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The World's Biggest Crustaceans! |
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What Are Crustaceans?
The word "Crustaceans"
may sound like a long word to you, but this group of animals includes
some very
familiar ones. Crabs, lobsters,
crayfish, shrimp and barnacles are all crustaceans. The crustaceans all
belong to a larger group of animals, called Arthropods, which
also includes insects, spiders and scorpions.
Where do Crustaceans live?
Most of them live in the sea or fresh water. Some of
them are
able to live on land, such as hermit crabs which
some people keep as pets in an aquarium! Crustaceans have a hard shell
to protect
themselves from their enemy. Usually, their body is divided into two
parts, a
head and an abdomen. They have antennae
which they use
to sense the world around them, finding food or avoiding danger. The
abdomen includes the heart, digestive system
and reproductive system. They have strong legs for crawling and
swimming. Many crustaceans uses their claws which help them
to eat.
What kinds of crustaceans are there?

The Japanese Spider Crab is the World's Biggest Crustacean, and in fact the world's biggest Arthropod
Scientists group Crustaceans into groups, which they call
"classes". These are
- There are about 900 types of Branchiopods.
These tend to be quite small - they look like little shrimps. They can
survive in environments that other animals cannot, such as an almost
dried-out lake. The famous "Sea-Monkeys" kept as pets are Branchiopods.
- The 17 types of Remipedes are blind, and spend their time
swimming upside-down on their backs at the bottom of the sea. They have
a very complicated head, with a long trunk and fangs. Very little is
known about them.
- The
Horseshoe Shrimps are small creatures that live in the mud on the sea
floor. They eat by sitting still and whooshing water and mud into their
mouths, hoping that something yummy will be washed in. Scientists call
them Cephalocarida.
- The Maxillopods
have a small body and legs compared with their head. The most extreme
are the Barnacles,which stick themselves permanently to any convenient
underwater surface.
- There are 13000 living species of Seed Shrimp. These tiny
crustaceans make up part of what we call Plankton, so are important
food for many sea animals. Others live on, or in the sea floor, or even
in damp forests soil!
- The last group (scientists call them Malacostraca)
contains all the most familiar (and all the largest) crustaceans. There
are
- The tiny Leptostraca
(the name means "thin shell") live throughout the world's oceans.
- The
Mantis Shrimps are not shrimps, but look like them. There are about 400
different species, the biggest can grow over a foot long (30 cm). They
have very powerful claws, and are sometimes called "thumb splitters" or
"prawn killers".
- Woodlice, pillbugs, crabs, lobsters, prawns and shrimp
all belong to the third and final subclass of Malacostraca. Many of
these are eaten by humans. All the biggest crustaceans belong to this
group.
What is the world's biggest crustacean?
The
world largest crustacean is the Japanese Spider Crab. It can weigh up
to 20kg (45 lb). If it stretches out its legs, they can reach up to 4
metres (13 feet) from tip to tip! It
gets its name because its long legs remind people of an enormous spider.
On the other hand, the American Lobster (though smaller) weighs more
than the Japanese spider crab. It
can bulk up to weighs up to 22kg (48 lb) and measure almost
1.2 metres (1.3 yards) long.
Both the Japanese Spider Crab and the American Lobster live in
the sea. The Coconut Crab, Birgus latro,
is not just the largest land-living crustacean, it's the
largest land arthropod and the largest land
invertebrate of all! It has a body that measure up to
40 cm long (16 inches) and weighs up to 4 kg
(8.8 lb). Its legs
may span
1 m (39 inches). It gets its name from its favorite food.
The largest freshwater crustacean is the
Giant Fairy
Shrimp, Branchinecta
gigas which has a body length of 15cm (6 inches). The largest
barnacle is the Giant Acorn Barnacle, Balanus nubilis,
reaching 7 cm (2.8 in) in diameter and
12.7 cm
(5 in) high. The largest crustacean which stays in a cave is
the
species Godzillius
robustus. It is 4.5 cm in length.
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