The clade of shrimp called pistol or snapping shrimp, are one of the most commonly traded clades of shrimp in the aquarium trade. The species in question are those with the habit of forming symbuotic associations with particular fishes. Such a shrimp species is Randall's pistol or snapping shrimp,Alpheus randalli, which is also traded as the red and white striped pistol shrimp. Among the pistol shrimp this species is outstanding for its distinctive, red banded color pattern.
A. randalli is indigenous to parts of the Indian and Pacific oceans, at tropical latitudes. There it associates with gobies of the genera Amblyeleotris, Stonogobiops, Tomitamaichtgys, and Flabelligobius. This shrimp reaches a length of 3 centimeters, or over 1 inch long, so it is suitable for small aquariums. As this species is nainly a detrivore, it is not difficult to feed it in a reef aquarium with an established sandbed. When they are housed in established aquariums, these gentle shrimp will not need feeding per se, as their food will already be abundant in the substrate
Pistol shrimp are often confused with mantis shrimp because of the noise they make, which frightens paranoid fishkeepers. The claw and the noise it creates are actually of scientific interest, and they are very different, in fact, from the striking arm of the mantis shrimp clade. In fact snapping shrimp cannot employ their claws to hunt large animals, as do mantis shrimp, and the two kinds of crustacean are dissimilar as well as only distantly related: the snapping shrimp is more closely related to crabs and lobsters, in fact.
The claw of the snapping shrimp is employed as a weapon, though not one that is used to subdue large victims. If anything, their impressive claws are more amazing than are those of the mantis shrimp clade; for they have evolved to produce powerful bubbles of air, to blast and stun an opponent. Pressure increases when the claw opens wide, at which point surrounding water flows into a small chamber at the bend of the claw, which was once an ordinary shrimp pincer. Rapidly the claw snaps together, causing a small plunger to force out the water by pressure. Thus the shrimp launches the trapped water as a high speed projectile - these animals are truly a marvel of natural selection. But they can neither hunt fish nor break aquarium glass.
The habit of A. randalli is to dig into fine grained sand or silt substrates, and thus this species requires a suitable sand substrate in the aquarium. They make use of coarser material such as coral or seashell fragments to reinforce their burrow walls, therefore these elements must also be mixed into the otherwise fine material of the aquarium substrate. Despite the frequent and paranoid confusion of snapping shrimp with predatory mantis shrimp, they are in fact peaceful to ornamental fish and crustaceans. They are also completely harmless to corals and macroalgae, but although they can survive unpartnered with a goby, it is inauthentic for both species fare better together in the wild.
Gobies of the prawn associating species associate and partner with a snapping shrimp such as A. randalli, after the shrimp has begun to burrow itself a new home. That only young shrimp usually live without a goby partner, indicates the extreme usefulness of the remarkable shrimp-goby partnership to them in the wild. A pistol shrimp without a burrow is extremely vulnerable to predators, and such a shrimp without a burrow will instinctively not feed whilst it concentrates all of its energy on excavating a safe, basic lair. The goby is better than the shrimp at watching for predators - like a watchdog, whereas the shrimp performs digging duties, and has the defensive weapon.
Like the photogenic association of clownfishes (Amphiprion sp.) with certain sea anemones, the association of gobies with snapping shrimp, is a textbook example of mutualism - the close and habitual co-existence of two organisms, that bestows benefits to both the living things in the partnership. The relationship and co-operation of gobies with snapping shrimp is one of such friendships that can be stimulated and observed in the aquarium, because both animals are easy to care for, and fascinating to watch as they behave as they would in the wild.
Generally snapping shrimp are simply traded as snapping shrimp, either alone or partnered with a goby as a pair. Alpheus randalli is distinctive enough to be traded; other distinctive species include A. bellulus, the tiger pistol shrimp, a close ally on A. randalli that may be considered similarly by the aquarist; although A. bellulus is the larger species, growing up to 5 centimeters or 2 inches long. Although the two species share a banded color pattern, that of A. bellulus is brownish against yellowish white.
