Morphological analysis of the hagfish heart. II. The venous pole and the pericardium

José M. Icardo, Elvira Colvee, Sarah Schorno, Eugenia R. Lauriano, Douglas S. Fudge, Chris N. Glover, Giacomo Zaccone

Research output: Contribution to journalJournal Articlepeer-review

9 Citations (Scopus)


The morphological characteristics of the venous pole and pericardium of the heart were examined in three hagfish species, Myxine glutinosa, Eptatretus stoutii, and Eptatretus cirrhatus. In these species, the atrioventricular (AV) canal is long, funnel-shaped and contains small amounts of myocardium. The AV valve is formed by two pocket-like leaflets that lack a papillary system. The atrial wall is formed by interconnected muscle trabeculae and a well-defined collagenous system. The sinus venosus (SV) shows a collagenous wall and is connected to the left side of the atrium. An abrupt collagen-muscle boundary marks the SV-atrium transition. It is hypothesized that the SV is not homologous to that of other vertebrates which could have important implications for understanding heart evolution. In M. glutinosa and E. stoutii, the pericardium is a closed bag that hangs from the tissues dorsal to the heart and encloses both the heart and the ventral aorta. In contrast, the pericardium is continuous with the loose periaortic tissue in E. cirrhatus. In all three species, the pericardium ends at the level of the SV excluding most of the atrium from the pericardial cavity. In M. glutinosa and E. stoutii, connective bridges extend between the base of the aorta and the ventricular wall. In E. cirrhatus, the connections between the periaortic tissue and the ventricle may carry blood vessels that reach the ventricular base. A further difference specific to E. cirrhatus is that the adipose tissue associated with the pericardium contains thyroid follicles. J. Morphol. 277:853-865, 2016.

Original languageEnglish
Pages (from-to)853-865
Number of pages13
JournalJournal of Morphology
Issue number7
Publication statusPublished - 1 Jul. 2016


  • Eptatretus cirrhatus
  • Eptatretus stoutii
  • Myxine glutinosa
  • atrioventricular canal
  • atrium
  • sinus venosus
  • thyroid follicles


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