[en] Diarrhetic shellfish poisoning (DSP) toxins constitute a group of marine toxins displaying wide geographic distribution and involved in frequent toxic episodes (Harmful algal blooms, HABs) in coastal areas. Okadaic acid (OA) and its derivatives the dinophysistoxins (DTXs) are the main toxic compounds of this group. Seafood contamination by DSP toxins, especially bivalve molluscs, constitutes the principal cause of diarrhetic shellfish poisoning syndrome (DSP) in human consumers. In order to reduce its prevalence, efficient pollution control programs are currently conducted in shellfish farming industries, causing collateral economic losses. Despite the toxicity caused by DSP toxins in human and mammalian cell lines, bivalve molluscs show an apparent resistance to these compounds. This thesis evaluates, for the first time, the early effects of DSP toxins in the mussel Mytilus galloprovincialis using cellular and molecular biomarkers. Accordingly, the genotoxic and cytotoxic effects of OA were evaluated in hemolymph and gill cells in vitro. This approach was supplemented with the in vivo assessment of the effects of DSP-toxin-producing dinoflagellate Prorocentrum lima. Additionally, the transcriptional and biochemical responses of several antioxidant enzymes were determined in mussels exposed in vivo to P. lima. The results presented in this thesis increase the general knowledge pertaining the genotoxic and cytotoxic potential of DSP toxins in marine organisms and, more especifically, in the case bivalve molluscs. In addition, this work helps elucidate the connection between the exposure to these toxins and the induction of oxidative stress. Similarly, the results obtained suggest that the resistance of these organisms to DSP toxins is associated with the ability of their antioxidant system to respond immediately to damage. In conclusion, this thesis lays the foundation for the future development of efficient monitoring programs.

[gl] As toxinas diarreicas (Diarrhetic shellfish poisoning, DSP) constitúen un grupo de toxinas mariñas de ampla distribución xeográfica responsable de frecuentes episodios tóxicos de contaminación en áreas costeiras. Os principais compostos tóxicos que conforman este grupo son o ácido ocadaico (Okadaic acid, OA) e os seus derivados as dinofisitoxinas (Dinophysistoxins, DTXs). A contaminación por toxinas DSP en mariscos, especialmente en moluscos bivalvos, causa intoxicación diarreica (síndrome DSP) en consumidores humanos. Para reducir a súa prevalencia lévanse a cabo programas de control eficientes, pero que provocan perdas económicas colaterais no cultivo de moluscos. A pesar da toxicidade causada polas toxinas DSP en liñas celulares de humanos e mamíferos, os moluscos bivalvos mostran aparente resistencia a estes compostos. Nesta tese avaliáronse, por primeira vez, os efectos temperáns das toxinas DSP no mexillón Mytilus galloprovincialis mediante o uso de biomarcadores celulares e moleculares. Para iso levouse a cabo unha primeira aproximación mediante o estudo in vitro dos efectos xenotóxicos e citotóxicos do OA en células de hemolinfa e branquia de mexillón. Esta aproximación complementouse co estudo in vivo dos efectos do dinoflaxelado produtor de toxinas DSP Prorocentrum lima. Ademais, determinouse a resposta transcricional e bioquímica de varias enzimas antioxidantes de mexillón á exposición in vivo a P. lima. Os resultados obtidos na presente tese incrementan o coñecemento do potencial xenotóxico e citotóxico das toxinas DSP nos moluscos bivalvos e relaciónano co estrés oxidativo. Do mesmo xeito, a resistencia destes organismos ás toxinas DSP asóciase coa capacidade do sistema antioxidante para responder de forma inmediata aos primeiros danos. En xeral, nesta tese séntanse as bases para o desenvolvemento futuro de mecanismos eficientes de monitoraxe.