Gomphoneis hastata (Wislouch) Kociolek & Stoermer (1988: 100)

Kociolek, John P., Kulikovskiy, Maxim S. & Solak, Cüneyt N., 2013, The diatom genus Gomphoneis Cleve (Bacillariophyceae) from Lake Baikal, Russia, Phytotaxa 154 (1), pp. 1-37 : 4-5

Gomphoneis hastata (Wislouch) Kociolek & Stoermer (1988: 100) ( Figs 1–11 , 376–379)

Basionym: Gomphonema quadripunctatum var. hastata Wislouch (1924: 166)

Valves clavate, with headpole broadly rounded, footpole rounded. Length 27–62 µm, breadth 10–14 µm. Axial area straight, forming an orbicular central area that does not extend to the margin. Raphe lateral, with distinctly dilated external proximal raphe ends. External distal raphe ends extend nearly straight from the valve face to mantle, bisecting the distinct apical pore fields at footpole. Central area with 4–7 isolated stigmoids around the central area. Striae costate, individual areolae not visible with LM. Striae strongly radiate about the center of the valve, becoming parallel at both poles. Striae 13–15 in 10 µm. Prominent septa and pseudosepta at both poles.

In the SEM, the interior of G. hastata is dominated by the round central area ( Figs 376, 377). The central nodule is raised internally, and the elevated raphe terminates on the central nodule with proximal raphe ends that are recurved in the same direction ( Fig. 377). Around the base of the central nodule is located 4 isolated stigmoids. The stigmoids are occluded with siliceous coverings, around the base of each are small pores ( Fig. 377). Septa are associated with girdle bands at the poles ( Fig. 376). Externally, the central area has the stigmoids that occur in small, round depressions ( Fig. 378). Proximal raphe ends are elongated and dilated ( Fig. 378). The doubly-punctate striae extend from the mantle to the valve face, terminating next to the axial area with 1 or 2 areolae ( Figs. 378). Valvocopula has a single row of pores ( Fig. 379).

Observations:— The orbicular shape of the central area, not extending to the margin and the costate nature of the striae help to distinguish this species from other, similar species in the genus.

Figures

PLATE 1: LM. Figs 1–11: Gomphoneis hastata. Figs 12–17: G. parahastata sp. nov. Fig. 15 is of the holotype. Scale bar = 10 µm for all figures.