Synteny analysis is a useful tool to study the evolutionary relationships between genes. In this study, we carried out the synteny analysis using the Genomicus in some fishes and found that the synteny relationship near the jacalin locus existed in some fish's genomes. The synteny analysis of jacalins from D. rerio and P. formosa were taken as examples to model more detailed genome evolution among different fishes, respectively. The results indicated that the detected jacalin genes presented conserved synteny in some fishes, suggesting the remained partially conservation in these regions since their last common ancestor ( Fig. 4). Synteny analysis cannot only provide important observation about the evolutionary patterns of jacalins in these fishes, but also provide detailed genomic comparison among these species. In addition, we also found that some jacalin genes were distributed in clusters on the chromosome 7 and Scaffold K1520082.1 segments of D. rerio and P. formosa, respectively, implying that the expansion of the jacalin gene family is partly due to tandem duplication in some fishes ( Fig. 4). Tandem duplication is one of the most important gene duplication mechanisms in eukaryotes [53]. In the process of biological evolution, some tandem duplicated genes maintain the similar function; while others followed by divergence frequently generate novel functions, and such genetic novelty could increase organismic complexity and adaptation processes [54]. In this study, some tandem jacalin genes found in D. rerio and P. formosa can accumulate or diversify the immune responses to different stimuli, which itself is a kind of biological adaptation to the environment.