Mastogloia jahniae Al, 2021

Al-Handal, Adil Y., Wulff, Angela & Pennesi, Chiara, 2021, Mastogloia jahniae sp. nov., a new diatom (Bacillariophyceae) from the Baltic Sea coast of Sweden, Phytotaxa 484 (1), pp. 121-128 : 123-126

Mastogloia jahniae Al –Handal & Pennesi sp. nov. (Figs LM 2–13, SEM 14–25)

LM observation: Cells are solitary. Valves are elliptical to elliptical-lanceolate with rounded apices, 21.5–35 μm long, 10–15 μm wide (n=30). Transapical striae are radiate, alternating short and long on both sides of the central area, 17–20 in 10 μm. Axial area is very narrow and linear, central area is rounded. Raphe branches are slightly sinuous. Partecta are slightly displaced toward the middle of the valve by a siliceous flange that shows oblique partectal ducts. Transapically rectangular partecta are of uniform size (2.6–3 μm wide), 8-9 in 10 μm.

SEM observation: Valves are elliptical to elliptical-lanceolate with rounded apices ( Figs 2–13 , Figs 14, 17 , 22, 24 ). Externally, the raphe branches are sinuous, ending centrally in expanded pores ( Figs 14, 15 ) and distally in terminal fissures bent towards the same side in a form of a hook and reach mantle margin ( Fig. 14, 16 ). Raphe-sternum is narrow, with roundish central area ( Figs 14 , arrowhead, 15, 22), terminating at each pole with a distinct hyaline apical nodule around terminal raphe endings ( Figs 14, 16 , 22 ). Externally the transapical striae are uniseriate, strongly radiate and crossed in a quincunx pattern, continue from the axial area to valve mantle margin ( Figs 14 , 22 ). Areolae are rounded and of similar size except in the longitudinal row adjacent to the raphe sternum where they become slightly larger. The areolae surrounding the central area are slightly elongated ( Figs 14, 15 ). Internally, raphe slits are straight and bordered by siliceous ribs ( Figs 17 , 24 ). Proximal raphe endings terminate in the borders of the slightly elevated central nodule ( Figs 18 , 25 ). Distal raphe endings terminate in a weakly raised helictoglossa ( Fig. 21 ). The valve surface is structured with silicified costa-like virgae ( Figs 17, 19, 21 , 24 ), each two encompassing two rows of striae, giving the appearance of biseriate striae internally ( Figs 23, 25 ). Four to six of these structures in the middle part of the valve fuse with each other before reaching the central area and correspond to the shorter striae on the external valve face ( Fig. 24 ). The partectal ring is slightly displaced toward the middle line of the valve by a small siliceous flange ( Figs 3, 5, 8, 13 , 17, 20 ), attached to the valvocopula, which show oblique partectal ducts ( Fig. 17 , arrowhead), and small crater-like pores ( Fig. 20 , black arrowhead). The partecta continue almost up to the apices along each side of the valve ( Fig. 17 ), opening at poles through a narrow cleft, sometimes with an irregular lacuna ( Fig. 19 ). Small septum present at the far end of each pole ( Figs 21 , 24 ). Partecta are transapically rectangular, uniform in shape and size ( Figs 13 , 17, 20 ), and are ornamented with tiny pores arranged inwardly in parallel rows ( Figs 17, 20 ). Partecta open on the valvocopula through partectal pores ( Fig. 20 , arrow head).

Holotype: Permanent slide containing frustules of Mastogloia jahniae sp. nov. with reference number B 40 0045142 deposited in the Botanischer Garten und Botanischer Museum ( BGBM), Berlin, Germany. PhycoBank number: http://phycobank.org/102579.

Isotype: Permanent slide containing frustules of Mastogloia jahniae sp. nov., deposited in Gothenburg Herbarium, University of Gothenburg, Sweden under number GB-0190977.

Type locality: Skatan coast, Baltic Sea , 345 km north of Stockholm (62° 11’ N, 17° 30’ E) .

Etymology: The specific epithet is in honor of our friend and colleague, Dr. Regine Jahn of the Diatom Research Group, Botanischer Garten und Botanisches Museum Berlin (BGBM), for her outstanding contribution to the study of taxonomy and phylogeny of diatoms.

Ecology: Mastogloia jahniae is an epipelic species found at Skatan on the Baltic Sea, east coast of Sweden. Water temperature at time of collection was 15.5 oC and salinity 3.9 psu. M. jahniae was rather rare in the samples and associated with dominant taxa including Diatoma tenuis Agardh , Caloneis permagna (Bailey) Cleve , Navicula salinarum Grunow and Staurosirella sp.

Figures

FIGURES 2–13. Light micrographs of Mastogloia jahniae sp. nov. in different focal planes. Acid cleaned material showing valve shape variant, striations and partectal rings. Scale bar10 µm.

FIGURES 14–21. SEM micrographs of Mastogloia jahniae sp. nov. Fig. 14. External view of the valve showing sinuous raphe branches and central area (arrowhead). Fig. 15. External view of the central area showing the elongated areolae around the central area. Fig. 16. External view of apex with hyaline area and hooked terminal raphe fissure. Fig. 17. Internal valve view showing partectal ring, siliceous ribs and partectal ducts (arrowhead). Fig. 18. Internal view showing central nodule. Fig. 19. Internal view of apex showing cleft and lacuna. Fig. 20. Partectal ring showing ornamentations and crater-like pore (arrowhead). Fig. 21. Internal view of apex showing septum. Scale bars in Figs 14–17, 5 µm, Figs 18, 20, 1 µm, Figs 19, 21, 2 µm.

FIGURES 22–25. SEM micrographs of Mastogloia jahniae sp. nov. Fig. 22. Tilted view of the external valve side showing girdle band (arrowhead). Fig. 23. Areolae structure and arrangement. Fig. 24. Internal valve side showing central nodule, raphe branches, siliceous ribs, septa and silicified costa-like interstriae. Fig. 25. Internal valve side showing silicified costa-like virgae and areola on the valve internal surface. Scale bars in Figs 22, 24, 5 µm, Figs 23, 25, 1 µm.