A new brackish diatom, Pinnularia sakurajimensis O.Ishii & Ji.Tanaka from Japan

Abstract

A new diatom species, Pinnularia sakurajimensis O.Ishii & Ji.Tanaka, is described from brackish waters in the coastal area of Japan. Valve shape is linear with broadly rounded ends. Raphe fissure is filiform with straight central endings and bent terminal fissures to the secondary side. Axial area is linear. Central area forms a narrow fascia, and sweeping depressions exist at both sides of central raphe endings in the central area. Striae are almost parallel. Each stria consists of an alveolus with a rounded aperture on the inside of the valve. In LM, an array of the apertures is observed as a longitudinal line across the striae. Cingulum is composed of a valvocopula (an opened band with central protrusions), a short segmental band which lines the open end of the valvocopula and a pleura (a closed ring). This species has similarities to the figure by Peragallo & Peragallo (1897–1908) of Pinnularia cruciformis (Donkin) Cleve in valve length and stria densities, but the latter differs by possessing broader longitudinal lines on the striae.