Squid Giant Axon

Due to its sheer size, the squid giant axon became the standard model to study the transmission of signal alongside the axon of a neuron.

Its first famous use was for the Nobel prize-winning experiments of Drs. Hodgkin and Huxley on the action potential. From the Loligo forbesi species, they obtained giant axons around 500 μm wide allowing them to insert stimulating electrodes into the lumen of the axon.

The largest squid axons ever recorded actually belong to the Humbolt squid, with axon reaching up to 1 mm in diameter and characterized as "spaghetti-like".

This giant axon provides some evolutionary advantage to these species of squid. This neuron has been linked to the propulsion motion of the squid, and a larger diameter triggers faster signal transmission, therefore improving the speed of their flight response in face of a threat.