A new species of Climaconeis Grunow (Bacillariophyceae: Bacillariophyta): Climaconeis heteropolaris sp. nov. from the southwestern coast of India

Abstract

The newly identified diatom species, Climaconeis heteropolaris sp. nov., stands out due to its distinctive heteropolar valve shape. The valve structure is lanceolate-clavate with rounded capitate apices. The middle of the valve is slightly wider but gradually tapers towards the ends. Its size ranges from 76.5 to 120.5 μm in length and 9.5–14.5 μm in width. The striae radiate outward near the centre, align parallelly in the middle section and converge near the tips, with 17–22 per 10 μm. A rectangular stauros intersects the valve, flanked by short striae. The areolae vary in shape, ranging from round to more elongated forms. A narrow, linear axial area runs through the valve, bordered by longitudinal ribs that meet linear helictoglossae near the ends. The raphe is straight and forms a ‘tuning fork' shape at the centre. Scanning electron microscopy reveals a generally flat valve with a slightly curved mantle. The striae near the raphe have a parallel orientation but radiate outward as they extend from the centre. The shapes of the areolae also vary depending on their position on the valve. Internally, the raphe is flanked by longitudinal ribs, while a raised stauros occupies the central area. At the raphe’s tips, a ‘porte-crayon'-like feature marks the distal terminations. When compared to other members of the Climaconeis genus, C. heteropolaris is distinguished by its unique valve shape and stria patterns. This feature differentiates it from relatives like C. colemaniae, C. undulata, C. stromatolitis, C. mabikii, C. scalaris and C. scopulorioides. Differences in valve shape and stria arrangement confirm its placement within Climaconeis while also hinting at possible affinities with Stauroneis and Frustulia.