Description of an Indian Population of Urosomoida perthensis (Ciliophora: Oxytrichidae) with 16 FVT Cirri from a Pond located at Rajghat, Delhi, India

Ciliates constitute a vast monophyletic group of unicellular eukaryotes. However, the knowledge and understanding of ciliate taxonomy and biodiversity are still limited, especially from the Indian subcontinent. The present study aims to report an Indian population of Urosomoida perthensis [16], which is a new record to the Indian fauna. U. perthensis was isolated from a man-made pond located in the Rajghat, Delhi India. The species of the genus Urosomoida are indistinguishable from the species of genus Oxytricha in live cell as both have flexible bodies. However, it differs from Oxytricha in two features i.e. lack of fragmentation of 3rd dorsal kinety (DK3) and the presence of less than 18 frontal-ventral-transverse (FVT). These two features are the autapomorphies of this genus. This genus is placed in “non-oxytrichid Dorsomarginalia” because they lack fragmentation of dorsal primordium (DP3). The morphology and ontogenesis of Indian population of U. perthensis is described on the basis of protargol impregnation. Some of the morphological salient features of U. perthensis are as follows: size of protargol stained cells- ~50 x 14 μm; anterior rounded end and posterior tapering end; 2 macro-nuclear nodules and 2 micronuclei; 16 Frontal-Ventral-Transverse (F1-8, V1-5, T1-3) cirri; four dorsal rows of bristles- three dorsal kineties (DK1-3) and one dorso-marginal (DM₁); No split in DP3; 3 caudal cirri, a gap in DK1 continuity; on an average 17 adoral membranelles; 16 right marginal cirri; 13 left marginal cirri; flexible body; buccal cavity flat and narrow and undulating membranes (UMS) in the typical Oxytricha pattern; morphogenesis in typical Urosomoida pattern [11]; Primordia V & VI of proter are formed by the anterior movement of kinetosomes of primordial V & VI of opisthe.