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1. Lowered sensitivity of bitter taste receptors to β-glucosides in bamboo lemurs: an instance of parallel and adaptive functional decline in TAS2R16?

   https://doi.org/10.1098/rspb.2021.0346  

   Itoigawa, Akihiro; Fierro, Fabrizio; Chaney, Morgan E.; Lauterbur, M. Elise; Hayakawa, Takashi; Tosi, Anthony J.; Niv, Masha Y.; Imai, Hiroo (April 2021, Proceedings of the Royal Society B: Biological Sciences)

   null (Ed.)

   Bitter taste facilitates the detection of potentially harmful substances and is perceived via bitter taste receptors (TAS2Rs) expressed on the tongue and oral cavity in vertebrates. In primates, TAS2R16 specifically recognizes β-glucosides, which are important in cyanogenic plants' use of cyanide as a feeding deterrent. In this study, we performed cell-based functional assays for investigating the sensitivity of TAS2R16 to β-glucosides in three species of bamboo lemurs ( Prolemur simus, Hapalemur aureus and H. griseus ), which primarily consume high-cyanide bamboo. TAS2R16 receptors from bamboo lemurs had lower sensitivity to β-glucosides, including cyanogenic glucosides, than that of the closely related ring-tailed lemur ( Lemur catta ). Ancestral reconstructions of TAS2R16 for the bamboo-lemur last common ancestor (LCA) and that of the Hapalemur LCA showed an intermediate sensitivity to β-glucosides between that of the ring-tailed lemurs and bamboo lemurs. Mutagenetic analyses revealed that P. simus and H. griseus had separate species - specific substitutions that led to reduced sensitivity. These results indicate that low sensitivity to β-glucosides at the cellular level—a potentially adaptive trait for feeding on cyanogenic bamboo—evolved independently after the Prolemur – Hapalemur split in each species. 

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2. The Evolution of Cognitive Control in Lemurs

   https://doi.org/10.1177/09567976221082938  

   De Petrillo, Francesca; Nair, Parvathy; Cantwell, Averill; Rosati, Alexandra G. (September 2022, Psychological Science)

   Cognitive control, or executive function, is a key feature of human cognition, allowing individuals to plan, acquire new information, or adopt new strategies when the circumstances change. Yet it is unclear which factors promote the evolution of more sophisticated executive-function abilities such as those possessed by humans. Examining cognitive control in nonhuman primates, our closest relatives, can help to identify these evolutionary processes. Here, we developed a novel battery to experimentally measure multiple aspects of cognitive control in primates: temporal discounting, motor inhibition, short-term memory, reversal learning, novelty responses, and persistence. We tested lemur species with targeted, independent variation in both ecological and social features (ruffed lemurs, Coquerel’s sifakas, ring-tailed lemurs, and mongoose lemurs; N = 39) and found that ecological rather than social characteristics best predicted patterns of cognitive control across these species. This highlights the importance of integrating cognitive data with species’ natural history to understand the origins of complex cognition. 

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3. Primate hibernation: The past, present, and promise of captive dwarf lemurs

   https://doi.org/10.1111/nyas.15206  

   Blanco, Marina B; Greene, Lydia K; Welser, Kay H; Ehmke, Erin E; Yoder, Anne D; Klopfer, Peter H (August 2024, Annals of the New York Academy of Sciences)

   Abstract The dwarf lemurs (Cheirogaleusspp.) of Madagascar are the only obligate hibernators among primates. Despite century‐old field accounts of seasonal lethargy, and more recent evidence of hibernation in the western fat‐tailed dwarf lemur (Cheirogaleus medius), inducing hibernation in captivity remained elusive for decades. This included the Duke Lemur Center (DLC), which maintains fat‐tailed dwarf lemurs and has produced sporadic research on reproduction and metabolism. With cumulative knowledge from the field, a newly robust colony, and better infrastructure, we recently induced hibernation in DLC dwarf lemurs. We describe two follow‐up experiments in subsequent years. First, we show that dwarf lemurs under stable cold conditions (13°C) with available food continued to eat daily, expressed shallower and shorter torpor bouts, and had a modified gut microbiome compared to peers without food. Second, we demonstrate that dwarf lemurs under fluctuating temperatures (12–30°C) can passively rewarm daily, which was associated with altered patterns of fat depletion and reduced oxidative stress. Despite the limitations of working with endangered primates, we highlight the promise of studying hibernation in captive dwarf lemurs. Follow‐up studies on genomics and epigenetics, metabolism, and endocrinology could have relevance across multidisciplinary fields, from biomedicine to evolutionary biology, and conservation. 

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4. Stable and transient structural variation in lemur vaginal, labial, and axillary microbiomes: Patterns by species, body site, ovarian hormones, and forest access

   https://doi.org/10.1093/femsec/fiaa090  

   Bornbusch, Sally L; Grebe, Nicholas M; Lunn, Siera; Southworth, Chelsea A; Dimac-Stohl, Kristin; Drea, Christine (May 2020, FEMS Microbiology Ecology)

   Abstract Host-associated microbiomes shape and are shaped by myriad processes that ultimately delineate their symbiotic functions. Whereas a host's stable traits, such as its lineage, relate to gross aspects of its microbiome structure, transient factors, such as its varying physiological state, relate to shorter-term, structural variation. Our understanding of these relationships in primates derives principally from anthropoid studies and would benefit from a broader, comparative perspective. We thus examined the vaginal, labial, and axillary microbiota of captive, female ring-tailed lemurs (Lemur catta) and Coquerel's sifakas (Propithecus coquereli), across an ovarian cycle, to better understand their relation to stable (e.g. species identity/mating system, body site) and transient (e.g. ovarian hormone concentration, forest access) host features. We used 16S amplicon sequencing to determine microbial composition and enzyme-linked immunosorbent assays to measure serum hormone concentrations. We found marked variation in microbiota diversity and community composition between lemur species and their body sites. Across both host species, microbial diversity was significantly correlated with ovarian hormone concentrations; negatively with progesterone and positively with estradiol. The hosts’ differential forest access related to the diversity of environmental microbes, particularly in axillary microbiomes. Such transient endogenous and exogenous modulators have potential implications for host reproductive health and behavioral ecology. 

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5. Diverse Circular DNA Viral Communities in Blood, Oral, and Fecal Samples of Captive Lemurs

   https://doi.org/10.3390/v16071099  

   Paietta, Elise N; Kraberger, Simona; Lund, Michael C; Vargas, Karla L; Custer, Joy M; Ehmke, Erin; Yoder, Anne D; Varsani, Arvind (July 2024, Viruses)

   Few studies have addressed viral diversity in lemurs despite their unique evolutionary history on the island of Madagascar and high risk of extinction. Further, while a large number of studies on animal viromes focus on fecal samples, understanding viral diversity across multiple sample types and seasons can reveal complex viral community structures within and across species. Groups of captive lemurs at the Duke Lemur Center (Durham, NC, USA), a conservation and research center, provide an opportunity to build foundational knowledge on lemur-associated viromes. We sampled individuals from seven lemur species, i.e., collared lemur (Eulemur collaris), crowned lemur (Eulemur coronatus), blue-eyed black lemur (Eulemur flavifrons), ring-tailed lemur (Lemur catta), Coquerel’s sifaka (Propithecus coquereli), black-and-white ruffed lemur (Varecia variegata variegata), and red ruffed lemur (Varecia rubra), across two lemur families (Lemuridae, Indriidae). Fecal, blood, and saliva samples were collected from Coquerel’s sifaka and black-and-white ruffed lemur individuals across two sampling seasons to diversify virome biogeography and temporal sampling. Using viral metagenomic workflows, the complete genomes of anelloviruses (n = 4), cressdnaviruses (n = 47), caudoviruses (n = 15), inoviruses (n = 34), and microviruses (n = 537) were determined from lemur blood, feces, and saliva. Many virus genomes, especially bacteriophages, identified in this study were present across multiple lemur species. Overall, the work presented here uses a viral metagenomics approach to investigate viral communities inhabiting the blood, oral cavity, and feces of healthy captive lemurs. 

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