Orthoseira tropica (Krasske) Metzeltin & Lange-Bert.

Kochman-Kedziora, Natalia & Van de Vijver, Bart, 2024, The genus Orthoseira (Orthoseiraceae, Bacillariophyta) in Papua New Guinea with the description of two new species, Plant Ecology and Evolution 157 (2), pp. 113-124 : 113

publication ID	https://dx.doi.org/10.5091/plecevo.115801
persistent identifier	https://treatment.plazi.org/id/CDE5571B-E15B-5BC8-A8B2-D3EE6ACB0124
treatment provided by	by Pensoft
scientific name	Orthoseira tropica (Krasske) Metzeltin & Lange-Bert.
status

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Fig. 2 View Figure 2

Melosira roeseana var. tropica Krasske, 1948 (basionym), Svensk Botanisk Tidskrift 42: 422, fig. 1: 1-2 ( Krasske 1948).

Orthoseira roeseana var. tropica (Krasske) Lange-Bert. & Willmann in Lange-Bertalot et al. (1996).

Material used.

Sample 156 (Boisa Island, Papua New Guinea).

LM description.

Frustules short, cylindrical in girdle view, connected to each other with spines forming short chains (Fig. 2F View Figure 2 ). Valves disc-shaped. Valve dimensions (n = 15): diameter 9.5-39.0 μm, mantle height 5-14 µm. Valve surface flat, sloping abruptly at the valve face/mantle junction, visible in LM as a darker circular edge. Spiraling to straight thick, siliceous ridges extending from the valve edge to almost 2/3 onto the valve face, leaving only a small central area. Central area small, maximum 1/4 to 1/5 of the total valve diameter, irregular in shape, hyaline in the middle, surrounded by short series of scattered areolae. Three large, rounded carinoportulae present, number constant irrespective of the valve diameter. Striae on the mantle short, uniseriate, composed of rather large areola, located between the ridges, 16-18 in 10 μm. Valve face areolae rather small, arranged in irregular uniseriate striae, ca 22 in 10 µm. Caverns, internal undulations or internal valves not observed. Copulae number variable. Figure 2A-F View Figure 2 .

SEM description.

Cingulum composed of several broad, open copulae. One complete and one incomplete rows of small poroids present on the copulae (Fig. 2 G-I View Figure 2 ). All copulae open bearing a long ligula and fimbriate edge (Fig. 2G-I View Figure 2 ). Mantle rarely shallow (Fig. 2J View Figure 2 ), usually deep (Fig. 2H View Figure 2 ), occasionally with a clear step halfway the valve mantle (Fig. 2H View Figure 2 ). Advalvar mantle edge with several irregular series of small areolae (Fig. 2G, J View Figure 2 ). Abvalvar edge broad, hyaline. Marginal pore fields absent. Platelike ridges extending from the valve face onto the advalvar edge of the mantle. Areolae visible between the ridges (Fig. 2G, H View Figure 2 ). Valve face flat in the central part surrounded by a ring of spiralling to straight, platelike linking structures, radially arranged on the valve face/mantle junction (Fig. 2J View Figure 2 ). Between the plates, up to three series of areolae present. Central area hyaline surrounded by scattered areolae. Three carinoportulae visible, each surrounded by a low, cylindrical collar (Fig. 2J-K View Figure 2 ). Areolae covered in the valve interior by individual hymenate vela (Fig. 2L, M View Figure 2 ). Carinoportulae pit-like, visible as large, rounded depressions, filled with siliceous plug (Fig. 2M View Figure 2 ). Between the carinoportulae, three long slits present (Fig. 2M View Figure 2 ), arranged in a star-shaped manner. Internal caverns not observed. Figure 2G-M View Figure 2 .

Kingdom	Animalia
Phylum	Bacillariophyta
Class	Bacillariophyceae
Order	Melosirales
Family	Orthoseiraceae
Genus	Orthoseira