Mayamaea densestriata, Du & Wei & Li & Xu & Li & Zhang, 2025

Du, Fei-Chao, Wei, Na, Li, Hao-Yu, Xu, Zhen-Quan, Li, Yu-Hang & Zhang, Man, 2025, Morphology and molecular phylogeny of Mayamaea densestriata sp. nov. (Bacillariophyceae), a new terrestrial species from Henan Province, China, PhytoKeys 268, pp. 33-44 : 33-44

Mayamaea densestriata sp. nov.

Fig. 1 , Table 2

Description.

In LM (Fig. 1 A – G ), valves small, elliptic to linear elliptic, with pronounced sternum and broadly rounded apices, 7.6–9.0 μm in length and 3.4–4.8 μm in width (n = 20). Raphe narrow, straight. Axial area lanceolate, broad towards valve center, fusing with transverse expanded central area. Central area wide, irregular, bordered on each margin by 7–10 shortened striae. The striae radiate throughout, 32–40 in 10 μm.

In SEM (Fig. 2 ), internally, raphe linear with thick distinct sternum (Fig. 2 A ). Central raphe endings slightly deflected to the same side of the valve (Fig. 2 B ). Distal raphe fissures terminated in small helictoglossae (Fig. 2 C ). Areolae small and round. Striae composed of 2–9 areolae. Central area wide. Externally, proximal raphe ends expanded and pore-like, surround by a shallow grove and slightly deflected in one direction (Fig. 2 D, E ). Terminal fissures bend markedly to the opposite direction of the proximal ends (Fig. 2 F ). Areolae small, round, and occluded by hymens. Striae composed of 6–8 round areolae and extended slightly onto the shallow margin of the valve.

Holotype.

The holotype is represented by the specimen illustrated in Fig. 1 . The slide MBMCAS 288335 is deposited in the Marine Biological Museum, Chinese Academy of Sciences ( MBMCAS), Qingdao, China .

Type locality.

Surface of moist agricultural soil ( 35°05.40'N, 114°08.59'E) in Yuanyang County, Henan Province, China. The type material was collected by Feichao Du on 10 May 2024.

Etymology.

The specific epithet Mayamaea densestriata refers to the unusually high number of areolae per stria observed in this species. It highlights a key diagnostic feature that distinguishes it from its morphologically similar congeners.

Distribution and ecology.

Mayamaea densestriata is currently known only from its type locality. It is a terrestrial species associated with moist soil environments within cultivated agricultural landscapes.

Gene sequences.

The two sequences of Mayamaea densestriata have been deposited in the GenBank (SSU rDNA: PV 733928, rbc L: PV 740453).

PhycoBank registration.

http://phycobank.org/105610

Molecular phylogenetic analyses

The BLASTn search results showed that the SSU rDNA sequence of Mayamaea densestriata shares 89.37 % identity with M. permitis (GenBank accession PV 156110), while the rbc L gene exhibits 91.50 % identity with M. atomus var. permitis ( JN 418670 ). Phylogenetic analyses based on concatenated SSU rDNA and rbc L genes place M. densestriata firmly within the well-supported clade comprising all currently recognized Mayamaea species (Fig. 3 ). Within this clade, M. densestriata occupies an independent branch and is placed at the basal position relative to a subclade including M. terrestris , M. pseudoterrestris , M. arida , M. vietnamica , M. atomus var. atomus , M. permitis , M. atomus , M. fossalis var. fossalis , and M. atomus var. permitis ( ML = 92, BI = 0.68). Together, they are resolved as the sister to another Mayamaea subclade, including M. sweetloveana and M. ectorii with high support ( ML = 100, BI = 1.00). The clade of Mayamaea is resolved as the sister group to a clade composed of Pinnularia Ehrenberg and Caloneis Cleve species ( ML = 99, BI = 1.00), forming a monophyletic lineage of the family Pinnulariaceae .

Figures

Figure 1. Valve face of M. densestriata under LM. A. Holotype; B – G. Valve size series. Scale bars: 5 μm (A – G).

Figure 2. A – F SEM photographs of M. densestriata. A. Internal view of the whole valve; B. Internal valve central area showing wide, irregular, bordered margins with several shortened striae; C. Internal raphe fissures terminating in small helictoglossae at the apices; D. External view of the whole valve showing the terminal fissures slightly deflecting in one direction; E. External central area of the valve showing proximal raphe fissures ending in pore-like structures and slightly deflecting in one direction; F. Terminal fissures. Scale bars: 1 μm (A – F).

Figure 3. Phylogenetic trees using both maximum likelihood (ML) and Bayesian inference (BI) methods based on concatenated SSU rDNA and rbc L gene sequences. Nodal support values are presented as ML bootstrap percentages and Bayesian posterior probabilities, respectively. Only bootstrap values exceeding 50 % are displayed. Solid circles denote full support in both analyses (ML = 100 %, BI = 1.00), whereas asterisks mark topological discrepancies between the ML and BI trees.