Seasonal variation in glucose and insulin is modulated by food and temperature conditions in a hibernating primate.

Feast-fast cycles allow animals to live in seasonal environments by promoting fat storage when food is plentiful and lipolysis when food is scarce. Fat-storing hibernators have mastered this cycle over a circannual schedule, by undergoing extreme fattening to stockpile fuel for the ensuing hibernation season. Insulin is intrinsic to carbohydrate and lipid metabolism and is central to regulating feast-fast cycles in mammalian hibernators. Here, we examine glucose and insulin dynamics across the feast-fast cycle in fat-tailed dwarf lemurs, the only obligate hibernator among primates. Unlike cold-adapted hibernators, dwarf lemurs inhabit tropical forests in Madagascar and hibernate under various temperature conditions. Using the captive colony at the Duke Lemur Center, we determined fasting glucose and insulin, and glucose tolerance, in dwarf lemurs across seasons. During the lean season, we maintained dwarf lemurs under stable warm, stable cold, or fluctuating ambient temperatures that variably included food provisioning or deprivation. Overall, we find that dwarf lemurs can show signatures of reversible, lean-season insulin resistance. During the fattening season prior to hibernation, dwarf lemurs had low glucose, insulin, and HOMA-IR despite consuming high-sugar diets. In the active season after hibernation, glucose, insulin, HOMA-IR, and glucose tolerance all increased, highlighting the metabolic processes at play during periods of weight gain versus weight loss. During the lean season, glucose remained low, but insulin and HOMA-IR increased, particularly in animals kept under warm conditions with daily food. Moreover, these lemurs had the greatest glucose intolerance in our study and had average HOMA-IR values consistent with insulin resistance (5.49), while those without food under cold (1.95) or fluctuating (1.17) temperatures did not. Remarkably low insulin in dwarf lemurs under fluctuating temperatures raises new questions about lipid metabolism when animals can passively warm and cool rather than undergo sporadic arousals. Our results underscore that seasonal changes in insulin and glucose tolerance are likely hallmarks of hibernating mammals. Because dwarf lemurs can hibernate under a range of conditions in captivity, they are an emerging model for primate metabolic flexibility with implications for human health.

Identification of 3 novel herpesviruses in prosimians with lymphoproliferative disease.

Although many studies have characterized catarrhine and platyrrhine primate herpesviruses, little is known about herpesviruses in prosimians. We aimed to identify and characterize herpesviruses in prosimians with proliferative lymphocytic disease. DNA was extracted from tissues of 9 gray mouse lemurs (Microcebus murinus) and 3 pygmy slow lorises (Nycticebus pygmaeus) with lymphoproliferative lesions, and we performed nested PCR and sequencing for detection of herpesviruses and polyomaviruses. We identified 3 novel herpesviruses and performed phylogenetic analyses to characterize their relationship with other herpesviruses. A gray mouse lemur herpesvirus clustered with other primate herpesviruses within the subfamily Betaherpesvirinae, just basal to the genus Cytomegalovirus. The other gray mouse lemur herpesvirus and the pygmy slow loris herpesvirus clustered within the subfamily Gammaherpesvirinae, although the relationships within the subfamily were less resolved. Quantitative PCR assays were developed for the 2 new gray mouse lemur viruses, providing specific, faster, less expensive, and quantitative detection tools. Further studies are needed to elucidate the relationship between the presence of these viruses and the severity or presence of lymphoproliferative lesions in prosimians.

On the modulation and maintenance of hibernation in captive dwarf lemurs.

In nature, photoperiod signals environmental seasonality and is a strong selective "zeitgeber" that synchronizes biological rhythms. For animals facing seasonal environmental challenges and energetic bottlenecks, daily torpor and hibernation are two metabolic strategies that can save energy. In the wild, the dwarf lemurs of Madagascar are obligate hibernators, hibernating between 3 and 7 months a year. In captivity, however, dwarf lemurs generally express torpor for periods far shorter than the hibernation season in Madagascar. We investigated whether fat-tailed dwarf lemurs (Cheirogaleus medius) housed at the Duke Lemur Center (DLC) could hibernate, by subjecting 8 individuals to husbandry conditions more in accord with those in Madagascar, including alternating photoperiods, low ambient temperatures, and food restriction. All dwarf lemurs displayed daily and multiday torpor bouts, including bouts lasting ~ 11 days. Ambient temperature was the greatest predictor of torpor bout duration, and food ingestion and night length also played a role. Unlike their wild counterparts, who rarely leave their hibernacula and do not feed during hibernation, DLC dwarf lemurs sporadically moved and ate. While demonstrating that captive dwarf lemurs are physiologically capable of hibernation, we argue that facilitating their hibernation serves both husbandry and research goals: first, it enables lemurs to express the biphasic phenotypes (fattening and fat depletion) that are characteristic of their wild conspecifics; second, by "renaturalizing" dwarf lemurs in captivity, they will emerge a better model for understanding both metabolic extremes in primates generally and metabolic disorders in humans specifically.

A role for gut microbiota in host niche differentiation.

If gut microbes influence host behavioral ecology in the short term, over evolutionary time, they could drive host niche differentiation. We explored this possibility by comparing the gut microbiota of Madagascar's folivorous lemurs from Indriidae and Lepilemuridae. Occurring sympatrically in the eastern rainforest, our four, target species have different dietary specializations, including frugo-folivory (sifakas), young-leaf folivory (indri and woolly lemurs), and mature-leaf folivory (sportive lemurs). We collected fecal samples, from 2013 to 2017, and used amplicon sequencing, metagenomic sequencing, and nuclear magnetic resonance spectroscopy, respectively, to integrate analyses of gut microbiome structure and function with analysis of the colonic metabolome. The lemurs harbored species-specific microbiomes, metagenomes, and metabolomes that were tuned to their dietary specializations: Frugo-folivores had greater microbial and metagenomic diversity, and harbored generalist taxa. Mature-leaf folivores had greater individual microbiome variation, and taxa and metabolites putatively involved in cellulolysis. The consortia even differed between related, young-leaf specialists, with indri prioritizing metabolism of fiber and plant secondary compounds, and woolly lemurs prioritizing amino-acid cycling. Specialized gut microbiota and associated gastrointestinal morphologies enable folivores to variably tolerate resource fluctuation and support nutrient extraction from challenging resources (e.g., by metabolizing plant secondary compounds or recalcitrant fibers), perhaps ultimately facilitating host species' diversity and specialized feeding ecologies.

Virus discovery reveals frequent infection by diverse novel members of the Flaviviridae in wild lemurs.

Lemurs are highly endangered mammals inhabiting the forests of Madagascar. In this study, we performed virus discovery on serum samples collected from 84 wild lemurs and identified viral sequence fragments from 4 novel viruses within the family Flaviviridae, including members of the genera Hepacivirus and Pegivirus. The sifaka hepacivirus (SifHV, two genotypes) and pegivirus (SifPgV, two genotypes) were discovered in the diademed sifaka (Propithecus diadema), while other pegiviral fragments were detected in samples from the indri (Indri indri, IndPgV) and the weasel sportive lemur (Lepilemur mustelinus, LepPgV). Although data are preliminary, each viral species appeared host species-specific and frequent infection was detected (18 of 84 individuals were positive for at least one virus). The complete coding sequence and partial 5' and 3' untranslated regions (UTRs) were obtained for SifHV and its genomic organization was consistent with that of other hepaciviruses, with one unique polyprotein and highly structured UTRs. Phylogenetic analyses showed the SifHV belonged to a clade that includes several viral species identified in rodents from Asia and North America, while SifPgV and IndPgV were more closely related to pegiviral species A and C, that include viruses found in humans as well as New- and Old-World monkeys. Our results support the current proposed model of virus-host co-divergence with frequent occurrence of cross-species transmission for these genera and highlight how the discovery of more members of the Flaviviridae can help clarify the ecology and evolutionary history of these viruses. Furthermore, this knowledge is important for conservation and captive management of lemurs.

MORTALITY IN COQUEREL'S SIFAKAS ( PROPITHECUS COQUERELI) UNDER HUMAN CARE: A RETROSPECTIVE SURVEY FROM THE DUKE LEMUR CENTER 1990-2015.

Coquerel's sifakas ( Propithecus coquereli) are diurnal, folivorous lemurs native to Madagascar and one of only two members of the genus Propithecus currently housed in human care settings outside of Madagascar. This species has a lifespan of approximately 30 yr but minimal information exists regarding morbidity and mortality in human care settings. In this retrospective study, medical records, postmortem exam, and autopsy reports from 56 animals housed at the Duke Lemur Center from 1990 to 2015 were evaluated. Mortality assessments included age, sex, time of year, histopathological findings, major organ system impacted, and etiological factors. Mortality was most prevalent among adults greater than 2 yr of age (42.9%) and neonates less than 7 days of age (30.4%). The top four morphological diagnoses accounted for 51.7% of all deaths and included stillbirths (19.6%), enteritis-colitis (12.5%), failure to thrive (10.7%), and systemic protozoal infections (8.9%). The two most commonly affected organ systems in animals over 7 days of age were multisystem disease (30.8%) and the gastrointestinal system (28.2%). Infections were the most common etiology with bacterial being the most prevalent followed by protozoal infections. The results provide insight into common causes of mortality of this species and can be used to guide management of this endangered primate and improve longevity in human care settings.

Molecular surveillance of novel tick-borne organisms in Madagascar's lemurs.

The discovery and characterization of emerging tick-borne organisms are critical for global health initiatives to improve animal and human welfare (One Health). It is possible that unknown tick-borne organisms underlie a subset of undiagnosed illness in wildlife, domesticated species, and humans. Our study lends support to the One Health concept by highlighting the prevalence of three blood-borne organisms in wild lemurs living in close proximity to domesticated species and humans. Previously, our team identified three novel, presumably tick-borne, intravascular organisms, belonging to the genera Babesia, Borrelia, and Neoehrlichia, circulating in two of Madagascar's lemur species. Here, we extend our previous observation by developing a targeted molecular surveillance approach aimed at determining the prevalence of these organisms in lemurs. Using quantitative PCR, we provide Babesia, Borrelia, and Neoehrlichia prevalence data for 76 individuals comprising four lemur species located in eastern Madagascar. Our results indicate a high prevalence (96%) of Babesia across sampled individuals with lower prevalences for Neoehrlichia (36%) and Borrelia (14.5%). In light of our results, we recommend additional studies of these tick-borne organisms to determine pathogenicity and assess zoonotic potency to other animals and humans in Madagascar.

BASELINE HEALTH AND NUTRITION EVALUATION OF TWO SYMPATRIC NOCTURNAL LEMUR SPECIES (AVAHI LANIGER AND LEPILEMUR MUSTELINUS) RESIDING NEAR AN ACTIVE MINE SITE AT AMBATOVY, MADAGASCAR.

Extractive industries can have significant impacts on ecosystems through loss of habitat, degradation of water quality, and direct impact on floral and faunal biodiversity. When operations are located in sensitive regions with high biodiversity containing endangered or threatened species, it is possible to minimize impact on the environment by developing programs to scientifically monitor the impact on resident flora and fauna species in the early phases of operation so that effects can be mitigated whenever possible. This report presents the baseline health, nutrition, and trace mineral evaluation for 33 Avahi laniger (Eastern wooly lemur) and 15 Lepilemur mustelinus (greater sportive lemur) captured and given complete health evaluations that included the measurement of fat-soluble vitamins and trace minerals in addition to routine complete blood counts, serum chemistries, and parasite evaluations. All lemurs appeared healthy on physical examination despite the presence of minor wounds consistent with interspecies aggression in some individuals. Serum chemistry values were within expected ranges for other lemur species; however, A. laniger erythrocytes were significantly smaller than those of L. mustelinus. Serum nickel values were markedly higher than expected in both species, and selenium, copper, and cobalt levels were higher in L. mustelinus compared with A. laniger at the study site, as well as values for I. indri or P. diadema reported from other locations. Endoparasites and ectoparasites were typical of those reported in other wild lemur species, but load and diversity varied between A. laniger and L. mustelinus despite inhabiting the same forest ecosystem. This baseline assessment provides the foundation for ongoing monitoring.

Minimum Alveolar Concentration and Cardiopulmonary Effects of Isoflurane in Ring-tailed Lemurs (Lemur catta).

The goal of this study was to determine the minimum alveolar concentration (MAC) and cardiopulmonary effects of isoflurane in ring-tailed lemurs (Lemur catta). The MAC of isoflurane was determined by using a tail-clamp stimulus in adult ring-tailed lemurs (6 male, 4 female). Once MAC was determined, another group of 10 adult ring-tailed lemurs (5 male, 5 female) were anesthetized and instrumented similarly as the previous group and maintained at 0.5, 1, 1.5, and 2 times MAC for 15 min each with no external stimulation. Five lemurs were exposed to increasing concentrations (that is, 0.5 times MAC increasing to 2 times MAC), and the other 5 animals were exposed to decreasing concentrations. MAC of isoflurane for ringtailed lemurs was 1.9%. The animals became hypotensive, but no significant differences were found in heart rate or systolic, mean, and diastolic blood pressures at the different multiples of MAC examined. At 1 MAC, all lemurs developed a moderate respiratory acidosis, which became more severe at 2 MAC. Given these findings, isoflurane at 0.5 to 2 times MAC in ringtailed lemurs does not result in predictable depression of blood pressure, but hypoventilation occurs at 1 MAC or greater.

Blood transcriptomes reveal novel parasitic zoonoses circulating in Madagascar's lemurs.

Zoonotic diseases are a looming threat to global populations, and nearly 75% of emerging infectious diseases can spread among wildlife, domestic animals and humans. A 'One World, One Health' perspective offers us an ideal framework for understanding and potentially mitigating the spread of zoonoses, and the island of Madagascar serves as a natural laboratory for conducting these studies. Rapid habitat degradation and climate change on the island are contributing to more frequent contact among humans, livestock and wildlife, increasing the potential for pathogen spillover events. Given Madagascar's long geographical isolation, coupled with recent and repeated introduction of agricultural and invasive species, it is likely that a number of circulating pathogens remain uncharacterized in lemur populations. Thus, it is imperative that new approaches be implemented for de novo pathogen discovery. To this end, we used non-targeted deep sequencing of blood transcriptomes from two species of critically endangered wild lemurs (Indri indri and Propithecus diadema) to characterize blood-borne pathogens. Our results show several undescribed vector-borne parasites circulating within lemurs, some of which may cause disease in wildlife, livestock and humans. We anticipate that advanced methods for de novo identification of unknown pathogens will have broad utility for characterizing other complex disease transmission systems.

Ectoparasites of Propithecus diadema (Primates: Indriidae) With Notes on Unusual Attachment Site Selection by Haemaphysalis lemuris (Parasitiformes: Ixodidae).

An examination of ectoparasite loads in two populations of wild diademed sifakas, Propithecus diadema Bennett, yielded seven species-four mite species, a louse, a hippoboscid fly, and a leech. Prevalence of the tick Haemaphysalis lemuris Hoogstraal, the mites Liponyssella madagascariensis (Hirst) and Lemuralges propithecus Bochkov et al., and the louse Trichophilopterus babakotophilus Stobbe was quite high, at least 20%. H. lemuris was the most common ectoparasite in one population, while completely absent in a second one. When present, the most common attachment site for H. lemuris males was in the nares of their hosts.

Lemuralges propithecus sp. n. (Acariformes: Psoroptidae), an ectoparasite of the diademed sifaka Propithecus diadema (Primates: Indriidae).

A new species of the genus Lemuralges Fain, 1963 (Acariformes: Psoroptidae: Makialginae) is described from the Malagasy lemur Propithecus diadema (Bennett) (Primates: Indriidae) based on all postembryonic instars. This new species differs from the only known species in this genus, Lemuralges intermedius Fain, 1963, by the following features: both sexes of L. propithecus sp. n. show a pair of medioventral projections of the subcapitulum (vs without projections in L. intermedius) and the propodonotal shield is slightly ornamented (vs unornamented); in males the hysteronotal shield is completely covered by longitudinal striae (vs median part without striae), setae c2 are 120-140 µm long (vs 200-210 µm long), and femur III has a short transverse furrow dorsally (vs a longitudinal furrow); in females, setae h2 are, at least, 2 times shorter than h3 (vs slightly longer, or subequal to, h3), tibia IV has a ventro-apical projection (vs without projection). Larvae and protonymphs of the new species show some unique developmental delays. Female and male tritonymphs differ by their external morphology.

Persistent viremia by a novel parvovirus in a slow loris (Nycticebus coucang) with diffuse histiocytic sarcoma.

Cancer is one of the leading health concerns for human and animal health. Since the tumorigenesis process is not completely understood and it is known that some viruses can induce carcinogenesis, it is highly important to identify novel oncoviruses and extensively study underlying oncogenic mechanisms. Here, we investigated a case of diffuse histiocytic sarcoma in a 22 year old slow loris (Nycticebus coucang), using a broad spectrum virus discovery technique. A novel parvovirus was discovered and the phylogenetic analysis performed on its fully sequenced genome demonstrated that it represents the first member of a novel genus. The possible causative correlation between this virus and the malignancy was further investigated and 20 serum and 61 organ samples from 25 animals (N. coucang and N. pygmaeus) were screened for the novel virus but only samples collected from the originally infected animal were positive. The virus was present in all tested organs (intestine, liver, spleen, kidneys, and lungs) and in all banked serum samples collected up to 8 years before death. All attempts to identify a latent viral form (integrated or episomal) were unsuccessful and the increase of variation in the viral sequences during the years was consistent with absence of latency. Since it is well known that parvoviruses are dependent on cell division to successfully replicate, we hypothesized that the virus could have benefitted from the constantly dividing cancer cells and may not have been the cause of the histiocytic sarcoma. It is also possible to conjecture that the virus had a role in delaying the tumor progression and this report might bring new exciting opportunities in recognizing viruses to be used in cancer virotherapy.

Primate communication in the pure ultrasound.

Few mammals-cetaceans, domestic cats and select bats and rodents-can send and receive vocal signals contained within the ultrasonic domain, or pure ultrasound (greater than 20 kHz). Here, we use the auditory brainstem response (ABR) method to demonstrate that a species of nocturnal primate, the Philippine tarsier (Tarsius syrichta), has a high-frequency limit of auditory sensitivity of ca 91 kHz. We also recorded a vocalization with a dominant frequency of 70 kHz. Such values are among the highest recorded for any terrestrial mammal, and a relatively extreme example of ultrasonic communication. For Philippine tarsiers, ultrasonic vocalizations might represent a private channel of communication that subverts detection by predators, prey and competitors, enhances energetic efficiency, or improves detection against low-frequency background noise.

Timing the origin of human malarias: the lemur puzzle.

BACKGROUND: Timing the origin of human malarias has been a focus of great interest. Previous studies on the mitochondrial genome concluded that Plasmodium in primates, including those parasitic to humans, radiated relatively recently during a process where host switches were common. Those investigations, however, assumed constant rate of evolution and tightly bound (fixed) calibration points based on host fossils or host distribution. We investigate the effect of such assumptions using different molecular dating methods. We include parasites from Lemuroidea since their distribution provides an external validation to time estimates allowing us to disregard scenarios that cannot explain their introduction in Madagascar. RESULTS: We reject the assumption that the Plasmodium mitochondrial genome, as a unit or each gene separately, evolves at a constant rate. Our analyses show that Lemuroidea parasites are a monophyletic group that shares a common ancestor with all Catarrhini malarias except those related to P. falciparum. However, we found no evidence that this group of parasites branched with their hosts early in the evolution of primates. We applied relaxed clock methods and different calibrations points to explore the origin of primate malarias including those found in African apes. We showed that previous studies likely underestimated the origin of malarial parasites in primates. CONCLUSIONS: The use of fossils from the host as absolute calibration and the assumption of a strict clock likely underestimate time when performing molecular dating analyses on malarial parasites. Indeed, by exploring different calibration points, we found that the time for the radiation of primate parasites may have taken place in the Eocene, a time consistent with the radiation of African anthropoids. The radiation of the four human parasite lineages was part of such events. The time frame estimated in this investigation, together with our phylogenetic analyses, made plausible a scenario where gorillas and humans acquired malaria from a Pan lineage.

Nutrition and behavior of lemurs.

Attention to nutritional and behavioral factors is important for appropriate care of lemurs in captivity. Although only a few species are commonly held in captivity, differences between them are important. Knowledge of feeding ecology and natural diet guide nutrition guidelines, as well as management and prevention of common nutrition-related disorders, including obesity, diabetes, and iron-storage disease. Behavioral characteristics that influence captive management are related to social organization, reproductive behavior, territoriality, and infant care. Housing animals in appropriate social groupings in adequately complex environments reduces abnormal behaviors, and addition of enrichment activities and operant conditioning encourages normal behaviors.

Comparison of biomedical evaluation for white-fronted brown lemurs (Eulemur fulvus albifrons) from four sites in Madagascar.

Health and nutritional assessments of wildlife are important management tools and can provide a means to evaluate ecosystem health. Such examinations were performed on 37 white-fronted brown lemurs (Eulemur fulvus albifrons) from four sites in Madagascar. Comparison of health parameters between sites revealed statistically significant differences in body weight, body temperature, respiratory rate, hematology parameters (white cell count, hematocrit, segmented neutrophil count, and lymphocyte count), serum chemistry parameters (aspartate aminotransferase, alanine aminotransferase, serum alkaline phosphatase, total protein, albumin, phosphorus, calcium, sodium, chloride, and creatinine phosphokinase), and nutrition parameters (copper, zinc, ferritin, retinol, tocopherol, and 25-hydroxycholecalciferol). Two of 10 lemurs tested were positive for toxoplasmosis; none of 10 were positive for Cryptosporidium or Giardia. Enteric bacteria and endo- and ectoparasites were typical. Statistically different values in hematology and chemistry values probably do not reflect clinically significant differences, whereas nutrition parameter differences are likely related to season, soil, and forage availability.

Evaluation of iron status in lemurs by analysis of serum iron and ferritin concentrations, total iron-binding capacity, and transferrin saturation.

OBJECTIVE: To assess serum iron and ferritin concentrations, total iron-binding capacity, and transferrin saturation as indicators of iron metabolic status in 3 genera of lemurs and determine whether these variables are useful for screening for iron overload. DESIGN: Cross-sectional study. ANIMALS: 11 ring-tailed lemurs (Lemur catta), 11 black lemurs (Eulemur macaco macaco), and 11 red-ruffed lemurs (Varecia rubra). PROCEDURES: Blood samples were collected weekly for 3 weeks and assayed for serum iron and ferritin concentrations and total iron-binding capacity. Liver biopsy specimens were evaluated histologically and assayed for total iron, nonheme iron, and trace mineral concentrations. Deposition of iron was scored on Prussian blue-stained slides. RESULTS: Hepatic iron content ranged from 497 to 12,800 Pg/g dry weight (median, 2,165 Pg/g). Differences were seen in mean hepatic iron content across genera, with ruffed lemurs having the highest concentrations and ring-tailed lemurs having the lowest. Iron accumulation in the liver was mild, and cellular pathologic changes associated with iron storage disease were not detected in any lemur. Ferritin concentration was the only variable that correlated significantly with hepatic iron content in all 3 genera of lemurs; however, both transferrin saturation and serum iron concentration were correlated with hepatic iron concentration in ring-tailed and ruffed lemurs. CONCLUSIONS AND CLINICAL RELEVANCE: Serum ferritin concentration was the only variable that was consistently correlated with hepatic iron content in all 3 genera. Mean hepatic iron content varied across genera, suggesting that the propensity for lemurs to develop iron overload in captivity may vary across taxa.

Comparison of serum iron, total iron binding capacity, ferritin, and percent transferrin saturation in nine species of apparently healthy captive lemurs.

Lemurs kept in captivity have been reported to be highly prone to accumulate excessive amounts of iron in tissues (hemosiderosis). Diagnosis of the condition is most commonly made during a postmortem examination because an antemortem diagnosis requires a liver biopsy, a procedure that may not be well tolerated by all animals. The lack of a noninvasive method to evaluate iron status in captive lemurs limits investigators' ability to effectively screen animals for the presence of hemosiderosis, and to detect the condition early when treatment protocols are most effective. This study was conducted in an effort to provide data regarding iron analyte values in healthy captive lemurs of multiple species. The relationship of various iron-related metabolites was evaluated in 177 clinically normal lemurs of nine different species. Serum iron (sI), total iron binding capacity (TIBC), and ferritin concentration were measured directly and the percent transferrin saturation (TS) was calculated. Significant differences in various iron metabolites were observed among several species, suggesting that normal reference values for iron metabolites in lemurs may need to be developed on a species by species basis.

Retrospective evaluation of the incidence and severity of hemosiderosis in a large captive lemur population.

Significant concern has been generated about the susceptibility of captive lemurs to iron storage disease, which has led some researchers to propose husbandry changes regarding dietary iron. In the current study we sought to determine the history, severity, and prevalence of iron storage disease within a large captive lemur population. Iron concentration and hemosiderin accumulation in a target organ, the liver, were assessed in necropsy specimens from 15 different species (n=153) of lemurs over a 12-yr period at the Duke University Primate Center. Banked liver tissue was used to quantify liver iron concentration (LIC) via neutron activation analysis (NAA). Prussian blue staining was used to accentuate the presence of liver iron for evaluation using an established scoring system. Of the 153 reports examined, 49 (32%) of the animals were considered positive for the presence of hemosiderin in the liver, lymph node, duodenum, and kidney, with 36 of the 49 (73%) showing deposition of iron in the liver. Total iron scores (TIS) ranged from 0.3+/-0.3 in Lemur catta to 33.3+/-1.7 in Cheirogaleus medius. The mean LIC ranged from 209+/-1.4 microg/g wet weight in L. catta to 2957+/-414 microg/g in C. medius. Management practices may have contributed to some of the results observed in this study. Although evidence of excess iron deposition in the liver was present across several species studied, the levels were not as pervasive as previously reported in other captive lemur populations. Hemochromatosis was not observed, and excess iron was not related to the cause of death in any of the animals studied. The current findings suggest that iron overload in lemurs may be more complex than was previously believed.