The primary role of heat shock proteins (HSPs) is to function as molecular chaperones. Their up-regulation also represents an important mechanism in the stress response [70] , and their activity is closely linked to the innate immune system. HSPs mediate the mitochondrial apoptosis pathway and affect the regulation of NF-kB [71] . HSPs are well studied in bivalves. For R. philippinarum, several assays have been developed to better understand the HSPs profile in response to heavy metals and pathogen stresses [72] [73] [74] . The most important and well-studied groups of HSPs were present in our R. philippinarum transcriptome (HSP27, HSP40/ DnaJ, HSP70 and HSP90), but other, less common HSPs were also represented (HSP10, HSP22, HSP83 and some members from the HSP90 family).