Septins are upregulated in colonial cells. (a) Unlike the average for all genes in the genome, septins, the septin-associated Polo and Aurora kinases, and Anillin are each significantly upregulated in colonial cells. FPKM, fragments per kilobase per million reads. Error bars are standard error: *P < 0.05, **P < 0.01. (b) Conserved and similar residues shared between S. rosetta septins and human septins (red) on monomer surfaces predicted to interact in human septin filaments  suggest that S. rosetta septins also form filaments. (c) Septins regulate cytokinesis in metazoans and fungi [14, 16], providing a potential connection to the narrow intercellular bridges (arrowhead), likely formed through incomplete cytokinesis, that connect neighboring cells in S. rosetta colonies.