Orthoseira iserentantii Kochman-Kedziora & Van de Vijver, 2024

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

Orthoseira iserentantii Kochman-Kedziora & Van de Vijver sp. nov.

Fig. 3

Type locality.

Mont Wilhelm, Papua New Guinea, 9 Apr. 1987, leg. M. Fagnant.

Type.

Mont Wilhelm, Papua New Guinea, sample 17; holotype: slide BR-4817, BR; the valve representing the type is illustrated here in Fig. 3F ; isotype: slide 433, University of Antwerp , Belgium .

Registration.

http://phycobank.org/104292

LM description.

Frustules cylindrical in girdle view. Valves disc-shaped. Valve dimensions (n = 20): diameter 8.0-21.5 μm, mantle height 5.0-7.5 µm. Valve face flat, sloping abruptly at the valve face/mantle junction, visible in LM as a darker circular edge. Central area very small, maximum 1/5 of the total valve diameter, irregular in shape. Three large, rounded carinoportulae present, number constant irrespective of the valve diameter. Between the carinoportulae scattered areolae present. Striae on the mantle long, uniseriate, ca 24 in 10 μm. Valve face areolae small, arranged in radiate, uniseriate striae, 20-22 in 10 µm. Caverns, internal undulations or internal valves not observed. Figure 3A-G .

SEM description.

Cingulum composed of open, ligulate girdle bands bearing several, often incomplete, rows of large, rounded poroids (Fig. 3H-I ). Parallel, uniseriate series of rounded, fairly large areolae present on the valve mantle, ca 24 in 10 µm. Often a clear step present halfway the valve mantle (Fig. 3J ). Valve face flat, plate-like structures, irregular in shape, surrounding the entire valve face (Fig. 3K, L ). Plate-like structures lacking perforations become linking plates, continuing onto the mantle as weakly raised, sometimes bifurcated ridges, flattening in the middle of the mantle height (Fig. 3H, J-L ). Irregular pattern of smaller siliceous ridges, varied in length, present in the central part of the valve face, also between carinoportulae (Fig. 3L, N ). Usually three carinoportulae surrounded by a siliceous collar present in very small pore-free central area (Fig. 3L, N ). Striae radial composed of rounded areolae. Striae between ridges continuing on the mantle (Fig. 3H, K ). Internally areolae appearing as small poroids with irregular caltrop-like structure inside (Fig. 3M, O, P ). Slit-like openings present between the areolae (Fig. 3P ). Carinoportulae unoccluded, ornamented with small granules (Fig. 3O ). Between the carinoportulae, three long slits present (Fig. 3O ), arranged in a star-shaped manner. Internal caverns not observed. Figure 3H-P .

Etymology.

The species is named in honour of our (retired) colleague Dr Robert Iserentant (UCL, Belgium) to honour his life-long career as a diatom scientist.

Figures

Figure 3. Orthoseira iserentantii Kochman-Kedziora & Van de Vijver sp. nov. LM (A-G) and SEM (H-P) pictures taken from the holotype material (BR- 4817, sample 17, Mont Wilhelm, Papua New Guinea). A - F. LM pictures of valves in valve face view. G. Valve in girdle view showing marginal spines. H - I. SEM pictures of frustules in girdle view showing the structure of girdle bands. J. Sibling valves in girdle view showing the structure of linking plates. K. SEM external detail of linking plates and mantle structure. L. SEM external view of a valve face showing the structure of plates and smaller siliceous ridges. M. SEM internal view of a complete valve. N. SEM external detail of the central part of the valve face showing carinoportulae surrounded by a siliceous collar and the network of small siliceous ridges. O. SEM internal detail of the carinoportulae ornamented with small granules. P. SEM internal detail of the areolae and slit-like openings present between the areolae. Scale bars: A-M = 10 µm; N-P = 1 µm.