Physiological adaptation to increased environmental temperatures has been studied experimentally in a number of fish species, with the up-regulation of several genes identified as being associated with the process, such as the warm-acclimated protein (wap65). This article describes the cloning and characterisation of the wap65-2 gene from the Antarctic plunderfish (Harpagifer antarcticus). The transcriptional expression of this gene in response to elevated seawater temperatures over a time course series is presented. Initially there is strong down-regulation of this gene to a maximum of 40-fold within 4 h, followed by recovery to almost control levels within 48 h, indicating that this gene does not play a role in the potential temperature adaptation of H. antarcticus.