Staurosira construens Ehrenberg
Cells in girdle view are rectangular and joined in linear colonies (Fig. 1, adapted from Hustedt 1930). The cells are joined together by short linking spines around the margin (Fig. 2, SEM of valve exterior). Colonies are planktonic or attached to the substrate by a mucilaginous pad secreted by apical pore fields (Fig. 2). Valves are cruciform, with an inflated center, and with bluntly rounded, slightly rostrate or subcapitate apices (Fig. 3, SEM of valve interior). The striae are radiate and slightly curved on either side of a broad sternum. The size range is 6-15µm long, 5-9µm wide, with 14-16 striae in 10µm according to Morales (2010); but 7-25µm long and 5-12µm wide with 14-8 striae in 10µm according to Patrick & Reimer (1966)
This is a freshwater species, found throughout the U.S. and the world, apparently preferring slightly alkaline environments (Patrick & Reimer 1966). The valve shape is polymorphic, from ovoid to lanceolate (Morales 2001, 2010), and has led to a number of varieties that may or may not have separate taxonomic identities; some have been transferred to other genera (Williams & Round 1987). Although it is subject to misidentification with light microscopy, it was confirmed as adventitious and rare in the IRL, seen in the St. Lucie River and the San Sebastian River mouths, and in the Banana River.
Hustedt F. 1930. Bacillariophyta (Diatomae). Süsswasser-Flora Mitteleuropas 10: 1- 466.
Morales EA. 2001. Morphological studies in selected fragilarioid diatoms (Bacillariophyceae) from Connecticut waters (USA). Proc Acad Nat Sci Philadelphia 151: 105-120.
Morales E. 2010. Staurosira construens. In: Diatoms of the United States. Retrieved July 16, 2015 from http://westerndiatoms.colorado.edu/taxa/species/staurosira_construens.
Patrick R, Reimer CW. 1966. The diatoms of the United States. Monogr Acad Nat Sci Philadelphia 13: 1-688.
Williams DM, Round FE. 1987. Revision of the genus Fragilaria. Diat Res 2: 267-288.