Notes from the Trenches with Scott Chevalier

"Fisherman Attacked by Giant Shrimp"
"Mantis Shrimp Ate My Baby!"
"Stomatopod Sinks Fleet"
"Mantis Shrimp Destroys World; Film at 11…"

Outside of the National Enquirer, headlines such as the above are unlikely. Then again, after months of reading the mantis shrimp forum on Reef Central (which you'd think would be about mantis shrimp-keeping, not mantis shrimp-extermination), various posts on other message boards and dealing with customers' questions while working part-time in a local fish store, I wouldn't be surprised at all by any of those headlines. In fact, some of those are fairly tame. Mantis shrimp tend to get a fairly horrible reputation for all manner of atrocities (see the headlines above again). While the occasional aquarist or diver may actually get a split-thumb, I'd argue that someone was most likely putting their thumb where it didn't belong.

Mantis Meets World!

The most commonly made false accusations include:

- Mantis shrimp can and will kill anything.
- Mantis shrimp can and will kill anything for fun.
- Mantis shrimp can and will kill anything for fun and nothing else in the tank could've done it (including the reefkeeper).

At the root of this prejudice against mantis shrimp is the wrongly held belief that the shrimp, also known as stomatopods, are evil. Fascinating? Yes. Adept hunters? Certainly. Evil? Not so much, unless feeding themselves is considered evil. Stomatopods are guilty of simply doing what they were born to do; their diet just isn't compatible with what many reefkeepers encountering them in their tanks are willing to tolerate. In the same way that each fish has a specific diet it prefers, so, too, do stomatopods.

Fishes are often grouped into general dietary categories in order to allow fishkeepers to more easily meet their feeding requirements. In fact, specific 'formulae' of food are even distributed by some vendors; one mix of food for sponge-eaters, another mix for "bug-" eaters and a third for herbivorous fish. The same generalizations can be made for mantis shrimp, though the labels would have to be changed a bit; maybe to read "Formula Smasher" and "Formula Piercer."

Stomatopods generally fall into two broad categories: smashers and spearers. Smashers have raptorial appendages designed for cracking open shells of gastropods and crustaceans. Spearers' raptorial appendages are specialized for snagging fish from the water column by impaling them.

While the spearers do indeed sound like a menace capable of making fish disappear, they are also very rarely encountered in our tanks. Almost without exception, stomatopods that pierce and eat fish are found in muddy areas of the ocean floor where they can dig burrows more easily. This makes it very rare for them to be imported on live rock or with corals.

The much more common hitchhiking smashers are often hitchhikers on live rock, and are often small species that, in time, can dramatically down-size a cleaning crew, but they aren't doing it out of malice. Speaking from my limited experience as a hobbyist, most accidentally imported smashers tend to feed mostly on "bugs," whatever the tank is fed (frozen or flake) and tiny or juvenile snails. While some people choose to feed their mantis shrimp silversides or even flaked food, this is not their preferred diet. In the anecdotal adventures of my own caped stomatopod, he faces off occasionally with crustaceans of various shapes and sizes. When victorious in capturing his crabby cohabitants he does feast on their remains, but these crusty critters are definitely listed below most snails on his "favorite foods" list. I imagine the menu of choice varies greatly between species. Very large smashers are, incidentally, available for sale in the aquarium trade, "Peacocks" and/or "Clowns" most notable among them, but these are rare hitchhikers indeed and, like spearers, are usually special-ordered.

As a final rebuttal to the "Mantis shrimp can and will kill anything" line, my experience with four smaller species of stomatopod suggests that the mantis shrimp is more likely to fear fish than to intimidate them. My experience includes a Gonodactylus smithii, which is known to "bluff" with its threat display more often than many other species of stomatopod. The threat display of many smashers can be used to spook and scare away other competitors or perceived threats. It is also shown right before a strike as well. So, just as in poker, you'll have to learn to read other tell-tale signs. Of the others, kept more briefly, Haptosquilla glyptocercus was the most bold. Though it never attacked fish and typically stayed holed-up when fish were around, it did seem completely unafraid as it snapped brine shrimp or mysids from the water column, even directly in front of the fish. Neogonodactylus wennerae is the most varied I have seen, with no two individuals looking anything alike at first glance. I didn't spend enough time with this species to say much more then they seem to be one of the most commonly imported and their behavior varies almost as much as their coloration. Another small unidentified mantis shrimp I've dealt with may have actually died of fright while acclimating to the sump. It seemed genuinely terrified by any movement above or outside its container.

Mantis shrimp scoping out possible prey.

So then, what might we assume from the above? When the stomatopod is bigger than or stronger than or, in fact, regards itself to be in any position of overwhelming superiority (such as when pitted against brine shrimp) the mantis shrimp is likely to appear to be the most fearsome creature ever seen in a reef tank. At the same time if the mantis shrimp feels even slightly under-prepared for the encounter it may display, but will ultimately run away and hide or, in certain cases, stay bold for too long and lose an eye.

It's all fun and games until someone loses an eye…

"So, enough about fish, I heard they also destroy corals and even eat the heads off chickens…"

Smashers are certainly a constructive lot. My own Gonodactylus smithii was found under the base of a large toadstool leather. In the weeks leading up to finally taking him home, I did notice that he would occasionally groom the base of the leather when it encroached too closely to the entrance of his cave. In over a year in captivity since then, he has rearranged several corals, including the occasional chip of zoanthids or, most recently, half a colony of translucent cup coral he seems to have some attraction toward (it sounds like more than it is… half the colony is a branch with one polyp at the end). In all of those rearrangements he has never destroyed a coral, and in most cases I suspect that he cared little for the polyps and was more interested in the shape or size of the rubble to which they were attached. I may be underestimating his aesthetic sense, though. Maybe he was after the rubble with the corals attached because he wanted to add a little color to his home. More practically, he could have been trying to better camouflage his home, as well.

Regarding eating the heads off live chickens, I think that went out of style in the '80s. Though, just this week, I did feed a treat of roasted turkey breast to one seemingly happy G. smithii.

"Fine, mantis-lover; then what should I do about it if I do find one and don't want it?"

First, make sure that's the beast you're hunting. If you've determined you have a mantis by sound alone, many things can be misheard as mantis-clicks. Pistol shrimp can, to the untrained ear, sound very much like a stomatopod smashing away at rock or snails. After adding a fighting conch to my display, I spent a week fully convinced I had a mantis; the sound of the large snail as it encountered the aquarium walls sounded very much like a mantis. Likewise, any snail may be capable of making similar noises when traversing the glass walls of its tiny "captive ocean" home.

Let's assume for a moment that you have a visual ID on your unwanted (at least in the main display) stomatopod. Many drawings and descriptions on Reef Central and elsewhere around the web detail the construction of mantis traps. These traps are simple and may even help catch other more destructive creatures from your rockwork (crabs, hermits, fish etc.). Other means involve removing the rock containing the stomatopod's home or using freshwater, soda or seltzer water to force the shrimp's exit from its burrow. While this doesn't sound pleasant it also shouldn't necessarily be lethal unless you let the mantis drown in the wastewater.

Whatever course you choose, should you not desire to keep the wayward stomatopod for yourself, let others know about it through local reef clubs or in the Mantis Shrimp Forum on Reef Central. Many "mantis-lovers" are out there without a mantis to love and would welcome such a guest to a tank.

Links of Interest:

Mantis Shrimp Forum on Reef Central
The Blueboard "Lurkers Guide to Stomatopods"
Tim's Continuing Adventures
A special thanks to Legendary Lures for permission to use an image of one of their lures.

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Mantis Shrimp Destroys World; Film at 11.. by Scott Chevalier -