Noctural Pistol Shrimp Activity

[Calappidae]

I've been sneek peaking in my tank for past couple of nights at around 2AM.. and I was surprised to find my tiger pistol shrimp just wondering around in the dark without a goby or anything. It was just casually walking around, (and by that I mean walking a few inches into a rock, pausing for a few minutes, then turning around and running into something else). Good thing I noticed this behavior as I was going to add an additional pair to the aquarium.

Now I figured, well this is strange I've never heard of this activity and it was just a one time occurance... so I checked again the next night around same time, it made the EXACT same movement pattern in the tank, stood and paused in the EXACT same positions.. it was like I was watching a replay of everything from the previous night.. BUT this time I did turn the atinics back on to see if it was grabbing food or anything in these pauses, and the shrimp (slowly) returned to it's burrow after the lights went on. (Probably my clanging and vibration getting to the timer.) I couldn't see any behavioral activities in the pauses.

Has anybody else seen their snappers roaming alone at night? I'm just wondering if this is something out of the norm with my specimen.

My only hypothesis on what this might have been, is a search for a mate as I can't see it roaming for any other reason. Oh the irony, there is a mantis shrimp in the sump that makes clicking noises at night too, that would be one literal heart breaking relationship between them. Perhaps they are signaling each other. :uzi::hammer:

 

[pache11]

They actively hunt at night. Sometimes will kill a hermit crab or two.

 

[pache11]

If you watch during the day, sometimes when the pistol is hungry it will stroke the goby's underside until it defecates.

 

[Calappidae]

They actively hunt at night. Sometimes will kill a hermit crab or two.

That is false.. pistol shrimp don't hunt for anything, they're scavengers. Their "gun" is used strictly for scaring aware threats and signaling mates.

 

[Adetia]

That is false.. pistol shrimp don't hunt for anything, they're scavengers. Their "gun" is used strictly for scaring aware threats and signaling mates.

Oh really?

World's Deadliest - Amazing Pistol Shrimp Stun "Gun": http://youtu.be/KkY_mSwboMQ

 

[Betta132]

I've seen a pistol bigger than that shoot a (non-watchman) goby in the face multiple times, at point-blank range, and the goby wasn't even that bothered.
That video has something up with it. A stunned shrimp doesn't just instantly go stiff, it usually kind of motors its swimmerets a bit. Plus, a pistol shrimp just isn't that powerful. If they shoot from the burrow, the purpose is to scare away the intruder, not kill and eat it. It looks more like the shrimp is doing the jerk-backwards thing they do when frightened, and then somebody is putting a dead shrimp in front of the burrow.
Mine killed and ate bristleworms, but I think he did it accidentally. He would shoot at them when they got into the burrow, then he would jab them with his claws when they didn't go away. He ended up accidentally killing them and then ate them because there was dead food. Beyond that, he doesn't hunt. He does steal hermit crabs, but I can see him pushing them against the wall of the tunnel- he just wants the shell, he doesn't seem to realize there's a crab in there.

 

[Adetia]

Either way, a quick search on Google shows quite a few results that mention pistol shrimp using their snapping claw for hunting as well as communication.

 

[Calappidae]

Oh really?

World's Deadliest - Amazing Pistol Shrimp Stun "Gun": http://youtu.be/KkY_mSwboMQ

World's Deadliest is well known to overdramatize their videos. Infact, the species in that video is Alpheus armatus which is associated in hosting sea anemones.. never once have I seen the species harm anything other than in that obviously staged video.

It's kinda the same case as confusing the terms "force and acceleration" when describing mantis shrimp punches (which you can clearly see them do in other world's deadliest videos.)

 

[pache11]

I have seen my Tiger pistol kill and then proceed to eat 2 wheelers gobies that I had tried to pair with it. I was going to trade with someone else until I paired it with a yellow watchman goby. Randall's pistols never seem to attack shrimp gobies of any type. the Tiger is alot larger than the Randall's and more agressive with some fish. Don't speak of what you have only heard of and not experienced yourself. Our tanks are not the ocean and even "peaceful" occupants behave differently in our limited environment.

 

[Calappidae]

There had to be something wrong with the wheeler gobies for the shrimp to cause any harm to them. Never, not once have I heard, seen, or experienced a disappearence via snapping shrimp besides small hermits and snails being buried alive. Video proof of a snapping shrimp killing something, that isn't staged like world's dramatic videos, then I'll be able to see any form of predatory nature in them. I've heard as many death reports via snapping shrimp as cleaner shrimp from google searching.. with the exception that snapping shrimp rarely interact with other livestock and mostly just hide when in danger.

I've witnessed, and watched my yellow tang get shot in the face repeatedly as it swam infront of the shrimp while it was digging, no harm done.

There is also the theory that it's possible the "gun" does not work in aquariums like it does in the ocean due to different water pressure impacting the capatation bubble. Whether or not that's true I don't know.. I think it might be false according to slow motion videos in aquariums where you can still see the explosion.

 

[MidwesternTexan]

I have a pistol shrimp I got in a trade a few months ago.
Since putting it in my DT, I have never 'seen' it again.
I occasionally hear the pistol- like just a little while ago this morning.

I've had a blue spotted watchman goby, now full grown for years, and I never see them together either.

I look as well as I can, and never see the pistol, even at night using an LED flashlight.

Nice thread, good info, just sharing mine so far.

 

[Adetia]

Like I said before, there are many hits on Google that talk about pistol shrimp using their snapping claw for hunting. Here is just one example but you can continue to believe what you want based on what you see in your aquarium:

The most well-known and studied behavior of bigclaw snapping shrimp is their ability to create loud "pops" with their modified pistol claw. These "pops" are used in communication and during the hunting of prey. This phenomenon is accomplished by the physical process of cavitation, the rapid formation and implosion of cavities in a liquid in which the pressure of the liquid falls below its vapor pressure. The study by Versluis et al. (2000) was the first to describe the physics behind this extraordinary ability. The rapid firing of the modified pincer causes a high-velocity water jet. This water jet exceeds speeds needed for cavitation to occur and causes a very small and very brief bubble to form and implode within an incredibly short time (less than 300 μs). A study by Lohse et alia (2001) found that as the bubbles formed by the water jets collapsed, they emitted an intense flash of light. From this they concluded that at the time of the collapse of the cavitations, extremely high pressures (unmeasured) and temperatures (above 5000 °C) occur. These high pressures and temperatures are the cause of the ability to stun prey or even kill them if they are within a few millimeters of the tip of the snapping claw.

Bigclaw snapping shrimp are omnivores and often feed on a variety of small marine animals including worms, crustaceans, shellfish, and small fish. They also graze on algae, but this has been documented only in laboratory environments. Most of their food is obtained by ambushing their prey and using their snapping claw to create a jet of water that kills or stuns prey.

http://animaldiversity.org/accounts/Alpheus_heterochaelis/

 

[Calappidae]

I'll look into that. Alpheus heterochaelis is a species that doesn't pair with gobies, predatory behavior might explain this.

 

[Adetia]

That same article says they do:

In areas where the predators of bigclaw snapping shrimp occur, the shrimp are known to form mutualistic relationships with other fish, particularly gobies (in particular, Cryptocentrus cryptocentrus). The gobies benefit by living in burrows built by the shrimp, and the shrimp benefit by using their antennae to receive tactile signals from the gobies that communicate the absence of predators.

Another interesting thing in that article is it says they actually modify their snaps to be just a warning snap without the cavitation bubble, which may be why other animals sometimes seem to be unphased by their snaps:

The aggressions of bigclaw snapping shrimp toward members of the same species are also expressed with the modified pistol claw. These aggressive interactions are often a result of intrusion upon an occupied dwelling area or hunting ground. They are not life-threatening to either shrimp, but instead warn against some displeasing behavior. When said agonistic intraspecific encounters occur, one shrimp will shoot jets of water toward an intruding shrimp, but will do this within a range that will not allow for formation of a bubble(usually 9 or 10 mm). At this distance the intruding shrimp is neither killed nor stunned, but only warned that the area upon which he has intruded is occupied.