Studies were undertaken to determine ecotoxicological effects of model manufactured or engineered nanoparticles (ENPs), either alone or in combination with a representative polycyclic aromatic hydrocarbon (i.e. PAHs: fluoranthene) at different levels of biological organisation (viz. biochemical, histological and behavioural levels) in a sentinel, widely distributed marine invertebrate species, Mytilus edulis. With the current and predicted levels of pollution in the marine and coastal environment, there is an urgent need to establish the potential effects of persistent and emerging contaminants which includes ENPs and PAHs, to protect human and environmental health. In this study, initially, it was aimed to optimise the induction of biotransformation enzyme P-450 as a robust biochemical tool and good progress (chapter 3) was made to standardise P-450 in mussel. Due to certain technical and logistic limitations however we could not apply measurement of P-450 as potential biochemical biomarkers in this species. The possibility of using glutathione levels instead in the cell-free component of haemolymph samples as an indicator of oxidative stress, in an analogous way to that used in mammals was evaluated (chapter 4). The evidence suggested that cell-free haemolymph samples collected from adductor muscle of Mytilus edulis may be significantly contaminated with intracellular contents of myocytes of this organ (i.e. adductor muscle) and adductor muscle tissue is more generally useful to determine glutathione system responses. The validation study of different assays using copper as a relevant environmental contaminant (chapter 5) suggested the existence of clear relationships between genotoxic (as determined by induction of DNA strand breaks using the Comet assay) and higher level effects. The results further suggested the feasibility of adoption of an integrated approach and robustness of selected biomarkers to evaluate short and long-term toxic effects of pollutants. A multiple biomarker approach was then used to determine the potential interactive effect of C60 fullerenes in combination with fluoranthene. Where appropriate analytical tools (i.e. ICP-MS, GC-MS) were used to determine the levels of contaminant exposure and characterise the properties of the ENPs. The combined exposure of fluoranthene and C60 fullerenes produced enhanced biological damage at approximately at an- “additive” rather than synergistic level, which appeared to be as a result of oxidative stress (chapter 6). The final experiments were carried out in both the early and adult life stages to test the potential toxicity resulting from photochemical transformation of C60 fullerenes in Mytilus edulis (chapter 7). In general, the results showed, for the first time, genotoxic and developmental impact of the photochemically transformed C60 fullerenes at different life stages of marine mussel. Further research is required to identify the degraded products of C60 fullerenes and to understand the mechanism by which fresh and aged C60 fullerenes induces biological responses including oxidative stress and affect ecologically relevant aquatic organisms at different life stages. The thesis has taken the opportunity to discuss (chapter 8) the importance of applications of biological responses in hazard and risk assessment posed by anthropogenic chemicals in a broader context.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 129-148.

Proefschrift Universiteit van Amsterdam. / Met lit. opg. - Met samenvatting in het Nederlands.

Thesis (M.Sc.) -- Memorial University of Newfoundland, 1984. / Bibliography: leaves 127-144. Also available online.

Global climate change imposes physiological constraints on marine ecosystems that can alter the distribution of intertidal organisms. In one such instance, the native cold-adapted mussel Mytilus trossulus is being replaced along its southern range by the invasive warm-adapted Mytilus galloprovincialis. These blue mussels occur throughout rocky intertidal zones where they are subjected to greatly varying environmental conditions known to induce oxidative stress. We hypothesize that while under acute stress, related Mytilus congeners undergo a shift in redox potential from NADH-fueled respiratory pathways to pathways producing NADPH as a way to decrease the production of reactive oxygen species (ROS) and provide reducing equivalents to detoxify ROS. Additionally, we hypothesize that sirtuins (SIRT; a family of NAD-dependent deacetylases) might be involved in the regulation of this metabolic transition. To test the latter, a discovery approach will be used to analyze the proteomic response of M. galloprovincialis and M. trossulus to the pro-oxidant menadione, and sirtuin-inhibitors nicotinamide and suramin. Menadione can induce oxidative stress by increasing endogenous peroxide and superoxide radicals, while suramin and nicotinamde both inhibit sirtuin activity. Organisms were exposed to these compounds in filtered seawater for 8 h, followed by a 24.5 h recovery period under constant aeration. A multivariate analysis utilizing 2D-gel electrophoresis and protein identification via mass spectrometry showed that 18% and 17% of all identified protein spots detected demonstrated changes in abundance in M. galloprovincialis and M. trossulus, respectively. Using matrix-assisted laser desorption ionization (MALDI) tandem time-of-light mass spectrometry, we were able to identify 32-41% of proteins, depending on the species. The two Mytilus congeners showed the greatest differences in changes of protein abundance for oxidative stress proteins (including NADP-dependent isocitrate dehydrogenase). Both congeners showed similar effects in response to simultaneous sirtuin inhibition and MIOS for proteins involved in protein degradation (proteasome), cytoskeletal modifications (actin and tubulin), proteins regulating actin filament growth (F-actin capping protein), amino acid metabolism and stress signaling (G-proteins, small G-proteins and MAPK). Results indicate that protein acetylation plays an important role in the oxidative stress response of M. galloprovincialis. More specifically this suggests that sirtuins play an important role in regulating the general stress response in M. galloprovincialis and thus contribute to the greater stress resistance of this species. Furthermore, changes in the abundance of several molecular chaperones suggest a greater effect of sirtuins in regulating the cellular response to heat stress, which could in part explain why this species is more heat-tolerant than the native M. trossulus.

Understanding species-specific physiological tolerances to environmental extremes is key in determining the factors that contribute to regulating species distribution. This understanding will aid in determining which species will manage to thrive in a changing global climate. According to the IPCC (2013) it is expected that, in the coming years, many different types of abiotic factors will change as a result of global climate change. The intertidal habitat is a model habitat for studying environmental extremes as it is located at the interface between the marine and terrestrial environments, making it one of the most stressful marine habitats. It is characterized by a 24 hr light: dark cycle and a 12.4 tidal ebb and flow that exposes animals inhabiting this habitat to a wide array of aerial-associated stressors such as changes in temperature, aerial exposure, low oxygen or hypoxic conditions and desiccation stress. Sessile organisms such as marine mussels of the genus Mytilus, are an ideal study species for studying physiological tolerance at the environmental extremes of the intertidal habitat. In particular, M. trossulus and M. galloprovincialis are an excellent study system for examining physiological tolerance at environmental extremes due to the recent change in biogeographic range of both species. M. galloprovincialis, a native of the Mediterranean, has been taking over the coast of California and has been displacing the heat sensitive native M. trossulus. The effects of salinity stress and heat stress on the physiologies of these species have been investigated by Braby and Somero (2006a and 2006b), Tomanek and Zuzow (2010) and Tomanek et al. (2012). The results of these studies indicate that the invasive M. galloprovincialis is more heat tolerant but is sensitive to hyposalinity while the reverse is true for the native M. trossulus.. The next logical environmental stress to study is low tide or aerial-emersion as both species can be found both tidally and subtidally. According to Grieshaber et al. (1994) and Müller et al. (2012) Mytilus edulis mussels have mechanisms for mitigating aerial-emersion hypoxia; however, very few studies have been performed using the study system of M. trossulus and M. galloprovincialis in regard to aerial-emersion hypoxia. This study aimed to observe the responses of both M. trossulus and M. galloprovincialis to aerial-emersion hypoxic stress or low tide. The study also looked to see if the recent habitat history (tidal or subtidal) can play a role in the response of the mussels to hypoxia. The results of the experiment indicate that the invasive M. galloprovincialis may be less sensitive to hypoxic stress when compared to the native M. trossulus. This difference in sensitivity may be due to the difference in mechanisms of energy metabolism proteins and proteostasis proteins used to mitigate the effects of hypoxic stress. Moreover, tidal acclimation appears to better prepare the mussels for subsequent aerial exposure in both species, possibly based upon the principles of stress-hardening outlined by Kültz (2005).

Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 78-90.

Graduation date: 2006 / This study investigated whether a device commonly used to measure settlement of mussel larvae for ecological studies, the Tuffy™, functions uniformly whether placed in a bed of filamentous algae or on bare rock. During the summers of 2004 and 2005, the number of mussel larvae settling on Tuffys in patches of the filamentous algae Endocladia muricata and Neorhodomela larix, known to be natural substrata for settlement of mussels, was shown to be the same as on Tuffys on adjacent patches of bare rock. The data provide no evidence that adjacent filamentous algae affects settlement to Tuffys and support the utility of this technique for measuring the intensity of larval settlement.

No description available.

Les peptides antimicrobiens sont des éléments clés des mécanismes d'immunité innée développés pour combattre les microorganismes. Parmi ceux-ci, il y a les peptides antifongiques dont l'un, la mytimycine (MytM), avait été partiellement décrite chez la moule Mytilus edulis. Les buts de cette thèse consistaient en la caractérisation complète de la MytM chez M. edulis et chez M. galloprovincialis, ainsi qu'en la compréhension du rôle de ce peptide dans l'immunité de la moule. Les résultats montrent (i) une diversité des séquences nucléotides et en acides aminés en fonction de l'origine géographique des moules, résultant probablement d'une adaptation aux conditions environnementales; (ii) que 2 gènes différents codant la MytM sont simultanément présents dans le génome d'une même moule; (iii) que le niveau d'expression du gène de la MytM dépend de la nature du stimulus, suggérant l'existence de processus de reconnaissance spécifiques; et (iv) que le niveau d'expression du gène de la MytM varie d'une moule à l'autre. En conclusion, la MytM joue un rôle essentiel et spécifique chez la moule. Les données apportées par cette thèse enrichissent notre connaissance sur l'immunité innée des invertébrés. / Antimicrobial peptides are crucial elements of the innate immune mechanisms developed to fight microorganisms. Among them are antifungal peptides from which one, named mytimycin (MytM), had been partially reported in the blue mussel, Mytilus edulis. The purposes of this thesis were to fully characterize MytM in M. edulis and M. galloprovincialis and to understand how this peptide participates in mussel immunity. Results showed (i) the diversity of MytM mRNA and translated amino acid sequences according to geographic origin of mussels, probably resulting from adaptation to their environments; (ii) that 2 different MytM genes are simultaneously present in the genome of the same individual mussel; (iii) that expression level of MytM gene depends on the nature of the challenge, suggesting specific recognition processes; and (iv) MytM expression level was different from one mussel to another. In conclusion, MytM appeared to play a prominent and specific role in mussels. The advancement of our works added new data to the knowledge of innate immunity in invertebrates.