Lyrella pontieuxini 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 : 6-8

Lyrella pontieuxini Nevrova, Witkowski, Kulikovskiy & Lange-Bert. , sp. nov. ( Figs 14–18 )

Valvae late ellipticae vel late elliptico-lanceolatae apicibus paulatim obtuse subcuneatim rotundatis; longitudo 60–80 μ m, latitudo 22–31 μ m; ratio longitudo/latitudo 2.25–2.45. Raphe anguste lateralis extremis centralibus distincte dilatatis et parum ad latus secundem valvae deflexis fissurisque terminalibus hamatis ad latus idem. Area axialis cum ramis ambabus angustissime lanceolatis, id est levissime vel leviter (quoad specimina maiora) inflatis in mediis partibus utroque. Area centralis conspicue transverse rectangulata coniunxa cum areis lateralibus 3–4 μ m latis nudis modice geniculatis in medio tum gradatim attenuatis et curvatis versus aream axialem, terminantibus 5–7 μ m sub apicibus. Striae transapicales marginales subparallelae in media parte valvae tum radiantes sub polos sinuatae, 9–10 in 10 μ m. Striae adaxiales ex 2–4 areolis compositae omnes subparallelae vel parum radiantes numquam convergentes. Areolae 22–24 in 10 μ m.

Diagnosis differens versus Lyrella rattrayi (Pant.) comb. nov. ( Fig. 19 ) proprie differt valvis rhombico-lanceolatis etiam areis lateralibus circiter 7 μ m latis et striis transapicalibus radialibus usque sub apices non sinuatis. Lyrella abrupta (W. Greg.) D.G. Mann differt areis lateralibus apicaliter curtioribus et transapicaliter angustioribus. Etiam lineamenta valvarum lineari-elliptica cum apicibus late rotundatis non subcuneatis differt.

Valves broadly elliptical to broadly elliptical-lanceolate, becoming gradually subcuneately rounded to the ends; length 60–80 µm, breadth 22–31 µm; length-to-breadth ratio = 2.25–2.45. Raphe narrow-lateral with distinctively expanded central endings that are very slightly deflected to the secondary side of the valve. Terminal fissures hooked to the same side. The two branches of the axial area weakly expanded lanceolate and respectively near central pores and terminal fissures, respectively. Central area conspicuously transapically expanded rectangular, connected with the 3–4 µm broad lateral areas lacking any markings, geniculate in the middle, tapering to a position in 5–7 µm distance from the poles and curving towards the axial area. Marginal striae are subparallel proximally becoming continually more radiate, finally few stria-pairs again subparallel but wavy, 9–10 in 10 µm. Adaxial striae, consisting of 2–4 areolae, are subparallel or slightly radiate, never convergent. Areolae 22–24 in 10 µm.

Lyrella rattrayi (Pant.) comb. nov. ( Fig. 19 ) is distinguished by its rhombic-lanceolate valve with slightly rounded poles, ca. 7 µm broad lateral area, and striae that do not become sinuous at the ends. However, Navicula abrupta var. rattrayi ( Pantocsek 1889: 52) H. et M. Peragallo (1897: 132 pl. 21, figs 38, 30) (= Navicula rattrayi Pantocsek 1889: 52 ) conforms more closely to Lyrella pontieuxini (see Fig. 19 ), whereas Lyrella abrupta differs by its valve outline, which has a strong tendency to become linear-elliptical with broadly rounded ends in larger cell cycle stages and narrower, apically shorter lateral area.

Type: — BLACK SEA: Omega Bay , st. 22, depth 1,5 m (44 o 35’55”N, 33 o 26’56”E), sand substrate, Elena Nevrova , 28.07.200 4 (Holotype SZCZ slide 11095, illustrated in Fig. 15 ; isotype FR Eu-Black Sea 002, no. Crimea B220 03, illustrated in Fig. 18 ; isotype praep. no OM22-04 in Coll. E. Nevrova, IBSS NASU, Sevastopol, Ukraine, illustrated in Fig. 14 ) .

Etymology: —The name of this species refers to the ancient Greek name given to the Black Sea – Pontus Euxinus, meaning Hospitable Sea.

Distribution: —Black Sea, found along the south-west (e.g. Omega Bay) and south-eastern part of the Crimean Peninsula (e.g. Dvujakornaya Bay).

Figures

FIGURES 14–19: Figs 14–17: Lyrella pontieuxini sp. nov. Valve view, show variation in size and outline. LM, scale bar = 10 µm. Specimens from the Black Sea (Balaklava Bay, Omega Bay, Dvujakornaja Bay) Holotype is illustrated in Fig. 15. Fig. 18: Lyrella cf. pontieuxini, external view, SEM, scale bar = 20 µm. Fig. 19: Lyrella rattrayi comb. nov., reproduction of published line-drawing by H. & M. Peragallo (1874–1908: pl. 21, fig. 38) as Navicula abrupta var. rattrayi, scale bar = 10 µm.