Phylogenetic analysis of zebrafish, mouse, and human aGPCRs. The evolutionary history of the zebrafish aGPCRs relative to their mammalian orthologs was inferred using the Maximum Likelihood (ML) method based on the JTT matrix-based model using MEGA5. The bootstrap consensus tree inferred from 1000 replicates is shown as a representation of the possible evolutionary history of the 7TM domain of zebrafish (zf), mouse (m) and human (h) aGPCRs. The topology inferred from ML analysis was also supported by Markov Chain Monte Carlo (MCMC) analysis, using the Bayesian approach implemented in MrBayes version 3.2. Blue circles with solid red outlines were shown for the nodes that had more than 90% confidence support from ML bootstrap analysis and Bayesian posterior probabilities (PP). White circles with solid red outlines denote nodes that had 90% PP support but less than 90% bootstrap support. Supports are only shown for nodes recovered by both ML and Bayesian inference, with BPP > 0.9 and bootstrap > 50%. Zebrafish gene identifiers/names are highlighted in brown text. It must be noted here that the topology supported by ML and Bayesian methods for Group 1 and Group VIII slightly differ from each other, although both methods recovered the overall clusters of Group 1 and Group VIII. The variations are that zfLphn1b and zfGpr56 are placed basal to their respective groups in the ML tree, however, with a relatively low bootstrap support. Nevertheless, the topology showing the homologous relationships of zfLphn1b and zfGpr56 with their mammalian counterparts are supported by Bayesian topology with PP > 90% (see Additional file 2).