Glass squids (family Cranchiidae) live in the boundless waters of the twilight, or mesopelagic, zone. With no protective shell and nowhere to shelter, they need to get creative. Transparency is one way to thrive in a home with few places to hide.

Like other cephalopods, glass squids are covered in tiny pigment sacs called chromatophores. They often keep their chromatophores closed so their skin is basically see through. This invisibility cloak hides them from both predators and prey.

When the glass squid’s cover is blown, they expand their chromatophores to darken their appearance. Some may fill their body cavity with ink instead, presumably to blend into the darkness. And when danger still looms, a glass squid may ink into the water and jet away. A ghostly shroud of ink creates a distraction so the squid can escape.

But the future of midwater animals is in jeopardy. The deep seafloor holds buried treasure: nodules of precious minerals critical to modern technologies. Mining these metals will release plumes of wastewater that will cloud the ocean's twilight zone. Investigating how deep-sea animals sense their surroundings will help us predict how much harder mining will make their day-to-day lives.

We urgently need to identify the impacts deep-sea mining will have across all ocean habitats, from the midwater to the seafloor. Help protect the glass squid by sharing what you've learned. Together we can build a community of ocean champions!

Learn more about this and other fascinating animals of the deep: https://mbari.co/AnimalsOfTheDeep

Learn more about the possible impacts of deep-sea mining: https://annualreport.mbari.org/2020/s...

Script writers: Kyra Schlining, Raúl Nava
Editor: Ted Blanco
Narrator: Raúl Nava
Motion Graphics: Madeline Go
Production team: Heidi Cullen, Madeline Go, Larissa Lemon, Raúl Nava, Kyra Schlining, Nancy Jacobsen Stout, Susan von Thun
Music: 'Space Discovery' by jabameister and 'Contemplating Deception' by Jayson Wayne Brown

References:
Bush, S.L. and B.H. Robison. 2007. Ink utilization by mesopelagic squid. Marine Biology, 152:485-494. http://dx.doi.org/10.1007/s00227-007-...