Centre d'Etudes Biologiques de Chizé

Molecular data are widely used to resolve complex phylogenetic relationships between cryptic species, particularly in cases where morphological features are insufficient to confirm taxonomic distinctness. For benthic shallow-water octopuses, several successes and failures have been reported when attempting to delineate species using individual nuclear or mitochondrial markers. In this study, we investigated the potential of shallow random shotgun sequencing to assess the phylogenetic placement of an undescribed southern hemisphere lineage within the Octopus vulgaris species complex, which could not be conclusively delimited using single-marker approaches. A total of 338 nuclear loci, along with complete mitochondrial genomes, were generated for two specimens presently classified as Octopus vulgaris (Type III) that originated from the southeastern Atlantic coast of South Africa and Amsterdam Island in the southern Indian Ocean. Our combined phylogenomic approach reveals that this lineage is genetically distinct from O. vulgaris sensu stricto (ss) from the Mediterranean and the northeast Atlantic, as well as from the closely related O. sinensis from East Asia. A further separation of O. vulgaris (Type III) into distinct South African and Amsterdam Island lineages cannot be proven. These findings add to the growing body of evidence that supports O. vulgaris Type III as a genetically distinct lineage within the O. vulgaris species complex, and emphasise that the taxonomic classification of this southern hemisphere lineage warrants re-evaluation.

Per- and polyfluoroalkyl substances (PFAS) are toxic and persistent compounds widely distributed in the environment and accumulate in top predators, including seabirds. Because of the biomagnification potentials of some PFAS, diet is thought to be a key exposure route for PFAS. However, other factors such as habitat use, may mask interspecific differences in PFAS exposure expected from trophic structure. Among seabirds, gulls are generalists that forage in both terrestrial and marine habitats, making them relevant models to concurrently investigate the influence of foraging habitats and trophic position on PFAS exposure. We combined plasma PFAS concentrations with GPS tracking and stable isotopes to define foraging habitats (δ13C; δ34S; GPS) and trophic positions (δ15N) in three sympatric gull species breeding in France (Isle of Ré). In herring gulls (Larus argentatus), long-chain perfluoroalkyl carboxylic acids (PFCAs) were positively correlated with high trophic resources from marine habitats. We found compound- and sex-dependent relationships between PFAS concentrations and stable isotope values in lesser black-backed gulls (Larus fuscus), while no association was found with habitat use. No association was found between PFAS levels and stable isotopes in great black-backed gulls (Larus marinus). Our study suggests that coastal habitat could be a source of PFCA contamination and highlights that the influence of habitat use on gull exposure to PFAS varied depending on species, sex, and compounds.

Large cetaceans face several anthropogenic threats. Among these, collisions are a major cause of anthropogenic mortality. Assessing and limiting their impact on populations is essential, as these species play an essential ecological role. All types of vessels, including offshore racing vessels, can collide with cetaceans. When a collision occurs between an offshore racing vessel and a large cetacean, the consequences are severe for both the whale, which is often injured or even killed and the vessel, which can suffer severe damage and be forced to withdraw from the race. Our study aimed to develop an encounter model that takes the characteristics of both cetaceans and racing vessels into account to estimate the number of encounters along vessel routes. The model was applied to three different routes commonly used in offshore racing: the first between Newport, USA and Skagen, Denmark; the second between Dover, England and the Gibraltar Strait; and the third between the Gibraltar Strait and Genoa, Italy. The number of encounters was estimated to be 1.7 for Route 1, 4.1 for Route 2 and 2.6 for Route 3. The model was also used to estimate the impact of routing vessels away from any exclusion zones that may be established in areas of high cetacean abundance. This routing could significantly reduce the number of encounters and offer potential solutions to reduce collisions between cetaceans and all types of vessels. The issue of collisions is becoming increasingly important and requires the development of methods to reduce the number of collisions worldwide.

Environmental unpredictability challenges the transmission success of vector-borne parasites like Plasmodium, whose fitness depends on synchronizing the production of transmission forms, called gametocytes, with vector availability. Although mosquito bites are known to trigger Plasmodium responses, it remains unclear whether parasites respond specifically to competent vectors or adopt a generalist strategy. We experimentally infected birds with the avian malaria parasite Plasmodium relictum and exposed them to bites from either a competent (Culex quinquefasciatus) or a non-competent (Anopheles gambiae) vector species. Both exposures induced a rise in parasitaemia, but the response was significantly stronger to the non-competent species. Host inflammatory, humoral and stress markers remained similar across mosquito treatments, implying that unidentified physiological cues may underlie the parasite’s response. No species-specific modulation of gametocyte conversion rate or sex ratio was observed. These findings suggest that P. relictum does not discriminate between mosquito species, instead employing a generalist, possibly bet-hedging strategy in response to any mosquito bite. Our results highlight the importance of mosquito community composition in shaping parasite transmission dynamics. If non-vector mosquitoes enhance Plasmodium transmission investment, shifts in vector assemblages due to climate change or control measures may have unanticipated effects on disease ecology.

Abstract. Wind forcing plays a pivotal role in driving upper-ocean physical and biogeochemical processes, yet direct wind observations remain sparse in many regions of the global ocean. While passive acoustic techniques have been used to estimate wind speed from moored and mobile platforms, their application to profiling floats has been demonstrated only in limited cases and remains largely unexplored. Here, we report on the first deployment of a profiling float equipped with a passive acoustic sensor, aimed at detecting wind-driven surface signals from depth. The float was deployed in the northwestern Mediterranean Sea near the DYFAMED meteorological buoy from February to April 2025, operating at parking depths of 500–1000 m. We demonstrate that wind speed can be successfully retrieved from subsurface ambient noise using established acoustic algorithms, with float-derived estimates showing good agreement with collocated surface observations from the DYFAMED buoy. To evaluate the potential for broader application, we simulate a remote deployment scenario by refitting the acoustic model of Nystuen et al. (2015) using ERA5 reanalysis as a proxy for surface wind. Refitting the model to ERA5 data demonstrates that the float–acoustic–wind relationship is generalizable in moderate conditions, but high-wind regimes remain systematically biased—especially above 10 m s-1. Finally, we apply a residual learning framework to correct these estimates using a limited subset of DYFAMED wind data, simulating conditions where only brief surface observations—such as those from a ship during float deployment—are available. The corrected wind time series achieved a 37 % reduction in RMSE and improved the coefficient of determination (R2) from 0.85 to 0.91, demonstrating the effectiveness of combining reanalysis with sparse in-situ fitting. This framework enables the retrieval of fine-scale wind variability not captured by reanalysis alone, supporting a scalable strategy for float-based wind monitoring in data-sparse ocean regions—with important implications for quantifying air–sea exchanges, improving biogeochemical flux estimates, and advancing global climate observations.

The annual molt, when penguins replace their entire plumage within a short period while fasting ashore, is the energetically most challenging period of their annual cycle. During molt, king penguins (Aptenodytes patagonicus) lose most of their insulating subcutaneous fat and half of their pectoral muscle mass. Such massive changes might impact their physiological capacity during deep foraging dives of their post-molt trip, when they need to recover body reserves for the upcoming breeding season. In immature king penguins, the dive/foraging performance following molt is significantly altered, suggesting physiological constraints as a consequence of the severe changes during molt. To investigate whether adult king penguins are similarly affected by their molt fast, we implanted data-loggers into six adult birds before their annual molt cycle and recorded dive behavior and subcutaneous temperature as an index of peripheral perfusion. The results suggest that physiological dive capacity following molt is less affected in adults. For example, unlike in immatures, recovery time at the surface for dives to a given depth did not differ between pre- and post-molt trips in adults. Nevertheless, important foraging parameters, such as the time spent at foraging depth, were significantly reduced following molt, suggesting some carry-over effects, which probably explain the longer period spent at sea. Subcutaneous temperature changes, reflecting differences in perfusion, illustrate the interplay between conflicting physiological demands (fat deposition/mobilization and feather synthesis versus heat loss/thermoregulation). Despite all these challenges, adult birds managed to rebuild their subcutaneous fat layer during post-molt, the most important energy source for their upcoming courtship/incubation fast.