Deep-sea squids glow to communicate in dark

[Still Waters 51,162]

The deep sea is vast, empty and dark—not an ideal place for animals to communicate via visual signals. Yet the Humboldt squid (Dosidicus giga), a social species that lives in groups of hundreds of individuals, can communicate visually at depths of 600 feet or more.

Cephalopods including squid, octopus and cuttlefish are known for a stunning array of visual displays. These marine creatures possess pigment cells called chromatophores surrounded by muscles that expand and contract, allowing for a wide variety of colorful patterns. While researchers understood these abilities, a question remained regarding just how deep-sea cephalopods might make these displays visible in their dark, deep environment.

https://www.smithsonianmag.com/science-nature/humboldt-squid-glow-communicate-dark-180974576/