Cardiovascular functions in two macruran decapod crustaceans (Procambarus clarkii and Homarus americanus) during periods of inactivity, tail flexion and cardiorespiratory pauses

Abstract

Arterial hemolymph flow was measured in restrained crayfish (Procambarus 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 thoracic artery and ventral abdominal artery, allowing determination of flow simultaneously in several arteries over a period of 4 days. Calculated Doppler hemolymph flow showed a strong correlation (P<0.05) with 'pumped' hemolymph flow as determined by in situ calibration. Arterial flow patterns remained constant during quiet conditions. In crayfish, cardiac output was 7.5&plusmn;1.1 ml min-1 (252 ml kg-1 min-1), of which the anterior aorta received 1.3&plusmn;0.15 ml min-1 (20.1&plusmn;4.0 %), the posterior aorta received 0.8&plusmn;0.1 ml min-1 (12.3&plusmn;2.7 %) and the sternal artery received 5.2&plusmn;1.4 ml min-1 (67.5&plusmn;37.0 %). Mean heart frequency at rest was 125.6&plusmn;5.2 beats min-1 and stroke volume was 0.06&plusmn;0.01 ml beat-1 (1.98 ml kg-1 beat-1). In lobsters, cardiac output was 60.8&plusmn;4.4 ml min-1 (93.6&plusmn;6.8 ml kg-1 min-1), with the anterior aorta receiving 7.8&plusmn;0.8 ml min-1 (12.8&plusmn;2.7 %), the lateral arteries receiving 0.6&plusmn;0.2 ml min-1 (1.0&plusmn;0.5 %), the posterior aorta receiving 12.6&plusmn;1.0 ml min-1 (20.7&plusmn;3.3 %) and the sternal artery receiving 38.9&plusmn;4.1 ml min-1 (64.0&plusmn;13.4 %). Flows in the branches of the sternal artery were 0.3&plusmn;0.05 ml min-1 (0.5&plusmn;2 %) in the ventral abdominal artery and 4.0&plusmn;0.1 ml min-1 (6.5&plusmn;0.3 %) in the ventral thoracic artery. Lobster heart rate was 82.5&plusmn;2.9 beats min-1 and stroke volume was 0.7&plusmn;0.05 ml beat-1. Periods of constant hemolymph flow were interrupted by tail flexions (abdominal flexion) and, in lobsters, periods of cardiac/respiratory pause. Tail movement increased flow (peak height and minimum flow values) in both crayfish 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 the low heart rate.