Today on Animal Fact Files we’re discussing giant isopods. There are nearly twenty classified
species of these deep sea crustaceans and probably more to be discovered - it's just
really expensive to study them! Giant isopods are a prime example of deep sea gigantism.
Like the giant squid, giant isopods are far larger than their smaller sized relatives. Most of the
more than 10,000 isopod species only reach about an inch (2.54cm) at maximum length, but giant
isopods have been recorded at 16 inches (41cm) and possibly even longer! Not all these deep sea
giants reach this massive size, but they still top the charts compared to other isopod species.
These invertebrates live along the ocean floor, though they can also swim! They can be found in
the Atlantic, Pacific, and Indian oceans, and it's likely there are populations that haven't been
discovered. Giant isopods live in water as shallow as 550 feet (170m) to depths more than over 6,500
feet (2000m)! Where they live all depends on the species, and sometimes the other species around
them! Some species rule the seafloor and patrol from continental shelves to the abyssal plain,
but others are limited in their range. In some areas, multiple species of giant isopods
live in a single location. The smaller species control the shallower
areas while the larger species are restricted to the deepest depths.
Giant isopods are commonly known as scavengers, but this is only part of their dietary picture.
These animals opportunistically eat just about anything that falls to the seafloor.
This debris is known as marine snow and can include fish heads and whale bodies. When it
finds a huge meal, a giant isopod can eat so much food it loses mobility! In fact,
their giant stomachs can take up up to two thirds of their body if necessary!
These invertebrates also munch on live animals, like sponges, sea cucumbers,
and even fish caught in deep sea cages - much to the annoyance of those trying to catch the fish!
Giant isopods have seven sets of legs and the first pair is used to bring food to their mouth
where four sets of slicing jaws wait to tear into a meal. In fact, these crustaceans have
been known to chew through wires of deepsea camera equipment! So they can be some tricksy beasts!
Like the roly polys that live on land,
giant isopods can curl up into a ball to protect themselves from predators.
Fortunately for them, they have few of these. This may be in part why they've been able to reach
such gargantuan sizes! Of course, humans do pose a threat to these invertebrates through plastics,
which have been found in giant isopod stomachs, and trawling, which can disrupt brooding females.
While little is known about giant isopod reproduction,
what is known is that the females develop a brood pouch in which their eggs are kept safe from harm
on her body and mature into fully formed adults. When they hatch, giant isopod babies completely
forgo a larval stage and emerge as tiny replicas of their parents. Passing a larval stage is likely
beneficial as it could mean fewer chances of predation. How long they live is unknown,
though one unfortunate individual managed to survive five years without eating in captivity.
The different giant isopod species can be told apart by the different structures and formations
of their shells. All of them, however, have long antennae they use to navigate their environment
and large eyes that, like a cat's eyes, reflect light that hits them making them appear to glow.
For more facts on giant isopods, check out the links below. Give a thumbs up if
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