Three new species of Delicatophycus M.J. Wynne (Bacillariophyta) from China, all possessing apical pore fields

Abstract

Delicatophycus wulingensis sp. nov., D. qinghainensis sp. nov., and D. menyuanensis sp. nov., are described, illustrated, and compared to similar taxa. Two types of apical pore fields (APFs) in the genus Cymbella are defined. The three new Delicatophycus all possess the type II APF found in some species of Cymbella, i.e. the APF is divided by the distal raphe fissure into two areas, one larger than the other. They also share a further three distinct features: variable central dorsal portion of valve, stigmata, and a notch on the dorsal side of the distal raphe fissure. Since there are many species of Delicatophycus without APFs, such as D. sinensis M.J. Wynne, D. williamsii M.J. Wynne and D. chongqingensis M.J. Wynne; D. williamsii and D. liuweii Li both possess stigmata, thus proposed diagnostic characters for Delicatophycus are the tilde-shaped areolae and the dorsally curved distal fissures.