HAL Portal UPF (Université de la Polynésie française)
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Sanction disciplinaire contre un agent communal : seul le maire doit décider
No full textInternational audienceNote sous CAA Lyon, 27 mars 2024, no 22LY0036
Diversity and functional specialization of oyster immune cells uncovered by integrative single cell level investigations
No full textMollusks are a major component of animal biodiversity and play a critical role in ecosystems and global food security. The Pacific oyster, Crassostrea (Magallana) gigas, is the most farmed bivalve mollusk in the world and is becoming a model species for invertebrate biology. Despite the extensive research on hemocytes, the immune cells of bivalves, their characterization remains elusive. Here we were able to extensively characterize the diverse hemocytes and identified at least seven functionally distinct cell types and three hematopoietic lineages. A combination of single-cell RNA sequencing, quantitative cytology, cell sorting, functional assays and pseudo-time analyses was used to deliver a comprehensive view of the distinct hemocyte types. This integrative analysis enabled us to reconcile molecular and cellular data and identify distinct cell types performing specialized immune functions, such as phagocytosis, reactive oxygen species production, copper accumulation, and expression of antimicrobial peptides. This study emphasized the need for more in depth studies of cellular immunity in mollusks and non-model invertebrates and set the ground for further comparative immunology studies at the cellular level
Bioindicator Species of Plastic Toxicity in Tropical Environments
No full textIn French Polynesia, pearl farming represents the second economic resource of the country. The distinctive black pearls produced there are globally recognized and appreciated. However, pearl farms extensively use submerged plastic materials. Through gas chromatography coupled with tandem mass spectrometry detection (GC/MSMS) analysis, we were able to identify various POPs (Persistent Organic Pollutants) and additives released after 24 hours of leaching into seawater from these “pearl plastics” composed of PE (Polyethylene) and PP (Polypropylene). Subsequently, we tested different concentrations of this plastic leachate on five tropical species commonly raised in the pearl and aquaculture sector in Polynesia: Pinctada margaritifera, Saccostrea cucullata, Holothuria whitmaei, Litopenaeus stylirostris, and Tripneustes gratilla. Monitoring the embryo-larval development of these organisms allowed us to establish a correlation between the decrease in the percentage of normal larvae and the plastic concentration. Through the use of regression models, the EC50 (Effective Concentration) of the plastic leachate for each species was determined, and demonstrated to range from 6.6 to 71.5g/L, depending on the species. The most sensitive species was the black teatfish Holothuria whitmaei, a tropical sea cucumber used for the first time for ecotoxicological tests. The sensitivity of this species, its large distribution in tropical areas, and the various advantages presented by its cultivation make it an interesting bio-indicator species for monitoring plastic pollution in tropical lagoons
Toothed whale and shark depredation and bycatch in the longline fishery of French Polynesia
No full textInternational audienceMarine megafauna feeding on fishery catches (depredation) or being incidentally caught on fishing gear (bycatch) have become important issues. Their socioeconomic and conservation stakes have been increasingly studied across the world fisheries. They remain understudied in the Pacific Ocean, where longline tuna fisheries reported such interactions. In this study, we provide the first assessment of bycatch and depredation by sharks and odontocetes on longlines in French Polynesia between 2000 and 2018, using data from observers reporting, captains’ logbooks, questionnaires and additional monitoring by authors during three fishing trip. We found that less than 2% of the catch had been depredated, and that shark depredation was more common than odontocete depredation. Shark bycatch was important (20,000 sharks annually, 0.5 shark every 1000 hooks) and odontocete bycatch seemed low (13 occurrences in 18 years), though we identified clear reporting flaws. We discuss the range of uncertainty associated with our assessment, based on the current reporting systems, and the potential consequences of depredation and bycatch on tuna fisheries, as well as on shark and odontocete populations in French Polynesia
Corrigendum: Reconstructing global chlorophyll-a variations using a non-linear statistical approach
No full textcorrigendum of https://doi.org/10.3389/fmars.2020.00464International audienc
Les Français Libres dans les Établissements Français d'Océanie (1940 - 1947)
No full textInternational audiencePrésentation de ma thèse aux 15e Doctoriales de l'Université de la Polynésie Française le 14 mai 2024
A Comparative Study of the Floristic Diversity and Structure of Relictual Littoral and Swamp Forests in the Island of Tahiti (French Polynesia, South Pacific)
No full textInternational audienceLittoral and swamp forests are among the most threatened native plant communities in the island of Tahiti (South Pacific) due to past and present anthropogenic pressures such as agriculture, urbanization, pollutions, and invasive alien species, including the mangrove tree Rhizophora stylosa. In order to provide reference data that are crucial to implement appropriate conservation and restoration strategies in these habitats, we assessed the composition and structure of seven littoral and swamp forests types in eighteen 10 × 20 m plots considering three different strata (trees and lianas, epiphytes, and understory). Forest types were compared using common diversity indices (e.g., Shannon index, Simpson index, and Pielou evenness) and indicator values. Results show that native submangrove swamp forests dominated by the tree Talipariti tiliaceum and the large erect fern Acrostichum aureum were the most species-rich, while introduced Rhizophora mangroves had an almost monospecific composition in the trees, lianas, and understory strata. The diversity of trees and lianas was higher in littoral forests with the highest understory cover in Talipariti-Barringtonia asiatica and Talipariti-Inocarpus fagifer plant communities. Surprisingly, epiphyte diversity and abundance were higher in swamp forests with lower canopy, especially in the mixed swamp forest with both A. aureum and R. stylosa. These counter-intuitive results highlight the potential role of introduced species in creating novel microhabitats suitable for the development of some native epiphytes. Conservation and restoration projects should however focus on the use of native species to maintain these remnant littoral and swamp habitats in Tahiti and other high volcanic islands of the Society archipelago, rather than nonnative and potentially harmful species such as R. stylosa
L'attribution de « jours de congés déguisés » face au décompte du temps de travail
No full textInternational audienc
Tissue Distribution and Metabolization of Ciguatoxins in an Herbivorous Fish following Experimental Dietary Exposure to Gambierdiscus polynesiensis
No full textCiguatoxins (CTXs), potent neurotoxins produced by dinoflagellates of the genera Gambierdiscus and Fukuyoa, accumulate in commonly consumed fish species, causing human ciguatera poisoning. Field collections of Pacific reef fish reveal that consumed CTXs undergo oxidative biotransformations, resulting in numerous, often toxified analogs. Following our study showing rapid CTX accumulation in flesh of an herbivorous fish, we used the same laboratory model to examine the tissue distribution and metabolization of Pacific CTXs following long-term dietary exposure. Naso brevirostris consumed cells of Gambierdiscus polynesiensis in a gel food matrix over 16 weeks at a constant dose rate of 0.36 ng CTX3C equiv g−1 fish d−1. CTX toxicity determination of fish tissues showed CTX activity in all tissues of exposed fish (eight tissues plus the carcass), with the highest concentrations in the spleen. Muscle tissue retained the largest proportion of CTXs, with 44% of the total tissue burden. Moreover, relative to our previous study, we found that larger fish with slower growth rates assimilated a higher proportion of ingested toxin in their flesh (13% vs. 2%). Analysis of muscle extracts revealed the presence of CTX3C and CTX3B as well as a biotransformed product showing the m/z transitions of 2,3-dihydroxyCTX3C. This is the first experimental evidence of oxidative transformation of an algal CTX in a model consumer and known vector of CTX into the fish food web. These findings that the flesh intended for human consumption carries the majority of the toxin load, and that growth rates can influence the relationship between exposure and accumulation, have significant implications in risk assessment and the development of regulatory measures aimed at ensuring seafood safety