Transcriptional responses of Mytilus chilensis exposed in vivo to saxitoxin (STX)

Saxitoxin (STX) is one of the main phycotoxins that contribute to paralytic shellfish poisoning (PSP). This toxin is mainly produced by marine microalgae of the genus Alexandrium. There is evidence of changes at the physiological level in bivalves exposed to STX, although transcriptional responses to STX in bivalves have not yet been studied. The present work evaluates the expression of 13 candidate genes associated with cellular stress and immune response in Mytilus chilensis exposed to STX. Analysis by qPCR showed higher gene transcription levels in M. chilensis injected with STX than in control mussels. High levels of differential gene expression were observed for superoxide dismutase, catalase, ferritin and heat-shock protein genes. To a lesser extent, ependymin, fibrinogen-like, galectin and mytilin B genes were also significantly more expressed in haemocytes of mussels injected with STX that in control mussels. Our results provide insights into how marine toxins could modulate the innate immune system of marine invertebrates.