Top 15 Gigantic Giant Isopod Facts

This remarkable creature could easily be cast for a role in the next Alien movie, and in this post, you’ll discover the ultimate list of interesting Giant isopod facts, one of the scariest animals in the ocean!

Interesting giant isopod facts

1. They are distant relatives of shrimps and crabs

The giant isopod also referred to as the “Bathynomus giganteus,” is a type of crustacean consisting of nearly 20 species of enormous isopods. These are distant relatives of crabs and shrimps which are referred to as “decapods.”

These creatures were first described by French zoologist Alphonse Milne-Edwards in 1879 after a juvenile was caught in the Gulf of Mexico around that time.

That must have been quite a shocker because not long before that it was assumed that no life could exist on the ocean floor!

Giant isopod 1879
To individuals / Mário NET /

2. They have a lot in common with this common creature

Perhaps one of the most fascinating giant isopod facts is that they are actually closer related to a very common bug called the woodlouse or “pil bug.”

Obviously, woodlice don’t suffer from deep-sea gigantism so they are a lot smaller. They do, however, share many of the morphological features with these giant creatures that live in the deep ocean.

A type of woodlouse / Ferenc Vilisics /

3. It’s assumed these are the largest isopods in the world

Even though it’s possible that there are similar species of the genus Bathynomus roaming around at the bottom of the ocean, as far as we know the Bathynomus giganteus is the largest isopod in the world.

The average size of these giants is anywhere between 19 and 36 centimeters (7.5 and 14.2 inches).

That’s quite huge, don’t you think?

4. They are divided into 2 categories of giants

With almost 20 species in the genus Bathynomus, it’s normal that their sizes differ quite a bit, especially because they suffer from deep-sea gigantism. That’s a condition in which deep-sea creatures for some reason grow much bigger than their counterparts living in shallow waters.

That’s why these creatures are divided into two categories:

  • The Giants – These have a total length of anywhere between 8 and 15 centimeters (3.1 and 5.9 inches).
  • The Supergiants – These grow to a length of anywhere between 17 and 50 centimeters (6.7 and 19.7 inches).

5. The largest confirmed individual was half a meter long

The largest recorded individual had a total length of 50 centimeters (20 inches), but it’s quite possible that there are even bigger individuals roaming around at the bottom of the ocean.

One such larger specimen reportedly measured up to 76 centimeters (30 inches) but this hasn’t been officially confirmed.

Giant isopod size
The huge animal / x768 /

6. They are capable of protecting themselves in a particular way

The giants of the deep sea are protected by a pretty firm outer skeleton which allows these animals to protect themselves from predators.

They also have the ability to roll up in a ball which is a similar defensive tactic as woodlice. Then, only the outer shell is exposed which protects their vulnerable abdomen.

7. These creatures have 7 pairs of legs

One of the most prominent features of these animals is their huge eyes, which are not only spaced far apart but also consist of almost 4,000 separate clusters of compound eyes.

In order to move around, they are equipped with 7 pairs of legs of which the first pair allows them to pick up food and bring it to any of their 4 jaws. Their two pairs of antennae allow them to sense the world around them.

8. They are found in all major oceans

Because there are nearly 20 species of giant isopods, one type can be found in just about every major ocean on the planet. This includes the Atlantic, Pacific, and Indian Oceans.

There are 4 known species living in the Atlantic Ocean which are B. obtusus, B. miyarei, B. maxeyorum, and B. giganteus. The latter Supergiant is the only type of giant isopod that has been recorded off the coast of the United States.

Equally remarkable is that one species can only occur in either the Atlantic Ocean or the Indo-Pacific, not in both oceans. You also won’t find these animals from the East Atlantic or East Pacific.

Obviously, this data is what we know about this mysterious animal.

Giant isopod habitat
In an aquarium / Kentaro Ohno /

9. Their natural habitat is the extreme depths of the ocean

The main reason why we haven’t been able to uncover all secrets of these peculiar beasts is that they live in places that we simply can’t reach. At least, the biggest individuals can live up to depths of 2,500 meters (8,200 feet), a completely dark place with extreme levels of pressure!

Some of the smaller species such as for example the B. miyarei lives at depths of between 22 and 280 meters (72 and 919 feet), quite a difference!

What we do know is that over 80% of the biggest species, the B. giganteus, lives at depths between 365 and 730 meters (1,198 and 2,395 feet).

10. They prefer cold water, but not too cold

Even though they appear to exist in just about all areas of the deep sea, they are pretty particular when it comes to the temperature they live in. The B. giganteus only lives in temperatures between 3.25 and 13 °C (37.8 and 55.4 °F)

More individuals are found at the colder end, but if it gets too cold, you won’t find any of these creatures at all!

11. These are carnivorous animals

These giants are carnivores which are considered to be important scavengers on the ocean floor. They feed on dead animals which include whales, various types of fish, and squid.

If they can’t find any dead bodies on the bottom of the ocean, then they might as well prey on small and slow-moving animals as well such as sea cucumbers, sponges, or roundworms.

Check the video below to see how they feast on a dead tuna fish.

12. They are known to attack trawl catches

One of the most remarkable giant isopod facts is that they are known to attack trawl catches. After all, these caught fish are bound to end up dead anyway so as these creatures are true scavengers, they just want a piece of it!

One study examining 1651 specimens concluded that they mostly feed on fish as that’s probably the most common dead animal at the bottom of the ocean.

13. They can survive for extended periods without food

Perhaps one of the most incredible giant isopod facts is that they can go for extended periods of time without eating anything. And we don’t mean a couple of days, we’re talking about years!

One such creature living in an aquarium in Japan devoured a fish in January of the year 2009, but didn’t eat anything for the next 1,500 days!

This giant eventually continued without eating for all of 2013 before dying on Valentine’s Day of 2014. That’s well over 5 years without food, quite the record!

14. These creatures existed over 160 million years ago

Fossil records discovered off the coasts of Australia, India, and Mexico, revealed that these creatures already existed 160 million years ago!

What’s even more remarkable is that even though their evolutionary path happened in different locations, they look almost completely identical! That’s because where they live, it’s pretty much completely dark, something that clearly hinders evolutionary development.

15. Newborns look pretty much the same as adults

Little is known about the reproduction cycle of these creatures, even though it’s assumed that their reproductive activity increases during spring and winter because of a lack of food in the summer months.

One of the most intriguing giant isopod facts is that when young emerge from the eggs laid by the females, they look like little versions of matures!

This means they don’t have a larval stage and are fully developed at birth, pretty astounding, don’t you think?

Giant and shrimp / Laika AC /

This concludes the ultimate list of interesting giant isopod facts, one of the most fascinating creatures in the ocean which suffers from a serious case of deep-sea gigantism!