CARDIOVASCULAR FUNCTIONS IN 2 MACRURAN DECAPOD CRUSTACEANS (PROCAMBARUS-CLARKII AND HOMARUS-AMERICANUS) DURING PERIODS OF INACTIVITY, TAIL FLEXION AND CARDIORESPIRATORY PAUSES

Arterial hemolymph how was measured in restrained crayfish (Procambaru s clarkii) and lobsters (Homarus americanus). Implanted pulsed Doppler flow transducers were used to measure arterial flows in the anterior aorta, posterior aorta, sternal artery, lateral artery, ventral thorac ic artery and ventral abdominal artery, allowing determination of flow simultaneously in several arteries over a period of 4 days. Calculate d Doppler hemolymph flow showed a strong correlation (P<0.05) with 'pu mped' hemolymph flow as determined by in situ calibration. Arterial fl ow patterns remained constant during quiet conditions. In crayfish, ca rdiac output was 7.5+/-1.1 ml min(-1) (252 ml kg(-1) min(-1)), of whic h the anterior aorta received 1.3+/-0.15 ml min(-1) (20.1+/-4.0%), the posterior aorta received 0.8+/-0.1 ml min(-1) (12.3+/-2.7%) and the s ternal artery received 5.2+/-1.4 ml min(-1) (67.5+/-37.0%). Mean heart frequency at rest was 125.6+/-5.2 beats min(-1) and stroke volume was 0.06+/-0.01 ml beat(-1) (1.98 ml kg(-1) beat(-1)). In lobsters, cardi ac output was 60.8+/-4.4 ml min(-1) (93.6+/-6.8 ml kg(-1) min(-1)), wi th the anterior aorta receiving 7.8+/-0.8 ml min(-1) (12.8+/-2.7%), th e lateral arteries receiving 0.6+/-0.2 ml min(-1) (1.0+/-0.5%), the po sterior aorta receiving 12.6+/-1.0 ml min(-1) (20.7+/-3.3%) and the st ernal artery receiving 38.9+/-4.1 ml min(-1) (64.0+/-13.4%). Flows in the branches of the sternal artery were 0.3+/-0.05 ml min(-1) (0.5+/-2 %) in the ventral abdominal artery and 4.0+/-0.1 ml min(-1) (6.5+/-0.3 %) in the ventral thoracic artery. Lobster heart rate was 82.5+/-2.9 b eats min(-1) and stroke volume was 0.7+/-0.05 ml beat(-1). Periods of constant hemolymph flow were interrupted by tail flexions (abdominal f lexion) and, in lobsters, periods of cardiac/respiratory pause. Tail m ovement increased flow (peak height and minimum flow values) in both c rayfish and lobsters, although the general wave form of hemolymph flow and pressure did not change. In lobsters, periodic respiratory pauses were observed during which all arteries received hemolymph, despite t he low heart rate.