Eunotia pacificomonodon, Bąk & Kociolek & Lange-Bertalot & Łopato & Witkowski & Zgłobicka & Seddon, 2017

Bąk, Małgorzata, Kociolek, John P., Lange-Bertalot, Horst, Łopato, Daria, Witkowski, Andrzej, Zgłobicka, Izabela & Seddon, Alistair W. R., 2017, Novel diatom species (Bacillariophyta) from the freshwater discharge site of Laguna Diablas (Island Isabela = Albemarle) from the Galapagos, Phytotaxa 311 (3), pp. 201-224 : 211-213

Eunotia pacificomonodon sp. nov. Lange-Bertalot, Bąk & Kociolek

Figs 88–106

Description: —Light microscopy—Valves arched with non-parallel margins. Dorsal margins arched convex than ventral margins curved concave. Ends protracted, subcapitate, ending with slightly cuneate outlines. Length 55–80 μm, breadth 8–10 μm (n=20). Terminal raphe nodule close to valve pole. Terminal raphe fissures on valve face very long, parallel to valve pole, extending to dorsal margin. Striae rather evenly spaced, 10–11 in 10 μm, becoming slightly denser near valve poles, 12–13 in 10 μm. Areolae difficult to resolve with light microscopy on valve face but rather coarse on copulae in girdle view, where ca. 15 in 10 μm ( Fig. 100 ).

Scanning electron microscopy:—Valve face and valve mantle positioned at right angle. Each stria positioned in shallow groove. Shortened striae present on abvalvar margin of valve mantle ( Fig. 106 , arrow). Dorsal or polar spines lacking. External opening of areolae simple round or elliptical. Areolae density 30 in 10 μm. External raphe slit long and slightly deflected on valve face ( Fig. 104 —arrow).

Type: — ECUADOR. Galápagos Islands: Isabela (Albemarle) Island, Diablas wetlands, 0.95731°S, 90.98685°W, 23 July 2012, holotype (designated here):—Slide no. 20779 (species code—7874 MCCDRS) in Coll. Herbarium ( CDS) of the Charles Darwin Foundation at Galapagos, represented by Fig. 95 .

Type locality: —Floating moss, at the mouth of the stream to the lagoon in the Diablas wetlands—a permanent, brackish coastal lagoon network located at sea level on the south side of Isabela Island.

Etymology: —The composite name refers to location at one of the Galápagos Islands in the Pacific Ocean and resemblance to E. monodon .

Distribution: —Species so far found only in one sample.

Comments: —The newly established E. pacificomonodon most closely resembles a group of taxa including: E. monodon Ehrenberg (1843: 414) , E. metamonodon Lange-Bertalot et al. (2011: 153) , E. monodontiforma Lange-Bertalot & M. Nörpel in Rumrich et al. (2000: 121), E. major (W. Smith 1856: 14) Rabenhorst (1864: 72) (detailed comments are given in the comprehensive monograph of Lange-Bertalot et al. 2011). As explained more thoroughly in the discussion, the differences in measurements of the newly established species and the above listed taxa merit the description of E. pacificamonodon as new species.

Figures

FIGURES 88–100: Eunotia pacificomonodon sp. nov. LM images. Figs 88–98: valve views, size diminution series, Figs 99, 100: valves in girdle view. Fig. 95 is of the holotype. Scale bar = 10 μm.

FIGURES 101–106: Eunotia pacificomonodon sp. nov. SEM external valve views. Fig. 101: valve arched with non-parallel margins with rather evenly spaced striae. Figs 102–105: terminal raphe fissures on valve face very long, parallel to the pole, extending to the dorsal margin (arrow in Fig. 102). Fig. 106: specimen in a girdle/valve view. Shortened striae present on the abvalvar margin of the valve mantle (arrow).