Development of Vision and the Effect of Spectral Environment on the Cone Photoreceptor Mosaic of the Bluefin Killifish, Lucania Goodei.

Previous studies have shown the bluefin killifish, Lucania goodei, to be a useful model for investigating the role of environment in driving visual system evolution and plasticity (Fuller et al 2003, 2004, 2005). Environmental plasticity in opsin expression and cone frequency has been demonstrated, but it is unclear how this variation is reflected in the retina. In an effort to determine when and how this plasticity is manifest, the retinal development and the cone photoreceptor mosaic of this fish were examined. Immunolabeling, a behavioral assay, RT-PCR, and in situ hybridization were used to characterize visual system development of the bluefin killifish and to describe the cone photoreceptor mosaic of fish reared in clear and tea-stained water. This study reveals that at the time of hatching, bluefin killifish possess a functional visual system, with cone photoreceptors present in the square mosaic pattern that will be maintained in the adult. This study demonstrates that the observed plasticity in levels of opsin expression does not correspond to plasticity in the cone photoreceptor mosaic. Rather, plasticity may reside at the level of opsin gene transcription, protein translation, or turnover.