learn only 3 things about them ...
They resemble familiar prawns and shrimps, but belong
to a totally different group.
Mantis shrimp can hurt you. Don't touch them!
have pincers modified into fearsome weapons.
These large and busy shrimp-like animals are often seen on our Northern
shores, especially among seagrasses.
What are mantis shrimps? Mantis
shrimps are not in the same group as prawns, although they appear
similar. Mantis shrimps belong to Order Stomatopoda, while other shrimps
and prawns belong to Order Decapoda which includes true crabs.
Features: Mantis shrimps seen
on our intertidal shores are mostly juveniles rarely exceeding 10cm,
but some species can grow to 30cm as adults! While those found among
seagrasses tend to be well camouflaged, mantis shrimps found in deeper
waters near 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.
In fact, like a living swiss army knife, all kinds of strange gadgetty
limbs are folded under the little animal, ready to be unleashed with
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 fishes and prawns.
The pincers of smasher mantis shrimps 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 eyes are so fascinating that a
study suggests that the structure of their eyes
may inspire better DVD and CD players!
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 are 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
for passing prey.
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.
The males have well developed copulatory projections called penes
at the base of the last pair of legs. 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
hard to catch. Their solitary and anti-social nature makes them impossible
to farm. 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.
Status and threats: Our mantis
shrimps are not listed among the threatened animals of Singapore.
However, like other creatures of the intertidal zone, they are affected
by human activities such as reclamation and pollution. Trampling by
careless visitors and over-collection by hobbyists also have an impact
on local populations.
Changi, Jul 05
Deadly pincers of a spearer mantis shrimp.
Changi, Jul 05
This is all that is usually seen
of a mantis shrimp in hiding.
Changi, Jul 04
shrimps on Singapore shores
Stomatopoda recorded for Singapore
*from Tan, Leo
W. H. & Ng, Peter K. L., 1988, A Guide to Seashore Life
**from Lim, S., P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of
the Sea: The Life and Times of Labrador Beach.
- Lim, S.,
P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life
and Times of Labrador Beach. Division of Biology, School of
Science, Nanyang Technological University & Department of Zoology,
the National University of Singapore. 160 pp.
- Jones Diana
S. and Gary J. Morgan, 2002. A Field Guide to Crustaceans of
Australian Waters. Reed New Holland. 224 pp.
Helmut, 2001. Crustacea
Guide of the World: Atlantic Ocean, Indian Ocean, Pacific Ocean
IKAN-Unterwasserachiv, Frankfurt. 321 pp.
Terrence M., David W. Behrens and Gary C. Williams. 1996. Coral
Reef Animals of the Indo-Pacific: Animal life from Africa to Hawaii exclusive of the vertebrates
Sea Challengers. 314pp.