Alpheidae Family of Caridean Snapping Shrimp
Coral Pistol Shrimp, Alpheus lottini. A representative of the Alpheidae Family of Pistol Shrimp.
Phylogeny: The Pistol Shrimp are members of the Alpheidae Family of Caridean Snapping Shrimp which has six hundred twenty-five known members of which sixty-three are found along the Pacific coast of Mexico. They are also known as Alpheid Shrimp and Snapping Shrimp. Caridean Snapping Shrimp belong to the Phylum Arthropoda. They are in the Class Malacostraca and the Infraorder Caridae.
Morphology: The most obvious characteristic of Alpheidae Shrimp is that, in the great majority of species, one claw is much larger than the other. The larger powerful claw functions as a multipurpose tool and as a defensive and offensive weapon. It is not the crushing power of this claw that makes it a formidable weapon, but the shock wave it can produce that kills or stuns prey or potential predators. The extremely rapid (<1/1000th of a second) closure of the claw produces a jet of water that can exceed 100 km per hour and the implosion of cavitation bubbles. This implosion produces a loud snapping sound. This sound can exceed 218 decibels and may be heard up to 1 km. This is one of the loudest noises produced by any animal underwater. This implosion also produces a flash of light (sonoluminescense) and a burst of heat approaching 5,000oC. If the shrimp loses this large claw, the smaller claw will grow and become the large claw, and the missing claw will regenerate in to a small claw. The Alpheidae Shrimp have 5 head segments, 8 thoracic segments, and 6 abdominal segments. Their head and thorax are usually combined as a cephalothorax. The head includes a pair of antennae, a pair of antennules, and mouth parts. These animals have a 2 chambered stomach. Pistol Shrimp, like crabs, crayfish and lobsters are decapods indicative that they have 5 pairs of appendages function as legs (pereiopods), 3 pairs function as mouth parts (maxillipeds), and 1 pair is modified into enlarged pincers (chalae). Decapods, other than crabs, usually have 6 pairs of biramous (dividing to form 2 branches) appendages along their abdomen. The first 5 pairs function as swimmerets (pleopods). The last pair is flattened to form a tail fan. They have cylindrical carapace that is somewhat laterally, or dorso-ventrally, compressed. Unlike Penaeid or Segestrid shrimps, their abdomen is not compressed. Alpheid Shrimp prey on small arthropods, detritus, fish and zooplankton. In turn they are preyed upon by crabs, fish and octopus. They range in size from 3.0 cm (1.2 inches) to 7.0 cm (2.8 inches). They may be brown, greenish, red, or white in color.
Distribution: Alpheidae are found worldwide in temperate and tropical seas. Alpheid Shrimp are one of the most abundant and ecologically diverse families of decapods. They are found in freshwater, marine, and stygobitic (caves) environments. They may live within burrows in sand or mud substrate, or in crevasses in rock or coral reefs. Many are associated with mangroves, oyster beds and sea grass beds. Most species are found in shallow coastal waters, but some species reach depth of 1,000 m (3,280 feet).
Ecosystem Roles: Many species of Alpheid Shrimp have symbiotic relationships with cnidarians, echinoderms, mollusks, sponges and other crustaceans, and with gobies.
Reproduction: Alpheid Shrimp have two sexes and reproduce sexual, with the male fertilizing the eggs that the female attaches externally to her body.