Olifantiella elisabethiana Van de Vijver, 2016

Vijver, Bart Van De, Mertens, Adrienne & Dam, Herman Van, 2016, Olifantiella elisabethiana, a new raphid diatom species (Bacillariophyta) observed in the Port of Antwerp (Belgium), Phytotaxa 261 (3), pp. 251-259 : 252-255

Olifantiella elisabethiana Van de Vijver , sp. nov. ( Figs 1–31 )

Light microscopy ( Figs 1–15 ): Valves almost linear, becoming more elliptic to elliptic-lanceolate in smaller specimens ( Figs 14, 15 ) with parallel, straight margins and rostrate, clearly protracted, bluntly rounded, truncated apices. Valve dimensions (n=50): length 8–17μm, width 3.5–4.0 μm. Axial area very narrow, linear, not widening towards the central area. Central area almost nonexisting, asymmetrical due to the shortening of one stria. Raphe filiform located on a slightly raised sternum, widening near the central area ( Fig. 5 ). Proximal raphe endings simple to very weakly enlarged, slightly unilaterally deflected. Distal raphe endings not visible in LM. Striae clearly visible, parallel throughout becoming occasionally weakly radiate near the apices, 31–32 in 10 μm. Areolae not discernible in LM. SEM ( Figs 16–25 ): valve face flat. External view: large hyaline zone running from apex to apex, parallel to the axial area ( Figs 16, 20 ). Striae composed of one large slitlike macroareola, equidistant ( Figs 16, 18 ). Part of the striae near the axial area covered in the areolar canal by a finely perforated hymen. Most outer part of the striae open ( Fig. 18 ). Large, lanceolate zone visible on the valve face on both sides of the axial area corresponding to the underlying hymena ( Fig. 16 ). ‘Fenestrulae’ (non-covered part of the areolae according to Riaux-Gobin (2015) though not formally defined) very small ( Fig. 18 ). Central area asymmetrical due to one shortened vestigial stria, located close to the hyaline marginal zone ( Fig. 17 ). Opening of the buciniportula narrow, transapically elongated, slitlike ( Fig. 17 ), located on the secondary side. Raphe branches weakly undulating, placed between two very low ridges ( Fig. 16 ). Proximal raphe endings very weakly droplike expanded, almost straight ( Fig. 17 ). Distal raphe fissures very short, unilaterally deflected to the secondary side, terminating in simple endings ( Fig. 19 ). Internal view: raphe branches straight. Proximal raphe endings indistinct, straight. Central nodule weakly raised. Small, raised siliceous rectangular wart located between the proximal raphe endings ( Figs 21, 24 ). Distal endings terminating onto small raised helictoglossae ( Figs 21, 23 ). Buciniportula solitary, weakly raised ( Figs 24, 25 ), rounded, flattened, plugged by a sort of finely punctated hymen, similar to that of the areolae. Virgae thickened, clearly raised with the striae in between, clearly sunken ( Fig. 22 ), covered by finely perforated hymenes. Marginally a large canal present, surrounding the entire valve. Internal and external layer of the valve split from the valve margin towards the axial area, fused again via perforated hymenes with the striae, almost halfway between the margins and the axial area ( Figs 21, 22 ). Near the valve margin, small, rounded, perforated plates present at the end of each stria covering small bulbous structures at the valve margin ( Figs 21, 23 ). Virgae terminating near the split of internal and external layer, continuing as a narrow ridge ( Fig. 28 ). Frustules in girdle view not observed due to severe cleaning. Girdle composed of several, open copulae usually bearing a double perforation ( Figs 26, 27 ). TEM ( Figs 29–31 ): striae composed of one transapically elongated areola, extending from the axial area till almost halfway between axial area and valve margin ( Figs 29, 30 ). Virgae with small ridges continuing towards the valve margins clearly visible ( Fig. 29 ). Small, rounded plates near the valve margins clearly visible ( Figs 29, 30 ). Bucinoportula clearly slitlike, covered by a rounded, siliceous plug ( Fig. 31 ).

Type:— BELGIUM. Port of Antwerp : Kanaaldok B 2, sample 352846 (wharf 669), B. Van de Vijver, 20 May 2008 (holotype: BR! slide no. 4446; isotype: PLP! slide no. 301, University of Antwerp, Belgium) .

Etymology:—The new species is named after Miss. Elisabeth Wilfert, stepdaughter of the author, on the occasion of her 8 th birthday (20/06/2016).

Ecology and associated diatom taxa:— Olifantiella elisabethiana was recorded in several samples from the Kanaaldok in the Antwerp harbor. The samples were characterized by a fairly high Cl- level (2.6 g /l), high conductivity levels (627 mS/m), an almost circumneutral pH (7.8) and moderate nutrient values (TN 5.0 g/l, TP 0.17 g /l) (all values from Van Dam et al. 2008). The flora in the samples was dominated by brackish and marine species such as Nitzschia filiformis var. conferta ( Richter 1879: 65) Lange-Bertalot in Lange-Bertalot & Krammer (1987: 18), Psammothidium punctulatum ( Simonsen 1959: 75) Bukhtiyarova & Round (1996: 14) , Tabularia fasciculata ( Agardh 1812: 35) Williams & Round (1986: 326) and Berkeleya spp. Unfortunately, no raw material is kept making observation of the lifeform of the new species not possible.

Figures

FIGURES 1–20. Olifantiella elisabethiana. LM & SEM pictures taken from the holotype population (sample 352846) from Kanaaldok B2, Port of Antwerp, Belgium. 1–15. Light microscopy observations. 16. External view of an entire valve. 17. External detail of the central area with one shortened stria near near the valve margin and the external opening of the buciniportula. 18. External detail of the striae showing the transapically elongated areola (=macroareola), the hymenous covering in the areola and the open outer part of the striae. 19. External detail of the valve apex.20. External detail of the valve margin with the thick hyaline zone at the valve face/mantle junction.Scale bar represents 10 μm for Figs 1–16 and 1 μm for Figs 17–20.

FIGURES 21–25. Olifantiella elisabethiana. SEM pictures taken from the holotype population (sample 352846) from Kanaaldok B2, Port of Antwerp, Belgium. 21. Internal view of an entire valve. 22. Internal detail of the valve margin and the striae with the finely perforated hymenes covering the areolae, the siliceous, hymenous velum extending from the valve margin to halfway the margin and the axial area. 23. Internal detail of the valve apex with the helictoglossa. 24. Internal detail of the central area with the buciniportula. 25. Internal detail of the siliceous plugged buciniportula. Scale bar represents 10 μm for Fig. 21 and 1 μm for Figs 22–25.

FIGURES 26–28. Olifantiella elisabethiana. SEM pictures taken from the holotype population (sample 352846) from Kanaaldok B2, Port of Antwerp, Belgium. 26. Internal view of an entire valve with part of the girdle structure still attached to the valve. 27. Detail of the perforated girdle bands. 28. Internal detail of a damaged valve showing a cross-section of the marginal canal, the hymena and the virgae. Scale bar represents 10 μm for fig. 26 and 1 μm for figs 27, 28.

FIGURES 29–31. Olifantiella elisabethiana. TEM pictures taken from the holotype population (sample 352846) from Kanaaldok B2, Port of Antwerp, Belgium. 29. View of tan entire valve. 30. Detail of the valve margin and the striae, showing the areolae and the narrow ridges of the continuing virgae. 31. Inter detail of the central area with the buciniportula. Scale bar represents 10 μm for Fig. 29 and 1 μm for Figs 30–31.