Squid how many eyes

The deep ocean is so dark that bigger eyes probably don't help the giant squids pinpoint and hunt small food. However, drawing in even a bit more light could help them see larger shadowy shifts in the depths -- like those produced by an enormous predator. A study published in March suggested that giant squids could detect a moving sperm whale from feet meters with those big eyes. Giant squid have more than just giant eyes.

Learn about the giant squid's beak, suckers, and other over-sized body parts in this video with Smithsonian scientist Clyde Roper. This is larger than the entire visual cortex of a human the visual cortex is our 'optic lobe' , and shows how important vision is to these huge squid.

The colossal squid, like many squid, has light organs — one on each eyeball. Each light organ is a vertical band on the rear of the eyeball, beside the outer edge of the lens.

The light organs, or photophores, are used like headlights. When the eyes turn inwards to focus directly in front of the arms and tentacles, the light organs provide enough light for the squid to see its prey in the dark.

Using binocular vision, the colossal squid can accurately judge the distance the tentacles need to move to strike and grab the prey. The light from the photophores is produced by a chemical reaction involving bacteria, and is a type of bioluminescence.

The light stays on all the time. Many deep-sea animals show this kind of bioluminescence. Some squid, like Taningia, have light organs at the ends of their tentacles. The colossal squid probably can't see in colour. Squid in general can't see in colour, and deep-sea animals typically can't see in colour. Colossal squid live in very deep waters in the ocean, at about 1, metres below the sea surface, where sunlight does not penetrate.

Human eyes have a visual threshold that can only detect light to a depth of around metres. The colossal squid not only has large eyes and lenses — its pupils are also large, around mm across. A large pupil allows the eye to collect every last photon of light in the incredibly deep and dark waters where it lives. Large eyes may also mean that the colossal squid has high spatial resolution — the ability to distinguish detail.

It is possible that neural mechanisms in the optic lobe use the signals from groups of neighbouring photoreceptors, making the visual 'pixels' larger and much brighter.

With enormous eyes and a large, complex optic lobe, colossal squid have very good vision in the dark ocean depths where they live.

But does a big giant squid necessarily mean a strong one? If they were proportionally as strong as their smaller cousins, the Humboldt squid Dosidicus gigas , giant squid would be VERY strong, says Smithsonian squid expert Clyde Roper.

However, that doesn't make them sluggish weaklings. They have thousands of suckers working in unison on eight arms and two tentacles, with a rapidly-contracting mantle, to help capture and kill prey. The giant squid is not just a single species -- or is it? Some researchers think there are as many as 8 species in the genus Architeuthis Greek for "chief squid" , each a different kind of giant squid. But other researchers think there is just one Architeuthis that swims in the world's ocean.

There is no consensus because the squid are so hard to track and there are so few specimens available for study. However, it is certain that Architeuthis has an abundance of evolutionary relatives.

The ocean holds an estimated species of squid—and almost all of those are in the same taxonomic order as the giant squid, called Oegopsina. Some are surprisingly tiny—only about 1 inch 2. Others are impressively large, including the colossal squid Mesonychoteuthis hamiltoni , which can grow to be even bigger than the giant squid, reaching 45 feet 14 meters.

These squid species are closely related to snails, clams, and even slugs: they are all mollusks , which are defined by their soft bodies.

Some of these soft bodies are encased in hard shells, such as clams and snails, but not the squids. Squids belong to a particularly successful group of mollusks called the cephalopods , which have been around for about million years.

Some ancestors of modern-day squids had shells, such as the ammonites , which ruled the waves million years ago. Of those that are still around, one small group—the nautiluses—has an external shell. The other—which includes squids, cuttlefishes, and octopods—does not, although squids and cuttlefishes have an internal, backbone-like support made of chitin called a pen. Shell or no shell, all cephalopods have well-developed brains and are very active, jet-propelling themselves through the ocean.

Most have ink sacs. And many can change skin color and texture in the blink of an eye. Giant squid are thought to swim in the ocean worldwide, based on the beaches they've washed upon, as shown in the map via Wikimedia Commons. However, they're rarely found in tropical and polar areas. They commonly wash up on the shores of New Zealand and Pacific islands, make frequent appearances on the east and west sides of the Northern Atlantic, and the South Atlantic along the southern coast of Africa.

How long does it take to grow so big? Unlike mammals, including people, and many fish species, cephalopods grow very quickly and die after a short life. Evidence from statoliths a small mineralized mass that helps squid balance , which accumulate "growth rings" and can be used to measure age, suggests that giant squid live no more than five years -- which means each squid must grow incredibly quickly to reach 30 feet in just a few years!

To grow at such a rate, giant squid must live in areas of the ocean where there is an abundant supply of food to provide enough energy. Smaller than the head of a pin, this arrow squid Doryteuthis plei embryo looks like a miniature adult and is almost ready to hatch! Depending on the squid species, the development from a fertilized egg to a nearly-hatched larva can take one or several weeks. Talk about pressure! Giant squid males don't use a modified arm hectocotylus to transfer sperm like most squid; instead, the spermatophore sperm packet is expelled from a penis, which sticks out through the funnel and can be as long as the animal's mantle, up to 7 feet long.

Once the male finds a female -- whether it happens by chance or by following a chemical signal is unknown -- the male injects sperm packets directly into the female's arms. The rest of the story from here is mostly guesswork. The sperm could travel through her arms to fertilize the eggs internally. But researchers suspect that the arm-shot of spermatophores triggers the female squid's ovaries to release eggs bound together with jelly, which she holds in her arms. Then the sperm sense the eggs nearby and migrate in that direction to fertilize the eggs.

Females then release millions of tiny, transparent fertilized eggs into the water in a jellied clump called an egg mass. Most are quickly snatched up as food by other marine animals. But a few survive -- and within a few years, they become giant marine predators.

Hunting in the deep dark ocean isn't easy, but these cephalopods have adapted to their environment. In addition to their foot-wide eyes, which help them to absorb as much light as possible to glimpse prey, they also have long feeding tentacles. These tentacles are more than twice their body length, and the squids can shoot out to long distances like a net. This allows these big, comparatively conspicuous squids to sneak up and catch prey.

But what do giant squids eat? Although scientists have not witnessed a giant squid feeding, they have cut open the stomachs of squids washed up on beaches to see what they had eaten recently. Giant squid mostly eat deep water fishes and other squids—including other giant squids. They also will attack schools of fish from below, quickly ascending into shallower waters to grab a meal before retreating to safer depths away from predators.

Once prey is caught by the suckers and teeth on the feeding tentacles, the squid will rein it in and bring it towards its beak with its eight arms. The beak breaks the food down into smaller pieces, and the radula, a tongue-like organ covered in teeth, grinds it down further. Then the food goes down the esophagus —which travels through the squid's brain—to get to the stomach. Evidence from a washed ashore squid suggests giant squid will steal the captured meal of another squid, presumably in order to reduce the risk of an attack by a sperm whale in shallow depths.

The dead squid's two tentacles were ripped from their base and large sucker marks covered the mantle.