GRAFS and Rhodopsin phylogenetic trees. (A) Overall topological view of the combined S.mansoni and S. mediterranea GPCR complements. Maximum parsimony analysis (bootstrap value = 100) was carried out using putative full-length non-Rhodopsin GPCRs and a subset of full-length Rhodopsin-like GPCRs. In addition to the phylogenetic clustering of sequences into the primary GRAFS families, this analysis reveals the presence of two distinct phylum-specific groupings: PROF1 and PARF1. * Sequence family is present in S. mediterranea. ** Sequence family is present in both S. mansoni and S. mediterranea. (B) Neighbor-joining tree of flatworm Rhodopsin-like GPCRs. To maximize the number of sequences included in this analysis, a sequence block housing TM domains I-IV was extracted from the overall alignment. This allowed for inclusion of 312 Rhodopsin-like sequences: 90 S. mansoni and 224 S. mediterranea receptors (bootstrap value = 200). The amine, opsin, peptide, melatonin, and PROF1 groupings are highlighted. Branches terminating in S. mansoni receptors are shown in green, and branches terminating in S. mediterranea receptors are shown in blue.