Mantis
shrimps are not in the same group as prawns, although they appear
similar. Mantis shrimps seen in the tidepools of Chek Jawa are mostly
juveniles rarely exceeding 10cm, but some species can grow to 30cm
as adults! While those found in the seagrass lagoon tend to be well
camouflaged, mantis shrimps found in reefs can be quite colourful.
Perilous Pincers: Mantis shrimps
got their common names from their huge front pincers that snap with
great speed and force. These resemble those of the Praying mantis
insect or the blade of a pocket knife that folds into the handle.
Mantis shrimp pincer modifications are generally of two types: spearers
and smashers.
| Spearer mantis shrimps pincers are
armed with sharp spines, from 2 to 20 spines. These pincers
extend and retract much faster than an eye blink and the sharp
spines impale soft, fast-moving prey like fish and prawns. |
It
takes only two milliseconds for a spearer to extend its pincer.
The blink of an eye is 100 milliseconds.
--From Secrets
of the Stomatopod
|
The pincers of Smasher mantis shrimp are modified into clubs. These
are used to bludgeon shelled prey. While snails and clams are simply
dragged back to the burrow, crabs are often first immobilised by blows
to the claws and legs. In the safety of the burrow, the victim's shell
is further cracked. The blows of smasher mantis shrimp are so powerful
that they have been known to break aquarium glass!
Warrior shrimp: Mantis shrimps
have other modifications that make them deadly predators. They have
compound eyes that are considered among the most complex. They can
see more colours than we can, and can see both UV and infra-red light.
With just one eye, they already have binocular vision, important for
accurately judging distance. So if they lose an eye, they can still
hunt with the remaining eye! Their eight pairs of legs are modified
for various uses. The second pair of legs are modified into the deadly
pincers described above. Remaining legs used for walking. They also
have five pairs of powerful paddle-shaped swimmeretes under the abdomen
which are also used for burrowing. Their tails are heavily armoured
to defend against the blows of other mantis shrimp in their territorial
battles.
Shy mantis: Although common, mantis
shrimps are rarely seen. During the day, mantis shrimps usually retire
in their burrows or hiding places. They hunt at night. Some forage
for prey, crawling about on the bottom or swimming with powerful beats
of their swimmeretes. Others lie in wait at their burrow entrances.
Anti-social shrimps: Like many
predators, most mantis shrimp are solitary. They can be highly territorial
and some have developed complex social behaviour to defend their space
from rivals. Mantis shrimp are apparently quite smart: they can learn
and remember well for a little crustacean!
Baby mantis shrimps: Mantis shrimp
are of separate genders. In some species, the males have larger pincers.
In most species, after mating, the female lays her eggs in a safe
place like a burrow or carries them until they hatch. Some mantis
shrimp species are monogamous. The mated pair share a burrow and while
the female looks after the eggs, the male hunts for both of them.
The free-swimming larvae look nothing like their parents and drift
among the plankton for a while before settling to the bottom and changing
into adult form. Here is a fascinating photo
of a mantis shrimp larva on Image
Quest 3-D Marine Library
Human uses: Mantis shrimp are
said to be edible but not worth collecting commercially because they
are solitary and hard to catch. They are also not popular for the
aquarium trade as they are ferocious predators. Smashers also can
damage aquariums. However, mantis shrimp in the wild are attractive
subjects for divers and other visitors to marine habitats. |
|
Spearer
mantis shrimp |
Smasher
mantis shrimp |
Highly
developed eyes
Give the mantis shrimp excellent vision
to judge its strike accurately
The armoured tail
Protects from powerful blows of rival mantis
shrimps
|
