Stomatopods as Pests
How do you tell if there's a mantis shrimp in your
(A) Fishes and invertebrates like shrimps and crabs start to
- The continued loss of fishes and invertebrates may mean
that there is a mantis shrimp somewhere in your tank.
Note however that other inhabitants of the aquarium may
in fact be responsible for this. Sally Lightfoot Crabs,
for example, have been known to devour an inhabitant or
two, and predatory fishes that have been mistakenly
placed along with more timid (or smaller) fishes may also
be the actual culprits. By a process of elimination, make
sure that these are no other possible candidates.
- This external
link takes you to an article whose author is doubtful
whether many of the fish disappearances are actually
caused by mantis shrimps. I agree with many of his
arguments, however, you should note that many of the
newsgroup posts concerning problems with mantis shrimp
have reported BOTH the loss of fish/invertebrates AND the
presence of what they take to be mantis shrimps.
Therefore, there seems to be strong circumstantial
evidence that mantis shrimps can be the cause of massive
losses in livestock. In addition, the author seems to
conclude (mistakenly) that all smashers are restricted to
a diet of hard-bodied animals. This is not true. Both
smashers and spearers can take fishes and shrimps. The
smasher raptorial appendage can be used to impale or
severely wound soft-bodied prey.
(B) Loud clicking noises are heard coming from the tank.
- A lot of people seem to be confused about this. Pistol
shrimps, which are "generally" viewed as
non-harmful to most inhabitants of the tank, can and do
make these clicking noises using one of their enlarged,
specialized claws. Mantis shrimps cannot by themselves
produce such noises. However, they can and do produce
clicking noises whenever they use their raptorial
appendages to hammer something hard, whether it be the
armored shell of some luckless crab or mollusk, or the
walls of their cavities. I have read somewheres
that one way to tell from the clicking noises is that
pistol shrimps tend to snap in ones and twos, whereas
mantis shrimps make rapid multiple hits.
- The point here is that clicking noises don't prove
anything. However, in conjunction with the continued loss
of inhabitants, and the lack of any other viable culprit,
you can probably assume that you do have a mantis
What's the difference between mantis shrimps and
(taken from an email I sent to a reader)
NOTE: For pics of the two types go to this Marine
Aquarist Society of Australia page.
- At the very basic level, the two are very different
critters, with pistol shrimps belonging to a completely
different group of organisms which include lobsters and
crabs, while mantis shrimps make up the only living order
in a superorder called the hoplocarida. You can tell both
apart very quickly by the ff:
- Pistol shrimps have two relatively large claws (one
significantly larger than the other) that it holds
extended in front of it, while mantis shrimps hold their
enlarged forelimbs very close to their bodies.
- The carapace of a pistols is relatively "long"
(ie. covers the head and thoracic segments), whereas in
mantises the carapace is extremely short, which makes
them look more "wormlike" because of the
exposed abdomen and some thoracic segments. This makes
the mantises very flexible, and they like rolling around
a lot inside their burrows or cavities.
- Pistols seem to have a very normal looking shrimplike
"rostrum" (I don't own a pistol, so I'm basing
this on pics), which is a sharplike extension jutting
outwards from their head, while mantis shrimps do not
clearly show this structure.
- The eyes of pistols are recessed, whereas mantises have
extraordinarily stalked and eminently moveable eyes.
- Mantis shrimps have a pair of "winglike"
antennal scales along the sides of their head, which you
can very clearly see if you look at them face to face.
- Pistol shrimps make those clicking noises by using one of
their specially modified claws. Based from different
sources, these are either used in mating, hunting (by
stunning small prey), and in fighting with other pistol
shrimps. Mantises cannot make clicking noises per se....
instead, any clicking noises from a mantis shrimp are due
to using its forelimbs to hit something else, either
inanimate objects or (more likely) hardshelled prey such
as snails or hermit crabs.
- Whether or not pistols are deadly to other inhabitants of
the aquarium seems to be an open debate. Some have said
they do eat others, while I've read in some reference
books that they feed on already dead stuff. I suppose
it's really a combination of both, with the shrimp
feeding on much smaller prey when the opportunity arises.
The mantis is deadly to others (especially when it's
pretty hungry), although one mantis that I have has (so
far) left other inhabitants alone when kept amply fed.
I've seen pics of gobies and pistols cooperating, while
I'm sure the mantis would rather eat the fish than live
with it. Since your question was sort of general, I gave
you a broadsided answer. If you had a specific question,
please feel free to email me.
alan san juan.
Web Site Author: A. San Juan
Site Created February 3, 1998
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