Morphological analyses of the retinal photoreceptor cells in the nocturnally adapted owl monkeys

Abstract

Owl monkeys are the only one species possessing the nocturnal lifestyles among the simian monkeys. Their eyes and retinas have been interested associating with the nocturnal adaptation. We examined the cellular specificity and electroretinogram (ERG) reactivity in the retina of the owl monkeys by comparison with the squirrel monkeys, taxonomically close-species and expressing diurnal behavior. Owl monkeys did not have clear structure of the foveal pit by the funduscope, whereas the retinal wholemount specimens indicated a small-condensed spot of the ganglion cells. There were abundant numbers of the rod photoreceptor cells in owl monkeys than those of the squirrel monkeys. However, the owl monkeys’ retina did not possess superiority for rod cell-reactivity in the scotopic ERG responses. Scanning electron microscopic observation revealed that the rod cells in owl monkeys’ retina had very small-sized inner and outer segments as compared with squirrel monkeys. Owl monkeys showed typical nocturnal traits such as rod-cell dominance. However, the individual photoreceptor cells seemed to be functionally weak for visual capacity, caused from the morphological immaturity at the inner and outer segments.

The Heterochromatin Block That Functions as a Rod Cell Microlens in Owl Monkeys Formed within a 15-Myr Time Span

“…This study did not include any animal experiments; the retina sample used in this study was a surplus of that used in our previous study on retinal morphology ( Kuniyoshi et al 2018 ), which had been conducted as an approved animal experiment described therein. This study involved a recombinant DNA experiment and was approved in advance by the Recombinant DNA Experiment Safety Committee of Kyoto University (approval number 190058).…”

“…The retina sample and the A. lemurinus animal from which the sample originated are described in our previous paper ( Kuniyoshi et al 2018 ). Essential information is as follows: animal identification number, Y20802; sex, male; age, 6 years; sampling process, excision of eyeball from euthanized animal, and isolation of retina.…”

Selected Ophthalmic Tests and Ocular Dimensions in Relation to Activity Pattern in Three Neotropical Nonhuman Primates: Black-Tufted Marmoset (Callithrix Penicillata), Guianan Squirrel Monkey (Saimiri Sciureus), and Azara's Night Monkey (Aotus Azarae Infulatus)

“…6 The same feature is also found in another monkey from the genus Aotus , the three-striped night monkey, Aotus trivirgatus , 15,19 and the gray-bellied night monkey, Aotus lemurinus . 11 Ocular anatomy and globe dimensions are discussed regarding their visual ecology to provide insight into correlations that, together with reference interval information, may provide predictive value for application of clinical information across other species.…”