Cardiovascular anatomy and physiology of the black‐lip abalone, Haliotis ruber

Abstract

AbstractThe anatomy of the cardiovascular system of Haliotis ruber is described on the basis of observations from dissection, routine histology, and scanning electron microscopy of vascular casts and critical‐point dried tissue. The finest channels, lacunar tissue spaces, were around 10 μm and appear to lack an endothelial lining. A vascular connection, which exists between the cephalic arterial sinus and the cephalopedal venous sinus, may allow redirection of blood back to the heart during circumstances in which blood flow through the pedal vessels is prevented. 5‐Hydroxytryptamine (5‐HT) immunoreactive nerves were observed in atrial and ventricular walls, pericardium, cephalic arterial sinus, and afferent ctenidial vein. In unrestrained animals, pairs of in vivo pressure measurements were made from the right atrium, the ventricle, the pericardial chamber, the right efferent ctenidial vein, and the renal sac. All sites showed pulsatile pressures of low magnitude. Ventricular systolic:diastolic pressures were typically 8:4 cm water. In unrestrained animals, heart‐rate responses to changes in water temperature and pO2 were established and show H. ruber to be an imperfect regulator with respect to O2. Structural characteristics of the heart and vascular anatomy, pressure measurements, and heart rate are discussed in relation to whole animal function.