Retinal projections in the Tasmanian devil, Sarcophilus harrisii.

Abstract

Retinal projections were mapped in Tasmanian devils which had one eye injected with 3H-proline. The retinal fibers terminate in seven regions in the brain. These are (1) dorsal lateral geniculate nucleus (LGNd), (2) ventral lateral geniculate nucleus, (3) lateral posterior nucleus, (4) pretectum, (5) superior colliculus, (6) hypothalamus and (7) accessory optic system. The pattern of retinal input to six of these regions is similar to that seen in other marsupials. The pattern of retinal projections to the LGNd, while basically similar to that observed in other polyprotodont marsupials, is much simpler than that seen in the related native cat, Dasyurus viverrinus. The LGNd of Sarcophilus presents the simplest cytoarchitectural organisation of any marsupial examined so far. Each LGNd receives overlapping projections from both eyes. Suggestions of an intermittent lamination are seen in the LGNd contralateral to an eye injection of 3H-proline. On the ipsilateral side there are two patches of label, a large lateral patch and a smaller medial patch, both of which occupy areas receiving contralateral input. The monocular segment, occupying the ventral 40% of the nucleus, is more extensive than has been reported in any other polyprotodont marsupial.