Comparison of the morphology of the megachiropteran and microchiropteran eye
The structure of the eyes of two South African bat species, Rousettus aegyptiacus (Megachiroptera: Pteropodidae) and Rhinolophus capensis (Microchiroptera: Rhinolophidae) was examined and compared by means of light microscopy. The eyes of both species exhibit characteristics of a typical ‘nocturnal eye’ (presence pf only rods in the retina; the cornea shows a marked curvature and occupies about one third of the globe; the anterior and posterior chambers are very large in relation to the vitreous) and neither possess a fovea. The main difference occurs in the choroid and the retina. The fruit bat R. aegyptiacus shows a marked folding of the retina, as a result of papillae that project inwards from the choroid. This does not occur in the insectivorous bat R. capensis, where the choroid and the retina form a smooth layer. It is suggested that this unique feature of the fruit bat, and the associated increase in surface area and hence the number of photoreceptors is probably responsible for its good nocturnal vision.