|Distribution||All tropical seas|
|Maximum Size||Up to 7.5cm (3"), but most are smaller.|
|Sexual Dimorphism||Difficult to determine. Males have oval shaped gonopores on the coxae (basal segments) of the fifth set of pereopods, whereas females have U-shaped gonopore slits on the coxae of the third set of pereopods.|
|Temperature||Tropical: 23-27 deg C (73-81 deg F)|
|Water Parameters||SG: 1.020-1.025, pH: 8.1-8.4|
|Compatibility||Reef with caution|
|Lighting||Dim (in brightly lit aquaria, provide plenty of shady overhangs).|
|Reef Aquarium Compatibility||Usually excellent, particularly if acquired with its symbiont. Although not to be trusted with very small ornamental shrimps.|
Within the vast order Decapoda sits the family Alpheidae (Snapping Shrimps). Alpheidae is further split into 45 genera, one of which is Alpheus. This particular genus encompasses almost 300 described species of Snapping (or Pistol) Shrimp, with members typically characterised by their asymmetrical claws, of which one is disproportionately large - around half the length of the body. Pistol Shrimps are known from a variety of different tropical and subtropical habitats around the world, from the intertidal zone to great depths, occurring primarily in coral reefs, estuaries, and mangrove swamps. These nocturnal shrimps tend to have poor eyesight, and the majority share a mutually beneficial symbiotic relationship with various partners, most commonly burrowing Shrimp Gobies. Together, the shrimp and goby share the safety of a burrow which the shrimp digs/maintains, whilst the goby keeps watch for predators. As the shrimp is working, it maintains antennal contact with its goby partner posted at the entrance of the shared burrow. If the shrimp detects the quivering motion of the goby’s caudal fin during an unusual situation, it reacts by immediately withdrawing into the depths of the burrow. The entrance to the shared burrow will be closed at night, and only one entrance is usually open at any one time. The shrimp will only emerge from the burrow whilst it can have tactile contact with the goby. Provided with a reasonable depth of coral sand and a good selection of loose coral rubble pieces that vary in size (not too big to be moved), such a partnership can do very well in the home aquarium. The shrimp and goby can each survive without their partner, but if such a compatible duo can be acquired, this will benefit their long-term wellbeing. A natural partnership such as this will also provide a really fascinating display, captivating the observer for hours on end. Your dealer may be able to acquire the two together, it is certainly worth asking. Most alpheids are suitable for reef aquaria, but only those tanks which do not contain very small ornamental shrimps. The common name of Pistol Shrimp stems from the ability to produce a loud cracking sound with the oversized, modified 'snapper claw'. The claw has a pistol-like structure comprised of two parts, the dactylus and pollex. The dactylus has a protuberance known as the plunger, and the pollex contains a hollow socket. A joint allows the dactylus to draw back into a right-angled position, as the socket in the pollex fills with water. When the dactylus is released, it violently snaps shut against the pollex, the plunger filling the water filled socket - simultaneously creating an extremely powerful jet of water and cavitation bubble that is capable of stunning prey. As the bubble is released, it reaches speeds of around 100km/h and produces a sound of up to 218 decibels as it collapses, with the rapid change in pressure strong enough to stun small fish or punch holes in crustacean exoskeletons in the near vicinity. This snapping is used not only for hunting, but also in communication between shrimps; however, providing that your Pistol Shrimp is kept well fed, it will not need to employ such action in the home aquarium. Pictured above is the Bullseye Pistol Shrimp (Alpheus soror). This is a particularly unusual species in that it is a free-living reef shrimp, which unlike most of its close relatives, does not usually form a symbiotic relationship with a goby.
These shrimps will feed on most aquarium fare. Offer a variety of small meaty foods such as Mysis shrimp, vitamin-enriched brineshrimp, finely chopped krill/prawn/mussel/cockle/clam etc. Target feed with a turkey baster if necessary, with at least one feed after lights out.
In the wild, Alpheus spp. are monogamous, with the reproduction cycle directly related to the moult cycle of the female shrimp (the female only being receptive for a brief period following a moult). A precopulatory courtship ritual is common, with both olfactory and tactile cues. Eggs typically hatch after around 4 weeks. The resultant larvae develop quickly and pass through three larval stages in less than 1 week. The newly metamorphosed juvenile shrimps have small, equal sized claws, one of which enlarges considerably as the shrimps mature.