Comparative retinal histomorphometry and visual acuity of three bat species of the genus Artibeus (Phyllostomidae: Stenodermatinae)

Abstract

ABSTRACT: This study performed a histomorphometric analysis of the retina and estimated the visual acuity of three fruit-eating bats of the genus Artibeus, including Artibeus lituratus, Artibeus planirostris and Artibeus obscurus. In total, 13 animals were used for this study, in which the retinas were hemidisected, fixed, cut, and stained. The visual acuity was determined by the density of ganglion cells in the retina and the retinal layers were also measured from histological sections. The retinas of these bats are avascular, do not present tapetum lucidum in any quadrant, and have the 10 retinal layers common in mammals. Moreover, it was observed that the thickness of the retina in the central region was significantly higher in all measured parameters (p<0.001), except for the outer plexiform layer (OPL) which was significantly higher in the peripheral region (p<0.001). The retinas of the three species showed a horizontal visual streak with a higher concentration of retinal ganglion cells (RGCs) at the inferotemporal region. In addition, the species A. lituratus exhibited extras areas of high cell density in the retina. Thus, A. lituratus showed the highest visual acuity (1.92 cycles/degree), while A. planirostris showed a visual acuity of (1.77 cycles/degree) and A. obscurus exhibited the lowest visual acuity (1.50 cycles/degree). All these characteristics are related to the echolocation system and the eating habits of each species. Therefore, it can be concluded that bats of the genus Artibeus have a high visual acuity value compared to other echolocating bats and all these differences might be directly linked to the phylogeny of the genus.