Ebola Virus Glycoprotein with Increased Infectivity Dominated the 2013-2016 Epidemic.

The magnitude of the 2013-2016 Ebola virus disease (EVD) epidemic enabled an unprecedented number of viral mutations to occur over successive human-to-human transmission events, increasing the probability that adaptation to the human host occurred during the outbreak. We investigated one nonsynonymous mutation, Ebola virus (EBOV) glycoprotein (GP) mutant A82V, for its effect on viral infectivity. This mutation, located at the NPC1-binding site on EBOV GP, occurred early in the 2013-2016 outbreak and rose to high frequency. We found that GP-A82V had heightened ability to infect primate cells, including human dendritic cells. The increased infectivity was restricted to cells that have primate-specific NPC1 sequences at the EBOV interface, suggesting that this mutation was indeed an adaptation to the human host. GP-A82V was associated with increased mortality, consistent with the hypothesis that the heightened intrinsic infectivity of GP-A82V contributed to disease severity during the EVD epidemic.

Destabilizing effect of climate change on the persistence of a short-lived primate.

Seasonal tropical environments are among those regions that are the most affected by shifts in temperature and rainfall regimes under climate change, with potentially severe consequences for wildlife population persistence. This persistence is ultimately determined by complex demographic responses to multiple climatic drivers, yet these complexities have been little explored in tropical mammals. We use long-term, individual-based demographic data (1994 to 2020) from a short-lived primate in western Madagascar, the gray mouse lemur (Microcebus murinus), to investigate the demographic drivers of population persistence under observed shifts in seasonal temperature and rainfall. While rainfall during the wet season has been declining over the years, dry season temperatures have been increasing, with these trends projected to continue. These environmental changes resulted in lower survival and higher recruitment rates over time for gray mouse lemurs. Although the contrasting changes have prevented the study population from collapsing, the resulting increase in life-history speed has destabilized an otherwise stable population. Population projections under more recent rainfall and temperature levels predict an increase in population fluctuations and a corresponding increase in the extinction risk over the next five decades. Our analyses show that a relatively short-lived mammal with high reproductive output, representing a life history that is expected to closely track changes in its environment, can nonetheless be threatened by climate change.

Effects of binocular cue availability on leaping performance in Cheirogaleus medius: implications for primate origins.

Multiple competing hypotheses attribute the evolution of the suite of traits that distinguish primates from their closest relatives, including forward-facing eyes, which create a wide field of binocular vision, to specific behavioral and ecological factors. The grasp-leaping hypothesis suggests that the evolution of these traits in basal primates was driven by the demands of a form of leaping locomotion unique to primates. Whether the grasp-leaping hypothesis provides a viable mechanism for the evolution of primates' forward-facing eyes remains untested. To determine whether grasp-leaping locomotion may have contributed to driving the evolution of primates' forward-facing eyes, the importance of vision within the binocular field for this type of leaping was evaluated experimentally in Cheirogaleus medius, one of the cheirogaleid primate species considered reasonable living analogs of the earliest primates. Availability of binocular visual cues was experimentally restricted using a head-mounted blinder that narrowed the binocular visual field without altering the total visual field. Animals altered their launch behavior, reduced their horizontal leap speed, and were significantly more likely to select paths that offered the shortest available leaps when their binocular field was restricted. Restriction of binocular cue availability also significantly increased the probability of adverse landings even when statistically controlling for potentially confounding variables such as leap distance, horizontal leap speed, learning effects, etc. These results suggest a functional mechanism by which selection for improved grasp-leaping could also have contributed to the evolution of forward-facing eyes in the earliest crown primates.

Sex-specific heterothermy patterns in wintering captive Microcebus murinus do not translate into differences in energy balance.

The physiological mechanisms of responses to stressors are at the core of ecophysiological studies that examine the limits of an organism's flexibility. Interindividual variability in these physiological responses can be particularly important and lead to differences in the stress response among population groups, which can affect population dynamics. Some observations of intersexual differences in heterothermy raise the question of whether there is a difference in energy management between the sexes. In this study, we assessed male and female differences in mouse lemurs (Microcebus murinus), a highly seasonal malagasy primate, by measuring their physiological flexibility in response to caloric restriction and examining the subsequent impact on reproductive success. Using complementary methods aiming to describe large-scale and daily variations in body temperature throughout a 6-month winter-like short-day (SD) period, we monitored 12 males and 12 females, applying chronic 40% caloric restriction (CR) to 6 individuals in each group. We found variations in Tb modulation throughout the SD period and in response to caloric treatment that depended on sex, as females, regardless of food restriction, and CR males, only, entered deep torpor. The use of deeper torpor, however, did not translate into a lower loss of body mass in females and did not affect reproductive success. Captive conditions may have buffered the depth of torpor and minimised the positive effects of torpor on energy savings. However, the significant sex differences in heterothermy we observed may point to physiological benefits other than preservation of energy reserves.

Evidence of MHC class I and II influencing viral and helminth infection via the microbiome in a non-human primate.

Until recently, the study of major histocompability complex (MHC) mediated immunity has focused on the direct link between MHC diversity and susceptibility to parasite infection. However, MHC genes can also influence host health indirectly through the sculpting of the bacterial community that in turn shape immune responses. We investigated the links between MHC class I and II gene diversity gut microbiome diversity and micro- (adenovirus, AdV) and macro- (helminth) parasite infection probabilities in a wild population of non-human primates, mouse lemurs of Madagascar. This setup encompasses a plethora of underlying interactions between parasites, microbes and adaptive immunity in natural populations. Both MHC classes explained shifts in microbiome composition and the effect was driven by a few select microbial taxa. Among them were three taxa (Odoribacter, Campylobacter and Prevotellaceae-UCG-001) which were in turn linked to AdV and helminth infection status, correlative evidence of the indirect effect of the MHC via the microbiome. Our study provides support for the coupled role of MHC diversity and microbial flora as contributing factors of parasite infection.

Amyloid-ß targeting immunisation in aged non-human primate (Microcebus murinus).

Non-human primates have an important translational value given their close phylogenetic relationship to humans. Studies in these animals remain essential for evaluating efficacy and safety of new therapeutic approaches, particularly in aging primates that display Alzheimer's disease (AD) -like pathology. With the objective to improve amyloid-ß (Aß) targeting immunotherapy, we investigated the safety and efficacy of an active immunisation with an Aß derivative, K6Aß1-30-NH2, in old non-human primates. Thirty-two aged (4-10 year-old) mouse lemurs were enrolled in the study, and received up to four subcutaneous injections of the vaccine in alum adjuvant or adjuvant alone. Even though antibody titres to Aß were not high, pathological examination of the mouse lemur brains showed a significant reduction in intraneuronal Aß that was associated with reduced microgliosis, and the vaccination did not lead to microhemorrhages. Moreover, a subtle cognitive improvement was observed in the vaccinated primates, which was probably linked to Aß clearance. This Aß derivative vaccine appeared to be safe as a prophylactic measure based on the brain analyses and because it did not appear to have detrimental effects on the general health of these old animals.

Habitat and ecological niche characteristics of the elusive Hairy-eared Dwarf Lemur (Allocebus trichotis) with updated occurrence and geographic range data.

Ecological niche modeling (ENM) is particularly useful in the study of cryptic and elusive species that are only rarely seen, difficult to study in the wild, and simultaneously threatened by a multitude of anthropogenic factors. We collected presence records one such example, the understudied Hairy-eared Dwarf Lemur (Allocebus trichotis), from the literature and supplemented these with observations from surveys in previously unstudied areas to model its fundamental and realized niche throughout Madagascar. We further evaluated habitat characteristics at each sighting location to judge its conservation status and its adaptability toward habitat degradation. We found 31 presence localities in the literature and directly observed A. trichotis a further 23 times. According to the ENMs, precipitation of the driest quarter and maximum temperature of the warmest month mostly influenced its distribution, restricting it to the higher altitudes of the northeastern humid forests of Madagascar. Its fundamental niche, extent of occurrence, and area of occupancy were estimated as 65,819, 53,054, and 16,967 km² respectively. The latter, however, declined by 29.2% since 1990. On a habitat level, it was most often observed in primary forest habitats of different degradation stages (85.7%, n = 21). The fundamental niche of A. trichotis is most likely restricted by climatic factors. Although it can be found in moderately degraded forests, it is known to depend on the availability of tree holes and therefore old-growth forest structures. Ongoing deforestation and habitat fragmentation are likely to be the major threats to the survival of this species. Our ENMs provide evidence on where to intensify survey efforts on the elusive Hairy-eared Dwarf Lemurs of Madagascar.

Host-related and environmental factors influence long-term ectoparasite infestation dynamics of mouse lemurs in northwestern Madagascar.

Parasite infestations depend on multiple host-related and environmental factors. In the case of ectoparasites, which are exposed to the environment beyond the host, an impact of climate, expressed by seasonal or yearly variations, can be expected. However, long-term dynamics of ectoparasite infestations are rarely studied in nonhuman primates. We investigated the yearly variations in ectoparasite infestations of two small primates, the gray (Microcebus murinus) and the golden-brown (Microcebus ravelobensis) mouse lemur. For a more comprehensive evaluation, we also analyzed the potential effects of yearly and monthly climatic variation (temperature, rainfall) in addition to habitat, host sex, age, species, and body mass, on ectoparasite infestation. Individuals of both host species were sampled in two study sites within the Ankarafantsika National Park in northwestern Madagascar during several months (March-November) and across 4 years (2010, 2011, 2015, 2016). Our results show significant monthly and yearly variations in the infestation rates of three native ectoparasite taxa (Haemaphysalis spp. ticks, Schoutedenichia microcebi chigger mites, Lemurpediculus spp. sucking lice) and in ectoparasite species richness in both mouse lemur species. In addition, significant impacts of several host-related (species, sex, body mass) and environmental factors (habitat, temperature, rainfall) were found, but with differences in relevance for the different parasite taxa and partly deviating in their direction. Although some differences could be attributed to either permanent or temporary presence of the parasites on the host or to ecological differences between the host species, the lack of specific knowledge regarding the life cycle and microhabitat requirements of each parasite taxon precludes a complete understanding of the factors that determine their infestation dynamics. This study demonstrates the presence of yearly and monthly dynamics in lemur-parasite interactions in tropical, seasonal, dry deciduous forests in Madagascar, which call out for broad ecological long-term studies focusing both on primate hosts and their parasites.

Filarial infections in lemurs: Evidence for a wide geographical distribution and low host specificity among lemur species.

The relevance of emerging infectious diseases continues to grow worldwide as human activities increasingly extend into formerly remote natural areas. This is particularly noticeable on the island of Madagascar. As closest relatives to humans on the island, lemurs are of particular relevance as a potential origin of zoonotic pathogen spillover. Knowledge of pathogens circulating in lemur populations is, however, very poor. Particularly little is known about lemur hemoparasites. To infer host range, ecological and geographic spread of the recently described hemoparasitic nematode Lemurfilaria lemuris in northwestern Madagascar, a total of 942 individuals of two mouse lemur species (Microcebus murinus [n = 207] and Microcebus ravelobensis [n = 433]) and two rodent species (the endemic Eliurus myoxinus [n = 118] and the invasive Rattus rattus [n = 184]) were captured in two fragmented forest landscapes (Ankarafantsika National Park and Mariarano Classified Forest) in northwestern Madagascar for blood sample examination. No protozoan hemoparasites were detected by microscopic blood smear screening. Microfilaria were present in 1.0% (2/207) of M. murinus and 2.1% (9/433) of M. ravelobensis blood samples but not in rodent samples. Internal transcribed spacer 1 (ITS-1) sequences were identical to an unnamed Onchocercidae species previously described to infect a larger lemur species, Propithecus verreauxi, about 650 km further south. In contrast to expectations, L. lemuris was not detected. The finding of a pathogen in a distantly related host species, at a considerable geographic distance from the location of its original detection, instead of a microfilaria species previously described for one of the studied host species in the same region, illustrates our low level of knowledge of lemur hemoparasites, their host ranges, distribution, modes of transmission, and their zoonotic potential. Our findings shall stimulate new research that will be of relevance for both conservation medicine and human epidemiology.

RADseq data reveal a lack of admixture in a mouse lemur contact zone contrary to previous microsatellite results.

Microsatellites have been a workhorse of evolutionary genetic studies for decades and are still commonly in use for estimating signatures of genetic diversity at the population and species level across a multitude of taxa. Yet, the very high mutation rate of these loci is a double-edged sword, conferring great sensitivity at shallow levels of analysis (e.g. paternity analysis) but yielding considerable uncertainty for deeper evolutionary comparisons. For the present study, we used reduced representation genome-wide data (restriction site-associated DNA sequencing (RADseq)) to test for patterns of interspecific hybridization previously characterized using microsatellite data in a contact zone between two closely related mouse lemur species in Madagascar (Microcebus murinus and Microcebus griseorufus). We revisit this system by examining populations in, near, and far from the contact zone, including many of the same individuals that had previously been identified as hybrids with microsatellite data. Surprisingly, we find no evidence for admixed nuclear ancestry. Instead, re-analyses of microsatellite data and simulations suggest that previously inferred hybrids were false positives and that the program NewHybrids can be particularly sensitive to erroneously inferring hybrid ancestry. Combined with results from coalescent-based analyses and evidence for local syntopic co-occurrence, we conclude that the two mouse lemur species are in fact completely reproductively isolated, thus providing a new understanding of the evolutionary rate whereby reproductive isolation can be achieved in a primate.

Of fruits and fats: high-sugar diets restore fatty acid profiles in the white adipose tissue of captive dwarf lemurs.

Fat-storing hibernators rely on fatty acids from white adipose tissue (WAT) as an energy source to sustain hibernation. Whereas arctic and temperate hibernators preferentially recruit dietary polyunsaturated fatty acids (PUFAs), tropical hibernators can rely on monounsaturated fatty acids that produce fewer lipid peroxides during oxidation. Nevertheless, compositional data on WAT from tropical hibernators are scant and questions remain regarding fat recruitment and metabolism under different environmental conditions. We analyse fatty acid profiles from the WAT of captive dwarf lemurs (Cheirogaleus medius) subjected to high-sugar or high-fat diets during fattening and cold or warm conditions during hibernation. Dwarf lemurs fed high-sugar (compared to high-fat) diets displayed WAT profiles more comparable to wild lemurs that fatten on fruits and better depleted their fat reserves during hibernation. One PUFA, linoleic acid, remained elevated before hibernation, potentially lingering from the diets provisioned prior to fattening. That dwarf lemurs preferentially recruit the PUFA linoleic acid from diets that are naturally low in availability could explain the discrepancy between captive and wild lemurs' WAT. While demonstrating that minor dietary changes can produce major changes in seasonal fat deposition and depletion, our results highlight the complex role for PUFA metabolism in the ecology of tropical hibernators.

Population genomic structure in Goodman's mouse lemur reveals long-standing separation of Madagascar's Central Highlands and eastern rainforests.

Madagascar's Central Highlands are largely composed of grasslands, interspersed with patches of forest. The historical perspective was that Madagascar's grasslands had anthropogenic origins, but emerging evidence suggests that grasslands were a component of the pre-human Central Highlands vegetation. Consequently, there is now vigorous debate regarding the extent to which these grasslands have expanded due to anthropogenic pressures. Here, we shed light on the temporal dynamics of Madagascar's vegetative composition by conducting a population genomic investigation of Goodman's mouse lemur (Microcebus lehilahytsara; Cheirogaleidae). These small-bodied primates occur both in Madagascar's eastern rainforests and in the Central Highlands, making them a valuable indicator species. Population divergences among forest-dwelling mammals will reflect changes to their habitat, including fragmentation, whereas patterns of post-divergence gene flow can reveal formerly wooded migration corridors. To explore these patterns, we used RADseq data to infer population genetic structure, demographic models of post-divergence gene flow, and population size change through time. The results offer evidence that open habitats are an ancient component of the Central Highlands, and that widespread forest fragmentation occurred naturally during a period of decreased precipitation near the last glacial maximum. Models of gene flow suggest that migration across the Central Highlands has been possible from the Pleistocene through the recent Holocene via riparian corridors. Though our findings support the hypothesis that Central Highland grasslands predate human arrival, we also find evidence for human-mediated population declines. This highlights the extent to which species imminently threatened by human-mediated deforestation may already be vulnerable from paleoclimatic conditions.

Cryptic Patterns of Speciation in Cryptic Primates: Microendemic Mouse Lemurs and the Multispecies Coalescent.

Mouse lemurs (Microcebus) are a radiation of morphologically cryptic primates distributed throughout Madagascar for which the number of recognized species has exploded in the past two decades. This taxonomic revision has prompted understandable concern that there has been substantial oversplitting in the mouse lemur clade. Here, we investigate mouse lemur diversity in a region in northeastern Madagascar with high levels of microendemism and predicted habitat loss. We analyzed RADseq data with multispecies coalescent (MSC) species delimitation methods for two pairs of sister lineages that include three named species and an undescribed lineage previously identified to have divergent mtDNA. Marked differences in effective population sizes, levels of gene flow, patterns of isolation-by-distance, and species delimitation results were found among the two pairs of lineages. Whereas all tests support the recognition of the presently undescribed lineage as a separate species, the species-level distinction of two previously described species, M. mittermeieri and M. lehilahytsara is not supported-a result that is particularly striking when using the genealogical discordance index (gdi). Nonsister lineages occur sympatrically in two of the localities sampled for this study, despite an estimated divergence time of less than 1 Ma. This suggests rapid evolution of reproductive isolation in the focal lineages and in the mouse lemur clade generally. The divergence time estimates reported here are based on the MSC calibrated with pedigree-based mutation rates and are considerably more recent than previously published fossil-calibrated relaxed-clock estimates. We discuss the possible explanations for this discrepancy, noting that there are theoretical justifications for preferring the MSC estimates in this case. [Cryptic species; effective population size; microendemism; multispecies coalescent; speciation; species delimitation.].

Habitat use by the island lemurs of Nosy Be, Madagascar.

Madagascar's lemurs are threatened by forest loss, fragmentation, and degradation. Many species use flexible behaviors to survive in degraded habitat, but their ability to persist in very small areas may be limited. Insular lemurs, like those found on Nosy Be, an island off the northwestern coast of Madagascar, are at heightened risk of sudden population declines and extirpation. Nosy Be is home to two Critically Endangered species-the endemic Nosy Be sportive lemur (Lepilemur tymerlachsoni) and Claire's mouse lemur (Microcebus mamiratra)-as well as the Endangered black lemur (Eulemur macaco). Most of the remaining forest on Nosy Be is protected by the 862-ha Lokobe National Park. To document how Nosy Be lemurs use their restricted habitat, we conducted vegetation and reconnaissance surveys on 53 transects in and around Lokobe. We collected data on tree size, canopy cover, understory visibility, and elevation for 248 lemur sightings. We used a spatially explicit, multi-species occupancy model to investigate which forest-structure variables are important to lemurs. Our results represent some of the first data on habitat use by insular lemurs. Black lemurs preferred significantly larger trees and areas with less dense understory. They also occurred significantly less outside of Lokobe National Park, even when accounting for sampling effort and geography. The distributions of the sportive and mouse lemurs were not related to the forest structure variables we documented, but they did negatively predict each other-perhaps because their habitat requirements differ. These results also underscore the importance of the national park to protecting the black lemur population on Nosy Be and raise questions about what factors do influence the distribution of Nosy Be's smaller lemurs. Close monitoring is needed to prevent these populations and the ecosystem services they provide from disappearing, as have other island lemurs.

Molecular Liver Fingerprint Reflects the Seasonal Physiology of the Grey Mouse Lemur (Microcebus murinus) during Winter.

Grey mouse lemurs (Microcebus murinus) are primates that respond to environmental energetic constraints through strong physiological seasonality. They notably fatten during early winter (EW), and mobilize their lipid reserves while developing glucose intolerance during late winter (LW), when food availability is low. To decipher how the hepatic mechanisms may support such metabolic flexibility, we analyzed the liver proteome of adult captive male mouse lemurs, whose seasonal regulations are comparable to their wild counterparts. We highlight profound hepatic changes that reflect fat accretion in EW at the whole-body level, without triggering an ectopic storage of fat in the liver, however. Moreover, molecular regulations are consistent with the decrease in liver glucose utilization in LW, and therefore with reduced tolerance to glucose. However, no major regulation was seen in insulin signaling/resistance pathways. Fat mobilization in LW appeared possibly linked to the reactivation of the reproductive system while enhanced liver detoxification may reflect an anticipation to return to summer levels of food intake. Overall, these results show that the physiology of mouse lemurs during winter relies on solid molecular foundations in liver processes to adapt fuel partitioning while opposing the development of a pathological state despite large lipid fluxes.

Resting state functional atlas and cerebral networks in mouse lemur primates at 11.7 Tesla.

Measures of resting-state functional connectivity allow the description of neuronal networks in humans and provide a window on brain function in normal and pathological conditions. Characterizing neuronal networks in animals is complementary to studies in humans to understand how evolution has modelled network architecture. The mouse lemur (Microcebus murinus) is one of the smallest and more phylogenetically distant primates as compared to humans. Characterizing the functional organization of its brain is critical for scientists studying this primate as well as to add a link for comparative animal studies. Here, we created the first functional atlas of mouse lemur brain and describe for the first time its cerebral networks. They were classified as two primary cortical networks (somato-motor and visual), two high-level cortical networks (fronto-parietal and fronto-temporal) and two limbic networks (sensory-limbic and evaluative-limbic). Comparison of mouse lemur and human networks revealed similarities between mouse lemur high-level cortical networks and human networks as the dorsal attentional (DAN), executive control (ECN), and default-mode networks (DMN). These networks were however not homologous, possibly reflecting differential organization of high-level networks. Finally, cerebral hubs were evaluated. They were grouped along an antero-posterior axis in lemurs while they were split into parietal and frontal clusters in humans.

Linking cognition to ecology in wild sympatric mouse lemur species.

Cognitive abilities covary with both social and ecological factors across animal taxa. Ecological generalists have been attributed with enhanced cognitive abilities, but which specific ecological factors may have shaped the evolution of which specific cognitive abilities remains poorly known. To explore these links, we applied a cognitive test battery (two personality, ten cognitive tests; n = 1104 tests) to wild individuals of two sympatric mouse lemur species (n = 120 Microcebus murinus, n = 34 M. berthae) varying in ecological adaptations but sharing key features of their social systems. The habitat and dietary generalist grey mouse lemurs were more innovative and exhibited better spatial learning abilities; a cognitive advantage in responding adaptively to dynamic environmental conditions. The more specialized Madame Berthe's mouse lemurs were faster in learning associative reward contingencies, providing relative advantages in stable environmental conditions. Hence, our study revealed key cognitive correlates of ecological adaptations and indicates potential cognitive constraints of specialists that may help explain why they face a greater extinction risk in the context of current environmental changes.

Pedigree-based and phylogenetic methods support surprising patterns of mutation rate and spectrum in the gray mouse lemur.

Mutations are the raw material on which evolution acts, and knowledge of their frequency and genomic distribution is crucial for understanding how evolution operates at both long and short timescales. At present, the rate and spectrum of de novo mutations have been directly characterized in relatively few lineages. Our study provides the first direct mutation-rate estimate for a strepsirrhine (i.e., the lemurs and lorises), which comprises nearly half of the primate clade. Using high-coverage linked-read sequencing for a focal quartet of gray mouse lemurs (Microcebus murinus), we estimated the mutation rate to be among the highest calculated for a mammal at 1.52 × 10-8 (95% credible interval: 1.28 × 10-8-1.78 × 10-8) mutations/site/generation. Further, we found an unexpectedly low count of paternal mutations, and only a modest overrepresentation of mutations at CpG sites. Despite the surprising nature of these results, we found both the rate and spectrum to be robust to the manipulation of a wide range of computational filtering criteria. We also sequenced a technical replicate to estimate a false-negative and false-positive rate for our data and show that any point estimate of a de novo mutation rate should be considered with a large degree of uncertainty. For validation, we conducted an independent analysis of context-dependent substitution types for gray mouse lemur and five additional primate species for which de novo mutation rates have also been estimated. These comparisons revealed general consistency of the mutation spectrum between the pedigree-based and the substitution-rate analyses for all species compared.

Motion cues increase focused attention towards purely visual stimuli in a nocturnal primate and drive stimulus interaction and approach/avoidance in a context-dependent manner.

Visual information is of pivotal ecological importance to monkeys, apes, and humans, whereas its role in nocturnal primate ecology is less well understood. We explored how purely visual information modulates the behavior of a nocturnal primate. Abstract (shape), photographic (shape + detail), or video (shape + detail + motion) representations of arthropod prey (Zophobas morio; food context) or a male conspecific (social context) were systematically presented to 22 individuals of the gray mouse lemur (Microcebus murinus) using a touchscreen. We assessed stimulus-directed touch interactions, durations of focused visual attention towards the different stimuli, and durations spent in the half of the setup-chamber more distant to the touchscreen (as quantification of approach/avoidance). Focused attention towards the stimulus generally increased from abstract and photographic to videographic stimuli. For the food context, indications for a parallel increase in stimulus-directed touch interactions from abstract stimulus to video were found. Approach/avoidance was independent of the stimulus type within both contexts. A comparison between the contexts under the video condition revealed higher durations of visual attention and lower stimulus avoidance in the food context compared to the social context. The number of touch interactions with the video stimulus was not generally context-dependent, but context-dependency related to sex: In the food context, animals with high and low numbers of touch interactions were equally distributed across sexes. In the social context, females showed the highest numbers of touch interactions. Numbers in males declined compared to the food context. Our results demonstrate for the first time that purely visual information modulates mouse lemur behavior and focused attention in a content- and context-specific manner, suggesting that vision is of high importance for the ecology of these nocturnal primates. The findings emphasize the need for further vision-based experiments to gain deeper insight into the evolution of visual information processing and cognition in nocturnal primates.

Overview of age-related changes in psychomotor and cognitive functions in a prosimian primate, the gray mouse lemur (Microcebus murinus): Recent advances in risk factors and antiaging interventions.

Aging is not homogeneous in humans and the determinants leading to differences between subjects are not fully understood. Impaired glucose homeostasis is a major risk factor for cognitive decline in middle-aged humans, pointing at the existence of early markers of unhealthy aging. The gray mouse lemur (Microcebus murinus), a small lemuriform Malagasy primate, shows relatively slow aging with decreased psychomotor capacities at middle-age (around 5-year old). In some cases (∼10%), it spontaneously leads to pathological aging. In this case, some age-related deficits, such as severe cognitive decline, brain atrophy, amyloidosis, and glucoregulatory imbalance are congruent with what is observed in humans. In the present review, we inventory the changes occurring in psychomotor and cognitive functions during healthy and pathological aging in mouse lemur. It includes a summary of the cerebral, metabolic, and cellular alterations that occur during aging and their relation to cognitive decline. As nutrition is one of the major nonpharmacological antiaging strategies with major potential effects on cognitive performances, we also discuss its role in brain functions and cognitive decline in this species. We show that the overall approach of aging studies in the gray mouse lemur offers promising ways of investigation for understanding, prevention, and treatments of pathological aging in humans.