The nature of heat coma in Littorina littorea (Mollusca : Gastropoda)

The nature of heat coma was examined in the edible peri winkle Littorina li ttorea (L.). Duration of acclimation did not influence heat-coma temperatur e at 12 degreesC, although other acclimation temperatures were important in influencing thermal tolerance, with positive shifts in coma temperature ob served in response to elevated temperatures. Previous thermal history also influenced heat-coma temperatures. Individuals subjected to repeat heat-com a events on a daily basis showed significant declines (P < 0.05) in coma-te mperature; in contrast individuals exposed to repeat heat-coma events on a weekly basis showed no decline in thermal tolerance. Size-effects occurred at selected sites, where decreased heat-coma temperatures were recorded in large individuals.