Stress levels over time in Ruditapes philippinarum: The effects of hypoxia and cold stress on hsp70 gene expression

•The expression levels of RpHSP70 under hypoxia and cold stresses were analyzed by qPCR.•The RpHSP70 show different expression pattern in different color strains of Manila clam.•The RpHSP70 was up-regulated significantly at 2, 5 and 8 d under hypoxia stress in wild Manila clam. Ruditapes philippinarum is one of the most commercially important marine bivalves worldwide with a production over 4.0 million tons and 3.7 million USD in 2015. The Manila clam displays different shell color strains (white, zebra, and orange) in its natural habitat. Heat shock proteins (HSPs) play significant roles in response to adverse environmental stresses in aquatic animals. In this study, the expression levels of HSP70 gene were analyzed by qPCR in gills of Manila clams under hypoxia and cold stresses. The expression pattern of HSP70 was observed in different color strains of Manila clam under low temperature challenge. The expression of HSP70 was up-regulated significantly up to 8 days in cultured Manila clam under hypoxia stress. HSP70 expression in gill was inducible under hypoxia and low temperature stress. These findings contribute to our better understanding of the molecular response and biological function of HSPs in defending against low temperature and hypoxia challenges in R. philippinarum.