Adlafia decora 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 : 261-268

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

Figs 1‒18

Valves linear-lanceolate with rostrate apices, 18.2‒26.2 μm long, 4.6‒5.7 μm wide (n=30). Raphe sternum linear and narrow. Central area absent. Raphe filiform, distal raphe ends unilaterally bent to the secondary side of the valve and internally terminating at a small helictoglossa; proximal raphe ends slightly curved and internally deflected to the primary side of valve. Inner view of terminal nodule transversally expanded and t-shaped. Striae uniseriate, 24‒32 in 10 μm, radiate to abruptly convergent near the apices, running continuously onto the mantle; presence of two or more shortened striae in the median region of valve. Valve apex with two rows of small areolae on the mantle. Areolae rounded, 50‒54 in 10 μm, externally occluded by hymenes, inconspicuous at light microscopy.

Type:— BRAZIL. Mato Grosso do Sul: Bonito, Chapeninha Stream, epiphyton, 20°82’94.24”S, 56°54’85.77”W,

November 2015, E. Tusset s.n. (holotype UPCB! 78227—here depicted in Figs 7‒8 , isotype BM! 101847). Etymology: The specific epithet refers to elegant aspect of valve in electron microscopy.

Paratypes: — BRAZIL. Mato Grosso de Sul: Bodoquena, Salobra River UPCB! 76098 ; BRAZIL. Mato Grosso do Sul: Bonito, Formoso River UPCB! 76099 ; BRAZIL. Mato Grosso do Sul: Bonito, Perdido River UPCB! 78231 ; BRAZIL. Mato Grosso do Sul: Bodoquena, Boca da Onça Stream UPCB! 78240 .

Adlafia decora is characterized mainly by valve and apices shape. Adlafia coringii is the most similar morphologic species, but present wider valves with more elliptic contour and coarser striae density ( Table 2) ( Metzeltin & Lange-Bertalot 1998). The smaller specimens of A. decora resemble Navicula brehmioides Hustedt (1952: 404) described from Cupari river, Brazil. However, none of the valves of the new species observed showed subrostrate apices and valve dimensions as small as N. brehmioides ( Hustedt 1961 ‒1966, Simonsen 1987) ( Table 2). This fact leads us to consider them distinct taxa.

Similarities were also found between A. decora and Navicula crispa Krasske (1951: 650) described to São Francisco river, Brazil ( Hustedt 1961 ‒1966, Lange-Bertalot et al. 1996). However, N. crispa has larger valves with undulate margins, and lower striae density ( Table 2).

Navicula brehmioides and N. crispa have been described based on a single valve and there are no other records of these species since then. Both taxa certainly belong to the Adlafia genus by the striation pattern, the reduced or absent central area, and raphe. Therefore, we propose the new combinations below:

Adlafia brehmioides (Hustedt) Tremarin & T. Ludwig comb. nov.

Basionym: Navicula brehmioides Hustedt, Botaniska Notiser , p. 404, fig. 118, 1952.

Adlafia crispa (Krasske) Tremarin & T. Ludwig comb. nov.

Basionym: Navicula crispa Krasske, Archiv für Hydrobiologie 44: 651, fig. 11, 1951.

Adlafia decora was only found in karstic environments from Midwest Brazil. The species occurred with Gomphonema lagenula Kützing (1844: 85) , Cymbella turgidula Grunow (in Schmidt et al. 1875: pl. 9), Diploneis ovalis (Hilse) Cleve (1891: 44) , Navicula hintzii Lange-Bertalot (1993: 114) and Denticula kuetzingii Grunow (1862: 546) in the type material.

Adlafia drouetiana (Patrick) Metzeltin & Lange-Bertalot in Lange-Bertalot, Iconographia Diatomologica 5: 21, pl. 86, fig. 14‒19, pl. 186, fig. 6, 1998 emend. Tremarin, Tusset & T. Ludwig

Basionym: Navicula drouetiana Patrick, Boletim do Museu Nacional de Rio de Janeiro 2: 6, fig. 9, 1944.

Figs 19‒37

Valves linear-lanceolate, often with slightly triundulate margins, 14.7‒20.3 μm long, 4.0‒5.4 μm wide (n=31), capitate to subcapitate apices, shoulders developed. Raphe sternum linear and narrow. Central area absent. 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, 22‒28 in 10 μm, radiate becoming abruptly convergent near the apices, running continuously to the mantle; presence of shortened striae between long in the median region of valve. Valve apex with two rows of small areolae on the mantle. Areolae rounded to rounded-squared, 30‒50 in 10 μm, externally occluded by hymenes, inconspicuous at light microscopy.

Occurrence in samples: UPCB 47495, 47497, 47498, 47499, 47509, 47512, 47513, 47514, 47518, 47519, 47521, 47523, 47523, 47524, 47525, 73002, 72972, 72975, 72997, 72994.

Adlafia drouetiana was proposed by Patrick (1944:6, as Navicula drouetiana ) based on samples collected at Quadros lagoon, a coastal environment from Southern Brazil. The species is quite common in several localities of the country, but few studies present description or valve dimensions ( Table 3). Metzeltin & Lange-Bertalot (1998) present the only SEM image of this species. The lack of detailed study showing the morphological and ultrastructural features of A. drouetiana have hindered the recognition of the species and its comparison with similar taxa. In southern Brazil, the species has been misidentified as Navicula subtillisima Cleve (1891: 37) and as Navicula sp. by Rodrigues (1991), and as Adlafia bryophila ( Lobo et al. 2004, fig. 25, Schneck et al. 2008, fig. 5d). Patrick (1944) comments that A. drouetiana resembles Navicula subtilissima in the valve contour, but differs by having coarser striae, alternately longer and shorter in the median region of valve.

Adlafia drouetiana is similar to A. bryophila in the valve length and apices shape, but the latter species has narrower valves with straight or slightly convex margins, besides higher density of striae and areolae ( Table 3) ( Hustedt 1961 ‒1966, Lange-Bertalot 2001, Le Cohu & Azémar 2010, Hofmann et al. 2013).

In this study, we illustrate the wide variation in valve outline (LM) ( Figs 19–32 ) and the delicate valve morphology by scanning electron microscopy. We also expanded the valve dimensions range of A. drouetiana ( Table 3).

Adlafia minuscula (Grunow) var. minuscula Lange-Bertalot in Lange-Bertalot & Genkal, Iconographia Diatomologica 6: 32, pl. 22, figs 9‒11, 1999.

Basionym: Navicula minuscula Grunow in Van Heurck, Synopsis des Diatomées de Belgique, pl. 14, fig. 3, 1880.

Figs 38‒56

Valves elliptic-lanceolate with cuneate to cuneate-subrostrate apices, 9.2–15.5 μm long, 3.6–4.5 μm wide (n=25). Raphe sternum linear and narrow. Central area absent. Raphe filiform, distal raphe ends unilaterally bent; proximal raphe ends expanded in pore and slightly curved. Striae uniseriate, 32‒37 in 10 μm, radiate to abruptly convergent near the apices, running continuously to the mantle, inconspicuous at light microscopy; presence of one or three shortened striae in the median region of valve. Valve apex with two rows of small areolae on the mantle. Areolae rounded, 56‒61 in 10 μm, externally occluded by hymenes.

Occurrence in sample: UPCB 78234.

Morphological and metric variation of the observed valves agree with Adlafia minuscula var. minuscula in Krammer & Lange-Bertalot (1986), Lange-Bertalot (2001) and Kulikovskiy et al. (2010). Previous records of the taxon from Brazil (cited in Tremarin et al. 2009; Silva et al. 2011) correspond to Adlafia muscora . Thus, this is the first record of A. minuscula to Brazil.

Adlafia muscora (Kociolek & Reviers) Moser, Lange-Bertalot & Metzeltin, Bibliotheca Diatomologica 38: 89, 1998.

Basionym: Navicula muscora Kociolek & Reviers, Cryptogamie Algologie 17(3): 201, 1996.

Figs 57‒70

Valves linear-elliptic to elliptic-lanceolate with rostrate to subcapitate apices, 10.0‒17.6 μm in long, 3.1‒4.6 μm in wide (n=40). Raphe sternum linear and narrow. Central area reduced or absent. 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, 28‒32 in 10 μm, rarely biseriate, curve-radiate to abruptly convergent near the apices, running continuously to the mantle; presence of one or more shortened striae in the median region of valve. Valve apex with two rows of small areolae on the mantle. Areolae rounded, 50‒62 in 10 μm, externally occluded by hymenes, inconspicuous at light microscopy.

Occurrence in samples: UPCB 47500, 47510, 47512, 47515, 47524, 76099, 76100, 78231.

Adlafia muscora was proposed based on material from New Caledonia ( Lange-Bertalot 2001). The species is the typus generis of Adlafia , however little is known about its morphological variation ( Table 4). We found a large population of A. muscora in the analyzed material ( Table 4). They look very similar to Manguin’s specimens, as represented by Moser et al. (1998), especially in plate 6, figures 3‒4 ( Table 4). The valves from the studied Brazilian material present higher striae density, proximal raphe ends not expanded in pore and central ends more widely separated than those recorded by Moser et al. (1998, pl. 26, figs 1, 4, 6, 7). Whereas the distinction of Adlafia taxa is carried out based on the valve outline, apices and dimensions, we prefer to identify these populations as A. muscora .

Lange-Bertalot (2001) commented about the possible conspecificity between A. muscora and A. bryophila . Both species seem to differ only by valve outline, the more convex margins are uncommon for A. bryophila ( Table 4), and by geographical distribution ( Lange-Bertalot 2001).

Adlafia submuscora differs from A. muscora by the lanceolate valves with 2.5‒3.1 μm wide and by the higher striae density (40‒45 in 10 μm) ( Van der Vijver et al. 2013). Adlafia muscora also resembles A. pseudobaicalensis Kulikovskiy & Lange-Bertalot (in Kulikovskiy et al. 2012: 37), but this latter species has smaller valves (length: 11.5‒14.7 μm, width: 2.7‒3.3 μm), and subrostrate to bluntly rounded apices ( Kulikovskiy et al. 2012).

In Brazil, A. muscora has been recorded before in Negro River, and as A. minuscula in Guaraguaçu River ( Tremarin et al. 2009).

Figures

FIGURES 1‒15. Adlafia decora sp. nov. Figs 1‒9. Valve view, LM. Scale bar = 10 μm. Figs 7, 8. Holotype. Fig. 10. Detail of areolae occluded by hymenes, TEM. Scale bar = 0.5 μm. Fig. 11. Valve striation pattern, TEM. Scale bar = 2.5 μm. Figs 12, 13. Median region of valve showing the proximal raphe ends in external view, SEM. Scale bars = 2 μm. Figs 14, 15. Detail of valve apex showing the distal raphe end in external view, SEM. Scale bars = 1 μm.

FIGURES 16‒18. Adlafia decora sp. nov. Fig. 16. Internal valve view, SEM. Scale bar = 2 μm. Fig. 17. Internal view of median region of valve detailing the striation pattern and proximal raphe ends, SEM. Scale bar = 2 μm. Fig. 18. Internal view of valve apex showing the helictoglossa and terminal nodule, SEM. Scale bar = 1 μm.

FIGURES 19‒37. Adlafia drouetiana. Figs 19‒32. Valve view, LM. Scale bar = 10 μm. Figs 33, 34. External valve view, SEM. Scale bars = 2 and 2.5 μm, respectively. Fig. 35. Median region of valve showing the striation pattern and proximal raphe ends, SEM. Scale bar = 1 μm. Figs 36, 37. External view of valve apices and distal raphe end, SEM. Scale bars = 1 μm.

FIGURES 38‒56. Adlafia minuscula var. minuscula. Figs 38‒52. Valve view, LM. Scale bar = 10 μm. Fig. 53. Median region of valve showing the proximal raphe ends and external view of striae, SEM. Scale bar = 1 μm. Fig. 54. Distal raphe end in external view, SEM. Scale bars = 1 μm. Fig. 55. Valve striation pattern, TEM. Scale bar = 2.0 μm. Fig. 56. Detail of areolae occluded by hymenes, TEM. Scale bar = 0.5 μm.

FIGURES 57‒70. Adlafia muscora. Figs 57‒65. Valve view, LM. Scale bar = 10 μm. Fig. 66. Detail of areolae occluded by hymenes, TEM. Scale bar = 250 nm. Fig. 67. Valve striation pattern, TEM. Scale bar = 2.5 μm. Fig. 68. External valve view showing the proximal and distal raphe ends, SEM. Scale bar = 2 μm. Fig. 69. Internal view of median region of valve showing the proximal raphe ends, SEM. Scale bar = 1 μm. Fig. 70. Internal view of valve apex showing a small helictoglossa and distal raphe end, SEM. Scale bar = 1 μm.