One of the molecular responses which mostly contribute to the physiological plasticity of bivalves is the heat shock response mediated by heat shock proteins (HSP). Variations of HSP response were observed under environmental conditions, correlated with differences in environmental temperature and degree of heterogeneity across geographic thermal gradients and through time. Laboratory experiments characterized the expressions of different protein isoforms and coding genes, which are induced by heat as a prototypical stimulus. Nevertheless, other physical and chemical factors significantly induce HSP gene and protein expressions in bivalves, that can be different depending on tissues and the nature of the insult. Multiple alignments of the deduced amino acid sequences indicated that the bivalve HSP70 proteins share common structural and evolutionary features with the mammalian HSP70, while some appear to be exclusive. The rate at which new findings are made regarding the bivalve HSP response is still increasing. However, some major questions remain unanswered. Among them, the possibility that the bivalve HSP response is related to cell signalling pathways and acts as a component of the acute systemic response to stress is also discussed in this review.
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