Lyrella pseudolyra 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 : 12-14

Lyrella pseudolyra Nevrova, Witkowski, Kulikovskiy & Lange-Bert. , sp. nov. ( Figs 37–40 )

Navicula lyra var. constricta H & M. Peragallo (1897: 135, pl. 23, fig. 3)

Navicula lyra var. constricta sensu Heiden (1900 : fig. 10)

Navicula lyra var. constricta sensu Hustedt (1961 –1966: fig. 1553) (pro parte)

Navicula lyra var. constricta sensu W. Greg. (1854: pl. 9, fig. 13b)

Navicula lyra Ehrenb. sensu auct nonnull. (nec Ehrenberg 1843: 419 (131) pl. 1/1, fig. 9 a).

Valvae ellipticae vel plerumque lineari-ellipticae marginibus interdum leviter concavis in media parte (nec ellipticolanceolatae). Apices plus minusve curte protracti subrostrati denique obtuse rotundati. Longitudo 53–105 μ m, latitudo 35–40 μ m sed probabiliter etiam minus et plus quoad dimensiones. Raphe anguste-lateralis fere recta poris centralibus distincte expansis guttiformibus et parum deflexis ad latus secundum valvae, fissurisque terminalibus curte hamatis ad latus idem. Area axialis angusta linearis. Area centralis transapicaliter expansa et coniunxa cum areis lateralibus circiter 3 μ m latis concavis in medio tum paene rectis parum attenuatis usque 5–8 μ m sub apices extendentibus. Complexio arearum lateralium circiter 1/3 latitudinis valvae extendens vix lyriformis apparens quia distaliter vix curvata ad marginem valvae etiam non ad sternum versus deflexa. Striae transapicales marginales subparallelae rectae in mediis partibus valvae tum leviter radiantes (nec distincte curvatae et radiantes ipse valde radiantes in partibus distalibus valvae, vide Fig. 41 ), 10–13 in 10 μ m. Striae adaxiales ex 5–6 areolis compositae subparallelae vel leviter radiantes sed sub apices convergentes ordinatae. Areolae 12–15 in 10 μ m.

Lyrella pseudolyra versus Lyrella lyra (Ehrenb.) Karayeva sensu Ehrenberg (1843: 419 (131) pl. 1/1, fig. 9 a, Holotypus). Valves elliptical involving smaller cell cycle stages to linear-elliptical with almost straight or often more or less slightly concave margins in the middle of larger cell cycle stages (versus ellipticallanceolate valve outlines in L. lyra ). Ends more or less shortly protracted subrostrate, finally obtusely rounded; length 53–105 µm, breadth 35–40 µm, but probably having a broader size range if the entire cell cycle was known. Raphe narrow-lateral with very slightly deflected central ends and conspicuously expanded drop-like central pores; terminal fissures shortly hooked in valve face towards the same (secondary) side as the central endings. Axial area is narrow and linear throughout. Central area transapically expanded and variable in shape, not distinctively rectangular, connected with the lateral areas (2.5– 3 µm broad), slightly geniculate in the middle, slightly curved to almost straight towards the ends terminating 5–8 µm distant from the poles of the valve. The entire H-shaped complex extends to ca. 1/3 of the valve breadth and does hardly appear lyra-like since the apical ends of the lateral area are neither curving towards the valve margins nor towards the sternum, hence distinguished from the holotype and several other icons illustrating L. lyra as in Schmidt et al. (1874–1959: pl. 2, fig. 16). Marginal striae subparallel and straight in proximal parts becoming moderately radiate distally not distinctively curved and radiate becoming even strongly radiate, 10–13 in 10 µm ( Fig. 41 ). Adaxial striae, composed of 5–6 areolae, are subparallel or slightly radiate, becoming convergent near the ends. Areolae 12–15 in 10 µm.

The combination of characters of the holotype of Navicula lyra , originating from the Falkland Islands, has hardly been taken into consideration by alternative concepts of other authors. Thus, the concept of Hustedt (1961 –1966) was exaggerated by including numerous infraspecific taxa which can hardly be considered as conspecific in the more recent understanding of morphological species. Valve outlines appear comparatively similar with lyra-shaped lateral areas of Navicula lyra in the sense of Schmidt (1874–1959: pl. 2, fig. 16) in Schmidt et al. originating from Caribbean Sea, Campeche bank, leg. Gründler. However, even that population may be heterospecific since the distal striae are considerably less radiate. Moreover, the areola density is apparently lower. Generally, populations including larger cell cycle stages with straight and concave margins represent without doubt separate species rather than infraspecific offspring from the sub-Antarctic type population, just to compare with Lyrella lyroides , L. atlantica , L. abrupta etc .

Type:— BLACK SEA. Crimea, Sevastopol, Omega Bay , station 19 (44 o 35’60”N, 33 o 26’50”E), depth 3 m, sand substrate, Elena Nevrova , 28.07.200 4 (Holotype SZCZ slide 11094, illustrated in Fig. 39 ; isotype praep. no. OM19 _04 in Coll. E. Nevrova, IBSS NASU, Sevastopol, Ukraine, illustrated in Fig. 37 ) .

Etymology:— The specific epithet pseudolyra refers to this species’ similarity to Lyrella lyra .

Distribution: —Black Sea, inhabiting sandy substrate, known to occur at south-western and south-eastern part of Crimea (Omega Bay, Laspi Bay).

Figures

FIGURES 37–43: Figs 37–40: Lyrella pseudolyra sp. nov. Valve view, LM, scale bar = 10 µm. Holotype is illustrated in Fig. 39. Specimens from the Black Sea (Omega Bay, Laspi Bay) Figs 41–43: Lyrella lyra. Fig. 41: Valve from preparation No. 170407-b white (BHUPM, lectotype of Navicula lyra designated in Jahn et al. 2004: fig. 3; scale bar = 10 µm. Fig. 42: Reproduction of published line-drawing by Schmidt et al. (1874–1959: pl. 2, fig. 16 as the type ofNavicula lyra).Fig. 43:Reproduction of published line-drawings by C.G.Ehrenberg, sheet No.2046 in BHUPM by Jahn et al.2004:fig.2.