The ontogeny of the retina of Chinese sturgeon (Acipenser sinensis)

Vision is an important cue in larval survival to capture prey. Therefore, we examined the development of the retina structure in the Chinese sturgeon ( Acipenser sinensis), the density of single cones, the ganglion cells and the nuclei of the outer nuclear layer of newly hatched larvae, covering different developmental stages ranging from hatching ( 13.3-13.6 mm TL) to 180 days post-hatching ( dph) ( 290.7-301.6 mm TL). At hatching, larvae exhibited an undifferentiated retina. The retina at 3 dph ( 16.0-16.9 mm TL) had single cones ( SC) at high density. The rods appeared at 9 dph ( 24.8-25.5 mm TL), and it is assumed that at this time the visual system was developed completely. However, the larvae showed apparent retinomotor responses not before 25 dph ( 42.7-44.1 mm TL). The density of single cones ( SC) and ganglion cells ( G) decreased with proceeding development, while the density of the rods ( R) gradually increased. The ratio of nuclei of the outer nuclear layer to ganglion cells ( ON/G) per 100 mu m m increased during development, and so did the ratio of nuclei of the outer nuclear layer to single cones ( ON/SC). The investigation showed that the structure of the retina changes rapidly from 9 to 17 dph, and many become fully functional at 25 dph when retinomotor responses occur. This is the transitional period of the ontogenetic development of the visual system. These changes in the retina of the Chinese sturgeon are adaptive to their feeding requirements, and co-inciding with the ecological shift from surface ( pelagic) to benthic feeding habitats.