Heat shock protein responses in thermally stressed bay scallops, Argopecten irradians, and sea scallops, Placopecten magellanicus

The effects of thermal stress on the induction of heat shock proteins (HSPs) were examined in northern bay scallops, Argopecten irradians irradians, a relatively heat tolerant estuarine species, and sea scallops, Placopecten magellanicus, a species residing in cooler, deeper water. Polyclonal antibodies used in this work for analysis of inducible HSP70 and HSP40 only recognized proteins of 72 and 40 kDa respectively from the mantles of both scallop species. Additionally, HSP quantification using the antibody to HSP70 was equally effective by either immunoprobing of western blots or ELISA, demonstrating that either approach could be successfully employed for analysis of thermal response in scallops. Sea scallop HSP70 and HSP40 did not change when animals were heat-shocked for 3 h by raising the temperature from 10 °C to 20 °C; however, a 24 h treatment of the same magnitude elicited a significant response. Conversely, bay scallops displayed rapid and prolonged HSP70 and HSP40 responses during the recovery period following a 3 h heat shock from 20 °C to 30 °C. Temperature reduction from 20 °C to 3 °C for 3 h also caused significant HSP70 and HSP40 increases in bay scallops; this represents the first time cold shock was shown to induce HSP synthesis in bivalve mollusks. The onset of the HSP40 response was more rapid than for HSP70, occurring at the end of the cold shock itself prior to transfer to a recovery temperature. Both proteins responded maximally during recovery at control temperature. HSP responses of sea and bay scallops to thermal stress may be related to their habitat in the natural environment and they suggest a differential capacity for adaptation to temperature change. This is an important consideration in assessing the response of these scallops to different culture conditions.