Hagfish and Vascular Biology: Why the Marine Model Matters
Hagfish and Vascular Biology: Why the Marine Model Matters
This chapter focuses on the role of the hagfish as a model organism for understanding the evolutionary origins of human organ systems. While many invertebrates have blood vessels, none has a true cell lining (an endothelium). In contrast, all vertebrates examined to date have a closed system of blood vessels lined by endothelial cells. Hagfish is the oldest extant vertebrate, having appeared some 550 million years ago. As such, it is an ideal organism for studying the evolutionary origins of vertebrate systems. Does the hagfish have a closed circulation like other vertebrates? Are its blood vessels lined by endothelium? And if so, does the endothelium demonstrate, like its counterpart in higher vertebrates, heterogeneity in structure and function? To address these questions, we spent many summers at Mount Desert Island Biological Laboratory (MDIBL) in Maine, procuring, harvesting, dissecting and analyzing the cardiovascular system of the Atlantic hagfish, Myxine glutinosa. Our studies revealed that hagfish endothelium lining is far from uniform, but rather displays marked heterogeneity across the vascular tree. We were able to conclude that phenotypic heterogeneity arose as a core property of the endothelium between 550 and 600 million years ago.
Keywords: Atlantic hagfish, Myxine glutinosa, vascular biology, vertebrates, Mount Desert Island Biological Laboratory, evolutionary biology
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