Cymbella orientalis var. delicatula var. nov. (Bacillariophyta), a new epilithic stream diatom from Bulgaria
Stancheva, Rosalina; Ivanov, Plamen
Cymbella orientalis var. delicatula var. nov., collected from the epilithon of the Vesselina stream in Bulgaria is described. Comparison of C. orientalis var. delicatula and the nominate variety shows differences in frustule outline, the shape of the apices, and the number of the areolae in the striae. A considerable geographical distance separates the Far East populations of C. orientalis and the European population of the newly described variety. Valve morphology of C. orientalis var. delicatula is compared to closely related species from Asia. Both distribution and ecology of C. orientalis var. delicatula are discussed considering its rare occurrence and application in regional stream biomonitoring studies.