Kobayasiella tursujuqensis Alibert & Hamilton & Pienitz & Antoniades 2023, sp. nov.

Kobayasiella tursujuqensis sp. nov. (Figs 3 A-J; 7 A-F)

HOLOTYPE. — Canada. Québec, Lake 16-H, 56°15’10”N, 74°4’23”W, 256 m a.s.l., 16.VIII.2015, D. Antoniades (microscope slide designated as the holotype, holo-, CANA [CANA 129458]).

ISOTYPE. — Canada. Québec, Lake 16-H, 56°15’10”N, 74°4’23”W, 256 m a.s.l., 16.VIII.2015, D. Antoniades (iso-, ANSP [ANSP-GC68067]).

TYPE LOCALITY. — Canada. Québec, Lake 16-H, 56°15’10”N, 74°4’23”W, 256 m a.s.l.

ETYMOLOGY. —The epithet ‘tursujuqensis’ is named in recognition of Tursujuq National Park.

ECOLOGY AND DISTRIBUTION. — Kobayasiella tursujuqensis sp. nov. was found in eight lakes. The species was present in low relative abundances (mean 0.3%) with a maximum of 5.5% in Lake 16-H. No environmental distribution pattern can be distinguished related to water chemistry. However, this species seems to be more abundant in acidic waters (Appendix 3), with a pH optimum of 5.87, and in low specific conductivities (Appendix 1).

REGISTRATION. — http://phycobank.org/103918.

Frustules rectangular and narrow in girdle view. Valves small, linear to linear-lanceolate with subrostrate to subcapitate apices. Valve dimensions (n =12): length 17-19 µm, width 3-4 µm and striae 42-48 in 10 µm (SEM measurement).External valve face flat. Axial area linear to lanceolate and narrow. Central area absent, with 7-8 striae orientated between proximal raphe fissures. Raphe linear, with kink-like irregularity halfway between mid-valve and apex (Fig. 7A); externally, central raphe fissures widely spaced, linear expanded with rounded ends. Terminal raphe fissures curved,deflected,not hooked,to secondary side of valve opening with an external elliptic to funnel-like depression (Fig. 7D). Internally, raphe on a thickened sternum, straight, with no kink-like regularity. Proximal raphe fissures T-shaped and elevated on a central nodule (Fig.7F).Terminal fissures end on elongated helictoglossae, isolated from apex mantle (Fig.7E). Striae strongly radiate at mid-valve to strongly convergent at apices.A thickened valve margin separates valve face striae from mantle striae. From mid-valve to Voigt fault striae change from straight to flexed halfway between axial area and valve margin; from Voigt fault to apex striae change from flexed to straight. Mantle striae separated by thick hyaline ridge at valve face/mantle junction and not continuous around apices. Externally, striae sometimes expanded around central area, occluded with4-8 rows of pores.Distinct Voigt faults on primary and secondary side of valve at 2/3 distance between mid-valve to apex (Fig. 7D). Internally, multiseriate pores positioned between thickened virgae. This taxon is similar in valve outline to K. parasubtilissima but smaller, the apices are rostrate to subcapitate (not capitate as in K. parasubtilissima), the central raphe ends are closer together, the external terminal fissures are more hook-like with a larger grooved opening on the external face, and the internal virgae do not have silica projections into the striae. Finally, in some specimens the width of individual striae may vary, even forming bulbous expansions (Fig. 6C) around the central area. Other less similar unknown taxa for comparison include Kobayasiella species Nr 94/6-9 (?nov.) and Kobayasiella species Nr 94/6-9 (?nov.) from the Krasske material collected from Brazil (Metzeltin & Lange-Bertalot 1998). The current described size range of 17-19 µm is likely not the complete range, which is yet to be determined.