Gomphonema lagenula

Valves are asymmetric, with a slightly narrow lanceolate to elliptic valve margin. Both apices, headpole and footpole, are distinctly capitate. In the studied population, the footpole is consistently more protracted than the headpole, creating the appearance of being somewhat “bent.” The axial area is linear and narrow. The raphe is straight and filiform. The proximal and distal raphe ends are simple. In the central area, striae are parallel to slightly radiate. The central area is asymmetric. In the central valve, a longer stria is near a punctate stigmoid. On the opposite side of the stigmoid, a short stria is present. Areolae not visible with LM.

Gomphonema lagenula is similar to G. parvulum, and many floras treat G. lagenula as a variety of G. parvulum. Gene sequences of these taxa, however, show that they are distinct from one another. The morphologic feature of capitate to rostrate apices has been considered a distinguishing feature of G. lagenula (Abarca et al. 2014), feature also noted by Patrick and Reimer (1966).

Thus, this taxon could be considered as a distinct species, or as a member of the G. parvulum species complex. The question is up to each practitioner, to determine how they wish to treat this taxon for their particular study goals. Gomphonema lagenula is included as both a species page and as part of the G. parvulum species complex on this website.