Halamphora minima, An & Kim & Kang & Cho & Kim, 2022

An, Sung Min, Kim, Jihoon, Kang, Nam Seon, Cho, Kichul & Kim, Eun Song, 2022, Halamphora minima (Catenulaceae, Bacillariophyta), new brackish diatom species from the mudflat in Hampyeong Bay, Korea, Phytotaxa 572 (1), pp. 115-122 : 117-118

Halamphora minima sp. nov. S.M. An, J.H. Kim, N.S. Kang, K. Cho, J.A. Lee & E.S. Kim

Description: The valves are semi-lanceolate with a convex dorsal margin and nearly straight ventral margin ( Figs 2–10 ). The valve length is 5.6–7.4 μm and the breadth is 2.3–3.3 μm (n = 36, Table 1 ). The central area is expanded on the ventral side only and closed with striae near the valve margin ( Fig. 11, 17 ; asterisk). The raphe is straight with straight distal raphe ending and lie along the ventral margin ( Fig. 11 ). The raphe ledge is fairly well-developed to the dorsal side of the valve ( Figs 11, 13, 17 ; arrow). An axial longitudinal line is not present on the dorsal side. Striae slightly radiate on the dorsal side, but ventral striae parallel to the center and slightly radiated towards the apices. The dorsal striae (27–29 in 10 μm) are biseriate throughout the valve ( Table 1 ), composed of small round or ovoid areolae ( Figs 11–15, 17 ), and are separated by strongly developed costa. The ventral striae are almost invisible under a LM. In SEM, the ventral striae (43–45 in 10 μm, n = 13, Table 1 ) are uniseriate and interrupted by a central nodule area ( Figs 11, 17 ; asterisk). Internally, a single row of dorsal areolae close to the raphe is delimited by an internal longitudinal rib ( Fig. 14 ; arrow). The dorsal striae and areolae are arranged in one row between the internal longitudinal rib and the raphe ( Fig. 14 ). The areolae are occluded by hymens ( Fig. 15 ; arrows). The fused helictoglossae of the internal proximal raphe endings are small and tongue-shaped ( Fig. 14 ). The internal distal raphe endings terminate with poorly developed helictoglossae ( Fig. 14 ; arrowhead). The girdle bands are numerous, and round or ovoid poroids are arranged in two rows of 44 – 47 in 10 μm on the dorsal side ( Fig. 16 ).

Type material: Intertidal mudflat in Hampyeong Bay (35º03’41.94’’ N, 126º24’40.06’’ E), Muan-gun, Jeollanamdo, Republic of Korea (site: HP2-2). Jul 19, 2018.

Holotype: SEM stub no. MABIK DI00043438 (represented by the valve in Fig. 3 A ) was deposited at the National Marine Biodiversity Institute of Korea ( MABIK), Seocheon-gun , Chungcheongnam-do, Republic of Korea.

Isotype: Slide no. MABIK DI00043439 and cleaned material MABIK DI00043440 (preserved in 100% ethanol) .

Etymology: The specific name, minima (Latin = very small, smallest), relates to the small size of this species. Distribution: Currently known only in type locality.

Figures

FIGURES 2–10. Light microscopy (LM) micrographs of Halamphora minima sp. nov. Scale bars = 5 μm.

FIGURES 11–17. SEM micrographs of Halamphora minima sp. nov. Fig. 11. External whole valve view, with central area (asterisk), and dorsal raphe ledge (arrow). Fig. 12. Internal whole valve view. Fig. 13. Detail of external valve apex,with dorsal raphe ledge (arrow) Fig. 14. Detail of internal valve apex showing tongue-like proximal helictoglossae (double asterisk), poorly developed distal helictoglossae (arrowhead), and internal longitudinal rib (arrow). Fig. 15. Detail of internal dorsal areolae occluded by hymens (arrows). Fig. 16. Dorsal girdle bands with two rows of poroids. Fig. 17. frustules showing the ventral girdle bands with dorsal raphe ledge (arrow). Scale bars: Figs 11—14, 16, 17 = 1 μm, Fig. 15 = 0.5 μm.