Odontidium neomaximum Jüttner, D.M. Williams, Levkov, Falasco, Battegazzore, Cantonati, Van de Vijver, Angele & 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 : 18-25

Odontidium neomaximum Jüttner, D.M. Williams, Levkov, Falasco, Battegazzore, Cantonati, Van de Vijver, Angele & Ector , sp. nov. ( Figs 109–168 )

Synonyms: Odontidium maximum (Grunow) H. Peragallo & M. Peragallo (1899 –1901: 342, [1901], pl. 82, fig. 35), nom. illeg. [= Odontidium anomalum var. maximum Grunow (1862: 471 , pl. 4 (7), fig. 4, nom. superfl. = Odontidium anomalum var. longissimum (longissima) Grunow) = Meridion anceps (Ehrenb.) D.M. Williams (1985: 182) ]; Diatoma maxima ( maximum ) (Grun.) Fricke in Schmidt (1906: pl. 267, figs 7–11), nom. illeg.; Diatoma hiemale var. maxima ( maximum ) (Grun.) F. Meister (1912: 63), nom. illeg.; Diatoma hiemale var. truncata (truncatum) Ant. Mayer (1940: 103, pl. 3, figs 15–23).

LM ( Figs 109–154 ): Frustules rectangular in girdle view. Valves linear with slightly curved valve margins, small valves elliptic or linear-elliptic. Valve margins tapering slightly close to truncated or occasionally rounded poles; valve length 12.4–86.4 μm, width 7.5–11.7 μm. Transapical ribs nearly all primary, perpendicular or at a slight angle to the sternum, 2–4, rarely 5 in 10 μm. Striae between ribs parallel, 1–11 rows between pairs of ribs. Cingulum composed of many bands. SEM ( Figs 155–166 ). External valve surface rippled with larger and smaller, tightly spaced, interlinking spines along valve margin, including poles, and adjacent on mantle and sometimes valve face ( Figs 155–162 ). 1–3 spines irregularly positioned on virgae pointing outwards in variable directions ( Figs 156–158, 160–162 ). Virgae of varying widths, much shorter than vimines ( Figs 156, 157, 159 ). Striae uniseriate with small, round areolae, parallel, very slightly radiate near poles. Sternum irregular, varying from <1/5 to, rarely, 1/4 of valve width, extending into apical pore fields ( Figs 156–159 , 166 ). One or two rimoportulae in distal part of valve face, often close to pore field, within a stria, usually replacing 3–4 vimines, externally a simple slit, internally with protruding lips ( Figs 155–157 , 166 ). Large apical pore field present at each pole, composed of round porelli surrounded by rim ( Figs 156–158 , 166 ). Internally many ribs appear positioned slightly at an angle to valve margin and are wider than virgae ( Figs 164–166 ). Outer surface of mantle and bands covered with many small granules ( Figs 161–163 ). Girdle composed of many bands (5–6 observed), with alternating orientation. Valvocopula with parallel rows consisting mostly of 3 poroids on pars exterior; on adjacent copulae rows of 2 or 3 poroids on pars exterior, this varies within a single copula. Rows on narrow pleurae with 1 or 2 poroids on pars exterior. Single row of elongated poroids present on pars interior ( Figs 161–163 ).

Type:— SWITZERLAND: Lake Geneva, “Genfer See” (Z, Meister slides 805131!, holotype, and 805132!, “Lac de Genève ”, syntype). Odontidium anomalum var. maximum Grunow is a superfluous and invalid name as Odontidium anomalum var. longissimum (longissima) appeared earlier in the text to refer to the same specimens ( Grunow 1862: 357). Those specimens Grunow named Odontidium anomalum var. longissimum (longissima) are really members of Meridion anceps (see below). To typify Odontidium neomaximum the next available specimens are those described by Fricke in Schmidt’s Atlas der Diatomaceen-Kunde (1906: pl. 267, figs 7–11) as Diatoma maxima ( maximum ). These specimens are from “Genfer See” (Lake Geneva, Switzerland), the same locality as those investigated by Meister (1912). Although specimens are less abundant on the slides from Lake Geneva than on slide 902272 from an unspecified location in the Engadin, Meister’s slides 805131 and 805132 (both labelled “Lac de Genève ”) would be good type material. Illustrations for Meister slide 805131 = Figs 110, 112, 117 .

Additional material examined: — ITALY: Area of Bedonia, Parma Province, Emilia-Romagna, Italy , spring Penna “Diatomee bentoniche sorg. Penna 25/07/2011 epibryon” (TR slide cLIM007 DIAT 1971 !) ; Gesso della Valletta, Regional Natural Park of the Maritime Alps , Italy , rheocrene spring (slide and material NMW.C.2012.021.2012. Italy. 18!) ; MACEDONIA: Belcisko wetland, spring in village Velemej, Macedonia , on bryophytes (MKNDC slide 8312!) ; River Vardar near village Vrutok, Macedonia , on rocks (MKNDC slide and material 2165!) ; AUSTRIA: spring between Kühtai and Finstertaler Lake, Stubaier Alps , Austria (slide and material NMW.C.2012.019.2012. Austria. 7.bryo!) .

Observations:— In some populations the valve margins taper more abruptly towards the poles which therefore appear more clearly rostrate. There is only minor morphological variation between the various populations of this species as seen by the present authors, exemplified by those images depicted herein. Some specimens had mostly large spines positioned along the valve margins, while others had larger and smaller spines, some of which were located on the valve face. Circular pore occlusions were seen in a few specimens.

Distribution and ecology:— Odontidium neomaximum has been found in the European Alps, Italy and Macedonia in springs and rivers with a wide range of conductivities and calcium concentrations. Meister found it frequently in the Engadin Valley in eastern Switzerland (no specific locations were recorded) and in Lake Geneva, in the west of Switzerland. He reported that in both areas it was often found together with D. hyemalis var. genuina .

More recently, O. neomaximum has been rarely found in the Rhônes-Alpes region of France ( Bey & Ector 2013),

e. g. in the Merlet Creek at Saint-Alban-des-Villards, in the Isère River near Val d’Isère and its tributary the Romanche River near Bourg, well oxygenated rivers with alkaline pH, low conductivity and low content of organic material (Rémy Chavaux, pers. comm.). In northern Italy, it has been found in several springs, for example in the Emilia– Romagna Region at 1324 m a.s.l. on basalt bedrock in a beech forest (63 μS/cm conductivity, pH 6.6 and 1.2 mg /L NO 3) and in the Gesso della Valletta Valley, Regional Natural Park of the Maritime Alps in the Piedmont Region at 1800 m a.s.l. (32 μS/cm conductivity, pH 6.5). In Austria, it has been found in a rheocrene spring in the Stubaier Alps near Kühtai, and in Macedonia in the headwater area of the River Vardar ca. 50 m below a karstic spring (203 μS/cm conductivity, pH 7.8), and in a large karstic spring near the Belcisko wetland (ca. 220 μS/cm conductivity, pH 8.2).

Nomenclature:— Peragallo & Peragallo (1899 –1901) wished to raise what they believed to be Grunow’s variety Odontidium anomalum var. maximum to species level and so proposed the combination Odontidium maximum (Grunow) H. Peragallo & M. Peragallo (1899 –1901: 342, [1901], pl. 82, fig. 35). They explained their actions in the following manner: “Cette belle forme ne peut être rapportée à l’ Od[ontidium] anomalum , car elle n’a pas les cloisons caractéristiques de cette espèce. D’un autre côté, l’espèce décrite par Grunow est alpine, c’est pourquoi j’ai préféré prendre pour la forme marine de Banyuls le nom de la figure de Grunow, l’espèce d’eau douce devant conserver le nom du texte.” [This beautiful form cannot be named Od[ontidium] anomalum because it does not have the characteristic partitions of that species. On the other hand, the species described by Grunow was alpine and this is why I preferred to name the marine form from Banyuls after the name Grunow used for the figure, the freshwater form keeping the name given in the text] ( Peragallo & Peragallo 1899 –1901: 342).

“Cloisons caractéristiques” (characteristic partitions), was probably referring to the typical internal cells of Odontidium anomalum . Yet it is clear from the illustrations that Odontidium maximum (Grunow) H. Peragallo & M. Peragallo (here reproduced as Fig. 167 ) is not that illustrated by Grunow (here reproduced as Fig. 105 ), regardless of the name.

With respect to Odontidium neomaximum , a little later, Fricke illustrated a few valves of “ Diat. (Odont.) maximum Grun. ”, an account that is considered to be the new combination for Diatoma maxima ( maximum ) (Grun.) Fricke in Schmidt (1906: pl. 267; cf. Williams 1985: 139, for example, who followed VanLandingham 1969: 1300). Fricke’s specimens are from “Genfer See” (Lake Geneva, Switzerland). Interestingly, on the same plate as that which has the illustrations for Diatoma maxima ( maximum ), there are several specimens identified as “ Diatoma (Odont.) hiemale ” (Fricke in Schmidt 1906: pl. 267, figs 12-15) also from “Genfer See” suggesting perhaps that the specimens of maxima may indeed be initial cells (Fricke in Schmidt 1906: pl. 267, figs 7–11; reproduced here as Fig. 168 ).

Meister made the combination Diatoma hyemale ( hiemale ) (Heib.) var. maxima ( maximum ) referring to Diatoma maxima ( maximum ) Grunow in Schmidt (1906: pl. 267, figs 7–11) as its basionym ( Meister 1912). He investigated specimens from the Engadin Valley and Lake Geneva, Switzerland, provided a very brief description (valves 60–90 μm long, with 10–20 costae) and two line drawings of specimens in girdle and valve view ( Meister 1912: pl. 5, figs 22, 23, “Engadin”). Specimens are abundant on Meister’s slide 902272! (labelled “Engadin 1849”) and are associated with Hannaea arcus var. arcus (Ehrenberg) R.M. Patrick (1966: 132) . They are rarer on his slides 805131! and 805132! (both labelled “Lac de Genève ”) where the most abundant species belong to Surirella Turpin (1828: 362) and Cymatopleura W. Smith (1851: 12) .

Mayer (1919: 196) referred to Meister’s specimen from Lake Geneva, as depicted in Schmidt (1906: pl. 267, figs 7–11), when he rejected Grunow’s “form” Diatoma maxima ( maximum ). Mayer argued that Meister’s variety cannot be justified because it is distinguished from Diatoma hyemale ( hiemale ) var. genuina (genuinum) Grun. only by the length of the valves ( Meister 1912, 60–90 μm vs. 30–60 μm, respectively). For Mayer (1919), Meister’s variety Diatoma hyemale ( hiemale ) var. maxima ( maximum ) was really Diatoma hiemale [in the figure legend p. 213, Diatoma hyemale ( hiemale ) var. genuina (genuinum) as depicted in Schmidt (1906: pl. 267, figs 1–6, 12–15) and also referred to by Meister (1912) as Diatoma hyemale ( hiemale ) var. genuina (genuinum)]. In fact, the specimens in Schmidt (1906: pl. 267, figs 7–11) and in Mayer (1919: pl. 5, figs 39–43), the latter found in the rivers Saalach and Weissbach (460–555 m a.s.l.) near Bad Reichenhall, Bavaria, Germany, all most probably belong to O. neomaximum . In Mayer (1919: pl. 5, fig. 41) a smaller, more rounded valve is referred to as intermediate “Übergangsform” to Diatoma hyemale ( hiemale ) var. turgidula ( turgidulum ); in Grunow 1862: 356 as Odontidium hyemale ( hiemale ) var. turgidulum . Mayer (1940: 103, pl. 3, figs 15–23) described the new variety Diatoma hyemale ( hiemale ) var. truncata (truncatum) (20–70 μm long, 7 μm wide) also with reference to the specimens in Mayer (1919).

It would seem that the specimens illustrated by H. & M. Peragallo, Fricke in Schmidt and Meister remain undescribed and have no valid name, hence the name Odontidium neomaximum proposed herein. Both Williams (1985: 146) and Krammer & Lange-Bertalot (1991: 99, Taf. 97, figs 9–10) suggested that many of the specimens illustrated so far might now be identified as initial cells.

Figures

FIGURES 109–123. Odontidium neomaximum, LM. 109. Girdle view. 110-123. Valve views. 109, 111, 113–116, 118–123. Meister collection, Z 902272, “Engadin 1849”, Engadin Valley, Switzerland. 110, 112, 117. Meister collection, Z 805131, “Lac de Genève”, Lake Geneva, Switzerland. Scale bar = 10 μm.

FIGURES 124–135. Odontidium neomaximum, LM. 124, 135. Girdle views. 125–134. Valve views. 124–129. NMW.C.2012.019.2012. Austria.7.bryo, Stubaier Alps near Kühtai, Austria, spring. 130–135. TR cLIM007 DIAT 1971. Area of Bedonia, Emilia-Romagna, Italy, spring Penna. Scale bar = 10 μm.

FIGURES 136–154. Odontidium neomaximum, LM, valve views. 136–145. MKNDC 2165. River Vardar near village Vrutok, Macedonia. 146–154. MKNDC 8312. Belcisko wetland, spring in village Velemej, Macedonia. Scale bar = 10 μm.

FIGURES 155–160. Odontidium neomaximum, SEM. 155–158. Meister collection, Z material 396, Engadin, Switzerland. 159. NMW. C.2012.019.2012.Austria.7.bryo, Stubaier Alps near Kühtai, Austria, spring. 160. NMW.C.2012.021.2012.Italy.18, Gesso della Valletta Valley, Piedmont, Italy, spring. 155. View of whole valve. 156, 157. Details of valve face, poles, pore fields and rimoportulae. 158. Girdle view of pole and details of spines. 159. Detail of valve surface. 160. Girdle view of complete frustule. Scale bars = 2 μm (Figs 155–158, 160), 1 μm (Fig. 159).

FIGURES 161–166. Odontidium neomaximum, SEM. 161, 162, 164. Meister collection, Z material 396, Engadin, Switzerland. 163, 165, 166. NMW.C.2012.019.2012.Austria.7.bryo, Stubaier Alps near Kühtai, Austria, spring. 161. Girdle view of two valves linked together. 162. Spines on valve margin and mantle. 163. Details of girdle band surface. 164, 165. Internal view of whole valves. 166. Internal view of valve near pole and pore field. Scale bars = 3 μm (Fig. 165), 2 μm (Fig. 164), 1 μm (Figs 161, 162, 166), 0.2 μm (Fig. 163).

FIGURES 167–168. 167. Reproduction of the illustrations of Odontidium maximum (Grunow) H. Peragallo & M. Peragallo (1901: pl. 82, 35). 168. Reproduction of illustrations of Diatoma maximum (Grun.) Fricke in Schmidt [“Diat. (Odont.) maximum Grun.”] (Fricke in Schmidt 1906, pl. 267, 7–11, “Genfer See”).

FIGURES 101–108. 101, 103. Reproductions of the line drawings of Odontidium anomalum from Smith (1856: 16, pl. LXI, 376). 102. Specimens of Odontidium anomalum from BM 24007, Braemar, all valve views. 104, 108. Reproductions of William Smith’s drawings of Odontidium anomalum (Smith 1855: 7, pl. 1, 8). 105. Reproduction of line drawing for Odontidium anomalum var. longissimum (longissima) (Grunow 1862: pl. 4, 4). 106. Reproduction of Diatoma anceps var. anomala (anomalum) (W. Smith) Van Heurck (1896: 350, pl. 11, 473). 107. Reproduction of Diatoma anomala (anomalum) (W. Smith) Schönfeldt (1907: 98, pl. 5, 32, 32a).