Morphological and molecular characterization of Neogastrostyla aqua nov. gen., nov. spec. (Ciliophora, Hypotrichia) from River Yamuna, Delhi; comparison with Gastrostyla-like genera.

A novel hypotrichous ciliate, Neogastrostyla aqua nov. gen., nov. spec. isolated from River Yamuna, Delhi, India, is described using morphological, morphometric and morphogenetic characters from live and stained cells supplemented with derivation of phylogenetic relationships using SSU rRNA gene. Neogastrostyla aqua nov. gen., nov. spec., is characterized by light yellow cortical granules present singly or in clusters of two to five, distributed randomly; parental adoral zone of membranelles retained unchanged for proter; Oxytricha-pattern of paroral and endoral; 25-27 frontal-ventral-transverse cirri including a distinct bipartite frontoventral row of composite origin; three dorsal kineties with no fragmentation of the third kinety, two dorsomarginal kineties, three caudal cirri, two macronuclear nodules and two or three micronuclei. Though Neogastrostyla aqua nov. gen., nov. spec. has a frontoventral row like Gastrostyla species, it differs distinctly in the combination of characters from Gastrostyla and other genera with Gastrostyla-like ventral ciliature (Protogastrostyla, Hemigastrostyla, Apogastrostyla and Pseudogastrostyla) particularly in the colour and distribution of cortical granules as well as arrangement and formation of ciliature. According to the phylogenetic analyses, Neogastrostyla aqua nov. gen., nov. spec. clustered consistently with Gastrostyla sp. Y2 (no description available), Oxytricha granulifera and Architricha indica as close neighbours.