Coral - November/December 2010

species tank for a roughly 2½-inch (6-cm) Gonodactylaceus glabrous living in a (pre-drilled) tunnel in the rock, which it has enlarged using blows of its dactylus to suit its own requirements.

change color and transmit differ-
ent wavelengths. They narrow or
tune the light that’s transmitted
more towards the blue. It makes
the eye much more sensitive to
light, but it sees much less diversi-
ty of the spectrum. So, it’s a pretty
complicated eye.”
Research into stomatopod eyes is ongoing, but it is
clear that their faceted eyes can detect far more differ-
ent wavelengths than the human eye, and even polarized
light radiation that we cannot see at all. In addition ul-
traviolet radiation is a visible form of light radiation for
mantis shrimps, as they possess the appropriate optical
pigments. This allows them to communicate via color
signals that are totally undetectable to the human eye.

Mantis shriMps
in the aquariuM

In the case of mantis shrimps that don’t exceed an adult size of around 3 inches ( 8 cm), maintenance in the reef aquarium is, essentially, something that should be tried if such a shrimp is introduced into the tank with live rock. There is no need for panic in such cases; the creature will certainly not kill and eat the entire fish population, as many people assume—especially if the shrimp in question is a “smasher,” as these species are, as already mentioned, specialized in feeding on crustaceans, snails, and clams.It is the “spearers” that are more interested in fishes.

Anyone who spots a mantis shrimp in his aquarium doesn’t automatically have a problem— at least as long as there are no losses of livestock to report and there are no particularly vulnerable tankmates. And the mantis shrimp is more likely to behave itself if it is deliberately given some food two or three times per week. It will quickly learn to take a piece of table shrimp, krill, or fish flesh from a feeding stick, and this will become a feeding exercise well worth watching.

If, however, ornatmental shrimps— including cleaner shrimps, hermit crabs, and snails start to disappear, this should be taken as a possible sign of the presence of a mantis shrimp and you should then make a point of listening for nocturnal cracking sounds.

When it comes to removing a mantis shrimp from the aquarium, a trap and a little patience will usually do the trick. Another possibility is to provide an apparently ideal mantis-shrimp tunnel in a removable rock specially introduced into the aquarium for the purpose (Knop 2009), as if the shrimp enters the hiding-place it can easily be removed and housed in a filter or species tank. However, large species of mantis shrimps, whose appetites can present a real problem, rarely get into the reef aquarium accidentally, and if they do then their size alone makes them so bold and cheeky that they will enter a suitably-positioned and temptingly baited trap relatively quickly.