Heart (invertebrate)

Article By:

Calabrese, Ronald L. Department of Biology, Emory University, Atlanta, Georgia.

Cozzens, Christine S. Biology Laboratory, Harvard University, Cambridge, Massachusetts.

Last reviewed:February 2020

DOI:https://doi.org/10.1036/1097-8542.309800

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• Heart (invertebrate), published June 2014:Download PDF Get Adobe Acrobat Reader

The muscular organ that propels the flow of blood, hemolymph, or circulating fluid in invertebrates. As might be expected from the great diversity of invertebrate forms, the hearts of invertebrates and their associated circulatory systems are very diverse in structure and function. To begin with, the circulatory system of many invertebrates is open—the blood or hemolymph [a bloodlike circulating fluid containing hemocyanin (a copper-based protein) as an oxygen transporter] sloshes through a large open cavity (the hemocoel) to nourish and replenish the organs; there are no capillaries or veins. Moreover, the invertebrate hearts themselves are so diverse as to defy easy classification, ranging from the centralized hearts of mollusks and insects and other arthropods, which have open circulatory systems, to the distributed hearts and closed circulatory systems of segmented worms (annelids) [Fig. 1]. In addition, other invertebrates, such as roundworms (nematodes), completely lack a heart. See also: Annelida; Arthropoda; Cardiovascular system; Circulation; Insect physiology; Mollusca; Nemata (Nematoda)

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