Species Description: Within the large and unwieldy genus Cocconeis is a small group of species that are differentiated by a sigmoid raphe on the raphid valve, and with a straight or sigmoid sternum on the rapheless valve. In this case, only raphid valves have been seen, suggesting that it is rare in the IRL system.
Valves are broadly oval with a hyaline rim surrounding the margin (Fig. 1, light microscope brightfield). The raphe valve (Fig. 2; SEM of valve with fractured pericentral area) has a clearly sigmoid raphe with small hyaline areas surrounding the raphe endings, a central area almost lacking, with finely punctate, strongly radial areolae. Witkowski et al. (2000), citing the original description, gives 13-24µm long, 8-17µ wide, with 23-28 transapical striae in 10µm as morphometric characteristics. The specimen in Fig. 2 is 22.2 X 18.3µm, with 27 striae in 10µm.
The sparse literature records indicate that C. krammeri is coastal, epiphytic, and widely distributed in warmer waters. It was noted once in the IRL south of the Sebastian Inlet. The examples identified elsewhere as C. krammeri from Florida Bay may represent a novel species.
Witkowski A, Lange-Bertalot H, Metzeltin D. 2000. Diatom Flora of Marine Coasts I. Iconographia Diatomologica 7: 1-925.