Structure de la rétine chez quelques téléostéens marins du plateau continental

A detailed study of retinal structure in 20 pelagic and demersal species of fish indicates that valid correlations exist among the photic environment, activity of the fish, and its visual apparatus. Generally, the relative abundance of rods is inversely proportional to that of the cones. This relationship exists inter-specifically in the same retinal region and intra-specifically in different parts of the same retina. The topographical specialization of cones, or formation of a retinal area, is high in active pelagic species (Clupea, Alosa), less in sluggish demersal fish, and absent in the shore fish Tautogolabrus where a specific ocular behavior compensates. The resolving power of the retinal area is high in pelagic and shore fish, but is lower in demersal species. The distribution of the cone types within a retina suggests that photic sensitivity increases from single to quadruple cones. Cone arrangements are more refined in active species likely to detect fast-moving preys. Inter- and intra-specifically, the development of the inner retinal layers parallels that of the cones. The functional importance of the resolving power appears to rely heavily on the extent of summation at the bipolar and ganglion cell layer level. The cone/rod and single/double cone ratios are proportional to the abundance of bipolar neurons in the species examined.