Two complementary deoxyribonucleic acid (cDNA) clones encoding 2 different 70-kDa heat shock proteins (HSPs) were isolated from the prawn Macrobrachium rosenbergii. The cDNA clones were 2448 and 2173 bp in length and contained 1950- and 1734-bp open reading frames (ORFs), respectively. The ORFs encoded 649- and 577-amino acid polypeptides, which were named Mar-HSC70 and Mar-HSP70, respectively, according to the sequence identities with other known HSC70s and HSP70s and based on their inducibility in response to heat shock stress (at 35 degrees C). Genomic DNA sequence analysis revealed no introns in either gene. The major structural differences between the 2 proteins were a 60-amino acid segment and a 14-amino acid segment present in the N-terminal and C-terminal, respectively, of Mar-HSC70 that were not found in Mar-HSP70. Northern blotting and semiquantitative reverse transcription-polymerase chain reaction analyses indicated that the Mar-HSP70 gene was expressed under heat shock (35 degrees C) stress in a non-tissue-specific manner. In contrast, Mar-HSC70 messenger ribonucleic acid was constitutively expressed in every tissue except muscle, and its expression in response to heat shock (at 35 degrees C) changed only in muscle.