The distribution and sizes of ganglion cells in the retinas of five Australian marsupials.

Abstract

Maps of ganglion-cell distribution have been constructed from whole-mounted retinas of five Australian marsupial species. The pademelon wallaby (Thylogale billiardieri), the scrub wallaby or tammar (Macropus eugenii), and the carnivorous Tasmanian devil (Sarcophilus harissi) have both a visual streak and an area centralis. The retina of the brown bandicoot (Isoodon obesulus) also shows both these features but they are less prominent than in the former three species, whereas the burrow-dwelling, hairy-nosed wombat (Lasiorhinus latifrons) possesses a well-developed visual streak but seems to lack an area centralis. A study of ganglion-cell sizes comparing nasal and temporal retina, the visual streak, and/or the area centralis was undertaken in each species. Results show that as in the cat, small ganglion cells tend to concentrate in the visual streak. However, the temporal-nasal differences in cell sizes described in the cat (Stone et al., '80) could be detected only in those marsupials in which an area centralis was clearly recognizable.