Encyonema droseraphilum Bahls, 2013

Bahls, Loren, Pierce, John, Apfelbeck, Randy & Olsen, Lois, 2013, Encyonema droseraphilum sp. nov. (Bacillariophyta) and other rare diatoms from undisturbed floating-mat fens in the northern Rocky Mountains, USA, Phytotaxa 127 (1), pp. 32-48 : 36-38

Encyonema droseraphilum Bahls , sp. nov. ( Figs 3–10 )

Valvae 20–40 µm longae, 5–9 µm latae, ratio latitudinis et longitudinis 2.8–5.0. Margo ventralis leviter tumidus in centro ad planus vel leviter concavus in speciminibus minoribus. Striae dorsalis 8–11 in 10 µm. Striae ventralis curtae, 11–13 in 10 µm, 28–32 areolae in 10 µm. Extrema proximalia fissurarum externarum rhaphis leviter expansi dorsaliter declinati, extrema terminalia versus margines ventrales declinati. Extrema proximalia fissurarum internarum rhaphis ventraliter declinati ad anguli 90º, non recurvati atque E. silesiacum var. silesiacum . Extrema terminalia fissurarum internarum rhaphis terminans in linguliformibus helictoglossis.

Valves 20–40 µm long, 5–9 µm wide. Length to breadth ratio 2.8–5.0. Ventral margin slightly tumid in center to flat or slightly concave in smaller specimens. Dorsal striae 8–11 in 10 µm. Ventral striae short, 11–13 in 10 µm. Areolae number 28–32 in 10 µm. Proximal ends of external raphe fissures are slightly inflated, deflected dorsally; distal ends are curved toward ventral margins ( Fig. 9 ). Proximal ends of internal raphe fissures ( Fig. 10 , arrows) are bent dorsally at right angles, not hooked as in E. silesiacum (p. 184, pl. 2, fig. 7, Krammer 1997a). Distal ends of internal raphe fissures terminate in tongue-shaped helictoglossae ( Fig. 10 ).

Type:— USA. Montana: Helena National Forest, Indian Meadows Research Natural Area, Fen 4526, 47 o 06’ 19” N, 112 o 36’ 22” W, collected 03 September 2009, Sample No. 452601 collected by L. Bahls from sedge peat and interstitial water; taxon is abundant and accounts for approximately 18% of frustules in sample (Circled specimen ( Fig. 4 ) on slide marked MDC 452601(1) ( MONTU!) holotype, designated here; circled specimens on slides marked MDC 452601(2) ( Helena !) and GC 64892 ( ANSP!), isotypes, designated here).

Similar taxa: —This taxon is distinguished from Encyonema silesiacum (Bleisch in Rabenhorst) D. G. Mann (1990: 667) by its longer length-to-breadth ratio, more widely spaced dorsal striae, shorter ventral striae, and shape of the internal proximal raphe ends. Valve ends are directed ventrally, not laterally as in E. silesiacum var. elegans Krammer. This appears to be the same taxon as the Encyonema sp. from Kitzbühel, Schwarzsee, Österreich reported by Krammer (1997a, pl. 8, figs 6, 7).

raphe fissures. Scale bars: Figs 3–8 : 10 µm; Figs 9, 10 : 5 µm.

Distribution: —In North America, known only from the type locality.

Etymology: — Drosera refers to the genus of sundews, which are common associates of this diatom at the type locality; philum is from the Greek philus, which means “loving”.

Figures

FIGURES 3–10: Encyonema droseraphilum sp. nov. Figs 3–8: LM, size diminution series from the type locality. Fig. 4: Holotype specimen. Fig. 9: SEM, external valve view. Fig. 10: SEM, internal valve view. Arrows indicate dorsally bent (not curved) proximal