Why the Colossal Squid Also Has the Biggest Eyes in the Animal Kingdom

We know more about the vast expanse of our planetary system—and the celestial bodies within it—than we do about the incredible depths of our oceans and the deep-sea creatures that inhabit them. Despite centuries of marine biology, we have yet to see the surface, and about 95% of these depths have never been seen by humans. Example: Colossal squid, or Mesonychoteuthis hamiltoni.

This giant squid is so elusive that as of August 2024, we still haven’t been able to take clear pictures of an adult living in its natural habitat – the remote and inhospitable environment of deep water , the darkness of the South Sea, around. Antarctica. This is despite remarkable advances in camera technology and initiatives such as the KOLOSSAL project.

Here, at a depth of 3,280 to 7,218 meters, the colossal squid navigates a world of extreme cold, extreme pressure and endless darkness.

For the longest time, its more famous cousin the giant squid, chief architect it was believed to be the largest of its kind. That is, until 1925, when the first specimen of a colossal squid was described based on two tentacles found in the whale’s stomach. In fact, most of the information we know about it has only been obtained from parts found in the stomach of its biggest predator, the sperm whale.

Colossal Squid is a Product of ‘Abyssal Gigantism’

You may have heard about the phenomenon of island gigantism, where isolated species grow to enormous sizes. Abyssal gigantism is a similar concept, but takes place in the deep ocean.

The deep ocean acts like an island, according to a September 2006 article published in Journal of Biogeography. In both areas, food is scarce, leading to unique evolutionary pressures.

In the abyss, small species can become very large, as body size can be useful in the following ways:

• Larger bodies can increase the potential for energy conservation. This is important in an area where food is scarce.
• In addition, the large size may help these species survive longer in the cold, dark depths of the ocean, where biological activity is slow.

The colossal squid, with its large body, is a prime example of how abyssal gigantism allows deep sea creatures to thrive in extreme conditions.

These giants live up to 40 years, and are built like an underwater tank. They can grow up to 46 meters in length and weigh 1,091 kilograms, earning them the status of the world’s largest invertebrate. Unlike most squid, which have a thin, soft body, these plump seabirds have a strong, muscular coat – an outer covering that gives it a solid ‘ bodies. This can help them withstand the extreme pressures of their deep water environment.

World’s Biggest Eyes – Recorded up to 11 inches in diameter

Although the size of the eyes of the colossal squid is sometimes exaggerated in the popular media, it has the largest eyes on record of any known animal in the world.

“Giant and giant squid share the pelagic depths with many large vertebrates whose eyes are only a fraction of the size of a squid. “This strongly suggests that giant and colossal squid use their eyes for a purpose not shared by other animals,” the authors of the April 2012 published report Current Biology explain.

The largest colossal squid ever caught (as of 2012), an adult specimen from New Zealand, had eyes 11 inches in diameter. This gigantic creature has record for the largest eyes in the natural world, and their width is close to the theoretical size for colossal and giant squid.

For context, the fish with the largest eyes is the swordfish (Xiphias gladius), which can have eyes up to 9 cm (3.5 inches) in diameter. This one is about three times smaller than the eyes of the colossal squid. The swordfish’s large eyes help it hunt in the deep sea with dim light.

So What Is the ‘Alternative Purpose’ of the Colossal Squid’s Big Eyes?

The huge eyes of the colossal squid are designed to see large predators, especially sperm whales, at the bottom of the ocean. And unlike other sea creatures that may use their eyes to detect food or mates, the colossal squid’s eyes are specially tuned to detect bioluminescence—the dim light emitted by insects. the little ones who are troubled by the great beast that moves.

In the deep, dark waters where the colossal squid live, this bioluminescence can act as a warning signal, allowing the squid to detect an approaching sperm whale from a great distance away (up to 120 meters).

This ability is essential to the colossal squid’s survival—seeing bioluminescence from afar gives the behemoths the time they need to prepare to avoid the predator. So the purpose of the giant eyes of the squid is not only vision in general, but specifically for seeing the beast in the depths of the sea, where survival often depends on the ability to see and respond to these subtle signals.

As we approach the 100th anniversary of its discovery, efforts like the KOLOSSAL project and other research efforts are intensifying to unravel the many mysteries surrounding the colossal squid. This effort aims to learn more about its biology, behavior and the role it plays in the deep sea environment.

Does the presence of this gigantic creature make you feel small? Or does it ignite a deep connection with the mysteries of the natural world? Take this quiz to see how your perspective aligns with the wonders of our planet: Connecting to the Natural Scale