Expression pattern of genes is often associated with their functions in early development. We found all the zebrafish khdrbs genes were primarily expressed in the brain, while khdrbs1a was expressed in extra domains like the lateral line primordium, gonad primordium, and pronephric ducts. In adult fish, all the khdrbs also showed strong expression in the brain. Additionally, khdrbs1a, khdrbs1b, and khdrbs3 were found expressed abundantly in the gonads. These overlapping but distinct expression patterns may be a reflection of the sub-functionalization and/or neo-functionalization of gene duplicates after WGD. The split of bony fish from tetrapod happened around 450 million years ago. The fact that all the four khdrbs genes are retained in bony fish since the split may be because the KHDRBS proteins are signal-transduction related molecules (Putnam et al., 2008). Retained khdrbs genes may enrich their functions through changes in their expression patterns, which may then be co-opted in regulation network to generate physiological and morphological evolution.