Potentialities of two red algae species of the Asparagopsis genus : effects on the the European eel physiology and on its pathogens

• Main Author: Parchemin, Christelle
• Other Authors: Centre de recherches insulaires et observatoire de l'environnement (CRIOBE), Université de Perpignan Via Domitia (UPVD)-École Pratique des Hautes Études (EPHE), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre de Formation et de Recherche sur les Environnements Méditérranéens (CEFREM), Université de Perpignan Via Domitia (UPVD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Perpignan, Nathalie Bontemps
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2023
• Subjects: Chemical analysis; Endangered species; Experimentations; Microbiology / parasitology; Food supplements; Microbiologie/parasitologie; Espèce en danger d'extinction; Valorisation d'extraits d'algues; Expérimentations; Analyses chimiques; [CHIM.ORGA]Chemical Sciences/Organic chemistry; Anguilla anguilla; European eel
• Online Access: https://theses.hal.science/tel-04207577; https://theses.hal.science/tel-04207577/document; https://theses.hal.science/tel-04207577/file/These_Parchemin_Christelle_2023.pdf

In Europe, the eel (Anguilla anguilla) is a critically endangered species. In the Occitanie region, approximately160 professionals make a living from eel fishing. Beyond its economic interest, it plays a major ecological role in ecosystems, both as a source offood and as a predator. Infection by pathogens is considered to be one of the factors in the collapse of the eel population. In recent years,alternative, preventive and more environmentally friendly treatments to antibiotics have been developed, such as preparations based on terrestrialplants or algae. Studies have shown the potential of algae of the genus Asparagopsis as a supplement in aquaculture since their inclusion in thediet of certain fish has increased growth and the expression of certain genes related to immunity. In the Mediterranean, A. armata and A.taxiformis are considered invasive and represent a biomass that is little used in this context. Thus, the objective of the thesis is to study thepotential of two species of algae of the genus Asparagopsis to prevent/treat certain pathologies (bacterial infection by Edwardsiella anguillarumand parasitic infection by the nematode Anguillicola crassus), affecting the European eel. To do this, an approach combining metabolomics,metabarcoding, in vitro tests on parasites and bacteria, in vivo tests of feeding and infection by pathogens and transcriptomics was used. Thetransdisciplinary approach made it possible, firstly to better characterise the factors of variation in the metabolome, biological activities andmicrobiota of the two species of the genus Asparagopsis, and secondly, to evaluate the effects of in vitro algal extracts and in vivo algal powderon the physiology of the European eel and on its pathogens. Thus, the two species show significant differences in chemical composition whichcould explain the differences in effects on the survival of the parasite A. crassus observed in vitro and the differences in the palatability of eelsfed with the two algae. Furthermore, the antibacterial activity of ...