The species has been named in honour to professor emeritus Damir Viličić, S.B: Ph.D. supervisor and an outstanding scientist who considerably contributed to the knowledge on phytoplankton taxonomy and ecology in the Adriatic Sea.

Heterovalvate, monoraphid frustules composed of a raphe–bearing valve and a rapheless valve. Frustules relatively small. Raphe valve (RV): valve face relatively flat, rarely curved. Mantle very shallow. Raphe branches straight. Central raphe endings closely positioned to each other, shortly hooked, weakly expanded. Terminal raphe fissures bent, continuing onto the valve mantle. Striae composed of one macroareola, only near the valve apices continuous from axial area to valve margin. Most of the striae interrupted by large hyaline plate dividing the macroareolae in two parts. Areolae covered externally by porous hymenes. Virgae internally thickened, clearly raised. Raphe sternum clearly raised with developed central nodule. Central raphe endings straight to weakly deflected into opposite directions. Terminal raphe endings terminating onto small helictoglossae. Sternum valve (SV): Valves weakly convex with clearly developed, thickened, linear sternum. Mantle shallow. Striae composed of macroareolae, clearly interrupted by a large hyaline plate forming one rounded areola near the axial area and one transapically elongated areola at valve margin, both covered by porous external hymenes. Distinct, raised ridge surrounding the valve face, folded inwards over the valve margin. Internally, hyaline plate dividing the macroareolae obvious. Small vestige–like raphe slits present. Raphe sternum sunken. Girdle composed of at least two open, narrow, unperforated bands.

Majewskaea istriaca, sp. nov.

The specific epithet ‘istriaca’ refers to the Istrian peninsula where the loggerhead turtle was found.

Majewskaea istriaca was so far only found on the carapace of a loggerhead turtle. The associated diatom flora was very diverse and species–rich and composed of Catenula exigua Robert et al., an unknown Bifibulatia Takano species and several Nitzschia Hassall, Fallacia A.J.Stickle et D.G.Mann, Parlibellus E.J.Cox and Amphora Ehrenberg ex Kützing species.

Light Microscopy (Figs 1–39): Frustules heterovalvate. Valves linear, linear–lanceolate to lanceolate with straight to convex margins and weakly protracted, rostrate, broadly rounded apices. Smaller valves becoming almost elliptical. Valve dimensions (n=50): length 6–15 μm, width 3–4 μm. SV: Sternum raised above valve plain, often discernible in LM (Figs 8, 10, 12, 16). Striae parallel throughout almost the entire valve, becoming slight radiate towards the apices, 30–32 in 10 μm. RV: raphe sternum clearly developed, linear running distinctly from apex to apex. Raphe branches not or very weakly (Figs 22, 25, 29: discernible in LM. Axial area very narrow. Central area often rather distinctly but irregularly thickened. Striae nor areolae visible in LM.
Scanning Electron Microscopy (Figs 40–51): Girdle not well studied due to lack of observations, even of untreated material. Girdle bands open, narrow, thin, unperforated (Figs 40, 41). Fig. 44 showing open nature of girdle bands. SV (Figs 40–47): Mantle very shallow. Internally sternum depressed, linear (Figs 41, 42). Very short, vestige–like raphe slits visible near apices (Figs 41, 42, 44, arrow). Striae interrupted by continuous hyaline plate subdividing the areolae usually in two parts (Figs 41, 42). Axial sternum bordered by continuous series of large rounded, areolae, part of larger macroareolae (Fig. 42). Near valve edge transapically elongated parts of macroareolae present. Occasionally, third areola visible near valve margin (Fig. 42). Externally, well–developed ridge surrounding the entire valve, larger near valve center. Ridge clearly folded inwards, partly covering the marginal areolae of the striae (Figs 43, 46, 47). Sternum thick, raised, linear to lanceolate (Figs 40, 43). Virgae raised extending from the sternum towards the valve margins (Figs 40, 43, 47). Striae depressed between virgae (Figs 43, 45). Areolae clearly covered by perforated hymenes (Fig. 45, arrows). Vestigial raphe slits often visible at apices (Fig. 46, arrow). RV (Figs 48–52): Raphe branches straight with shortly, unilaterally hooked central endings bearing only weakly expanded pores (Figs 48, 50). Terminal raphe fissures bent, continuing onto the mantle (Fig. 48). Striae composed of macroareolae, subdivided by large hyaline plate, ca. 50 in 10 μm. Axial area bordered by series of transapically elongated, short areolae whereas larger part of macroareolae visible near valve margin (Fig. 48). At apices, macroareolae never subdivided, composed of one continuous stria (Fig. 48). Internally, raphe sternum well developed, clearly raised. Central nodule thickened, expanding irregularly towards the valve margins, however, never reaching the margins (Fig. 49). Virgae distinctly thickened with striae sunken between them. Raphe branches terminating onto small helictoglossae at the apices (Figs 49, 51). Centrally, raphe endings occasionally deflected in opposite directions (Fig. 49), usually straight (Fig. 52). Areola coverings visible as perforated, external hymenes (Fig. 52).

Van de Vijver, Bart; Robert, Kathe; Witkowski, Andrzej; Bosak, Suncica  (2020): Majewskaea gen. nov. (Bacillariophyta), a new marine benthic diatom genus from the Adriatic Sea // Fottea 20: 112-120, doi:10.5507/fot.2020.001.

From Latin adjective “pusilla” (miniature, tiny, very small) referring to the typical cell size.

Croatia: Adriatic Sea, south–eastern coast, open waters (N 42°24ʹ E 17°55ʹ). Plankton net sample collected on March 10, 2016 by S. Bosak. Holotype slide of the strain PMFBIOP1 deposited in The Friedrich Hustedt Diatom Study Centre, Bremerhaven, Germany as BRM ZU10/84. Isotype slide deposited at Macedonian diatom collection, Skopje, Macedonia under accession number 011647/ MNDC. GenBank accession numbers for PMFBIOP1 are MF000612 (18S rRNA), MF000640 (rbcL) and MF000626 (psbC).

Cells very small, with heavily silicified frustules with one plate–like plastid, not twisted around the apical axis: 9.7–14.1 μm long, 2.6–10.0 μm wide at constricted central part and 5.4–11.1 μm in widest part. Valves lanceolate with scalpeliform apices, 9.7–14.1 μm long, 2.3–3.8 μm wide in central part. The transition from the elevated keel to the valve body creates an impression of a straight line. Virgae are straight, simple, and parallelly extending through whole valve body, with few virgae shorter than the rest. Valve striae 40–55 in 10 μm. Keel striae 57–60 in 10 μm. The striae are closed by a hymen with very narrow dash-like perforations arranged in two parallel lines along the striae edges. Perforations within striae 64–75 in 1 μm near the keel margin and 49–50 in 1 μm near the valve margin. Basal fibulae sometimes interconnected with adjacent ones with transverse connections in shape H or Y, 4–5 in 1 μm. Sigmoid raphe with simple linear central endings and slightly hooked terminal endings. Raphe fibulae 50–60 in 10 μm, sometimes fused between each other forming H or K shape. Valvocopulae and copulae straight, with two rows of distinct teardrop shaped areolae, and with silica thickenings in interareolar area. Areolae density in copulae same as in valvocopulae, 40–45 in 10 μm. In valvocopula there are 14–29 and 24–32 perforations in abvalvar and advalvar areolae, respectively.

Mejdandžić, Maja; Bosak, Sunčica; Nakov, Teofil; Ruck, Elizabeth; Orlić, Sandi; Gligora Udovič, Marija; Peharec Štefanić, Petra; Špoljarić, Igor; Mršić, Gordan; Ljubešić, Zrinka (2018). Morphological diversity and phylogeny of the diatom genus Entomoneis (Bacillariophyta) in marine plankton: six new species from the Adriatic Sea // Journal of Phycology, 54, 2; 275-298. DOI:10.1111/jpy.12622.

Currently, we have type material for 16 described species in our Collection and two species are waiting to be described. Below, we have mentioned 11 described species from Croatia, which is an especially valuable part of our Collection.

Currently, we have type material for 16 described species in our Collection and two species are waiting to be described. Below, we have mentioned 11 described species from Croatia, which is an especially valuable part of our Collection.