Integrative taxonomic description of the marine species Cocconeis crawfordii (Bacillariophyceae) based on unialgal strains. Cocconeis crawfordi

Cocconeis crawfordii from the Southern Baltic Sea at Wismar, Germany, is described as new. It is based on three unialgal cultures. Two of the strains auxosporulated and showed an almost quadrupling of size in length and width. Morphologically, this species with its two different elliptical valves belongs to the genus Cocconeis. As with all Cocconeis species, the raphe valve is typically simple, thin and concave, has striae with uniseriate areolae continuing across the hyaline ring at the mantle of the valve. The sternum valve is very different, convex, and shows the differentiating features of this species such as biseriate areolae of irregular size grouped in alveolae producing in LM the image of dashes; at the mantle the areolae are triseriate and of regular size. Micromorphologically, this species possesses two different closed valvocopulae: the raphe valvocopula has slender and closer spaced fimbriae which show papillae with furrows, the sternum valvocopula has broader and wider spaced fimbriae which sit on cupules. Based on DNA sequence data, this species is closest to the published molecular data of the strain AmCo01a named C. cf. stauroneiformis from the North Sea but surprisingly different to all the other marine or freshwater Cocconeis. This species is named in honor of Richard Crawford who pioneered research on ultrastructures of diatoms, among others of the valvocopulae and areolae of Cocconeis.