Two new Nitzschia species (Bacillariophyceae) from China, possessing a canal-raphe-conopeum system

Abstract

Two new species in the diatom genus Nitzschia were found in the middle intertidal zone, Xiamen Bay, southern China. Both new taxa belong to the subgenus Nitzschia, as inferred from the presence of a canal-raphe-conopeum system. The valves of both new species are dorsiventral. In Nitzschia arierae sp. nov., the raphe system is positioned centrally, the conopea fuse to the valve face at supporting points, and the zone of valve face subtended by the conopeum has areolae. In Nitzschia gaoi sp. nov., the raphe system is centrally positioned or slightly eccentric, two large conopea extend out from near the raphe while two small conopea extend out from each transverse costa and cover the striae, most part of the zone of valve face subtended by the conopeum has no areolae, and there are two long produced rostrate apices that both arch toward the ventral side or one apex arches and the other is straight. Both new species are epipelic forms inhabiting the coastal environment.