Biology subjects

Ratsirarson, J.

Publications and source records attributed to Ratsirarson, J..

3 recordsLinked to original sources

bioRxiv2024

The resilience of the oral microbiome and lability of the hair microbiome across host environments in wild and captive lemurs

Microbiome diversity and composition in mammals is affected by the hosts environment and has been linked to important immune and physiological host functions, yet most of these data come from the gut microbiome. Research on the oral and hair microbiome in nonhuman primates has been far less common, and information from wild primates is even rarer. These overlooked patterns of environmental effects on microbial communities across the body may have important implications for a range of host functions. Therefore, in this study we characterized the gut, oral, and hair microbiomes across nine different captive and wild lemur species: Eulemur collaris, Eulemur coronatus, Eulemur mongoz, Lemur catta, Microcebus griseorufus, Microcebus murinus, Propithecus coquereli, Propithecus verreauxi, and Varecia rubra. We explored how host environment affects the microbiome diversity of these three body regions using 16S rRNA sequencing and found significant differences in microbiome composition, diversity, and environmental influence across body regions. The oral microbiome was least diverse and most resilient to different environmental effects; conversely, the hair microbiome was both most diverse and most labile. Differentially abundant bacterial taxa across oral, gut, and hair microbiota may also reflect selective regimes unique to each body region. These results emphasize the importance of accounting for body region when conducting microbiome studies. ImportanceAn organisms microbiome plays important roles in a wide variety of the host animals physiological functions, yet how these microbial communities in body regions beyond the gut are affected by the hosts environment is not clearly understood. We therefore analyzed how the oral, gut, and hair microbiomes of nine lemur species (genera Eulemur, Lemur, Microcebus, Propithecus, and Varecia) varied across wild and captive environments. We found that host environment affected the microbiomes of each body region in distinct ways, with the oral microbiome appearing conserved and more resilient to environmental effects, particularly compared to the diverse and widely variable hair microbiome. To our knowledge, this study is the most comprehensive multi-body-region analysis of the lemur microbiome to date. Our results demonstrate that the environment does not have a universal effect on the microbiome across body regions, but is instead mediated by body-region specific factors.

ecology↗

bioRxiv2021

Molecular adaptation to folivory and the conservation implications for Madagascar's lemurs

Folivory evolved independently at least three times over the last 40 million years among Madagascars lemurs. Many extant lemuriform folivores exist in sympatry in Madagascars remaining forests. These species avoid feeding competition by adopting different dietary strategies within folivory, reflected in behavioral, morphological, and microbiota diversity across species. These conditions make lemurs an ideal study system for understanding adaptation to leaf-eating. Most folivorous lemurs are also highly endangered. The significance of folivory for conservation outlook is complex. Though generalist folivores may be relatively well equipped to survive habitat disturbance, specialist folivores occupying narrow dietary niches may be less resilient. Characterizing the genetic bases of adaptation to folivory across species and lineages can provide insights into their differential physiology and potential to resist habitat change. We recently reported accelerated genetic change in RNASE1, a gene encoding an enzyme (RNase 1) involved in molecular adaptation in mammalian folivores, including various monkeys and sifakas (genus Propithecus; family Indriidae). Here, we sought to assess whether other lemurs, including phylogenetically and ecologically diverse folivores, might show parallel adaptive change in RNASE1 that could underlie a capacity for efficient folivory. We characterized RNASE1 in 21 lemur species representing all five families and members of the three extant folivorous lineages: 1) bamboo lemurs (family Lemuridae), 2) sportive lemurs (family Lepilemuridae), and 3) indriids (family Indriidae). We found pervasive sequence change in RNASE1 across all indriids, a dN/dS value > 3 in this clade, and evidence for shared change in isoelectric point, indicating altered enzymatic function. Sportive and bamboo lemurs, in contrast, showed more modest sequence change. The greater change in indriids may reflect a shared strategy emphasizing complex gut morphology and microbiota to facilitate folivory. This case study illustrates how genetic analysis may reveal differences in functional traits that could influence species ecology and, in turn, their resilience to habitat change. Moreover, our results support the contention that not all primate folivores are built the same and highlight the need to avoid generalizations about dietary guild in considering conservation outlook, particularly in lemurs where such diversity in folivory has probably led to extensive specialization via niche partitioning.

ecology↗

bioRxiv2017

Advancing A Science For Sustaining Health: Establishing A Model Health District in Madagascar

ObjectiveWe demonstrate a replicable model health district for Madagascar. The governments of many low-income countries have adopted health policies that follow international standards, and yet there are four hundred million people without basic access to primary care. Closing this global health delivery gap is typically framed as an issue of scale-up, accomplished primarily through integrating international donor funds with broad-based health system strengthening (HSS) efforts. However, there is no established process by which healthcare systems measure improvements at the point of service and how those, in turn, impact population health. There is no gold standard, equivalent to randomized trials of individual-level interventions, for health systems research. Here, we present a framework for a model district in Madagascar where national policies are implemented along with additional health system interventions to allow for bottom-up adaptation.\n\nSettingThe intervention takes place in a government district in Madagascar, which includes 1 district hospital, 20 primary care health centers, and a network of community health workers.\n\nInterventionThe program simultaneously strengthens the WHOs six building blocks of HSS at all levels of the health system within a government district and pioneers a data platform that includes 1) strengthening the districts health management information systems; 2) monitoring and evaluation dashboards; and 3) a longitudinal cohort demographic and health study of over 1,500 households, with a true baseline in intervention and comparison groups.\n\nConclusionThe integrated intervention and data platform allows for the evaluation of system output indicators as well as population-level impact indicators, such as mortality rates. It thus supports field-based implementation and policy research to fill the know-do gap, while providing the foundation for a new science of sustaining health.\n\nData Sharing StatementData can be made available upon request by emailing research@pivotworks.org.

epidemiology↗