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Hampyeong Bay diatom (Halamphora hampyeongensis) from a tidal mudflat in South Korea

Hampyeong Bay diatom (Halamphora hampyeongensis) from a tidal mudflat in South Korea

NEWS - Researchers describe a benthic diatom found in the intertidal mudflats of South Korea, based on morphological and molecular characteristics, similarities and differences between Hampyeong Bay diatom (Halamphora hampyeongensis sp. nov.) and other morphologically similar Halamphora species.

Several molecular phylogenetic studies provide strong evidence supporting the monophyletic status of Halamphora as a distinct group separate from Amphora sensu stricto. Since its recognition as a genus, there has been an increase in understanding of the diversity within Halamphora. Furthermore, there has been a significant increase in the determination of new species. The genus includes 155 valid species, including 8 varieties.

Sung Min An from the National Marine Biodiversity Institute of Korea in Seocheon and his team used light and electron microscopy to conduct morphological examinations of the new species isolated from the intertidal mudflats of Hampyeong Bay, South Korea. Molecular analysis used 18S rDNA and rbcL genes.

H. hampyeongensis has a semi-elliptical valve LM with a smoothly convex dorsal margin, a nearly straight ventral margin, and a narrowly rounded valve tip that curves slightly ventrally. The raphe is slightly curved and positioned midway to slightly ventrally on the valve surface. Dorsal and ventral striae are not visible. The valve length is 13.8-15.0 μm, and the valve width is 2.8-3.0 μm.

The specific epithet “hampyeongensis” refers to the type locality, Hampyeong Bay, Muan-gun, Jeollanam-do, South Korea. This species is a benthic species currently only known from the type locality. The sediment temperature and pore water salinity in the sediment at the time of sampling were 27.8°C and 24.9 psu, respectively.

The lengths of the 18S rDNA and rbcL gene sequences were 1,649 bp and 1,424 bp, respectively. Phylogenetic analysis provides strong support for a 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 is located in the Halamphora Clade Hal_H with low bootstrap value (bootstrap value = 25) and weak support (bootstrap value = 63) as the sister taxon to H. montana (Krasske) Levkov. This species is related to H. exilis, H. mosensis, H. specensa, H. maritima (J.G.Stepanek & Kociolek) and H. nipponensis (J.G.Stepanek, S.Mayama & Kociolek).

This clade is characterized by the absence of a dorsal marginal ridge, the presence of a biseriate internal areola occlusion and an internal areola occlusion of the hymen. In particular, H. maritima and H. nipponensis show clear differences from other species in the clade, particularly in their narrow ventral valves and ventral striae, which are composed of elongated areoles. In contrast, other species typically have relatively wide ventral valves and fine uniseriate ventral striae as in the new species.

H. hampyeongensis shares similarities with H. caribaea (Wachnicka & E.E.Gaiser) Rimet & R.Jahn, H. exilis, H. mosensis, and H. specensa in the overall valve outline, the relatively wide ventral side of the valve, and specific striae characteristics, including fine uniseriate ventral striae and biseriate dorsal striae near the axial area.

H. hampyeongensis has smaller areolae and denser striae with 34-38 in 10 μm, compared to 11-20 in 10 μm in H. caribaea and 24-26 in 10 μm in H. exilis. Unlike H. hampyeongensis, H. mosensis has multi-seriate dorsal striae and H. specensa has convex ventral margins and irregular bi-seriate dorsal striae.

H. hampyeongensis has smooth areolae like H. atacamana (Patrick) Levkov and H. montana. However, H. atacamana can be distinguished from H. hampyeongensis by its lower valve lines and striae density (25-28 in 10 μm) and H. montana has semi-stauros.

Although benthic diatoms are dominant organisms in benthic ecosystems in tidal areas and are known for their high diversity, a comprehensive understanding of them is still limited. In the future, further research is needed to explain the species richness of diatoms in tidal areas.

Original research

An SM, Kim J, Cho K, Hwang H-J (2024). Halamphora hampyeongensis sp. nov. (Amphipleuraceae, Bacillariophyceae), a new marine benthic diatom from a tidal mudflat in Hampyeong Bay, South Korea. PhytoKeys 248: 59-71, DOI:10.3897/phytokeys.248.135034

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