Halamphora hampyeongensis S. M. An & J. Kim, 2024

An, Sung Min, Kim, Jihoon, Cho, Kichul & Hwang, Hyun-Ju, 2024, Halamphora hampyeongensis sp. nov. (Amphipleuraceae, Bacillariophyceae), a new marine benthic diatom from a tidal mudflat in Hampyeong Bay, South Korea, PhytoKeys 248, pp. 59-71 : 59-71

Halamphora hampyeongensis S. M. An & J. Kim sp. nov.

Fig. 2

Description.

In LM, valves semi-elliptical with smoothly convex dorsal margin, nearly straight ventral margin and the valve ends narrowly rounded and slightly ventrally curved (Fig. 2 A – H ). Raphe slightly arched and positioned centrally to slightly ventrally on the valve face. Both dorsal and ventral striae not discernible. Valve length 13.8–15.0 μm; valve breadth 2.8–3.0 μm (n = 31).

In SEM, externally, the central area slightly expanded on the ventral side only (Fig. 2 I, K , asterisks). Central raphe endings straight, slightly expanded and positioned very close together (Fig. 2 K , arrowhead); distal raphe endings bent towards the dorsal side (Fig. 2 L , arrow). Raphe ledge well-developed on the dorsal side of the valve (Fig. 2 I, K ) and narrows sharply towards the dorsal valve margin. Siliceous outgrowths of various sizes arranged irregularly on the raphe ledge margin (Fig. 2 K , arrows). The axial area narrow, and difficult to distinguish because of the fine striae (Fig. 2 I ).

Dorsal striae slightly radiate. Ventral striae are slightly radiate and more distantly spaced at the valve middle, becoming parallel to slightly convergent and denser near the valve apices (Fig. 2 I, K, M ). Dorsal striae biseriate under raphe ledge with two rows of small, round areolae under SEM (Fig. 2 M , arrow); becoming uniseriate, composed of very small round areolae over the rest of the dorsal side (Fig. 2 K, M ), 34–38 in 10 μm (n = 13). Ventral striae uniseriate, almost identical in size and shape to dorsal striae, 46–48 in 10 μm (n = 13, Table 1 ). Axial longitudinal line absent on dorsal side. Internally, longitudinal rib absent. Areolae occluded by hymenes (Fig. 2 N , arrows). Proximal raphe endings finish onto small and tongue-shaped fused helictoglossae (Fig. 2 N , double asterisk). Poorly developed helictoglossae at distal raphe endings (Fig. 2 O , arrow). Round or ovoid poroids in girdle bands, arranged in two rows of 65–67 in 10 μm (Fig. 2 P , arrows).

Holotype.

Slide no. MABIK DI 00043482 (represented by the valve shown in Fig. 2 A ) was deposited at the National Marine Biodiversity Institute of Korea ( MABIK), located in Seocheon-gun, Chungcheongnam-do, South Korea.

Isotype.

SEM stub no. MABIK DI 00043483 and cleaned material no. MABIK DI 00043484 (preserved in 99 % ethanol) .

Type locality.

The intertidal mudflat located in Hampyeong Bay (35 ° 01.89 ' N, 126 ° 24.31 ' E), Muan-gun, Jeollanam-do, South Korea (site: HP 1-3), July 19, 2018.

Etymology.

The specific epithet “ hampyeongensis ” refers to the type locality, Hampyeong Bay, Muan-gun, Jeollanam-do, South Korea.

Distribution and ecology.

Halamphora hampyeongensis is a benthic species currently known only from the type locality. The sediment temperature and salinity of pore water in the sediment at the time of sampling were measured to be 27.8 ° C and 24.9 psu, respectively.

Gene sequences.

The nucleotide sequences were deposited in GenBank under accession numbers OQ 642108 (18 S rDNA) and ON 137728 (rbc L gene).

Phylogenetic analysis

The lengths of the 18 S rDNA and rbc L gene sequences were determined in this study for Halamphora hampyeongensis were 1,649 bp and 1,424 bp, respectively. Phylogenetic analysis was conducted to determine the relationship between H. hampyeongensis and the amphoroid diatom species retrieved from GenBank using ML and BI methods (Fig. 3 ). The topologies of the phylogenetic trees were similar regardless of the phylogenetic analysis methods and molecular regions utilized. Phylogenetic analysis provided robust support for the monophyletic grouping of Halamphora species including H. hampyeongensis , as indicated by a maximum likelihood bootstrap support of 98 % and a Bayesian posterior probability of 0.99. H. hampyeongensis was located in Halamphora Clade Hal _ H as described by Stepanek and Kociolek (2019) with a low bootstrap value (bootstrap value = 25). This species also showed weak support (bootstrap value = 63) as the sister taxon to H. montana (Krasske) Levkov.

Figures

Figure 2. A – H Light microscopy photomicrographs of H. hampyeongensis I – P scanning electron microscopy photomicrographs of H. hampyeongensis I external valve view, with central area (asterisk) and dorsal raphe ledge (arrow) J internal view of a valve K detail of a valve externally showing siliceous outgrowths (arrows) on the margin of the raphe ledge, central area (asterisk), and proximal raphe endings (arrowheads) L detail of external valve apex showing the dorsally bent distal raphe ending (arrow) M biseriate striae (arrows) in several rows under the raphe ledge N detail of areolae on the dorsal side internally occluded by hymenes (arrows) and tongue-like proximal helictoglossae (double asterisk) O detail of internal valve apex showing poorly developed distal helictoglossae (arrow) P girdle bands with two rows of poroids (arrows). Scale bars: 10 μm (A – H); 5 μm (I, J); 1 μm (K – M, O, P); 0.5 μm (N).

Figure 3. A molecular phylogenetic tree obtained from ML and BI analysis based on the concatenated dataset (18 S rDNA and rbc L gene) showing the phylogenetic positions of H. hampyeongensis. A phylogenetic tree was generated through a ML analysis. The values on each node indicate ML bootstrap and Bayesian posterior probabilities, respectively. The asterisk indicates 100 in ML and 1 in BI, and – indicates the topological incongruence between ML and BI trees. The H. hampyeongensis is highlighted in bold blue.