Contractile Performance of Cephalopod Hearts Under Anoxic Conditions

Abstract

The cephalopod circulatory system includes an efferent systemic ventricle and two afferent branchial hearts. Branchial hearts lack coronary arteries and thus must be nourished by only venous blood. During routine metabolism in normoxic water, oxygen availability to branchial hearts is only a small percentage of that to the systemic heart; during hypoxic excursions the venous oxygen content may, at least transiently, approach zero (Johansen, Brix & Lykkeboe, 1982; Houlihan, Innes, Wells & Wells, 1982). The extreme difference in oxygen delivery to these tissues suggests that branchial hearts are better able to meet their energetic demands through anaerobic metabolism than are systemic hearts. This hypothesis was tested by following isometric force development of the cardiac tissue of the cuttlefish, Sepia officinalis, during cyanide poisoning. Experiments were also conducted with the systemic heart of Octopus vulgaris, in order to allow a comparison between a decapod and an octapod.