Lyrella ruppelii Nevrova, Witkowski, Kulikovskiy & Lange-Bert., 2013

Nevrova, Elena, Witkowski, Andrzej, Kulikovskiy, Maxim, Lange-Bertalot, Horst & Kociolek, J. Patrick, 2013, A revision of the diatom genus Lyrella Karayeva (Bacillariophyta: Lyrellaceae) from the Black Sea, with descriptions of five new species, Phytotaxa 83 (1), pp. 1-38 : 8-10

Lyrella ruppelii Nevrova, Witkowski, Kulikovskiy & Lange-Bert. , sp. nov. ( Figs 20–26 , Figs 27–29 )

Valvae late ellipticae vel parum elliptico-lanceolatae ad lineari-ellipticae quoad specimina maiora et maxima. Apices paulatim obtuse cuneatim rotundati; longitudo 48–86 μ m, latitudo 27–37 μ m. Raphe anguste-lateralis recta extremis centralibus distincte expansis nec anguste nec distanter sitis inter se fissuris terminalibus fere curte in facie valvae hamatis apparentibus. Area axialis angusta linearis omnino. Area centralis aliquid variabilis ad instar coniunxa cum areis lateralibus semi-lanceolatis modice latis in mediis partibus ad 1/3 (non 1/3–1/2) latitudinis valvae, ornatis cum scissuris distinctis irregulariter sitis sed saepe transapicaliter ordinatis. Striae transapicaliter separatae areis lateralibus ut communiter in genere Lyrella . Areae laterales 4–6 μ m latae proximaliter. Striae adaxiales ex 1–4 areolis utroque compositae zonam 6–8 μ m latam formantibus. Haec striae leviter radiantes proximaliter sed distincte convergentes ad apices versus. Striae marginales radiantes omnino minus in partibus mediis (hic etiam subparallelae quoad individua maiora) tum fortius sub apices, 10–11 in 10 μ m mediis ex 10–13 areolis compositis. Areolae 15–16 in 10 μ m.

Diagnosis differens versus Lyrella hennedyi (W. Sm.) Stickle et D.G. Mann in Round et al. (1990: 672). Haec species complexum taxorum repraesentat. Varietas nominata numquam cum areis lateralibus ornatis illustrata in literatura vide Hendey (1964: pl. 33, fig. 14) et Hustedt (1961 –1964: figs 1516 b, c, e–h).

Valves broadly elliptical with longer specimens becoming very slightly elliptical-lanceolate and linear-elliptical in smaller specimens. Ends becoming gradually obtuse-cuneate to round. Length 48–86 µm, breadth 27–37 µm ( Figs 20–26 ). Raphe narrow-lateral, almost straight with distinctively expanded central ends that are neither narrowly nor widely spaced, not or very little deflected to the secondary side of the valve; terminal raphe fissures are rather short, curved in the valve face, curving longer onto the valve mantle ( Figs 27–29 ). Axial area narrow, linear, almost slightly, not conspicuously, widened towards the central nodule. Central area rather small and somewhat variable in shape, connecting the lateral areas. Lateral areas are semi-lanceolate, moderately broad, up to 1/3 (not extending 1/3 – 1/2 of the valve breadth compared with other taxa). Lateral areas possess irregular and regularly transapically orientated markings. Transapical striae, 10–11 in 10 µm, in the genus Lyrella are separated commonly by the lateral areas, with the striae, lying close to the sternum. These consist of 1–4 areolae on either side being slightly radiate proximally, becoming distinctly convergent distally. Marginal striae are radiate throughout, slightly radiate, in the longest specimens subparallel proximally, becoming strongly radiate at the ends. Areolae 15–16 in 10 µm (not 9-20 in 10 µm as in the case of L. hennedyi ).

The pattern of regular and irregularly distributed markings perforate only the external surface of the lateral areas, being absent internally (see Figs 27–29 ). The internal closing membranes of the areolae are illustrated in Fig. 29 .

The taxa of the species complex encompassing Lyrella hennedyi are most similar to each other. The nominate variety (see Figs 75–78 ) of this complex possesses broader lateral areas without external perforations (see also Hustedt 1961 –1964: figs 1516 b, c, e–h and Hendey 1960: pl. 33, fig. 14); variety bacillifera including formae and other varieties (see Pantocsek 1889: 42, pl. 5, fig. 80 and Hustedt 1961 –1964: figs 1522 a, b; fig. 1523). Variety bacillifera (see under Lyrella bacillifera (Pant.) comb. nov.) has a pronounced undulating external raphe fissure, the central ends are more densely spaced and the markings of the lateral areas appear longer and expanded over the areas throughout. Areola density is ca. 12 in 10 µm. The valves of Lyrella bacillifera sensu stricto are longer, 112–125 µm long, 48–62 µm broad, according to the protologue and hence represent a separate taxon.

Type:— BLACK SEA. North-western part within protected area of Zernov’s Phyllophorae Field, station 12, depth 19 m (45 o 50’38”N, 30 o 44’32”E), sandy-silt substrate, Nikolai Revkov, 05.11.201 0 (Holotype SZCZ slide 19438, illustrated in Fig. 21 ; isotype FR Eu-Black Sea 003 no. B635 001, illustrated in Fig. 27 ; isotype praep. no. FZ12- 10 in Coll. E. Nevrova, IBSS NASU, Sevastopol, Ukraine, illustrated in Fig. 20 ) .

Etymology:— The species is dedicated to our good colleague and friend Manfred Ruppel, SEM operator at the J.W. Goethe University, Frankfurt am Main, Germany.

Distribution: —Black Sea, found only from the north-western part of the Black Sea, e.g. Zernov’s Phyllophorae Field.

Figures

FIGURES 20–26: Lyrella ruppelii sp. nov. LM images. Figs 20–26: Valve view, scale bar = 10 µm. Specimens from the Black Sea (NWBS, Zernov’s Phyllophorae field). Holotype is illustrated in Fig. 21.

FIGURES 27–29: Lyrella ruppelii sp. nov. SEM images. Fig. 27: External view, note the slit-like irregular ornamentation of the lateral areas, scale bar = 20 µm. Fig. 28: Internal view, scale bar = 10 µm. Fig. 29: Internal view, note that the lateral areas are structureless at the valve interior, scale bar = 8 µm. Specimens from the Black Sea (NWBS, Zernov’ Phyllophorae field).

FIGURES 75–80: Lyrella hennedyi. Figs 75–77: Valve view, LM, scale bar = 10 µm. Fig. 78: Internal view, note the relatively narrow elevated, structureless lyrate lateral areas being relief-like, elevated above internal valve surface with dispersed areolae, SEM, scale bar = 7 µm. Specimens from the Black Sea (Laspi Bay, Vitino coast, Phyllophorae Field, Dvujakornaya Bay). Fig. 79: Navicula hennedyi, specimen from BM 23529; scale bar = 10 µm. Fig. 80: photograph of the type slide BM 23529.