RETINOFUGAL PROJECTIONS OF NON-ECHOLOCATING (PTEROPUS-GIGANTEUS) AND ECHOLOCATING (MYOTIS-LUCIFUGUS) BATS

The projections and terminations of retinofugal pathways were studied in nonecholocating (Pteropus giganteus) and echolocating (Myotis lucifugus) bats by two methods, that of anterograde axonal degeneration following unilateral enucleation and anterograde axoplasmic transport of isotope following unilateral intraocular injection of tritiated proline. In Pteropus giganteus crossed and uncorssed projections terminated in several brainstem areas and the nuclei of the accessory optic system. Bilateral projections to the hypothalamus ended in the suprachiasmatic nuclei (SCN). In the ventral thalamus the projection terminated bilaterally in internal (VLGi) and external (VLGe) divisions of the ventral lateral geniculate (VLG) nuclei, although the projection to VLGi was greater than that to the other subdivision of VLG. Three lateral laminae of the dorsal lateral geniculate (DLG) nucleus and a medial division were each involved in contralateral and ipsilateral projections of the retina to the dorsal thalamus. Partially segregated and partially overlapping patterns from the two eyes and concealed lamination were identified in the lateral three laminae at some levels. In addition, the projection to the dorsal thalamus involved the contralateral lateral posterior nucleus. In the pretectum the projection terminated bilaterally in the nuclei of the optic tract (NOT), pretectal olivary nuclei (PON), anterior pretectal nuclei (APN) and posterior pretectal nuclei (PPN). The pattern of termination in the superior colliculus was such that contralateral and ipsilateral projections ended in different tiers in the superficial gray (SG) layer, those on the contralateral side being largely confined to the upper and lower tiers and those of the ipsilateral side being confined to a middle tier. Projections to contralateral medial, lateral, and dorsal accessory optic nuclei traversed the accessory optic tract. In Myotis lucifugus crossed projections terminated in the SCN, VLG, DLG, pretectum and superior colliculus. The projection to the VLGe was greater than that to VLGi. In the DLG, retinal fibers terminated in two major subdivisions. The stratification of retinal terminals observed in Pteropus was not present in Myotis> Pretectal terminations were confined to two restricted areas which were tentatively identified as the NOT and the PON. In the contralateral superior colliculus the projection terminated in two tiers in the SG. A small uncrossed component of the projection was limited in its termination to the ipsilateral SCN, DLG and VLG. The accessory optic system did not appear to be present in Myotis. These results indicate that there are basic differences in the overall projection of the retina upon the brainstem of echolocating and nonecholocating bats. Copyright © 1979 The Wistar Institute Press