Platichthys krammeri Lange-Bertalot & Kulikovskiy, 2015

Lange-Bertalot, Horst, Witkowski, Andrzej, Seddon, Maxim S. Kulikovskiy Alistair W. R. & Kociolek, John P., 2015, Taxonomy, frustular morphology and systematics of Platichthys, a new genus of canal raphe bearing diatoms within the Entomoneidaceae, Phytotaxa 236 (2), pp. 135-149 : 141

Platichthys krammeri Lange-Bertalot & Kulikovskiy , sp. nov. ( Figs 39–60 )

Frustules in girdle view 27–35 μm long, 9–10 μm broad. Valves 3.5–4.0 μm broad, not including copulae ( Figs 39–49 ). The dorsal margins, are straight lightly convex or slightly concave proximally. Fibulae 5.5–7.5 in 10 μm, the two median ones are not ( Figs 48, 49 ) or not distinctly ( Figs 40, 41 ) wider spaced than the others. The occurrence of a central nodule can only be ascertained by observations in SEM ( Fig. 59 ). SEM. The girdle is composed of a few, open perforated copulae ( Figs 54, 57, 58 ). The number of rows of pores in a single copula was not counted. The raphe is positioned in a very narrow axial area ( Figs 50–53 ), the external central endings are simple, point-like, approximate, and the apical endings are strongly hooked ( Figs 56, 57 , 59 ). Transapical striae, 60–70 in 10 μm, areolae ca. 80 in 10 μm ( Figs 57 , 60 ), areolae occlusions have not been observed thus far. The areolae are arranged in straight uniseriate rows. Fibulae massive, arched, positioned at some distance below the raphe. Similarly to P. darwiniana , internally a few striae merge in one fibula ( Fig. 57 ).

Type: — CHILE. Province of Chacabuco: Chacabuco Bano, Andes Mountains, on wet grass in the efflux of the thermal spring, G. H. Schwabe, 1940 (holotype: FR! Individual in SEM stub no. A 77 in coll. Lange-Bertalot, illustrated in Fig. 50 . Isotype: KASSEL! slide no. 415 ex collection G.H. Schwabe).

Etymology: —this species dedicated to Dr. Kurt Krammer.

Ecology: —so far only found at the type location in thermal, freshwater spring. Associated with a rather scarce number of specimens of the new species are: Achnanthes inflata (Kützing) Grunow (1867: 7 ; basionym Stauroneis inflata Kützing 1844: 105 ), which is generally found in springs of extra-tropical South America (Lange-Bertalot personal unpublished observations); Caloneis spp. , at least three unidentified taxa; Halamphora sp. ; Diploneis spp. small and larger sized unidentified forms; Achnanthes exigua Grunow in Cleve & Grunow (1880: 21), with moderately high abundance; Nitzschia linearis (Agardh) W. Smith (1853: 39) or aff. linearis , Nitzschia spp. moderately abundant; Stauroneis sp. , naviculoid specimens of an unknown genus, Planothidium sp.

Comments: —The new genus is represented by two species that have been discovered and characterized in LM and EM. Though similar in gross morphology, the two species show differences in both LM and EM, which allow them to be distinguished. Although the longitudinal frustule size ranges of both taxa overlap (23–33 μm in P. darwiniana and 27–35 μm in P. krammeri ), they differ in the width of frustules and valves, as P. krammeri has broader frustules (9–10 μm), but narrower valves (3.5–4.0) than P. darwiniana (7–8 μm and 4.0–5.5 μm, respectively). Platichthys darwiniana and P. krammeri also differ in ultrastructural characteristics. Whereas the stria density in P. darwiniana is 48–61 in 10 μm, in P. krammeri it is 60–70 in 10 μm. The two species also differ with respect to the areola density within a stria, with 56 to 72 in 10 μm being found in P. darwiniana and ca. 80 in 10 μm in P. krammeri .

Figures

FIGURES 39–53. Platichthys krammeri sp. nov. 39–49. LM. Valve view, frustules in various position with different focus. Note in particular diffuse prolongation of fibulae into the valve transapically. 50–53. SEM. 50. External valve view. 51, 52. External view of valve end. Holotype specimen in straight and marginal view. Note copulae of epitheca and shallow valves lacking distinction between faces and mantles. 53. External valve view of specimen with slightly lacerated surface.

FIGURES 54–58. Platichthys krammeri sp. nov. SEM. 54. Broken valve showing external and internal valve views, specimen with strongly lacerated surface, with copulae of both valves lying between ruptured, collapsed valves. 55. External view of two frustules after cell division. 56–58. External view from keel-shaped edge towards ventral valve margin and copulae. 56. Note course of the raphe. 57. Note raphe below and parallel to ridge of the keel. 58. Close up of an intact valve with copulae.

FIGURES 59–62. Platichthys krammeri sp. nov. compared to Nitzschia sp. SEM. 59. External/internal valve view, the two broken valves of a frustules displaying valve cavity with range of fibulae (above); raphe slit outside (below) running parallel to the marginal crest; note transapical waves and the external central raphe endings—central nodule (arrow). 60. Internal view of areolae structure and fibulae. 61, 62. Nitzschia sp. from section Lineares for comparison, specimens associated in the same preparation. Main distinguishing feature vs. Platichthys gen. nov. is differentiation between valve faces and mantles with a consequently more or less rectangular cross-section.