A New Marine Epizoic Diatom, <i>Ceratanaulus alaris</i> sp. nov. (Bacillariophyceae), From Guangxi Zhuang Autonomous Region, the Southwest Coast of China

Diatoms (Bacillariophyceae) are diverse and abundant microalgae, and many of them are found in marine intertidal environments. Here, we present a new marine epizoic diatom isolated from Euspira gilva Philippi in intertidal area of Beihai city, Guangxi Zhuang Autonomous Region, named Ceratanaulus alaris L.J. Huang, Y.H. Gao & C.P. Chen sp. nov. Using light microscope (LM) and scanning electron microscope (SEM), we observed and described the morphology of C. alaris in detail. The valve center of C. alaris features a rimoportula with an external tube. The most notable characters in C. alaris are wing-like structures on both sides of the central tube. These structures extend from the central tube to the horn-like protrusions at the valve apices, with fissures evenly distributed on the wing-like structures. In this study, we compared the morphological structures of the new species with other species in the genus Ceratanaulus Górecka, Witkowski, Dabek & Ashworth, enhancing the understanding of the ultrastructure of C. alaris and facilitating the differentiation of this species from closely related taxa. The genus, Ceratanaulus, is newly recorded in China, thereby expanding the known geographical distribution of the genus.