Accessory pulsatile hearts

Definition

Small, muscular pumping structures that supplement the main dorsal heart in arthropods, typically located in the thorax, abdomen, or appendages to maintain hemolymph circulation through narrow body regions or limbs. Unlike the tubular dorsal heart, these hearts are usually segmental or paired, with their own ostia and variable innervation, and they beat asynchronously or in coordination with the main heart depending on taxon and physiological demand.

Etymology

From Latin accessorius (additional, supplementary) and pulsare (to beat), describing their auxiliary pumping function.

Example

In the abdomen of a caterpillar, paired segmental accessory hearts at the base of each leg-bearing segment propel hemolymph into the prolegs; in spiders, the anterior and posterior pairs of accessory hearts in the opisthosoma maintain circulation through the book lungs and spinnerets when the main heart cannot generate sufficient pressure.

Synonyms

• segmental hearts
• ampullary hearts
• auxiliary hearts

Related Terms

• dorsal vessel
• Hemolymph
• ostium
• aorta
• Pericardial sinus
• book lung circulation
• open circulatory system

Usage Notes

The term distinguishes these from the main dorsal heart and from non-muscular pulsatile organs (such as some antennal pulsatile organs that lack true myocardial structure). Number and location vary enormously: insects typically have abdominal segmental hearts, while arachnids may have multiple pairs in the cephalothorax and opisthosoma. Some authors restrict 'accessory heart' to muscular structures with ostia, using 'pulsatile organ' more broadly.