Squid ink is more than a culinary novelty. It is a chemically complex biological secretion evolved for defense, communication, and survival in the open ocean. When threatened, many squid species eject a dense cloud of ink from a specialized sac connected to the rectum. The ink mixes with mucus as it leaves the body, forming either a dark smokescreen or a structured “pseudomorph” that mimics the squid’s shape. While predators investigate the decoy, the squid escapes using jet propulsion. At the molecular level, squid ink is dominated by melanin, the same pigment responsible for color in human skin and hair. In squid, melanin is synthesized through the oxidation of the amino acid tyrosine via enzymes such as tyrosinase. The resulting melanin granules absorb light across a wide spectrum, producing the deep black coloration that makes the ink cloud visually effective underwater. But the chemistry goes beyond pigmentation. Squid ink also contains: • Dopamine and related catecholamines,...