Geissleria triundulata sp.nov., a new freshwater diatom (Cymbellaceae, Bacillariophyta) from the Mula-Mutha River Basin, India

While conducting a seasonal assessment of the Mula-Mutha River basin in Maharashtra, India, an unknown taxon of the genus Geissleria was observed from an oligotrophic stream connected to the Mutha River. This taxon is described here as new to science based on detailed light and scanning electron microscopic observations. The characteristics of this new species used to assign it to the genus Geissleria include triundulate valve margins, a straight and filiform raphe structure, lineolate striae, and the presence of annuli a circular or semi-circular hyaline area positioned on the valve apices. In G. triundulata sp. nov., the annulus is barely visible in light microscopy. The present study discusses the morphology of this new species compared to other Geissleria species, undertaking a thorough analysis of various morphological features observed in members of the genus Geissleria. This new taxon resembles G. lubilensis and G. fogedii in having a slightly triundulate margin but differs in their broad and protracted valve apices, holding differences from the new species. This study also presents a brief discussion concerning the ecology of the newly discovered species and the worldwide distribution of all Geissleria species.