Objective To observe the effects of Crumbs (Crb) proteins on different types ofzebrafish photoreceptors.Methods The retinal cell population dynamics of adult wild-type zebrafish and Tg (RH22:Crb2b-sfEX/RH2-2:GFP)pt108b transgenic zebrafish (called pt108b zebrafish for short) were evaluated by monitoring the densities of three categories of retinal photoreceptors (rod cells,UV cone cells and RGB cone cells) in different retinal regions,which were visualized by Feulgen nuclear staining histology technique.Results The wild-type zebrafish retinal photoreceptor cell densities are generally higher in the central region than the peripheral regions.Compared with wild-type zebrafish,pt108b zebrafish had much less RGB cone cells at the top of outer nuclear layer,and no RGB cone ceils at the central and intermediate regions of retina.While pt108b zebrafish had normal density of UV cone cells at the top of rods and the bottom of outer limiting membrane,they had much higher density of rods.Conclusions Crb proteins may affect the zebrafish retinal cell densities of different photoreceptor types.