Hsp70 expression in the south-eastern Australian sea urchins Heliocidaris erythrogramma and H. tuberculata

Heat shock protein (hsp) expression was used as a biomarker to compare the thermal stress response to acute temperature fluctuations in two closely related Australian sea urchins inhabiting different thermal environments, the intertidal Heliocidaris erythrogramma and shallow subtidal H. tuberculata. Urchins were collected in summer and held in the laboratory at ambient sea surface temperature (22 degrees C) for at least 3 days. Hsp70 expression was examined in H. erythrogramma and H. tuberculata adults following acute exposure to 18 degrees C, 22 degrees C (control), 25 degrees C and 30 degrees C. Hsp70 expression was similar between species where levels at 30 C were significantly elevated compared to 22 degrees C (control). The increase in hsp70 expression at 30 degrees C was especially marked in H. erythrogramma and may be a strategy to buffer against subsequent temperature extremes as often encountered in the intertidal environment.