As described above, some fishes, such as Danio rerio and Gadus morhua, have 11 jacalin genes, while, other fishes (Takifugu rubripes and Xiphophorus maculates) retain no any jacalins. This implied that the number of jacalin genes have been greatly changed in different fish species in evolution. To understand how the jacalin genes have evolved in the fishes, we also estimated the maximum number of gained and lost jacalin genes in 11 fish species. We only found one jacalin gene in Gasterosteus aculeatus and Tetraodon nigroviridis, respectively. Oreochromis niloticus and Astyanax mexicanus have two jacalin genes for each species. While, the number of jacalin gene family in Oryzias latipes exhibits 8 paralogous sequences. Reconciliation of gene trees with the species tree implied that there was one ancestral jacalin gene in the most recent common ancestor (MRCA) of these fishes ( Fig. 1). And then, 6 jacalin genes were got before the fishes were diverged. We also found that the number of jacalins showed a continuous decline for most clades in evolution. Some species, such as Takifugu rubripes and Xiphophorus maculates, lost all of the jacalin genes. In addition, the number of jacalin genes decreased approximately 28 and 71% since the divergence of these fishes from their MRCA in Lepisosteus oculatus and Oreochromis niloticus, respectively. For other fishes, such as Danio rerio and Gadus morhua, some jacalin genes have been obtained after the origin of these species.