Temperature effects on heart performance and regional hemolymph flow in the crab Cancer magister

Adult male Cancer magister crabs were subjected to a stepwise temperature change. Heart rate, cardiac output, stroke volume and hemolymph flow through lour arterial systems (anterior, anterolateral, sternal and posterior) were measured using pulsed Doppler probes. Heart rate showed a positive linear relationship with temperature. The majority oi cardiac output was directed through the sternal artery, with the anterolateral arteries receiving the next largest perfusion. Temperature change resulted in an increased sternal flow. Anterolateral flow increased with a temperature increase and decreased with a temperature decrease. Results suggest that anterolateral flow may be sensitive to metabolic concerns while sternal flow may be more responsive to activity. No major hemolymph flow redirection was observed with temperature variation. Cardiac output increased initially within each experiment regardless of the direction of temperature change, while stroke volume decreased with temperature increase.