Lyrella abruptapontica 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 : 3-6

Lyrella abruptapontica Nevrova, Witkowski, Kulikovskiy & Lange-Bert. , sp. nov. ( Figs 1–9 , Figs 10–13 )

Valvae late ellipticae apicibus paulatim obtuse subcuneatim rotundatis; longitudo 33–60 μ m, latitudo 20–29 μ m; ratio longitudo/latitudo 1.6–2.1. Raphe anguste-lateralis fere recta extremis centralibus distincte dilatatis et parum ad latus secundum valvae deflexis fissurisque terminalibus curte hamatis ad latus idem. Area axialis cum ramis ambabus anguste lanceolatis, id est leviter inflatis in mediis partibus utroque. Area centralis conspicue transverse rectangulata coniunxa cum areis lateralibus 2 μ m latis fortiter geniculatis curvatis in medio tum gradatim attenuatis et curvatis versus aream axialem denique abrupte terminantibus, 7–13 μ m sub apicibus. Areae laterales valvarum minarum diffuse ornatae lineis apicalibus punctorum irregulariter sitorum. Striae transapicales interruptae areis lateralibus ut communiter in genere Lyrella , modice vel magis radiales et sub apices saepe plus minusve sinuosae apparentes, 9–11 in 10 μ m. Areolae 28–30 in 10 μ m. Aspectus ultramicroscopicus internus vide.

Lyrella abrupta (W. Greg. 1857: fig. 14a) D.G. Mann in Round et al. (1990: 671) sensu auctorum differt proprie apicibus latius non cuneatim rotundatis etiam quoad rationem longitudo/latitudo 2.0–2.8 (nec 1.6–2.1), vide Hustedt (1961 –1966: 516, fig. 1558), Hendey (1964: pl. 33, fig. 12), Witkowski et al. (2000: 229, pl. 95,fig. 4, 5), Sims (1996: pl. 130, fig. 3).

Atque dimensiones speciei Lyrella abrupta auctorum nonnull. inconstantes sunt. Longitudo 145–148 μ m, latitudo 22–46 ( Hustedt 1961 –1966: 516, fig. 1558) sed 38–60 μ m longae, 16–28 μ m latae ( Hendey 1964: pl. 33, fig. 12) vel 12–85 μ m longae, 6–32 μ m latae ( Sims 1996 vide supra tabula 130: 3) probabiliter includentes species differentes. Navicula abrupta sensu Donkin (1870: 13 , pl. 2, fig. 6) se praestat lanceolata ad instar cum areis lateralibus longis non abruptis sub apicibus.

Valves broadly elliptical, becoming gradually narrowed to subcuneate, with broadly rounded ends; length 33–60 µm, breadth 20–29 µm, length-to-breath ratio 1.6–2.1. Raphe narrow-lateral, almost straight with distinctively expanded central ends being very weakly deflected to secondary side of valve. Terminal raphe fissures shortly hooked to the same side. Two axial area branches weakly expanded, narrowly lanceolate, becoming narrower near central pores and terminal fissures. Central area transapically rectangular, connected with 2 µm broad lateral area, strongly geniculate in middle, tapering to a position 7–13 µm distance from poles, curving weakly towards axial area ( Figs 1–9 ). Smaller specimens having within lateral area somewhat diffuse markings ( Figs 1–3 ). Marginal striae subparallel proximally becoming progressively radiate but finally, below the ends again more or less subparallel and wavy (sinuous), 9–11 in 10 µm. Adaxial striae (the striae between the raphe and the lateral areas) consisting of 1–4 areolae, subparallel to moderately radial, never convergent. Areolae 28–30 in 10 µm ( Figs 10–13 ).

Lyrella abruptapontica is most similar to Lyrella abrupta (W. Greg. 1857: fig. 14a) D.G. Mann in Round et al. (1990: 671), see also Brockmann (1950: 19; pl. 3, fig. 10), Hendey (1964: pl. 33, fig. 12), Hustedt (1961 –1966: 516, fig. 1558), Sims (1996: pl. 130, fig. 3) and Witkowski et al. (2000: 229, pl. 95, fig. 4, 5); but doubtful for Donkin (1870: 13, pl. 2, fig. 6), who transferred Navicula lyra var. abrupta W. Greg. (1857: fig. 14a) to Navicula abrupta (W. Greg.) Donkin (1870: 13 , pl. 2, fig. 6). Navicula lyra var. abrupta is distinguished mainly by its linear-elliptical valves and its hardly cuneate poles in longer specimens. Consequently its length-to-breadth ratio is considerably higher at 2.0–2.8 as compared to 1.6–2.1 (see above).

Type:— BLACK SEA. Crimea, Balaklava Bay , station 17_R-6 (44 o 29’12”N, 33 o 36’53”E), depth 12 m, sand substrate, Elena Nevrova , 14.10.200 6 (Holotype SZCZ slide 19691, illustrated in Fig. 1 ; isotype FR Eu- Black Sea 001, no. B337, illustrated in Fig. 11 ; isotype praep. no. BB0617 in Coll. E. Nevrova, IBSS NASU, Sevastopol, Ukraine, illustrated in Fig. 3 ) .

Etymology:— The specific epithet abruptapontica refers to this species’ similarity to Lyrella abrupta and to its type habitat in the Black Sea (Pontus Euxinus).

Distribution: —Black Sea, known to occur in the south-east (Karadag, Dvujakornaya Bay) and southwest (Balaklava Bay, Feolent Cape, Sevastopol Bay, Vitino) coasts of the Crimean Peninsula.

Figures

FIGURES 1–9: Lyrella abruptapontica sp. nov. LM images. Figs 1–9: Valve view, showing variation in size and outline, scale bar = 10 µm. Specimens from the Black Sea (Sevastopol Bay, Balaklava Bay, Karadag, Feolent Cape, Vitino coast). Holotype is illustrated in Fig. 1.

FIGURES 10–13: Lyrella abruptapontica sp. nov. SEM images. Fig. 10: Internal view, scale bar = 20 µm. Fig. 11: Internal view, scale bar = 10 µm. Fig. 12: Internal view, scale bar = 9 µm. Fig. 13: External view, note the raphe external central and apical endings, the areolae and the lateral areas. Specimens from the Black Sea (Karadag, Dvujakornaya Bay, Sevastopol Bay).