Neural organization of the retina of the turtleMauremys caspica:a light microscope and Golgi study

Abstract

The organization of the retina of the turtle speciesMauremys caspica, found in fresh water ponds of Israel, has been examined by light microscopical techniques including examination of fresh wholemount retina, one micron blue-stained vertical sections and Golgi-stained material. The anatomical findings onMauremysretina have been compared with those of thePseudemysretina (Kolb, 1982) which is more commonly used for electrophysiological and neurochemical studies in the USA. The photoreceptors ofMauremysare similar in type and oil droplet content toPseudemysphotoreceptors except for the double cone inMauremys.This cone type appears more abundant than inPseudemysand the principal member contains a yellow oil droplet instead of an orange oil droplet. Golgi staining reveals that all the cell types that have been seen inPseudemysare found inMauremyswith identical morphology. In addition, two amacrine cell types that were not before described forPseudemyshave been added to the classification. One of these is the tristratified dopaminergic amacrine cell described in immunocytochemical studies (Witkovsky et al., 1984; Nguyen-Legros et al., 1985; Kolb et al., 1987). We have used these anatomical studies onPseudemysandMauremysretina to form a catalogue of neural types for the turtle retina in general. We conclude with an attempt to combine findings from anatomy, electrophysiology, and neurochemistry to form an overview of the organization of this reptilian retina.