Odontidium apiculatum Jüttner, Falasco, Battegazzore & Ector, 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 : 27-29

Odontidium apiculatum Jüttner, Falasco, Battegazzore & Ector , sp. nov. ( Figs 197–224 )

LM ( Figs 197–218 ): Frustules rectangular in girdle view. Valves linear with tapering valve margins very close to apices. Poles broadly rounded, many valves with slightly apiculate apices; length 11.9–87.1 μm, width 6.4–11.4 μm, length/width ratio 1.6–8.6. Most transapical ribs primary, perpendicular or at a slight angle to sternum, 3–4, rarely 2 or 5 in 10 μm. Striae between ribs appear parallel,

2–8 rows between pairs of ribs. Cingulum composed of several bands. SEM ( Figs 219–224 ): External valve surface flat or very slightly rippled, with small spines positioned on virgae along valve margin, including poles, in one or two rows ( Figs 219–220 ). Virgae of varying widths, with much shorter vimines ( Fig. 219 ). Striae uniseriate, parallel, slightly radiate toward poles ( Fig. 219 ). Sternum narrow, sometimes extending into apical pore field in larger valves ( Figs 219, 221–223 ). One rimoportula per valve near apical pore field, within a stria replacing 3–7 vimines, externally a simple slit, internally with protruding lips ( Figs 219, 222 ). Simple apical pore fields at each pole, composed of round porelli ( Figs 219, 222, 223 ). Girdle composed of valvocopula and +3 copulae, with alternating orientation ( Figs 220, 224 ). Valvocopula with a row of 1–3 poroids on pars exterior; the adjacent copulae with a single row of poroids on pars exterior and a single row of elongated pores on pars interior.

Type: — ITALY. Piedmont, Cuneo Province, Valdieri municipality, spring in the Gesso della Valletta Valley , from stones (pebbles) and submerged vegetation dominated by bryophytes, Maurizo Battegazzore , 22 September 2012 (holotype: NMW.C.2012.021.2012. Italy. 18!; isotypes: Dipartimento di Biologia Animale e dell’Uomo, Università di Torino , and ARPA Piemonte, Italy) .

Additional material examined: — ITALY: Regional Natural Park of the Maritime Alps, Cuneo Province, Piedmont, springs and wetlands, (slide and material NMW.C.2012.021.2012.Italy.76, Gesso della Valletta Valley, spring; slides TO 9052, Valasco Valley, spring; TO 9053, Valasco Valley, wetland; TO 7059, Gesso della Valletta Valley, wetland; University of Turin, Life Sciences and Systems Biology, coll. Elisa Falasco, laboratory register numbers, project number SUP –02–S and SUP –01–W).

Etymology:— The name refers to the apiculate apices.

Observations:— One primary cell with an inflated central section of the valve was observed which lacked the apiculate apex ( Fig. 204 ).

Distribution and ecology:— Odontidium apiculatum has so far been found in springs and wetlands of the Regional Natural Park of the Maritime Alps, Cuneo Province, Piedmont, north-west Italy. One spring and a wetland were located in the Valasco Valley and another wetland and two rheocrenic springs were located in the Gesso della Valletta Valley. These sites are situated between 1638 and 1825 m a.s.l. on base-poor rocks with temperatures between 4.6 and 11.5 °C, pH ranging between 6.3–6.9 and conductivity values between 18–44 μS/cm ( Table 2). The species occurred on stones, submerged vegetation in particular bryophytes and detritus. In the Valasco Valley the species was more abundant on submerged mosses than on stones (20 and 11% vs. 4 and 2.4%). It was associated with Odontidium mesodon and Fragilariforma virescens ( Ralfs 1843: 110) D.M. Williams & Round (1988: 265 ; sample 9052) and with Achnanthidium minutissimum (Kützing 1833: 578) Czarnecki (1994: 157) , Aulacoseira alpigena (Grunow in Van Heurck 1882: pl. 86) Krammer (1991: 93), Meridion circulare ( Greville 1823: pl. 35) C. Agardh (1831: 40), Karayevia oblongella ( Østrup 1902: 252) Aboal in Aboal et al. (2003: 159) and Staurosira venter ( Ehrenberg 1854: pl. 8/1, fig. 12) Cleve & J.D. Möller (1879: No. 242; sample 9053).

Figures

FIGURES 197–218. Odontidium apiculatum, LM. 218. Girdle view. 197–217. Valve views. 204. Primary cell. Regional Natural Park of the Maritime Alps, Cuneo Province, Piedmont, Italy. 197–203. NMW.C.2012.021.2012.Italy.18, Gesso della Valletta Valley, spring. 204–210, 218. TO 9052, Valasco Valley, spring. 211–217. TO 9053, Valasco Valley, wetland. Scale bar = 10 μm.

FIGURES 219–224. Odontidium apiculatum, SEM. NMW.C.2012.021.2012.Italy.18, Gesso della Valletta Valley, Piedmont, Italy, spring. 219. View of whole valve. 220. Girdle view of complete frustule. 221. Internal view of whole valve. 222, 223. Internal view of valve near pole and pore field. 224. Girdle band. Scale bars = 2 μm (Figs 219, 221, 222, 224), 1 μm (Figs 220, 223).