CHARACTERIZATION OF THE STRESS PROTEIN RESPONSE IN 2 SPECIES OF COLLISELLA LIMPETS WITH DIFFERENT TEMPERATURE TOLERANCES

We have examined the role of stress proteins in adaptation through an interspecific study of the stress protein response in two species of Collisella limpets that occupy different intertidal habitats characterized by unique microclimates. Collisella scabra inhabits the high intertidal region, an unpredictable environment of temperature extremes. Collisella pelta lives in the more sheltered upper midtidal region. We conducted laboratory experiments to compare the temperature tolerance of each species and confirmed that C. scabra had a greater tolerance to acute heat shock. The stress protein response was also examined for both species using metabolic labeling and electrophoretic techniques. We found in C. scabra, but not in C. pelta, a highly complex group of low-molecular-weight (LMW) stress proteins (also called heat-shock proteins [hsp]) and multiple isoforms of hsp60. Other aspects of the response that also differed included (1) the temperature range at which the response was elicited, (2) the number of isoforms of hsp 70 synthesized, and (3) the presence of stress proteins in the 35-40-kDa range in C. scabra. Further, the increase of radiolabel incorporation into hsp 70 and the LMW stress proteins at higher temperatures relative to control temperatures was greater for C. scabra. These aspects of the stress protein response may play a role in allowing C. scabra to tolerate the temperature extremes of the high intertidal region that provides it with access to food sources not available to closely related but more temperature-sensitive species.