Gomphonema perolivaceolacuum Levkov, 2011

Levkov, Zlatko & Williams, David M., 2011, Fifteen new diatom (Bacillariophyta) species from Lake Ohrid, Macedonia, Phytotaxa 30, pp. 1-41 : 28-29

Gomphonema perolivaceolacuum Levkov , sp. nov. ( Figs 185–198 , 241–245 )

Valvae late lanceolate marginibus gradatum attenuata ad apices versus. Vertex leniter protractus et late rotundatus. Polus basalis subprotractus et anguste rotundatus vel subcapitatus. Longitudo valvae 31–53 µm, latitudo valvae 9.5–11.0 µm. Raphe filiformis poris centralibus distinctis. Area axialis angusta linearis, area centralis variabiliter dilatata. Stigma solitaria abest. Striae transapicales valde radiate in media parte, leviter radiate vel parallelae sub apices, 12–17 in 10 µm.

Type:— MACEDONIA. Lake Ohrid, Bay of St. Naum , shore, mosses, collection date: 17 March 2007 (accession No. MKNDC 001120), Slide BM 101478 (Holotype). Slide MKNDC 001120 (isotype) .

Valves broadly lanceolate, margins gradually narrowing towards head pole. Head pole slightly protracted and broadly rounded. Foot pole subprotracted and narrowly rounded to subcapitate. Valve length 31–53 µm, valve width 9.5–11.0 µm. Raphe filiform with distinct central pores. Axial area narrow, linear. Central area variable in width and shape. Striae strongly radiate at valve middle becoming slightly radiate to parallel near apices, 12–17 in 10 µm (LM).

Valve face flat, transition to valve mantle gradual ( Figs 241–242 ). Raphe centrally located ( Figs 241, 243 ). Proximal raphe endings widened into teardrop-shaped central pores ( Fig. 242 ). Distal raphe endings at head pole slightly expanded at helictoglossa, continuing as slightly curved terminal fissure passing onto the valve mantle ( Fig. 245 ). Striae biseriate, composed of small round areolae. Apical pore field present on base pole, bisected by distal raphe endings ( Fig. 244 ) ( SEM).

Observations:— Gomphonema perolivaceolacuum may be confused with G. olivaceolacuum (Lange- Bertalot & Reichardt) Lange-Bertalot & Reichardt (= G. olivaceum var. olivaceolacuum Lange-Bertalot & Reichardt in Lange-Bertalot (1993: figs 80: 1–8, figs 81: 3–4, figs 82: 1–4). However, the latter has valves that have broadly rounded to truncate ends and has a different ecology. Gomphonema olivaceolacuum is observed in meso– to eutrophic lakes, while G. perolivaceolacuum inhabits oligotrophic waters. Gomphonema olivaceum var. calcareum (Cleve) Van Heurck (1880 : fig. 25: 23) is narrower (B= 5–8 µm) and has a different shape at the head pole (narrowly rounded). Gomphonema olivaceum var. balticum (Cleve) Grunow (in Van Heurck 1880: fig. 25: 24) has lanceolate valves with narrowly rounded ends and occurs in brackish waters or freshwater with high conductivity.

Figures

FIGURES 185–209: LM micrographs. Figs 185–198. Gomphonema perolivaceolacuum. Figs 199–209. Gomphonema linearoides. Scale bar = 10 µm.

FIGURES 241–245: SEM micrographs of Gomphonema perolivaceolacuum. Figs 241, 243. External view of whole valves. Fig. 242. Detail of mid-valve showing small central area, teardrop-shaped central pores and biseriate striae. Fig. 244. Detail of base pole showing distinct APF and straight distal raphe fissure. Fig. 245. Detail of head pole, showing slightly deflected distal raphe fissure. Scale bars in Figs 241, 243 = 10 µm; Figs 242, 244, 245 = 2 µm.