Odontidium rostratum Levkov & Jüttner, 2015

Jüttner, Ingrid, Williams, David M., Levkov, Zlatko, Falasco, Elisa, Battegazzore, Maurizio, Cantonati, Marco, Vijver, Bart Van De, Angele, Catalena & Ector, Luc, 2015, Reinvestigation of the type material for Odontidium hyemale (Roth) Kützing and related species, with description of four new species in the genus Odontidium (Fragilariaceae, Bacillariophyta), Phytotaxa 234 (1), pp. 1-36 : 25

Odontidium rostratum Levkov & Jüttner , sp. nov. ( Figs 169–183 , 191–196 )

LM ( Figs 169–183 ): Valves linear-lanceolate with narrow rostrate apices, small valves lanceolate. Length 10–58 μm, width 4.5–9.0 μm. Valve margins of larger cells more or less parallel, tapering near the apices, in medium size cells tapering very slightly from the valve centre and in smaller valves tapering gradually from the valve centre towards the apices. Most transapical ribs primary, many at a slight angle to the sternum, 3–4, rarely 5 in 10 μm. Striae between ribs appear parallel or at a slight angle to the sternum, 2–6 rows between pairs of ribs. SEM ( Figs 191–196 ): External valve face slightly rippled and with spines (spinules) which are located along the valve margin including the pore fields in one or two rows ( Figs 191–195 ). Spines regularly positioned on the virgae pointing out in variable directions, sometimes two spines on each virga ( Figs 192, 193, 195 ). Virgae only of slightly varying widths and much shorter vimines ( Figs 192, 193 ). Striae uniseriate, parallel to slightly radiate towards the poles. Narrow sternum extending into the apical pore field ( Figs 192, 193 ). One rimoportula per valve, positioned close to the pore field, within a stria replacing mostly 4–5 vimines. A simple apical pore field at each pole, composed of round porelli ( Figs 192, 193, 196 ). Outer surface of mantle and bands covered with many small granules ( Fig. 195 ). Girdle composed of many bands (up to 8 observed), with alternating orientation, with a broad valvocopula and adjacent copulas ( Fig. 194 ). They have 1 sometimes 2 poroids per line on their pars exterior, and a line of elongated poroids, sometimes divided into two round poroids, on the pars interior.

Type: — MACEDONIA. Pelister Mountain: spring near Lake Golemo Pelistersko, on bryophytes, A. Pavlov, 17 September 2006 (holotype: MKNDC slide 2965!, isotype: NMW.C.2015.003.Macedonia.2965).

Etymology:— The name refers to the rostrate apices.

Observations:— The spines were occasionally broken, but in most valves closely spaced interlinking spines were observed.

Distribution and ecology:— Odontidium rostratum has only been found at the type locality in Macedonia, a small spring on the Pelister Mountain at ca. 2100 m a.s.l. The water was slow flowing, mosses ( Fontinalis sp. ) were abundant and the pH was slightly acidic (ca. 6.0–6.5). Some additional specimens, possibly referable to Odontidium rostratum , were found in a Norway spruce wood in the Borzago Valley, Trentino, Italy (a rheocrenic spring at 1300 m a.s.l. with pH 6.5, conductivity 35 μS/cm, Ca 5.2 mg /L) ( Figs 184–190 ). The valves were larger (length 31–62 μm, width 8.0–11.5 μm, length/width ratio 3.9–6.9) and the transapical ribs appear somewhat more robust and diffuse, relative to the sternum, than those in the Macedonian specimens. It is possible that these are another population of Odontidium rostratum , the larger valves initial cells or cells from early divisions ( Figs 184–188 ), or they might belong to a different species, pending further investigation.

Figures

FIGURES 169–183. Odontidium rostratum, LM, valve views. MKNDC 2965, spring near Lake Golemo Pelistersko, Macedonia. Scale bar = 10 μm.

FIGURES 191–196. Odontidium rostratum, SEM. MKNDC 2965, spring near Lake Golemo Pelistersko, Macedonia. 191, 192. View of whole valve and girdle bands. 193. Details of valve face with rimoportula and pore field. 194. View of whole frustule. 195. Details of valve mantle, spines and girdle bands. 196. Internal view of valve. Scale bars = 2 μm (Figs 191, 193, 194), 1 μm (Figs 192, 195, 196).

FIGURES 184–190. Odontidium cf. rostratum, LM, valve views. TR cLIM007 DIAT 393, Borzago Valley, Trentino, Italy, spring. Scale bar = 10 μm.