Alpheidae

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Snapping shrimp
Alpheus digitalis
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca Order: Decapoda Infraorder: Caridea Superfamily: Alpheoidea Family: Alpheidae Coutière, 1899
Genera
Alpheopsis Alpheus Athanas Automate Bannereus Betaeus Deioneus Leptalpheus Metabetaeus Potamalpheops Pterocaris Salmoneus Synalpheus Yagerocaris

Alpheidae is a family of caridean snapping shrimp characterized by having asymmetrical claws, the larger of which is typically capable of producing a loud snapping sound. Other common names of these species include pistol shrimp or alpheid shrimp.

The family is worldwide in distribution, comprising over 400 species ^[1]. The two most prominent genera are Alpheus and Synalpheus, with species numbering over 250 and 120, respectively ^{[2] [3]}. Most snapping shrimp dig burrows and are common inhabitants of coral reefs, submerged grass flats, and oyster reefs. While most genera and species are found in tropical and temperate coastal and marine waters, Betaeus inhabits cold seas and Potamalpheops is found only in freshwater caves.

Contents 1 Ecology 2 Snapping effect 3 Taxonomy note 4 References

[edit] Ecology

Some snapping shrimp species share burrows with goby fishes in a symbiotic relationship. The burrow is built and tended by the snapping shrimp, and the goby provides protection by watching out for danger. When both are out of the burrow, the shrimp maintains contact with the goby using its antenna. The goby, having the better vision, alerts the shrimp of danger using a characteristic tail movement, and then both retreat into the safety of the shared burrow ^[4]. So far this association has been observed in species that inhabit coral reef habitats.

Social behavior has been discovered in the genus Synalpheus. The species Synalpheus regalis lives inside sponges in colonies that can number over 300 members ^[5]. All of them are the offspring of a single large female, the queen, and possibly a single male. The offspring are divided into workers who care for young, and the soldiers who protects the colony with their huge claws. Most of the soldiers are males. So far only a few social species have been described, but many scientists think it is likely that there are more species in the genus with complex social behaviour that have not yet been found.

Snapping shrimp have also been noted for their ability to reverse claws. When the snapping claw is lost, the missing limb will regenerate into a smaller claw and the original small claw will grow into a new snapping claw. Laboratory research has shown that severing the nerve of the snapping claw induces the conversion of the small claw, resulting in a shrimp with two large claws, but this phenomenon of claw symmetry in snapping shrimp has only been documented once in nature ^[6].

[edit] Snapping effect

The pistol shrimp snaps a specialized claw shut to create a cavitation wave that generates noise in excess of 200 decibels and is capable of killing small fish. The snap can also produce sonoluminescence from a collapsing bubble, also known as cavitation bubble ^[7]. This has been dubbed "shrimpoluminescence". The light is of lower intensity than the light produced by typical sonoluminescence and is not visible to the naked eye. It is most likely a by-product of the shock wave with no biological significance. However, it is the first known instance of an animal producing light by this effect.

[edit] Taxonomy note

The problematic genera Pterocaris and Yagerocaris occupy uncertain positions in the family and may be removed.

[edit] References