Prawns & Shrimps
shrimps and prawns are decapods, the
term meaning 10 legged. Those most commonly
found, are the Common Shrimp Crangon
crangon and the Common Prawn Palaemon
serratus. Both of these creatures are
often confused with each other. This
is understandable as the division between
shrimps and prawns is not scientific
but only a layman’s grouping.
with other creatures that have an exoskeleton,
they have to shed this inflexible outer
coating of armour before they can grow.
After shedding the body has a chance
to expand before the new exoskeleton
hardens. This process of shedding the
exoskeleton and a new one hardening
is called ecdysis. As the exoskeleton
is there to protect, it is ineffective
until it hardens. Fortunately the process
of shedding the old takes under a minute
and reaches full strength in a couple of days. Young prawns and
shrimps grow fast during the summer
months and moult up to four times a
the rear of the body there are five
pairs of swimmerets, these are used
to swim forward. However if aggravated
a faster motion is obtained, by flexing
the abdomen which flicks the tail, propelling
the animal backwards.
can only occur after the female has
shed her exoskeleton and while her skin
is still soft. The female carries the
fertilised eggs (which number in the
thousands) under her body between the
swimmerets. This not only protects the
eggs but the pulsing swimmerets, keeps
them aerated. After hatching the larvae
are carried by the currents and join
Between the Common Prawn & Common
creatures are closely related and hence share
similar features. As decapods both have
five pairs of legs. The prawn walks
on the rear three pairs, the front two
pairs are used for eating and have pincers,
the largest being on the second pair.
The shrimp’s two front pairs are also
pincered, but in this case it is the
front pair that are the largest, and
considerably so. The prawn’s legs are
longer than those of the shrimp’s.
shrimps and prawns have their eyes on
the end of stalks. Both creatures have
two pairs of antenna used to detect
their food, one pair is much longer than
the prawn the head is extended in front
to form a spike the rostrum, which has
several toothed like projections on
top of it.
prawn is semi transparent its internal
organs can easily be seen, the shrimp
has more pigment typically sandy coloured.
common prawn is more of a rocky shore
animal, while the prawn is more of a
sandy shore creature.
Prawn Palaemon serratus
prawns are semi transparent creatures,
their internal organs visible through
the skin. They are found on rocky beaches.
common prawn can reach four inches
in length, but those seen in rock pools
never reach anywhere near this length.
with being transparent they are still
relatively easily seen, particularly
when they are disturbed as their jerky
backwards darting motion makes them
conspicuous in a calm rock pool.
first two pairs of legs have pincers
the second pair being the larger. These
are used for feeding on seaweed and
Shrimp Crangon crangon
common shrimp’s body has more colour
to match its background sand, this is
made more effective as the colour pigments
can be modified. They are an important
shrimp is a nocturnal bottom feeder,
hunting at night using its antenna to
detect its food. During the day they
bury in the sand with only their antennae
exposed. They may be very common on
a beach, but are only seen when disturbed
and this will be just a quick darting
movement highlighted by a small disturbance
in the sand.
first two pairs of legs have pincers
with the front pair pincers being enlarged.
Just like the common prawn, the common
shrimp is an opportunist feeder, consuming
seaweed, carrion but with its larger
pincers also smaller animals. The common
shrimp can reach up to two inches in