Small open reading frames (sORFs), which encode peptides are emerging as an important class of genes with roles in development, prey capture and defence against pathogens. Studying sORFs has proven challenging as they are difficult to predict in genome sequences without functional data. One class of sORFs that have been studied in some detail are small peptide toxins (SPTs). Our lab has been examining the evolution and expression of SPTs in cnidarians. We have found that SPTs show high turnover rates and changes in gene family size even among closely related cnidarian species. This research has also detailed that SPT gene families show highly divergent expression profiles across different tissue types and play a role in allorecognition and aggression in sea anemones.