A shrimp is generally defined as a decapod crustacean, an arthropod characterized by having ten legs and a segmented body with a hard exoskeleton. These creatures inhabit nearly every aquatic environment worldwide. The sheer number of species and their adaptation to diverse habitats mean that the term “shrimp” encompasses a vast biological spectrum, categorized by differences in anatomy and life cycle.
The Scale of Shrimp Diversity
The number of distinct types of shrimp is far greater than what is typically seen in a seafood market, with scientific estimates for described species ranging from over 2,000 to nearly 3,800. This count primarily focuses on the “true shrimp” within the infraorder Caridea, which is the most species-rich group. The exact total remains a shifting target because new species are continually being discovered and classified, particularly in deep-sea environments and remote freshwater systems.
Key Taxonomic Groupings
The most fundamental distinction in shrimp classification separates them into two major infraorders: Caridea and Penaeoidea. These groups are separated by clear morphological differences that reflect distinct evolutionary paths. Penaeoid shrimp, which include most commercial prawns, release their fertilized eggs directly into the water. In contrast, Caridean shrimp, often called “true shrimp,” carry their embryos attached to appendages underneath their abdomen until they hatch.
A close examination of their body structure also reveals differences, particularly in the gills and legs. Penaeoids possess three pairs of clawed legs, and their gills are branched, referred to as dendrobranchs. Carideans typically have only two pairs of clawed legs, and their gills are leaf-like structures known as phyllobranchs. In Caridea, the second abdominal segment overlaps the first and third, giving the body a characteristic curve.
Major Habitat Divisions
Shrimp diversity is categorized based on their preferred aquatic environment: marine, freshwater, or brackish water. The vast majority of species are marine shrimp, thriving in saltwater oceans from the tropics to the polar regions. Examples include the pistol shrimp, which uses a specialized claw to create a stunning sonic blast, and the cleaner shrimp, which removes parasites from fish on coral reefs.
Freshwater shrimp represent a smaller portion of the total, inhabiting rivers, lakes, and streams across the globe. The Amano shrimp is a well-known example valued in aquariums for its appetite for algae. These freshwater species are predominantly found in the Caridea infraorder. Brackish water shrimp, such as the Giant Tiger Prawn, live in estuaries and coastal areas where salt and fresh water mix, tolerating a wide range of salinity levels.
Economic and Culinary Importance
The various types of shrimp are significant as a global food source. Despite the thousands of species, only about 20 are commercially significant, and these are often grouped by market names rather than specific scientific species. The primary commercial types include White, Pink, Brown, and Tiger shrimp, which are color-based classifications that can each encompass multiple species. For instance, the market term “White Shrimp” may refer to the Gulf White Shrimp or the Pacific White Shrimp.
The vast majority of commercially available shrimp belong to the Penaeoidea infraorder, valued for their rapid growth and size, which makes them ideal for both wild harvest and aquaculture. Farmed shrimp, primarily the Pacific White Shrimp and Giant Tiger Prawn, now account for the greater portion of global production. Wild-caught types are often prized for their stronger, more pronounced flavor compared to their generally milder-tasting farmed counterparts.