I Spy… A Giant Squid Eye

Gaze into the enormous eye of a giant squid behind the scenes in the museum’s Invertebrate Zoology collection.

A giant eye sits in a clear, glass container next to a smaller octopus and squid in glass containers on either side of the eye.
Giant squids have the largest eyes of any living organism.  Capable of stretching almost a foot in diameter, these eyes help the gargantuan invertebrates see their prey and avoid predators in the dark. Emma Saaty, NMNH

With approximately 148 million specimens and objects in its collection, the vast majority of the National Museum of Natural History’s specimens are off display. But each of these specimens — whether it be a moth, meteorite, moss or mammoth — tells a story that helps museum researchers make sense of the natural world. Each month, the Specimen Spotlight series will highlight a different specimen or object from the world’s largest natural history collection to shed light on why we collect.

Floating in a colossal glass jar full of isopropyl alcohol is one of Earth’s most eye-catching ocular wonders — the soccer ball-sized eye of the elusive giant squid (Architeuthis dux). The supersized specimen, which is housed in the National Museum of Natural History’s Invertebrate Zoology collection, represents the largest eyeball in the animal kingdom.

In addition to widening the eyes of the countless marine researchers that visit the museum’s collections, this unique eyeball has offered a rare view into how giant squids and other cephalopods see in some of the darkest depths of the ocean. To celebrate the 15th anniversary of the opening of the Sant Ocean Hall in 2008, Smithsonian Voices takes a closer look at one of the museum’s most striking specimens.

NMNH invertebrate zoologist Clyde Roper (bottom, left) works with researchers from NOAA and the Delaware Museum of Nature and Science to dissect and preserve one of the two giant squids on display in the museum’s Sant Ocean Hall. G. Jackson Tanner, Smithsonian Institution

When researchers discovered the tangled body of a giant squid bobbing off the Florida coastline in the early 2000s, scavenging birds, fish and sharks had nearly destroyed the remains.  But the scientists were surprised to find that one of the squid’s eyes remained in good condition. They sent the eye to the Smithsonian’s cephalopod collection for long-term preservation.

“This is the only intact giant squid eyeball that I know of in the world,” said Mike Vecchione, the museum’s curator of Cephalopoda.  “When a cephalopod dies, the eyes are typically the first organs that are destroyed. But they are scientifically important, so this really was an incredible discovery.”

The squid measured 23 feet in length, and while its eye may seem larger than life, the specimen was still just a juvenile.  Adult giant squids regularly grow to an astounding 40 feet (tacky tentacles included) and sport eyes that can reach over 10 inches in diameter.

While many deep-sea organisms have tubular eyes, the rounded shape of giant squid eyes bear a striking resemblance to those of humans and other mammals.  These wider eyes allow cephalopods to see bioluminescent light over a broad field of vision. Kelly Carnes, NMNH

Over millions of years of evolution, giant squid eyes have been perfected to see the low levels of light that penetrate the ocean’s twilight zone between 200 and 1000 meters below the surface.  The bigger the eyeball, the bigger the pupil opening, which means more photons of light can reach the retina.  Although giant squids cannot see in color, research highlights how important it is for these deep-sea dwellers to sense the glow of bioluminescent organisms around them.

This 36-foot-long female giant squid was collected off the coast of Spain and is the larger of the two giant squids on display in the museum’s Sant Ocean Hall.  In a collaborative effort called Operation Calamari, researchers recruited the U.S. Navy and Air Force to help transport the colossal specimen to the Smithsonian. Don Hurlbert, Smithsonian Institution

“When something is moving through the deep ocean, the pressure waves and vibrations set off the bioluminescent animals,” said Vecchione.  “If a huge sperm whale is diving towards a squid through this soup of bioluminescent jelly that dominates the deep ocean, the giant squid needs to be able to see light far enough away that it has time to swim and hide.”

Unique specimens like the giant squid eyeball are vital to understanding how organisms live and interact in the deepest ocean ecosystems.  The museum’s Department of Invertebrate Zoology houses a collection of over 50 million specimens, representing 60 phyla and four kingdoms. This zoological bounty includes one of the most diverse collections of cephalopods anywhere in the world, containing more than 160 holotype specimens that have been used to officially describe new species, genera and families.

Mike Vecchione, the museum’s curator of Cephalopoda, holds a Dumbo octopod that he collected on a 2009 NOAA expedition to the Charlie-Gibbs Fracture Zone of the Mid-Atlantic Ridge.  Vecchione has named dozens of cephalopod species over the course of his career, including the bigfin squid, which is the deepest living squid known to science. Mike Vecchione, NMNH

The giant squid specimens featured in the Sant Ocean Hall are two of only a dozen giant squids on display in the world and have remained one of the museum’s most popular attractions since their arrival in 2008.  Clyde Roper, NMNH’s resident squid expert, has spent his career scouring the globe for giant squid and other cephalopod specimens, and has published over 150 research studies that have helped to unlock the secrets behind these ocean enigmas.

The specimens are also important for conservation, demonstrating that even marine organisms living hundreds of meters below the surface are experiencing the effects of climate change.  “There are two sides to conservation in the museum world,” said Vecchione. “There is protecting the specimens that we have in our collections, and then making sure that the living species out in the world don’t go extinct.  Our collections are used for both, and it's very important that we take good care of what we have and continue our research efforts.”

In recent years, Vecchione has noticed that the giant squid eye has started to degrade and come apart.  Small amounts of tissue have detached around the edges of the pupil, and Vecchione has begun to take extra precautions to ensure that the eye remains still and undisturbed.  As the only object of its kind in the world, it is vital that the eye is kept intact so future generations of scientists can take a closer look.

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