Ambo dajingensis HH Liu, Z Wang, YH Gao & CP Chen, 2022

Liu, Honghan, Wang, Zhen, Wu, Weiwei, Li, Chenhong, Zhang, Jiawei, Gao, Yahui, Li, Xuesong, Sun, Lin, Liang, Junrong, Zhang, Jun & Chen, Changping, 2022, A new marine epipsammic diatom species, Ambo dajingensis sp. nov. (Bacillariophyceae), from the coast of Southeast China, PhytoKeys 210, pp. 23-34 : 23

Ambo dajingensis HH Liu, Z Wang, YH Gao & CP Chen sp. nov.

Figs 2 , 3 , 4

Holotype

(here designated): slide DJ1805 (AU, Biology Department Herbarium, Xiamen University). Fig. 2E represents holotype.

Type locality.

Sand beach in Dajing County, Fujian Province, China, 26°42'34"N, 120°7'17"E, leg. Zhen Wang in May 2018

Etymology.

The epithet " Ambo dajingensis " refers to the site where this specimen was collected.

Description.

LM observations (Fig. 2A-I ): The cells are connected to each other to form short chains and they live in groups. The girdle is comprised of several plain and open bands. The valves are linear elliptic with two costae that are straight or slightly curved to the outside and protrude deeply into the valve. The valve is 6-10 μm long and 2.4-3 μm wide.

SEM observations (Figs 3 , 4 ): Through the observation of the samples treated by the critical point drying method, the cells on the girdle band valve are rectangular (Fig. 3A ), with a wrapped layer of membrane. Several girdle bands (Fig. 3D ) are connected between the epitheca and hypotheca valves. The girdle band has fine vertical lines (Fig. 3D ) but no obvious spot pattern. Areolae can be observed at both ends of the valve, and the area of the areolae extends to the sternum, but there are no areolae or other cell structures in the middle of the cell (Fig. 3A, B ). There is a circle of spines for cell connection at the edge of the valve (Fig. 3A-D ). The single row of slightly radial striae is distributed at both ends of the cell (Fig. 3A ). Observation of the samples processed by the acidification method showed striae at both ends of the cells and a narrow sternum in the center of the cells in the area of striae, but the sterna were not obvious. To the two ends of the valve, the striae at both ends of the valve extended from the valve in a single row, and the number of striae was 50-60 in 10 μm. The areolae on the valve are round, small, simple, and have no complex structure, such as a cribrum. A small circular area free of areolae is distinctly set off from the striae, and can be observed at the apical part of mantle area with several elongate areolae following the general pattern of the mantle (Fig. 3E, F ). On the edge of the valve, there is a row of densely distributed small spines.

Internally, the valves are divided into three sectors by robust costae (Fig. 4A, C ). The interior of the valve face is flat, the transition from the valve face to the mantle is abrupt (Fig. 4A ). The transapical striae are composed internally of small, round areolae, and they are parallel in the middle to slightly radiate at the apices. The sternum is narrow and linear, set off by costae (Fig. 4A ).

Distribution.

Marine, coastal. Collected from Dajing beach on sandy shores. Changchun Town, Xiapu, Ningde City, Fujian Province.

Molecular phylogeny

Phylogenetic analysis of molecular data was conducted using a rbc L-gene dataset. The tree inferred from Maximum-Likelihood Phylogenies (MLP) analysis (Fig. 5 ) of the concatenated rbc L-gene dataset recovered the genus Ambo (represented by A. tenuissimus , Ambo dajingensis and A. gallaeciae ) within the araphid diatoms, sister (bootstrap support [bs] = 100%) to a clade with Diatoma moniliforma , Diatoma tenue , and Asterionella formosa . Ambo dajingensis and A. gallaeciae were sister to a clade, but with low support. The phylogenetic relationships of the new species were sustained by genetic distance estimation. The sequences generated in the study were deposited in GenBank under access number OL457301.1.

Figures

Figure 2. Light micrographs (LM) of Ambo dajingensis sp. nov. A-F valve showing the size and shape G-I girdle view. Scale bar: 5 µm.

Figure 3. Scanning electron microscopy (SEM) images of Ambo dajingensis sp. nov. in an external view of the entire valve A, B external valve view of the whole specimen. There is a hyaline valve face over most of the length and transapical striae develop only at the valve apex, with a weakly expressed sternum at the apices C, E, F fan-shaped spines (arrows) are arranged along the valve margin, there is striation, a strongly expressed sternum on the valve apical part, a small circular striated area structure on the mantle apex D the girdle bands. Scale bar: 1 µm.

Figure 4. Scanning electron microscopy (SEM) images of Ambo dajingensis sp. nov. in an internal view of the entire valve A, C internal valve view of the whole specimen B, D the presence of costae (arrows) and the areolation. Scale bars: 3 µm (A); 1 µm (B); 5 µm (C); 2 µm (D).

Figure 5. Maximum-Likelihood Phylogenies tree. Maximum-Likelihood Phylogenies (MLP) tree (based on analysis of the rbc L dataset) of mediophycean strains related to Ambo.