conical, almost triangular
  • length 10–20 µm
  • 12–14 longitudinal rows of cilia
  • posterior third of body free from cilia
  • extrusome short rods, hard to see
  • contractile vacuole eccentric in posterior end
  • nucleus central with one spherical micronucleus
  • one caudal cilium, about body length
  • fast movement, circling, jumping
Urotricha agilis

Urotricha agilis occurs in almost all of my sampling sites. The specimens are often found in old samples of decomposing plant material.


Urotricha agilis is easily recognized by its conical body shape, which sometimes appears almost triangular. The ciliate is an extraordinarily fast swimmer, but always takes breaks in which it circles. The pharynx is apical and lined with rod-shaped trichites (s. figs. 1 c and 4). As with all representatives of the genus Urotricha, the posterior end is naked. In Urotricha agilis it is the posterior third (s. fig. 3 b). The very small micronucleus can only be recognized in squashed specimens (s. fig. 4). I could not clearly identify the short, rod-shaped extrusomes.


Fig. 1 a-f: Urotricha agilis. L = 14 µm. A freely swimming specimen. Note the apical pharynx (PH) surrounded by thin, rod-shaped trichites. CC = caudal cilium, CV = contractile vacuole. Obj. 100 X.


Fig. 2 a-f: Urotricha agilis. L = 15 µm. A second, freely swimming specimen. CC = caudal cilium, CV = contractile vacuole, PH = pharynx. Obj. 100 X.


Fig. 3 a-b: Urotricha agilis. Two focal planes of a squashed specimen. Note that the posterior third is free from cilia (FFC). CC = caudal cilium, CV = contractile vacuole, Ma = macronucleus, PH = pharynx. Obj. 100 X.


Fig. 4: Urotricha agilis. In a strongly squashed specimen the micronucleus (Mi) becomes visible. Ma = macronucleus, TR = one of the trichites surrounding the pharynx. Obj. 100 X.