[5][6] Fish have evolved retia mirabilia multiple times to raise the temperature[7] (endothermy) or the oxygen concentration of a body part above the ambient level.

The rete mirabile is an essential[8] part of the system that pumps dissolved oxygen from a low partial pressure (

[8] The higher supply of oxygen allows the teleost retina to be thick and have few blood vessels thereby increasing its sensitivity to light.

The cycle of diffusion continues until the partial pressure of oxygen in the arterial capillaries exceeds that in the swim bladder.

[11] The rete mirabile allows for an increase in muscle temperature in regions where this network of vein and arteries is found.

The opah utilizes retia mirabilia to conserve heat, making it the newest addition to the list of regionally endothermic fish.

[12] In mammals, an elegant rete mirabile in the efferent arterioles of juxtamedullary glomeruli is important in maintaining the hypertonicity of the renal medulla.

In the neck of the dog, a rete mirabile protects the brain when the body overheats during hunting; the venous blood is cooled down by panting before entering the net.

Retia mirabilia also occur frequently in mammals that burrow, dive or have arboreal lifestyles that involve clinging with the limbs for lengthy periods.

[13] The ancient physician Galen mistakenly thought that humans also have a rete mirabile in the neck, apparently based on dissection of sheep and misidentifying the results with the human carotid sinus, and ascribed important properties to it; it fell to Berengario da Carpi first, and then to Vesalius to demonstrate the error.