Squids do not possess ears, but they apparently can translate sound waves into electrical signals (much like a microphone would) via the dorsal side of their fin. And to demonstrate this fascinating science, the folks behind the excellent Backyard Brains went to the Marine Biological Laboratory in Woods Hole, Massachusetts and figured out how to monitor a squid's electrical signals as it "listened" to an iPod. Science-y speak, per the video:
The video is a view through an 8x microscope zoomed in on the dorsal side of the caudal fin of the squid. We used a suction electrode to stimulate the fin nerve. Chromatophores are pigmeted cells that come in 3 colors: Brown, Red, and Yellow. Each chromatophore is lined with up to 16 muscles that contract to reveal their color.
And thus, we have a squid listening to Cypress Hill's "Insane In The Membrane," and the results are spectacular, colorful, and certainly beautiful. [This Is Colossal]