bio

Rete mirabile

A vascular bundle of many fine arteries and veins running counter to each other and interleaved so closely they touch along their whole length. Cold arterial blood heading into the muscle picks up heat from warm venous blood heading out, so metabolic heat that would have been dumped through the gills is intercepted and recycled. The same geometry is reused for other jobs — concentrating gas in a swim bladder, conserving heat in cold-climate limbs — making it a textbook case of a bioengineering module reinvented for several purposes. A mako shark in cold water has warm eyes, a warm brain and a warm engine, and nothing else.