Adlafia triundulata Tusset, Tremarin & T. Ludwig, 2017

Tusset, Eduardo A., Tremarin, Priscila I., Straube, Arielli & Ludwig, Thelma A. V., 2017, Morphology of Adlafia taxa (Bacillariophyta, Cymbellaceae), with proposition of two new species from Brazil, Phytotaxa 306 (4), pp. 259-274 : 269-271

Adlafia triundulata Tusset, Tremarin & T. Ludwig sp. nov.

Figs 81‒97

Valves linear, triundulate, with capitate to subcapitate apices, 13.5‒17.4 μm in long, 2.9‒3.7 μm in wide (n=30), shoulders developed. Raphe sternum linear and narrow. Central area slightly expanded or reduced. Raphe filiform, distal raphe ends unilaterally bent and internally terminate in a small helictoglossa; proximal raphe ends slightly curved and internally deflected to the primary side of valve. Terminal nodule transversally expanded in t-shaped in inner view. Striae uniseriate, 30‒36 in 10 μm, radiate becoming abruptly convergent near the apices, running continuously to the mantle; presence of several shortened striae over a rather extent part in the median region of valve. Valve apex with two rows of small areolae on the mantle. Areolae rounded-squared, 63‒68 in 10 μm, externally occluded by hymenes, inconspicuous at light microscopy.

Type:— BRAZIL. Mato Grosso do Sul: Bodoquena, Boca da Onça Stream , epiphyton, 20°73’25.28”S, 56°73’43.68”, November 2015, E. Tusset s.n. (holotype UPCB! 78240—here depicted in Figs 91‒92 ; isotype BM! 101849) .

Etymology:—The specific epithet refers to undulated valve outline.

Paratypes:— BRAZIL. Mato Grosso do Sul: Bonito, Formoso River UPCB! 76099 ; BRAZIL. Mato Grosso do Sul: Bonito, Chapeninha Stream UPCB! 78227 ; BRAZIL. Mato Grosso do Sul: Bonito, Perdido river UPCB! 78231 ; BRAZIL. Mato Grosso do Sul: Jardim, Misteriosa Lagoon UPCB! 78234 .

Similar valves were previously recorded from a Japanese population, but identified as Adlafia bryophila by Kobayasi (1960, pl. 3, figs 31‒33), Ando (1979, figs 42, 43, 45), Fukushima et al. (1985, pl. 2, figs A‒W’), and from Austria as Naviculadicta bryophila (Petersen) sensu lato by Lange-Bertalot & Metzeltin (1996, pl. 83, fig. 27). Fukushima et al. (1985) distinguished two populations, a typical A. bryophila and another one with undulate contour, that was reffered as A. bryophila ?. Besides the valve outline, valve width range (3‒4 μm in A. bryophila ? and 4‒5 μm in A. bryophila ) differentiates both taxa ( Fukushima et al. 1985). However, this difference does not occur when considering the population variability found by other researchers to A. bryophila ( Table 5). We believe that an undulated outline justifies the new Adlafia species. Thus, A. triundulata differs from A. bryophila by the triundulate valve margins and by the higher areolae density ( Table 5). The morphology and valve dimensions of Brazilian exemplars were equivalent to those shown by Fukushima et al. (1985) to A. bryophila ? ( Table 5). We did not find any valve that was similar to A. bryophila in the analyzed material. We also believe that the occurrence of the latter species in Brazil is uncertain, and it seems that earlier reports of this taxon correspond to other Adlafia taxa.

The most similar taxon to A. triundulata is Navicula rautenbachiae Cholnoky (1957: 5) described from South Africa. Nevertheless, N. rautenbachiae has larger valve dimensions, strongly undulate margins, protracted apices and different striation pattern in the central area ( Table 5). Another similar species is Sellaphora tridentula (Krasske) C.E. Wetzel (in Wetzel et al. 2015: 228) with regard to the undulate valve outline, the shape of apices, the valve dimensions and the delicate striation pattern ( Table 5). However, S. tridentula presents more pronounced marginal undulations and wider central area. Moreover, S. tridentula possesses hooked distal raphe ends extending onto the mantle, radiate striae becoming slowly convergent near the apices, central area laterally expanded not reaching the margins, areolae occluded by internal hymenate layer and higher number of striae and areolae (Lange-Bertalot et al. 1996, Werum & Lange-Bertalot 2004, Le Cohu & Azémar 2010). Adlafia triundulata was previously recorded in Brazil as Sellaphora tridentula by Bertolli et al. (2010) and Marra et al. (2016). We recommend SEM analysis of the valves to a precise determination of the species.

Navicula tridentula var. tenuis (Krasske) Lange-Bertalot & Willmann (in Lange-Bertalot et al. 1996: 151) also resembles A. triundulata in LM observations, but the latter differs by the strongly undulate margins and capitate apices ( Table 5) (Lange-Bertalot et al. 1996). SEM analysis of N. tridentula var. tenuis is necessary to obtain frustule morphology details and to differentiate it from other related species.

Adlafia triundulata was found in neutral to alkaline waters (pH 7.0‒8.0) occurred in epiphytic material (moss, cyanophyceae and algae) ( Kobayasi 1960, Ando 1979, Fukushima et al. 1985, and present study) and in carbonate waters ( Lange-Bertalot & Metzeltin 1996, and present study). The most common taxa occurring with A. triundulata in the type material were: Adlafia muscora, Cocconeis placentula var. lineata (Ehrenberg) Van Heurck (1885: 133) , Nitzschia amphibia Grunow (1862: 574) , Sellaphora capitata Mann & McDonald (in Mann et al. 2004: 477), Rhopalodia gibberula var. vanheurcki Müller (1900: 292) , Frustulia amosseana Lange-Bertalot (in Rumrich et al. 2000: 129), Halamphora montana (Krasske) Levkov (2009: 207) , Mayamaea atomus var. permitis (Kützing) Lange-Bertalot (1997: 72) and Neidium ampliatum (Ehrenberg) Krammer (in Krammer & Lange-Bertalot 1985: 101).

Figures

FIGURES 81‒97. Adlafia triundulata sp. nov. Figs 81‒93. Valve view, LM. Scale bar = 10 μm. Figs 91, 92. Holotype. Fig. 94. Detail of areolae occluded by hymenes, TEM. Scale bar = 0.5 μm. Fig. 95. Striation pattern in the whole valve, TEM. Scale bar = 2 μm. Fig. 96. Internal valve view showing the striae, helictoglossa and proximal raphe ends, SEM. Scale bar = 2 μm, Fig. 97. External valve view detailing the proximal and distal raphe ends, SEM. Scale bar = 2 μm.