Adlafia umiujaqensis Alibert & Hamilton & Pienitz & Antoniades 2023, sp. nov.

Adlafia umiujaqensis sp. nov. (Figs 10 S-AG; 12 A-F)

HOLOTYPE. — Canada. Québec, Lake 22AA, 56°33’24”N, 76°28’47”W, 128 m a.s.l., 22.VIII.2015, D. Antoniades (microscope slide designated as the holotype, holo-, CANA [CANA 129481]).

ISOTYPE. — Canada. Québec, Lake 22AA, 56°33’24”N, 76°28’47”W, 128 m a.s.l., 22.VIII.2015, D. Antoniades (iso-, ANSP [ANSP-GC68068]).

TYPE LOCALITY. — Canada. Québec, Lake 22AA, 56°33’24”N, 76°28’47”W, 128 m a.s.l.

ETYMOLOGY. — The epithet ‘umiujaqensis’ is named for the Inuit village nearest to the lake where the species was observed.

ECOLOGY AND DISTRIBUTION. — Adlafia umiujaqensis sp. nov. was found in three lakes of this study, CEN-O, 22-Z and 22-AA. While it represented 7.1% of the diatom assemblage in lake 22-AA, it reached only 1.9% and 0.6% relative abundance, respectively, in lakes 22-Z and CEN-O. The low number of occurrences obscured any potential autecological patterns of this species (Appendices 1; 2; 3).

REGISTRATION. — http://phycobank.org/103919.

Frustules rectangular and narrow. Valves linear-elliptic to elliptic with rounded ends. Valve dimensions (n= 25): length 8-18.5 µm, width 4-4.5 µm and 30-33 striae in 10 µm. External valve face flat. Axial area weakly curved to linear and narrow. Central area round to elliptic, with 3-4 marginal striae between proximal raphe ends. Raphe linear to curved, with no kink-like irregularity halfway between mid-valve and apex (Fig. 12A, B). Externally, central raphe fissures narrow and not distinguished.Terminal raphe fissures curved down onto upper region of mantle (Fig. 12D). Ridged groove present adjacent to terminal raphe from valve face to upper mantle. Internally, raphe on evident sternum, straight, with no kink-like irregularity. Proximal raphe deflected strongly to one side of central nodule; nodule sometimes with surface depression or with an isolated pore (Fig. 12E). Terminal fissures end on small elevated helictoglossae, isolated from apex mantle. Internal hyaline area of apex more developed on secondary side. Striae more or less straight, weakly radiate at mid-valve to parallel or weakly convergent at apices and continuous from valve face to mantle. Voigt faults on secondary side of valve 2/3 of distance between mid-valve and apex. Striae continuous around apices. Areolae round to rectangular, 5-7 per stria, 3-4 at apices. Areolae covered by a fine poroid velum with 8-11 circular rows of small pores.

This taxon has a simple linear-elliptic to elliptic shape that could be assigned to many small taxa across different genera. The surface volate covers of the areolae, curved terminal fissures externally, simple bent proximal fissure internally and small terminal helictoglossae distinguish this as an Adlafia taxon. Electron microscopic examination of specimens may at times be necessary to document this species. Navicula muralis Grunow (synonym: A. minuscula var. muralis (Grunow) Lange-Bertalot) has a similar shape and the type material needs further study. Krammer & Lange-Bertalot (1986) present a representative TEM of a valve, under the name N. suchlandtii sensu lato, that matches our taxon.