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A study on the genus Micrambe Thomson, 1863 (Coleoptera, Cryptophagidae) from Madagascar and Réunion is presented. Six species are hitherto known from these countries: M. apicalis Grouvelle, M. brevitarsis Bruce, M. consors Grouvelle, M. madagascariensis Grouvelle, M. modesta (Grouvelle), and M. reuninensis Lyubarsky. A new species, M. leonardoi sp. n., is formally described from Boorg-Murat, Réunion Island. A key is presented to enable their identification. Micrambe consors Grouvelle previously known only from Congo is reported here for the first time from Madagascar.

Background In recent years, the Asian tiger mosquito Aedes albopictus has emerged as a species of major medical concern following its global expansion and involvement in many arbovirus outbreaks. On Réunion Island, Ae. albopictus was responsible for a large chikungunya outbreak in 2005–2006 and more recently an epidemic of dengue which began at the end of 2017 and is still ongoing at the time of writing. This dengue epidemic has seen a high number of human cases in south and west coastal regions, while few cases have been reported in the north and east of the island. To better understand the role of mosquito populations in such spatial patterns of dengue virus transmission in Réunion Island, we examined the genetic diversity and population structure of Ae. albopictus sampled across the island. Results Between November 2016 and March 2017, a total of 564 mosquitoes were collected from 19 locations in three main climatic regions (West, East and Center) of Réunion Island and were genotyped using 16 microsatellite loci. A high genetic diversity was observed with 2–15 alleles per locus and the average number of alleles per population varying between 4.70–5.90. Almost all F IS values were significantly positive and correlated to individual relatedness within populations using a hierarchical clustering approach based on principal components analyses (HCPC). However, the largest part of genetic variance was among individuals within populations (97%) while only 3% of genetic variance was observed among populations within regions. Therefore, no distinguishable population structure or isolation by distance was evidenced, suggesting high rates of gene flow at the island scale. Conclusions Our results show high genetic diversity but no genetic structure of Ae. albopictus populations in Réunion Island thus reflecting frequent movements of mosquitoes between populations probably due to human activity. These data should help in the understanding of Ae. albopictus vector capacity and the design of effective mosquito control strategies.

This study examines groundwater flow paths and geochemical processes in the Piton des Neiges volcano on Reunion Island. Using data from the Salazie Amont tunnel, bored at a depth of 1000 m under the planèze of Plaine des Fougères, we characterise groundwater composition and weathering processes in volcanic terrains. The study area features high permeability in shallow lava flows, enabling deep water infiltration, but also demonstrates a decrease in permeability with increasing depth due to mineral precipitation of secondary phases, mainly clays. Reactive transport in the vadose and phreatic zones was modelled with KIRMAT, a geochemical code simulating water–rock interactions. Initial rainwater undergoes chemical changes while percolating through volcanic rock, increasing in pH and mineral content. In the phreatic zone, simulation results suggested magmatic CO 2 input, impacting water pH and mineral composition. The model captured observed mineral trends effectively, predicting significant secondary mineral formation at depth, particularly clay minerals. Results illustrate how mineralisation reduces permeability in volcanic formations over time, progressively creating an impermeable barrier in the volcano’s core. This research provides insights into the long-term evolution of groundwater systems in shield volcanoes, contributing to the understanding of aquifer dynamics and material flow in volcanic environments.

Mesophotic coral ecosystems (MCEs) have gained considerable attention this last decade but the paucity of knowledge on these ecosystems is pronounced, particularly in the Southwestern Indian Ocean region. We explore the spatial variation in macro-benthic and scleractinian communities along a wide depth gradient (15–95 m) and among contrasted sites around Reunion Island. Values for percent cover of macro-benthic and scleractinian communities varied significantly along depth, resulting in a vertical zonation of communities. We recorded a transition of light-dependent communities towards heterotrophic organisms between shallow and upper mesophotic zones at 30–45 m, and a community shift in the lower mesophotic zone at 75 m. Despite overlaps in scleractinian genera distribution along the depth gradient, predominant genera of shallow depths were in low abundance in MCEs (> 30 m). Our findings highlight the importance of MCEs as distinct ecosystems sheltering diverse, unique habitats and harboring abundant cnidarian-habitat forming organisms. Supporting the ‘Deep Reef Refuge Hypothesis’, 56% of scleractinian genera spanned shallow to mesophotic depths, while one-third were depth specialists, either shallow or mesophotic. This highlights the limited refuge potential of mesophotic reefs for Southwestern Indian Ocean coral communities. Our findings establish baseline data for monitoring and conserving Reunion Island’s MCEs.

This paper analyses data related to 62 human–shark interactions in New Caledonia and 60 in Reunion Island from 1980 to 2022. A database on human–shark interactions in New Caledonia and Reunion Island was developed using the same variables and similar time steps for both locations. The discussion focuses on human–shark interactions in New Caledonia, with some comparisons to those on Reunion Island where possible. Environmental, contextual and individual variables related to human–shark interactions were analysed to identify potential influencing factors. The data analysis for New Caledonia revealed some correlations between variables related to the human–shark interactions. The main results showed that there was a concomitant increase in human–shark interactions since 2010 in the bays of Noumea and in the prevalence of human–shark interactions among people practising boardsports since 2007. The year 2007 was a pivotal year with respect to differences in important parameters of human–shark interactions. The results of this comparison between Reunion Island and New Caledonia were as follows: fatal human–shark interactions occurred among individuals practising boardsports and in turbid environments, whereas nonfatal human–shark interactions among individuals engaged in spearfishing and in clear water in New Caledonia.

Bats are the only indigenous mammals on Reunion Island, with one of the three species, Mormopterus francoismoutoui, being endemic, and another, Pteropus niger, endangered. The endemic bat is highly adapted to urban areas and coexists in proximity to humans, living in large colonies in rooftops of houses, schools, and churches, and also under bridges. These bats hold considerable importance for Reunion Island’s natural heritage, but at the same time, they carry diseases and leave dejections that can cause olfactory discomfort and respiratory problems. As conservation and management measures hold profound implications on both human and bat populations, we need to foster a proper understanding of stakeholder perspectives and find common ground. We applied Q methodology to explore stakeholder discourses of bats on Reunion Island, focusing on aspects of conservation, management, and public health. Our combined quantitative and qualitative analyses revealed three principal discourses. The human-oriented discourse advocates public education and addressing myths and misconceptions to protect bats. The nature-oriented discourse prioritizes the protection of natural habitats to conserve bats. The public health and policy-oriented discourse seeks to adapt bat conservation and management policies to ensure public health safety. All stakeholders agreed that there is a lack of awareness among local media, which at times diffuses sensational and erroneous information, and that as well there is a need to integrate research output into public outreach efforts to garner interest in bats. These results can aid in contextualizing conservation actions and policies and could potentially provide sustainable management solutions to human-bat coexistence on Reunion Island.

The Western Indian Ocean biodiversity hotspot hosts a remarkable array of endemic species, but invasive alien species increasingly threaten its unique ecosystems. Lizards of the West African Agama agama species group are successful colonizers, with recent introductions to Grande Comore (Comoros Archipelago) and Reunion Island. Systematic revisions within the native range of the A. agama species group have left many of the introduced populations without clear identity. We used molecular methods to determine the identities of the Agama species introduced to Grande Comore and Reunion Island, define their respective likely origin, and assess body size characteristics for each island population. We identified Agama picticauda as the species present on both islands with likely origins in two distinct Western African regions. Agamas from Reunion Island had longer and wider heads with greater body weight than Grande Comore individuals. Sexual size dimorphism on both islands was driven by weight, with males being heavier than females. We provide foundations for further research on the ecology and impacts of A. picticauda on Western Indian Ocean islands and to aid in the development of targeted management strategies for controlling this invasive reptile.

Effective management of invasive species within protected areas requires innovative solutions. In the Mascarene's archipelago, the national park of Reunion contains the largest area of intact vegetation, which faces alarming threats from invasive alien plant species. In response, the local government initiated an inclusive partnership in 2018 involving decision-makers, managers, and scientists to address the management of invasive alien plant species. An operational framework from planning to implementation has been established encompassing five key steps: (1) conduct a comprehensive site assessment, (2) model future threats, (3) prioritise interventions, (4) implement actions through a multi-stakeholder programme spanning multiple years, and (5) evaluate the effectiveness of implemented interventions. This study provides an in-depth examination of the research-action partnership and the operational framework, illustrating outputs for key priority sites. Our survey covered over 2500 ha, quantifying invasion degree in three vegetation strata at a fine-scale, and revealed significant areas within subalpine vegetation which remain remarkably pristine. By adapting participatory conservation planning approaches, we developed implementation-level outputs at a scale useful for managers which guided interventions on the ground. The partnership exemplifies a transdisciplinary approach with a broad array of stakeholders. Drawing from a checklist of essential components for successful partnerships, we highlight key insights from this initiative, providing valuable lessons for managing invasions in other regions. This framework holds promise for addressing several Global Biodiversity Framework Targets concerning plant invasions in island ecosystems or within landscapes characterised by multi-layered governance.

Background Spinal dysraphism (SD) requires lifelong multidisciplinary follow-up to prevent complications and optimize functional outcomes. In geographically fragmented healthcare systems, continuity of care may be challenging, particularly when patients cross regional or national borders to access specialized services. This study aimed to describe care trajectories and identify factors associated with optimal follow-up among children with SD managed in the southwestern Indian Ocean region. Methods We conducted a retrospective cohort study including children with SD who received active postnatal surgical management in the regional referral center of Reunion Island. Maternal, perinatal, clinical, and geographic characteristics were collected from hospital records. Optimal follow-up was defined according to the institutional multidisciplinary follow-up protocol. Results A total of 92 mother–infant dyads were included. Most pregnancies originated in Reunion Island (62.0%), followed by Mayotte (18.5%), the Comoros (16.3%), and Madagascar (3.3%). Prenatal diagnosis was established in 47.8% of pregnancies but varied substantially across territories. Surgical closure of the spinal defect was performed at a median age of 3 days, and ventriculoperitoneal shunt placement was required in 44.6% of patients. Overall, 39 patients (42.4%) were lost to follow-up. Optimal follow-up was achieved in only 13 patients (14.1%). Geographic factors were strongly associated with follow-up outcomes. Patients residing in Reunion Island were significantly more likely to achieve optimal follow-up than those living outside the island ( p  = 0.04). In contrast, clinical characteristics—including lesion level, surgical timing, ventricular shunt placement, and functional outcomes—were not associated with follow-up status. Conclusion Continuity of care for children with SD in the southwestern Indian Ocean region is strongly influenced by geographic and health system factors. Despite successful initial surgical management, long-term follow-up remains limited for many patients living outside Reunion Island. Strengthening regional healthcare coordination and cross-border care pathways may help reduce disparities in access to long-term multidisciplinary care.

Coral recruitment is an essential demographic mechanism that underpins the community structure and dynamics of coral reefs and facilitates post-disturbance coral recovery. However, information on coral recruitment patterns in mesophotic coral ecosystems (MCEs) is globally scarce, and no study describes patterns in the lower mesophotic zone (> 60 m depth). We quantified spatial variability in coral recruitment at shallow (15 m), upper (45 m) and lower (75 m) mesophotic depths across three contrasted locations (nine stations) around Reunion Island in the southwestern Indian Ocean. This study, the first to assess coral recruitment patterns on lower mesophotic habitats, highlighted a marked decline in recruitment rate in MCEs consistently across locations. Recruit composition varied significantly with depth, with Pocilloporidae dominating shallow habitats, while lower MCEs exclusively harbored “other” coral family recruits (i.e., other than Acroporidae, Pocilloporidae and Poritidae). Coral recruitment rate on tile surface orientation varied significantly with depth, with an overall higher proportion of recruits recorded on top surfaces at lower mesophotic depths. The abundance of Pocilloporidae recruits was positively correlated with confamilial adult coral cover, suggesting stock-recruitment or recruitment-limitation models for the dynamic of dominant shallow corals over a broad depth gradient. Upper MCEs could constitute substantial refuges for Pocilloporidae corals, while lower MCEs are of paramount importance for “other” coral families. Interannual surveys are necessary to better understand the spatiotemporal variability of coral recruitment in shallow habitats and MCEs and the driving forces of early post-settlement processes.