They combine the wholly separated left and right ventri-
cles seen in bird and mammal hearts – which maximises
oxygen content of blood reaching the tissues – with a
shunt capacity that is a considerable improvement on
that of other reptiles and amphibians. The latter enables
them to match the perfusion of blood through the lungs
to the availability and requirements for oxygen, with
some independence from the flow of blood through the
systemic circulation: something that mammals and birds
are incapable of achieving.
Complex crocodilian cardiovascular plumbing therefore
utilises the best features of mammals and birds, and
other reptiles, resulting in an incredibly flexible, sophisti-
cated and unique system. Cold-hearted, primitive
monsters? Nothing could be further from the truth!
Further Reading:
Axelsson, M., Franklin, C. E., Löfman, C. O., Nilsson, S., &
Grigg, G. C. (1996). Dynamic anatomical study of cardiac
shunting in crocodiles using high-resolution angioscopy.
Journal of experimental biology, 199(2), 359-365.
Franklin, C. E., & Axelsson, M. (2000). Physiology: An
actively controlled heart valve. Nature, 406(6798), 847.
Grigg, Gordon & Kirshner, David. Biology and evolution
of crocodylians. CSIRO Publishing, 2015.
Dedicated to Chris Donald, with love.
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