Photoperiodic regime influences onset of lens opacities in a non-human primate

Abstract

Background. Opacities of the lens are typical age-related phenomena which have a high influence on photoreception and consequently circadian rhythm. In mouse lemurs, a small bodied non-human primate, a high incidence (more than 50% when >seven years) of cataracts has been previously described during aging. Previous studies showed that photoperiodically induced accelerated annual rhythms alter some of mouse lemurs' life history traits. Whether a modification of photoperiod also affects the onset of age dependent lens opacities has not been investigated so far. The aim of this study was therefore to characterise the type of opacity and the mouse lemurs' age at its onset in two colonies with different photoperiodic regimen. Methods. Two of the largest mouse lemur colonies in Europe were investigated: Colony 1 having a natural annual photoperiodic regime and Colony 2 with an induced accelerated annual cycle. A slit-lamp was used to determine opacities in the lens. Furthermore, a subset of all animals which showed no opacities in the lens nucleus in the first examination but developed first changes in the following examination were further examined to estimate the age at onset of opacities. In total, 387 animals were examined and 57 represented the subset for age at onset estimation. Results . The first and most commonly observable opacity in the lens was nuclear sclerosis. Mouse lemurs from Colony 1 showed a delayed onset of nuclear sclerosis compared to mouse lemurs from Colony 2 (4.35 ± 1.50 years vs. 2.75 ± 0.99 years). For colony 1, the chronological age was equivalent to the number of seasonal cycles experienced by the mouse lemurs. For colony 2, in which seasonal cycles were accelerated by a factor of 1.5, mouse lemurs had experienced 4.13 ± 1.50 seasonal cycles in 2.75 ± 0.99 chronological years. Discussion. Our study showed clear differences in age at the onset of nuclear sclerosis formation between lemurs kept under different photoperiodic regimes. Instead of measuring the chronological age, the number of seasonal cycles (N = four) experienced by a mouse lemur can be used to estimate the risk of beginning nuclear sclerosis formation. Ophthalmological examinations should be taken into account when animals older than 5-6 seasonal cycles are used for experiments in which unrestricted visual ability has to be ensured. This study is the first to assess and demonstrate the influence of annual photoperiod regime on the incidence of lens opacities in a non-human primate.

Spontaneous Spongiform Brainstem Degeneration in a Young Mouse Lemur (Microcebus murinus) with Conspicuous Behavioral, Motor, Growth, and Ocular Pathologies

“…At that time, the mother was 4.9 y old, when age-related cataracts generally start to appear in mouse lemurs. 10 Neither parent showed any conspicuous deficits in social behavior, other behavioral traits, or motor function, including behavioral assessments in open-field and novel-object tests (data not shown). However, the case animal's mother had an unusual reproductive career in the Hannover colony.…”

“…A thorough ophthalmic examination was performed once (at postnatal day [P]113) by using routine methods. 9,10 Anatomic analyses. After the condition of the case animal had noticeably deteriorated on P125, the decision was made to perform MRI scans of the animal's brain to make a prognosis and to decide on a potential treatment or euthanasia.…”

Neurobiological substrates of animal personality and cognition in a nonhuman primate (Microcebus murinus)

“…All cognitive/behavioral experiments started during the long-day periods. Prior to the experiments, subjects were checked for good health and for eye diseases (Dubicanac et al, 2016(Dubicanac et al, , 2017 by a veterinarian, as some of the experimental procedures depended on visual information processing. All tested subjects were naïve to the touchscreen-based cognitive tests and to the open-field maze.…”

The Biological Clock in Gray Mouse Lemur: Adaptive, Evolutionary and Aging Considerations in an Emerging Non-human Primate Model

“…However, although these results have been observed in humans as well as other non-human primates and rodents (Vitiello et al, 1986; Czeisler et al, 1992; Valentinuzzi et al, 1997; Weinert et al, 2000; Weinert and Waterhouse, 2007; Zhdanova et al, 2011; Duffy et al, 2015), they do not explain whether these observed age-related alterations are due to a reduction of sensitivity to external light factors or to changes within the clock mechanism itself. However, a high incidence of ocular pathologies has been identified in mouse lemurs that are older than 7 years (Beltran et al, 2007; Alleaume et al, 2017; Dubicanac et al, 2017). This strongly suggests a decrease in light responsiveness through filtering of short wavelengths that are known to be efficient in the synchronization of daily rhythms in mouse lemurs (Gomez et al, 2012).…”