Fig. 1

Schematic drawing showing the phylogenetic positions of the subclasses Ceriantharia, Hexacorallia and Octocorallia (class Anthozoa), the classes Hydrozoa, Cubozoa, Scyphozoa, Staurozoa, and the subphylum Endocnidozoa. Cnidarians are a sister group to Bilateria. The figure also shows that X₁PRX₂amide (highlighted in purple), GRFamide (highlighted in yellow), and GLWamide peptides (highlighted in blue) are present in all tested Ceriantharia, Hexacorallia, Cubozoa, Scyphozoa, and Staurozoa species. However, the Octocorallia have apparently lost their GLWamide genes [52]. In the current paper, we are investigating the presence of these three neuropeptide families in Hydrozoa and Endocnidozoa. We found that hydrozoans contain all three neuropeptide families (X₁PRX₂amides, GRFamides, GLWamides). The endocnidozoans contain GRFamides and GLWamides, but have apparently lost their X₁PRX₂amide genes. In this figure we have presented the Endcnidozoa as two sister taxa, the Polypodiozoa and Myxozoa, but their mutual phylogenetic relationship is unclear