FIGURE 10.

Molecular data for PACAP and PACAP receptors in metazoan. The peptide is represented by pentagons and the receptors by circles. The major events associated with gene family evolution are indicated. In lamprey, a adcyap1 peptide gene precursor and adcyap1R1/vipr1 receptor gene were isolated (Ng et al., 2012). In the tunicate Chelyosoma productum two PACAP precursors (pacap1 and pacap2) were isolated but their existence remains to be confirmed, as do the PACAP precursors in the related species, Ciona intestinalis and in the scheme are represented by a dashed lined pentagon (McRory and Sherwood, 1997; Cardoso et al., 2010). The cephalochordate PACAP-like peptides and receptors are represented by striped pentagons and circles, respectively, as they are hybrids of the vertebrate PACAP/GCG peptide and receptor system (On et al., 2015). The genome duplication events that occurred earlier during the vertebrate radiation (1R, 2R) and the teleost specific (3R) are also annotated. The teleost peptide and receptor genes that resulted from 3R are represented by a and b. The major evolutionary events that explain existing molecular data are mapped with boxes with a flesh colored background. The main events associated with the appearance of the metazoan nervous system are also represented. The evolutionary relationship between the species represented was based on (Brunet and King, 2017). A cross (X) means not found in molecular databases (TSA and WGS) and likely to be absent in the species represented. ?- unknown existence.