Palaemonid Shrimp of the Palaemonidae Family are members of a very large and diverse family. Most Palaemonid Shrimp live in close relationships with other species. These relationships may be mutualistic, commensal, or semi-parasitic. Host animals include; sponges, corals, sea anemones, sea cucumbers, ascidians, and other decapods. Many species act as “cleaner shrimp”, cleaning fish of parasites and dead skin. One common name for this Family is Commensal Shrimp, based on these relationships. They are crustaceans in the Phylum Arthropoda and in the Class Malacostraca. They 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 the mouth. These animals have a 2 chambered stomach. Palaemonid Shrimps, like crabs, crayfish, and lobsters, are Decapods meaning that 5 pairs of appendages function as legs (pereiopods), 3 pairs function as mouth parts (maxillipeds), and 1 pair is modified into enlarged pincers (chalae). Palaemonid Shrimp are considered Caridean Shrimp, in the infraorder Caridea. These shrimp have a cylindrical carapace that is somewhat laterally, or dorso-ventrally, compressed. Unlike peneaid or sergestid shrimps, the abdomen is not compressed. In general, Palaemonid Shrimp are recognized as having pincers on their first and second thoracic legs, and a very long second pair of thoracic legs. They may be brightly colored, pale, or transparent (Glass Shrimps). The majority of Palaemonid Shrimp are less than 4.0 cm (1.5 inches) in length, but some reach at least 15 cm (5.9 inches).
Palaemonid Shrimp are found in freshwater, marine, and stygian (cave) environments. Most are either carnivores or detritivores, and feed by scavenging. They are prey for fish, octopus, and other decapods. The marine species are found worldwide in tropical and temperate seas. Most are found in shallow water, but some reach depths of 1,285 m (4,215 feet). Palaemonidae is the most specious Family of all the Caridean Shrimps. There are approximately 981 species of Palaemonid Shrimp, that have been placed into 130 genera of which at least 45 are found along Mexico’s Pacific Coast.