Porbeagles (Lamna nasus) have a stout body with a strong tail, pointed nose, big dark eyes, and large gill slits. This shark can be found throughout cold open waters in the Northern and Southern hemispheres. Living in cold waters can be a strain for many creatures, but not for the Porbeagle. This shark has an amazing adaptation that allows it to maintain its body temperature higher the water temperature surrounding them.
They accomplish this thermoregulation using a rete mirabilia (“wonderful net”) system. Retia mirabila are nets of arteries and blood vessels that are arranged to drive counter current heat exchange. This exchange can be found in the muscles and the viscera (internal organs in the main cavities of the body). As warm blood flows away from their cores and hot muscles, the heat flows into the blood vessels that are directing blood toward the core to keep heat in the body center, and a cooler blood at their peripheries. One amazing part of this process is the ability for sharks to change blood flow through vascular shunts. Being able to control their temperature and keep their muscles warm allows them to be fast predators feeding on a variety of fish.
Check out this video of Porbeagles taken from an ROV remotely operated underwater vehicle.
Edited by Felicia Van Stolk
Photography courtesy of ARKIVE (arkive .org): Andy Murchhttp://www.arkive.org/porbeagle/lamna-nasus/image-G49821.html