Gomphonella fogedii

Valves clavate, with broadly rounded headpole. Four isolated stigmoids are present in line with most proximal full length striae. One or two shortened striae are present at each margin at the valve center. Striae are weakly radiate throughout, more radiate at the footpole and nearly parallel at the headpole. The raphe is straight.

This taxon is a member of the quadra-stigmoid gomphonemoids, a difficult and presently confusing group of closely related species. As with many diatom species complexes, the group is deserving of more work because 1) the type specimens or material of many taxa in the group are not available; 2) Taxa that were described by early authors were not adequately circumscribed. For example, the original description of Gomphonema olivaceoides var. densestriata appears to be based on a single valve, with a stria count of 18 in 10 µm; 3) This variety is distinguished based on stria count, and it is likely that the population has a far wider range in stria density; 4) In North America, particularly in the Northwest, there are a number of undescribed taxa in this group. The work of Bahls (personal communication, 2017) has uncovered a great deal of variability in this group.

This taxon should be compared closely with Gomphoneis pseudo-okunoi, which has a narrow range in stria density (13-15 in 10 µm).

Levkov and Williams (2011) described a diatom with a similar sounding name, Gomphonema densistriatum, from Lake Ohrid, Macedonia. That taxon, however, is heterotypic and bears little resemblance to Gomphonella fogedii.