Cardiac frequency compensation responses of adult blue crabs ( Callinectes sapidus Rathbun) exposed to moderate temperature increases

Abstract

1. 1. Cardiac frequency patterns of Callincctes sapidus Rathbun were used to evaluate potential thermal stress after exposure to 5°C increases over a range of acclimation temperatures from 5° to 30°C. 2. 2. An acclimated rate-temperature curve (R-T curve), acute R-T curves of the stabilized rates at the increased temperatures and Q 10 temperature coefficients were used to assess the significance of the changes in rate frequency. 3. 3. The acclimated R-T curve showed that blue crabs go through a series of seasonal adaptation types characterized by a plateau of perfect adaptation for both cold and warm adapted organisms. Paradoxical adaptation occurred between the transition from cold to warm acclimation temperatures. 4. 4. The acute R-T curves showed that cardiac frequency was highly responsive to a 5°C increase when the organisms were acclimated to low temperatures. 5. 5. The Q 10's of the acute R-T curves at the warm acclimation temperatures approximated those values derived for the acclimated R-T curve. 6. 6. This suggests that the temperature increase had a negligible effect on the warm adapted crabs, that is, little or no thermal stress occurred.