Thermal resistance in sea cucumbers (Apostichopus japonicus) with differing thermal history: The role of Hsp70

Thermal history can affect organisms' thermal resistance, however, effects of thermal history on thermal resistance and roles of heat shock protein 70 (Hsp70) in sea cucumber Apostichopus japonicus are not well understood. In the present study, the lethal thermal limits and expressions of Hsp70 of sea cucumbers that were acclimated at different temperatures (22 °C or 12 °C) for 30 days were studied. The upper lethal temperatures (ULTs50) for sea cucumbers acclimated at 22 and 12 °C were 31.8 °C (31.5–32.1 °C) and 30.9 °C (30.6–31.3 °C), respectively. In heat shock experiments, sea cucumbers acclimated at different temperatures (22 °C or 12 °C) were exposed to several high temperatures (25, 27, 29, 31 and 32 °C) for 2 h, followed by 2 h recovery at 17 °C, and the levels of hsp70 were measured using semi-quantitative RT-PCR and western blotting. The maximum induction temperatures for sea cucumbers in 22 °C and 12 °C acclimation treatments were 31 °C and 29 °C, respectively. These results showed that the temperature acclimation could affect sea cucumbers' upper thermal limit, which was related to the changed expression pattern of Hsp70 in the sea cucumber. In practice, sea cucumbers that overwinter in southern China could acquire higher thermal resistance than those reared in the north.