Re:Peppermint Shrimp

Dear MySanity:

I’m very sorry to hear that your peppermint shrimp (Lysmata wurdemanni) fell victim to something in your aquarium.

It does sound as though something hiding in the live rock may have ambushed or attacked the peppermint shrimp, inflicting fatal injuries, but it’s very difficult to say what the culprit may have been. Large bristleworms in excess of 3-4 inches have strong jaws they can inflict a powerful bite, but they will typically hang onto their victim after they have clamped down on with their jaws, and it’s unlikely that a monster bristleworm could have inflicted a fatal wound on the peppermint shrimp while you were looking at it without the prickly pest being seen.

If there was a small mantis shrimp or a pistol shrimp lurking within a hidey hole in the live rock, it’s possible that it may have attempted to ambush the peppermint shrimp when it passed in front of its hiding place. Both pistol shrimp and mantis shrimp prey on small crustaceans and may have regarded the peppermint shrimp as suitable prey. The "smasher" category of mantis shrimp are armed with powerful hammer-like clubs on their forelegs, which they use to smash the carapace of small crustaceans. These devastating appendages are said to be strong enough to break aquarium glass. Their MO is to lunge at a victim that passes within striking distance of their burrow and deliver one or more crushing blows with their clublike raptorial appendages. So I suppose it’s possible that the unfortunate peppermint shrimp may have taken such a blow and managed to leap away, only to die from internal injuries later in the day. You may not have noticed the lightning strike of the mantis shrimp if it retreated to its burrow or hidey hole immediately after delivering the fatal blow.

It’s also possible that your peppermint shrimp may have run afoul of a pistol shrimp that hitched a ride on your live rock. The concussion from the shock wave they produce with their pistol shots can indeed stun and kill small fish and invertebrates. Pistol shrimp are quite territorial towards other shrimp, and it is therefore small live shrimp that are at the greatest risk of running afoul of a pistol shrimp in the aquarium. They are quite capable of killing cleaner shrimp and peppermint shrimp such as Lysmata wurdemanni and Lysmata amboinensis.

The concussion produced by the pistol shrimp is powerful enough to inflict damage from a short distance, so a pistol shrimp could have injured the peppermint shrimp from the safety of its hiding place without ever showing itself. It could be that the peppermint shrimp survived the shock of the initial attack, but later succumbed to internal injuries from the concussion it had absorbed. However, the pistol shots from these little sharpshooters are distinctly audible, and I imagine you would certainly have noticed the sharp "crack" if a pistoleer had attacked the peppermint shrimp.

So I think the most likely suspect may be a small "smasher" mantis shrimp, but that’s only a guess.

To be on the safe side, you might want to keep a close eye on the piece of live rock that they peppermint shrimp was near before it was injured for the next several days to see if you can detect any sign of an unwanted hitchhiker, such as a mantis shrimp or pistol shrimp or an extra large bristleworm. Check it during the day several times, but also be sure to check it once or twice after lights out, since it’s more likely to reveal itself under the cover of darkness. Wait until the aquarium light has been turned off for at least a half hour, and then use a flashlight to examine the area where you think the culprit may be lurking after the room has been darkened.

To be extra safe, you might also try setting a trap for the suspected mantis. Stomotopods or mantis shrimp can be trapped but you have to be patient and persistent to succeed. They are cautious animals and often need time to become accustomed to the presence of the trap, so you might have to be your trap for several days in succession before you bag the little bugger. A number of commercially made mantis traps are available, but you can easily fabricate your own from items around our house. For example, the following link shows how to construct a simple trap for stomotopods:

http://www.seahorse.org/library/articles/DIY/diyMantisTrap.shtml

There are quite a number of other methods that often work well for killing or capturing a mantis shrimp if you happen to know where it holes up. See the following website for a good discussion of various other techniques for removing mantis shrimp from your aquarium:

Click here: OZ REEF – Mantis Shrimp
http://ozreef.org/library/articles/mantis_shrimp.html

Best of luck solving the mysterious death of your peppermint shrimp, MySanity!

Respectfully,
Pete Giwojna