Changes in ganglion cell density during post-metamorphic development in a neotropical tree frog Hyla raniceps

Abstract

In the frog, as in many other vertebrates, the eye and, consequently the retina, continues to increase in size throughout life. In this paper ganglion cell densities in the retina of a Brasilian tree frog, Hyla raniceps, have been measured from methylene blue stained whole mounts. From a series of retinae, taken from individuals with body sizes ranging from that of a post-metamorphic juvenile to sexually mature adult, isodensity maps of cell density across the whole retina have been prepared. Concomitant measurement of the extent of the visual field of these animals allowed cell counts per mm 2 to be converted to cells per unit visual angle. Changes in both cell density and distribution were observed with increasing body size and in central retina these changes resulted in an increasing number of cells representing each degree of visual field. In contrast, in the inferior and superior periphery the angular separation of ganglion cells remained approximately constant. The developmental, physiological and ecological significance of these findings is discussed.