The role of the pericardium in the valveless, tubular heart of the tunicate Ciona savignyi

Lindsay D. Waldrop, Laura A. Miller

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Tunicates, small invertebrates within the phylum Chordata, possess a robust tubular heart which pumps blood through their open circulatory systems without the use of valves. This heart consists of two major components: the tubular myocardium, a flexible layer of myocardial cells that actively contracts to drive fluid down the length of the tube; and the pericardium, a stiff, outer layer of cells that surrounds the myocardium and creates a fluid-filled space between the myocardium and the pericardium. We investigated the role of the pericardium through in vivo manipulations on tunicate hearts and computational simulations of the myocardium and pericardium using the immersed boundary method. Experimental manipulations reveal that damage to the pericardium results in aneurysm-like bulging of the myocardium andmajor reductions in the net blood flowand percentage closure of the heart's lumen during contraction. In addition, varying the pericardium-to-myocardium(PM) diameter ratio by increasing damage severity was positively correlated with peak dye flow in the heart. Computational simulations mirror the results of varying the PM ratio experimentally. Reducing the stiffness of the myocardium in the simulations reduced mean blood flow only for simulations without a pericardium. These results indicate that the pericardium has the ability to functionally increase the stiffness of the myocardium and limit myocardial aneurysms. The pericardium's function is likely to enhance flow through the highly resistive circulatory system by acting as a support structure in the absence of connective tissue within the myocardium.

Original languageEnglish (US)
Pages (from-to)2753-2763
Number of pages11
JournalJournal of Experimental Biology
Volume218
Issue number17
DOIs
StatePublished - Sep 1 2015
Externally publishedYes

Keywords

  • Ascidian
  • Fluid dynamics
  • Immersed boundary method
  • Myocardium

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science

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