Performances physiologiques et forces d'attachement des moules triploïdes

RÉSUMÉ : La mytiliculture est une ressource économique importante pour le Canada, avec par exemple, une production de 26 000 tonnes en 2019 pour une valeur de plus de 43 millions de dollars. Cependant, une cause majeure de perte de production pour les mytiliculteurs provient du détachement des moules au cours de leur croissance. Ce phénomène est particulièrement important durant la saison de reproduction. En effet, les moules investissent la majeure partie de leur énergie dans la reproduction et ont donc moins d'énergie pour la byssogenèse. Cela conduit à un affaiblissement du byssus, qui peut ultimement mener au détachement des moules. De tels détachements peuvent considérablement réduire la productivité des mytilicultures et résulter en la perte de plus de 50% de la production. Récemment, il y a eu un intérêt croissant pour le développement des écloseries de moules et plus spécifiquement pour la production de moules triploïdes. En effet, il est connu que la triploïdie tend à réduire la fertilité des bivalves et peut même produire des bivalves entièrement stériles qui ont plus d'énergie à investir dans leur croissance et d'autres tissus vitaux (par exemple le byssus). L'objectif principal de cette thèse de doctorat était donc de valider les effets de la triploïdie chez Mytilus edulis, notamment concernant ses capacités de reproduction et d'attachement, ainsi que les potentiels impacts sur la physiologie et le métabolisme des moules. De plus, le développement de techniques de production de moules triploïdes dans des conditions d'écloserie était aussi un aspect important de ce projet. Le premier objectif de cette thèse consistait à développer des techniques efficaces d'induction de la triploïdie, applicables dans des conditions d'écloserie par un personnel non spécialisé. Afin d'induire la triploïdie, il a été décidé d'inhiber l'extrusion du second globule polaire d'œufs fécondés. Des traitements à chaud ou à froid ont été appliqués, ainsi que des traitements chimiques en utilisant de la 6-(Dimethylamino)purine (6-DMAP). De plus, l'efficacité des traitements a été comparée en fonction de leur moment d'application (post-fécondation). Les résultats ont montré que le traitement des œufs à 17 minutes post-fécondation avec 400 µM de 6-DMAP, a induit les plus forts taux de triploïdie avec plus de 90% d'induction. De plus, les larves triploïdes ont montré un avantage de croissance significatif jusqu'à la fin de l'étude, au moment de leur fixation. Le second objectif de cette thèse portait sur l'étude de la production et les propriétés mécaniques des fibres de byssus, chez des moules Mytilus edulis de petite taille ( 50 mm). Les résultats n'ont pas montré d'investissement reproductif important chez les moules 50 mm ont montré une réduction de l'investissement de reproduction chez les triploïdes, ainsi qu'une maturation incomplète des gamètes, des signes de résorption des gamètes et un sexe-ratio fortement altéré avec une absence de femelles. Le quatrième objectif était de comparer la production, les propriétés mécaniques, ainsi que la composition du byssus de moules de taille commercialisable (> 50 mm). La production de byssus et les analyses des propriétés mécaniques ont été faites selon la même méthodologie que pour le 2ème objectif. La composition en acides aminés et métaux des fibres a également été analysée. Les résultats ont montré des tendances similaires chez les moules > 50 mm avec les résultats présentés en lien avec le deuxième objectif. La composition et la structure en acides aminés des fibres n'étaient pas significativement différentes entre les 2 groupes. Cependant, certains métaux, tels que le B, Cu, SR, Os, W, Ag, Nb, Bi, et Tl étaient en concentration plus importante dans le byssus des moules diploïdes. Les moules triploïdes ont montré une augmentation du taux de filtration, du potentiel de croissance, ainsi que de la résistance de la coquille de respectivement 48%, 57%, 40%. Ensemble, les résultats de cette étude montrent un fort potentiel des moules triploïdes pour l'aquaculture, avec une croissance augmentée, la production de plus de fibres de byssus ayant des propriétés mécaniques supérieures, mais également moins d'investissement en reproduction et potentiellement plus d'énergie disponible pour d'autres activités métaboliques. Ainsi, la production de moules triploïdes pourrait réduire les pertes dues au détachement et augmenter les taux de production grâce à une croissance supérieure et une meilleure survie. -- Mot(s) clé(s) en français : Triploïdie, Byssus, Mytilus edulis, Bivalve, Attachement, Reproduction, Filtration, Potentiel de croissance, Croissance. -- ABSTRAT : Mussel farming is an important economic resource for Canada accounting for a production of 26,000 tonnes produced in 2019 and a value over＄43 million. A major cause of loss of production for mussel farmers originates from the fall-off of mussels during their growth. This phenomenon is particularly important during the reproductive season since mussels invest most of their energy in reproduction and therefore have less energy available for byssogenesis. This leads to a weakening of the byssus, which can ultimately result in the fall-off of the mussels. This can considerably reduce the productivity of mussel farms and result in the loss of more than 50% of production. Recently there has been a growing interest in the development of mussel hatcheries and more specifically in the production of triploid mussels. Indeed, it is known that triploidy tends to reduce the fertility of bivalves and can even produce sterile bivalves which would have more energy to invest in their growth and in other vital tissues (i.e. the byssus). The main objective of this doctoral thesis was therefore to validate the effects of triploidy in Mytilus edulis, in particular regarding its reproductive and attachment performances, as well as the potential impacts on its physiology and metabolism of mussels. In addition, the development of techniques to produce triploid mussels under hatchery conditions was also an important aspect of this project. The first objective of this thesis consisted in developing effective triploidy induction techniques applicable in hatchery conditions by non-specialized personnel. To induce triploidy, it was decided to inhibit the extrusion of the second polar body of fertilized eggs. Hot or cold treatments were applied, as well as chemical treatments using 6-(Dimethylamino)purine (6-DMAP). In addition, the efficiency of the treatments was compared according to their time of application (post-fertilization). The results showed that the treatment of eggs at 17 minutes post-fertilization with 400 µM of 6-DMAP induced the highest levels of triploidy with more than 90% induction. Additionally, triploid larvae showed a significant growth advantage until the end of the study when larvae settled. The second objective of this thesis focused on the production and mechanical properties of byssus threads in small Mytilus edulis mussels (˂ 30 mm), before their first investments in reproduction. Byssus production was stimulated by placing the mussels in a hydrodynamic flume for 3 days. At the end of the 3 days, the threads were counted, collected, tensiometric analyzes were applied to each thread. The results showed that although the mussels did not yet invest massive energy in reproduction, the triploids produced significantly more threads (65%) than the diploids, with altered mechanical properties and in particular an increase in Young's modulus of 45% in triploids. In addition, the clearance rate and scope for growth were respectively 40% and 260% higher in triploids compared to diploids. The third objective aimed to compare the reproductive performance of diploid and triploid mussels of two different size groups (˂ 30 mm and ˃ 50 mm). The results did not show significant reproductive investment in mussels ˂ 30 mm, nor any difference between diploids and triploids for this size group. On the other hand, mussels ˃ 50 mm showed a reduction in reproductive investment in triploids, as well as an incomplete maturation of gametes, signs of gamete resorption and a strongly altered sex ratio with an absence of females. The fourth objective compared the production, the mechanical properties, as well as the composition of the byssus of commercial size mussels ˃ 50 mm. The byssal production and the analyzes of the mechanical properties were made according to the same methodology as for the 2nd chapter. The amino acid and metal composition of the fibers were also analyzed. The results showed similar trends in mussels ˃ 50 mm with the results of the 2nd chapter. The structure and composition in amino acids of the byssal threads were not significantly different between the 2 groups. However, some metals, such as B, Cu, SR, Os, W, Ag, Nb, Bi, Tl were in higher concentration in the byssus of diploid mussels. The triploid mussels showed an increase in filtration rate, growth potential, as well as shell strength by 48%, 57%, 40% respectively. Together, the results of this study show a strong potential of triploid mussels for aquaculture, with increased growth, production of more byssal threads with superior mechanical properties, but also less investment in reproduction and potentially more energy available for other metabolic activities. Thus, the production of triploid mussels could reduce losses due to fall-off and increase the production rates through superior growth and better survival. -- Mot(s) clé(s) en anglais : Triploidy, Byssus, Mytilus edulis, Bivalve, Attachment, Reproduction, Clearance rate, Scope for growth, Growth

Effets des nanoparticules d'argents sur les composés organiques soufrés d'origine biologique

RÉSUMÉ: Il est connu que l’argent ionique ainsi que les nanoparticules d’argent (AgNPs) ont une forte affinité pour les composés soufrés aussi bien inorganiques qu’organiques. De nombreuses études ont en effet démontré des interactions entre les AgNPs et des acides aminés soufrés tels que la cystéine via le groupement thiol de la molécule. De plus, certaines recherches ont proposé que les AgNPs puissent se lier aux protéines via leurs groupements thiols. L’objectif principal de ce mémoire était d’analyser les interactions des AgNPs avec les composés soufrés organiques tels que la cystéine et l’albumine et de comparer les résultats obtenus avec les effets des ions Ag+ sur ces mêmes molécules. Par ailleurs il s’est présenté une occasion de rédiger une revue de littérature afin d’expliquer le comportement, les transformations et le devenir des AgNPs une fois introduites dans l’environnement aquatique ; cette revue fait partie de ce mémoire. Suite à des expériences de spectroscopie RAMAN et de matrices d’excitation-émission de fluorescence, des interactions entre l’argent ionique avec le soufre du groupement thiol de la cystéine ont été démontrées. De plus, les effets des ions Ag+ et des AgNPs sur la protéine d’albumine ont été mesurés. Les résultats obtenus ont montré des effets plus importants en présence des ions Ag+ que des AgNPs. Il a été proposé que les ions argent, étant plus petits que les AgNPs, aient un accès facilité à certains sites de liaisons sur la protéine d’albumine en comparaison des nanoparticules. Finalement, il a été indirectement observé que bien que les AgNPs aient des effets plus faibles que l’argent ionique sur l’albumine, elles sont tout de même capables d’affecter directement la protéine. À notre connaissance, aucune étude antérieure n’avait comparé les effets des ions argent à ceux des nanoparticules d’argent sur la protéine d’albumine. -- Mot(s) clé(s) en français : AgNPs, ROS, soufre, albumine, fluorescence, RAMAN, environnement. -- ABSTRACT: It is well known that silver ions as well as silver nanoparticles (AgNPs) have a high affinity for organic and inorganic sulfur compounds. Indeed, many studies have demonstrated the interactions between AgNPs and small amino acids such as cysteine through the thiol group of the molecules. Moreover, some studies suggested that AgNPs could bind to proteins through their thiol groups. The main objectives of this study were to analyse the interactions of AgNPs with sulfur organic compounds such as cysteine and albumin as well as to compare the obtained results with the effect of silver ions on these same organic compounds. Furthermore, there was an opportunity to produce a literature review on the behavior, transformations and future of AgNPs once in the aquatic environment. This review takes part in this document. Experiments using RAMAN spectroscopy and excitation-emission fluorescence matrix have demonstrated interactions between ionic silver and sulfur of the thiol group of cysteine. Also, effects of Ag+ ions and AgNPs on the protein of albumin have been measured. Results showed that the effects were enhanced in presence of silver ions compared with AgNPs. It was suggested that as silver ions are smaller than AgNPs, they may have promoted access for specific binding sites of albumin compared to the nanoparticles. Finally, it has been indirectly observed that although AgNPs had less impact on albumin than the silver ions, they are still able to directly affect the protein. To our knowledge, no previous study had compared the effects of silver ions and AgNPs on the protein of albumin. -- Mot(s) clé(s) en anglais : AgNPs, ROS, sulfur, albumin, fluorescence, RAMAN, environment

Effets des nanoparticules d'argents sur les composés organiques soufrés d'origine biologique

RÉSUMÉ: Il est connu que l’argent ionique ainsi que les nanoparticules d’argent (AgNPs) ont une forte affinité pour les composés soufrés aussi bien inorganiques qu’organiques. De nombreuses études ont en effet démontré des interactions entre les AgNPs et des acides aminés soufrés tels que la cystéine via le groupement thiol de la molécule. De plus, certaines recherches ont proposé que les AgNPs puissent se lier aux protéines via leurs groupements thiols. L’objectif principal de ce mémoire était d’analyser les interactions des AgNPs avec les composés soufrés organiques tels que la cystéine et l’albumine et de comparer les résultats obtenus avec les effets des ions Ag+ sur ces mêmes molécules. Par ailleurs il s’est présenté une occasion de rédiger une revue de littérature afin d’expliquer le comportement, les transformations et le devenir des AgNPs une fois introduites dans l’environnement aquatique ; cette revue fait partie de ce mémoire. Suite à des expériences de spectroscopie RAMAN et de matrices d’excitation-émission de fluorescence, des interactions entre l’argent ionique avec le soufre du groupement thiol de la cystéine ont été démontrées. De plus, les effets des ions Ag+ et des AgNPs sur la protéine d’albumine ont été mesurés. Les résultats obtenus ont montré des effets plus importants en présence des ions Ag+ que des AgNPs. Il a été proposé que les ions argent, étant plus petits que les AgNPs, aient un accès facilité à certains sites de liaisons sur la protéine d’albumine en comparaison des nanoparticules. Finalement, il a été indirectement observé que bien que les AgNPs aient des effets plus faibles que l’argent ionique sur l’albumine, elles sont tout de même capables d’affecter directement la protéine. À notre connaissance, aucune étude antérieure n’avait comparé les effets des ions argent à ceux des nanoparticules d’argent sur la protéine d’albumine. -- Mot(s) clé(s) en français : AgNPs, ROS, soufre, albumine, fluorescence, RAMAN, environnement. -- ABSTRACT: It is well known that silver ions as well as silver nanoparticles (AgNPs) have a high affinity for organic and inorganic sulfur compounds. Indeed, many studies have demonstrated the interactions between AgNPs and small amino acids such as cysteine through the thiol group of the molecules. Moreover, some studies suggested that AgNPs could bind to proteins through their thiol groups. The main objectives of this study were to analyse the interactions of AgNPs with sulfur organic compounds such as cysteine and albumin as well as to compare the obtained results with the effect of silver ions on these same organic compounds. Furthermore, there was an opportunity to produce a literature review on the behavior, transformations and future of AgNPs once in the aquatic environment. This review takes part in this document. Experiments using RAMAN spectroscopy and excitation-emission fluorescence matrix have demonstrated interactions between ionic silver and sulfur of the thiol group of cysteine. Also, effects of Ag+ ions and AgNPs on the protein of albumin have been measured. Results showed that the effects were enhanced in presence of silver ions compared with AgNPs. It was suggested that as silver ions are smaller than AgNPs, they may have promoted access for specific binding sites of albumin compared to the nanoparticles. Finally, it has been indirectly observed that although AgNPs had less impact on albumin than the silver ions, they are still able to directly affect the protein. To our knowledge, no previous study had compared the effects of silver ions and AgNPs on the protein of albumin. -- Mot(s) clé(s) en anglais : AgNPs, ROS, sulfur, albumin, fluorescence, RAMAN, environment

Triploid mussels for aquaculture could lead to better production yield with higher survival rate

Aquaculture Canada and WAS North America 2022, 15-18 AugustMussel farming is an important economic resource for Canada, producing 26101 tonnes of mussels in 2019 worth more than 43 million Canadian dollars. A major cause of loss of production for mussel farmers originates from the fall-off of mussels during their growth. This phenomenon is particularly important during the reproduction season, as mussels invest most of their energy in the reproduction and have less energy for byssogenesis. This leads to byssal weakening, which can ultimately end with the fall-off of the mussels. Recently, there has been an increasing interest in the development of mussel hatcheries and more specifcally on the production of triploid mussels. Indeed, it is known that triploidy often reduces the fertility of bivalves and can even produce sterile bivalves that have more energy to invest in their growth and other vital tissues (e.g. byssus). In this study, we compared the production and mechanical properties of byssal threads of diploid and triploid mussels in relation to their energy budget and reproductive investment. To determine the effect of triploidy on byssal threads, diploid and triploid mussels were placed in a recirculating fume to induce production of byssal threads, then their scope for growth were estimated. The threads were counted and collected for tensile testing. Results show that triploid mussels produced up to 40% more threads than diploidfmussels, with triploid threads eliciting better mechanical properties. From May to September, during the reproductive season, diploid and triploid mussels were harvested in Georgetown Harbour, Prince Edward Island. Gonadosomatic index (GSI), gonad volume, gonad maturation, and sex ratio were determined for both groups. Results showed that while triploid mussels do invest a part of their energy in reproduction, they had lower GSI and gonad volume than the diploids. Also, for all tested groups, triploid gonads were less mature than those of diploids, and their sex ratio was signifcantly altered with absence of females in triploids. Furthermore, triploid gonads showed signs of gamete resorption, suggesting that triploid mussels could use their gametes for energetic storage. This study shows that triploid mussels have lower energetic investment in reproduction and suggests that this energy could be usedffor a higher byssal production with better performance. Thus the creation and production of triploid mussels are of great interest for mussel farmers as they are less likely to fall-off during production, and have higher energy available after spawning, which could result in increased survival and productionN

Triploidy in Mytilus edulis allows better attachment which can result in higher production yields

2021 Physiomar & Australia New Zealand Marine Biotechnology Society (ANZMBS) Conference, 7-9 SeptemberDuring the last decades, intensive work has been put into the production of triploid bivalves, as triploidy can lead to reduced investment in fertility and faster growth. In mussel farming, the seasonal weakening of their byssal attachment can cause fall-off from mussel socks. In this study, we investigated the production and mechanical properties of byssal threads of diploid and triploid mussels related to their physiological performance by measuring the scope for growth. Finally, the seasonal gametes’ production of juvenile and adult stage were estimated through histological observations. Production of byssal threads was induced with the use of a hydrodynamic flume to standardize the abiotic factors, including current and turbulence conditions. The triploid mussels produced 40% more threads than diploids characterized by different mechanical properties, particularly a higher Young’s modulus. Scope for growth was calculated through measurement of clearance rates, respiration rates and excretion rates and triploid mussels showed higher scope for growth, as well as higher clearance rates. Preliminary results of the histological measurement tend to show a reduced investment or a delay in triploid gametogenesis. Indeed, primary observations, performed mid-May 2021 just before the beginning of spawning events demonstrated more advanced development stage in diploid gametes. Overall, this study showed that triploid mussels can be of great interest in mussel farming as they seem to have better attachment, better growth potential, and reduced or delay gametogenesis investmentN

Triploidy in Mytilus edulis impacts the mechanical properties of byssal threads

12 pages, 3 tables, 4 figuresA major problem in mussel farming is mussel fall-off from mussel socks due to weakened byssal threads. This weakening is particularly prevalent following spawning events. During the last decades, significant work has been devoted to the production of triploid bivalves, which have a lower reproductive investment. In this study, we compared the byssal properties and energetic rates of triploid and diploid 1-year-old mussels (˂30-mm). To determine the effect of triploidy on byssal threads, diploid and triploid mussels were placed in a recirculating flume to induce the production of byssal filaments. Our results showed that triploid mussels produced up to 65% more threads than the diploids. Furthermore, tensile measurements showed that byssal threads from triploid mussels had higher Young's modulus values (45% increase) and had multiple yield points. Energetic rates and metabolic investments were measured through food assimilation and oxygen consumption. The results showed that triploid mussels had a higher clearance rate (40% increase) and scope for growth (260% increase) when compared to diploids. Morphological comparisons showed variations between the two groups, with triploid mussels having a larger shell height than diploids of the same lengthThis work was supported by the Ressource Aquatiques Québec Research Network [Fonds de Recherche du Québec-Nature et Technologies, no. 2014-RS-171172] and Atlantic Aqua Farms in partnership with the Department of Fisheries and Oceans of Canada (Aquaculture Collaborative Research and Development Program) [Project 17-G-03]Peer reviewe

The transcription factor Rfx7 limits metabolism of NK cells and promotes their maintenance and immunity

Regulatory factor X 7 (Rfx7) is an uncharacterized transcription factor belonging to a family involved in ciliogenesis and immunity. Here, we found that deletion of Rfx7 leads to a decrease in natural killer (NK) cell maintenance and immunity in vivo. Genomic approaches showed that Rfx7 coordinated a transcriptional network controlling cell metabolism. Rfx7-/- NK lymphocytes presented increased size, granularity, proliferation, and energetic state, whereas genetic reduction of mTOR activity mitigated those defects. Notably, Rfx7-deficient NK lymphocytes were rescued by interleukin 15 through engagement of the Janus kinase (Jak) pathway, thus revealing the importance of this signaling for maintenance of such spontaneously activated NK cells. Rfx7 therefore emerges as a novel transcriptional regulator of NK cell homeostasis and metabolic quiescence