Fig. 3

Presence of the GLWamide (highlighted in blue), GRFamide (highlighted in yellow), and X₁PRX₂amide (where X₂ is either S, A, or G; highlighted in purple) peptides in the subclasses Ceriantharia, Hexacorallia, and Octocorallia and the classes Cubozoa, Scyphozoa, and Staurozoa. This figure has the same structure as Fig.1. It shows that the three peptide families are present in all mentioned classes and subclasses, except for the Octocorallia that lack the GLWamides. Nevertheless, it can be concluded that the three peptide families originated in the common cnidarian ancestor. The other neuropeptide families identified in this paper (Additional files 4, 5, 6, 7, 8, 9, and 10) are either class-, subclass-, or order-specific and are no good candidate for being primordial neuropeptides