Navicula friedelhinziae Wojtal, Ognjanova-Rumenova, Buczkó & Van de Vijver, 2015

Wojtal, Agata Z., Ognjanova-Rumenova, Nadja, Buczkó, Krisztina, Siwek, Janusz & Vijver, Bart Van De, 2015, Revision of Navicula striolata (Grunow) Lange-Bertalot and N. rumaniensis Hustedt with the description of N. friedelhinziae sp. nov., Phytotaxa 204 (3), pp. 177-192 : 185-187

Navicula friedelhinziae Wojtal, Ognjanova-Rumenova, Buczkó & Van de Vijver , sp. nov. ( Figs. 45–55 )

Navicula friedelhinziae shows some similarities to N. rumaniensis and N. striolata but differs by commonly wider valves, transversely widened central area and narrow-lateral raphe. Proximal raphe endings are slightly more deflected to the primary side in N. rumaniensis and N. striolata compared to N. friedelhinziae . Additional differences between these species are clearly visible in SEM. Externally, the sternum raphe of N. friedelhinziae is only very slightly elevated in the mid-valve part and internally the accessory rib running apically along the valve is lacking.

Type:— BULGARIA. Lom Neogene Basin , Upper Miocene-Lower Pliocene deposits, the borehole T-4, near to the village of Momin brod, depth 94.70–95.00 m (43º 46’ 52” N, 23º 12’ 30” E), sample 4274, Age range: Late Miocene - Early Pliocene , Ognjanova-Rumenova , 21/10/2009 (holotype slide no. LoB-T4/4274 deposited in Ognjanova-Rumenova Collection Geological Instutute , Bulgarian Academy of Sciences, Fig. 45 ; isotypes slide PLP –279, University of Antwerp, Belgium, and BR! 4403) .

Etymology: — The species is dedicated to our dear colleague Mrs Friedel Hinz (Hustedt Collection,AWI, Bremerhaven), curator of the collection, to thank her for all her efforts supporting diatom research.

LM:— ( Figs. 45–47 ): Valves broadly lanceolate with obtusely rounded apices, 47–74 μm long and 12–15 μm wide. Axial area lanceolate. Central area irregular, transversely widened. Transapical longer and shorter striae alternating in the mid-valve part. Raphe lateral. Proximal raphe ends expanded, drop-like, relatively widely spaced, deflected towards the secondary side. Transapical striae distinctly radiate in the mid-valve becoming convergent towards the apices, 7 – 8 in 10 μm. Lineolae coarse, 24–28 in 10 μm, clearly discernible in LM.

SEM:— ( Figs. 48–55 ): Externally sternum raphe very slightly elevated in the mid-valve part becoming confluent towards poles. Proximal raphe ends straight and drop-like expanded. Distal raphe fissures bent. Transapical striae extending from the valve face to the valve mantle. Foramina rectangular. Transapical striae near central area arranged of the longest foramina near the valve mantle and shortest near the central area. Internally, raphe slit narrow and straight, running on a thickened, raised sternum. Proximal raphe ends slightly expanded and unilaterally bent ( Figs. 50, 51 ). Hyaline area near helictoglossa asymmetric. One large poroid located over the helictoglossa ( Figs. 53 – 55 ). Virgae narrower than vimines, the latter running in relatively shallow grooves.

Geographical distribution and autecology:— The structural, textural and mineralogical composition of the sediments from the Brusartsi Formation of the Lom Neogene Basin led to the conclusion that sedimentation during the Dacian-Romanian (~3 4 Ma) period occured in a relatively shallow, broad basin with low hydrodynamics. Results from the diatom analysis confirm this conclusion and indicate that the basin was most likely an eutrophic freshwater lake. The temperature regime was similar to the lakes of the moderate latitudes. The existence of a lacustrine-paludal environment is also confirmed by the presence of thick clay deposits in all boreholes from the Momin Brod area within the Neogene Basin ( Yaneva et al. 2010). These results are in agreement with the conclusion based on geochemical and pollen analysis ( Stefanova et al. 2008) about the deltaic/limnic sedimentary environment. Several Navicula species such as N. haueri Grunow (1882: 143) , N. hasta Pant. (1892: pl. 5, fig. 74) or N. perobesa Hust. in Schmidt et al. (1934: pl. 395, figs. 22–25) known from freshwater Neogene material, have heavily silicified frustules ( Levkov et al. 2008, Buczkó et al. 2014). Some of them are known only from that geological period, other can be found in modern samples, especially in ancient lakes such as Lake Ochrid and Lake Baikal that can most likely be considered as their refugia ( Levkov et al. 2007, Kulikovskiy et al. 2012).

In recent samples from southern Poland, N. striolata was observed mainly in springs with a sandy bottom. The area is a karst region underlaid by Jurassic limestones and Cretaceous marls, covered with loess or fluvial deposits. The largest population was observed in Centuria, where a moderate conductivity, alkalinity and nitrate concentration, but high dissolved oxygen content was recorded ( Wojtal 2013). This observation corresponds well to the previously proposed autecology ( Van Dam et al. 1994, Lange-Bertalot 2001) although rare specimens of N. striolata were observed in waters showing a broad nitrate concentration range.

Figures

FIGURES 45–49. Navicula friedelhinziae Wojtal, Ognjanova-Rumenova, Buczkó & Van de Vijver, sp. nov. 45–47. LM images of N. friedelhinziae from Lom basin showing broadly lanceolate valves with obtusely rounded axial area and central area irregular, transversely widened. 45. Holotype from the slide LoB-T4/4274. 48, 49. External valves SEM images showing details of a valve central area. Scale bars: 45–48 = 10 μm; 49 = 5 μm.

FIGURES 50–55. Navicula friedelhinziae Wojtal, Ognjanova-Rumenova, Buczkó & Van de Vijver, sp. nov., SEM, internal images. 51. Details of a central area—raphe slit narrow and straight, running on a thickened, raised sternum. 52, 53. Raphe ends slightly expanded and unilaterally bent and one large poroid located over the helictoglossa. 54, 55.Two apices with corroded poroids showing their ultrastructure. Scale bars: 50 = 10 μm; 51, 52 = 4 μm; 53–55 = 1 μm.