Adlafia bryophila (J.B.Petersen) Lange-Bertalot

Alibert, Marie, Hamilton, Paul B., Pienitz, Reinhard & Antoniades, Dermot, 2023, Small naviculoid species of Kobayasiella Lange-Bertalot, Adlafia Moser, Lange-Bertalot & Metzeltin, Nupela Vyverman & Compère and Sellaphora Mereschowsky from Tursujuq National Park, Hudson Bay region, Nunavik, Québec, Cryptogamie, Algologie 20 (9), pp. 157-187 : 171-174

Adlafia bryophila (J.B.Petersen) Lange-Bertalot

( Figs 10 A-R; 11 A-F)

Bibliotheca Diatomologica 38: 89 ( Moser et al. 1998). — Navicula bryophila J.B.Petersen , The Botany of Iceland 2: 388 ( Petersen 1928).

ECOLOGY AND DISTRIBUTION. — Adlafia bryophila was commonly observed inTursujuq National Park, found in 23 lakes.It was generally present in low relative abundances, with a mean of 0.5% and maximum of 2.7%. No distributional pattern was found in relation to general environmental conditions, but it appears to be a circumneutral species ( Appendix 3 ). Moreover, its distribution may be affected by Mg and dissolved inorganic carbon (DIC) concentrations (Appendices 4; 5). This taxon has been identified from the circumpolar Arctic region.

DESCRIPTION

The frustules are rectangular and narrow in girdle view. The valves exhibit a linear to linear-lanceolate shape with rostrate ends. Based on a sample size of 28, the valve dimensions range from a length of 11.5 to 19 µm and a width of 3 to 4 µm. The stria number ranges from 28 to 30 in 10 µm. Externally, the valve face is flat. The axial area is weakly curved, lanceolate, and narrow. In LM, the axial area is almost indistinct. The central area is large, round to elliptic, favouring one side, and it possesses three to four marginal striae ( Fig. 11C ). The raphe is linear, without any kink-like irregularity halfway between the mid-valve and apex ( Fig. 11A ). Externally, the central raphe fissures are linearly expanded with small pores slightly deflecting to one side. The terminal raphe fissures are curved and extend down onto the upper region of the mantle ( Fig. 11E ). Adjacent to the terminal raphe, there is a ridged groove that runs from the valve face to the upper mantle. Internally, the raphe is located on an elevated sternum and appears straight, without any kink-like irregularity. The proximal raphe fissures are deflected to the same side ( Fig. 11D ). The terminal fissures end on small elevated helictoglossae, isolated from the apex mantle ( Fig. 11F ). The striae are radiate at the mid-valve and become convergent at the apices, and they are continuous from the valve face to the mantle. The striae are arched close to the mid-valve, and from the Voigt fault to the apex, they become straight. Voigt faults on the secondary side of the valve are located at approximately 2/3 of the distance between the mid-valve and apex. The striae are continuous around the apices. Areolae are round to rectangular, with five to six per stria and two to four at the apices ( Fig. 11E, F ). Externally, the areolae are covered with a fine poroid velum that exhibits eight to ten circular rows of small pores. Internally, the multiseriate pored velum is positioned between thickened virgae. Adlafia bryophila was first identified from Iceland by J.B. Petersen based on a small linear to linear-elliptic valve with distinct rostrate apices and fine striae.

The specimens from Tursujuq National Park are similar in size shape and form, but with a lower stria density (28- 30 in 10 µm versus c. 35 in 10 µm for Navicula bryophila (synonym: A. bryophila )). Petersen (1928) illustrated a line drawing with visible striae which would not be possible in the LM without specialized optics with 35 striae in 10 µm, so the stria density is also possibly less than 30 in 10 µm. In SEM, our specimens show the terminal raphe ends curving down onto the mantle, while the areolae have surface volate covers with fine poroids, which allows identification of this taxon as belonging to Adlafia . We appear to have two forms, one with a smaller central area and a second, more abundant form with a larger central area. There are a number of taxa with this general valve shape, including A. brockmanii (Hustedt) K.Bruder , A. coringii Metzeltin & Lange-Bertalot , A. drouetiana (Patrick) Metzeltin & Lange-Bertalot , A. muscora (Kociolek & Reviers) Moser, Lange-Bertalot & Metzeltin , A. parabryophila (Lange-Bertalot) Moser, Lange-Bertalot & Metzeltin , A. pseudobaicalensis Kulikovskiy & Lange-Bertalot , and A. suchlandtii (Hustedt) Moser, Lange-Bertalot & Metzeltin. Adlafia coringii and A. drouetiana are larger and broader (more elliptic), while A. parabryophila is constricted with a lower stria density. Adlafia pseudobaicalensis and A. suchlandtii are more elliptic with weakly rostrate apices. The differentiation of A. bryophila from A. brockmannii and A. muscora is less clear and needs further study, although the central area of A. brockmannii is a full fascia, and A. muscora has less attenuated rostrate ends.

Figures

FIG. 10. — Light micrograph diminution series of Adlafia Moser,Lange-Bertalot & Metzeltin,Sellaphora Mereschkowski and Nupela Vyverman & Compère species: A-R, Adlafia bryophila (J.B.Petersen) Lange-Bertalot; S-AG, Adlafia umiujaqensis sp. nov.; AH-AT, Adlafia ossiformis sp. nov.; AU-BJ, Sellaphora vincentiana sp. nov.; BK-BY, Nupela tenuicephala (Hustedt) Lange-Bertalot. Scale bar: 10 µm.

FIG. 11. — SEM images of Adlafia bryophila (J.B.Petersen) Lange-Bertalot: A, external view of the complete valve; B, internal view of the complete valve; C, external view of the central area showing the multiseriate poroid covers over the areolae; D, internal view of the central area showing hooked proximal fissures to one side. Copula with one row of large occluded pores; E, external view of the apex with a curved fissure onto the mantle. A curved ridge follows the fissure; F, internal view of the apex with a small elevated helictoglossa. Areolae are continuous around the apex. Scale bars: A, B, 5 µm; C, D, 2 µm; E, F, 1 µm.

APPENDIX 3. — Relative abundance of species as a function of pH values.