DRABEK,, C.M.; Whitman College: Getting to the heart of the matter: Morphological aspects of the heart and aorta of northern elephant seal weanlings

An investigation of the heart and aorta morphology of northern elephant seal weaned pups (Mirounga angustirostris) revealed adaptations to diving. The elephant seal’s heart is broader and the right ventricle is longer, in comparison to seals that are not known to be long, deep divers. In the ascending aorta, a highly elastic aortic bulb increases in diameter 42% over the diameter of its base and then immediately constricts 54% in diameter at the point of the ligamentum arteriosum at the beginning of the thoracic aorta. The morphology of the right ventricle probably serves to increase lung perfusion during brief surface recovery after a long dive, and the enlarged, distensible aortic bulb would contribute to maintain a high blood pressure throughout the cardiac cycle during diving bradycardia. Before the weaned pups go to sea for the first time, their cardiovascular systems must undergo critical anatomical development to support long, deep foraging dives. The cardiovascular morphology of elephant seal pups is comparable to that reported for pups of deep diving hooded seals. This is the first description of the heart and aortic bulb of pups of the deepest diving pinniped.