The confusion over whether shrimp and prawns are the same creature is common, largely because their names are often used interchangeably in seafood markets and restaurants worldwide. While both are ten-legged crustaceans belonging to the order Decapoda, they represent distinct biological groups. Understanding this distinction requires moving beyond commercial labels to clarify the true anatomical differences that separate these two popular invertebrates.
The Defining Biological Distinction
The separation between shrimp and prawns begins at a high level of taxonomic classification, specifically at the suborder and infraorder levels. True shrimp belong to the infraorder Caridea, placing them in the suborder Pleocyemata, a group that also includes familiar animals like crabs and lobsters. Conversely, true prawns fall under the suborder Dendrobranchiata, a classification biologically more distant from shrimp than shrimp are from lobsters.
These classification differences correspond directly to fundamental anatomical features, such as the structure of their respiratory organs. Shrimp possess lamellar, or plate-like, gills that are relatively simple and smooth. Prawns, however, are characterized by branching gills, which is reflected in their suborder’s name, as Dendrobranchiata translates to “tree-gilled.”
The arrangement of their limbs also provides a reliable biological differentiator. Shrimp typically have two pairs of legs with small claws, or pincers, with the front pair often being the largest. Prawns feature three pairs of clawed legs, and in many species, the second pair of pincers is noticeably larger than the other two.
Visual Differences in Body Structure
Translating the biological differences into observable features provides practical ways to tell the two crustaceans apart when looking at a whole specimen. The most immediate visual cue is the curvature of the body. Shrimp possess a significant bend in their abdomen, which gives them a distinct comma-like or curled shape, even when they are alive or raw. Prawns, due to the rigidity of their exoskeleton, maintain a much straighter body posture, appearing more elongated and less flexible.
A more precise identifier involves examining how the abdominal segments overlap, similar to the armor plates on a shell. In shrimp, the second abdominal segment noticeably overlaps both the first and the third segments, which contributes directly to their characteristic body curl.
Prawns, by contrast, have an abdominal shell structure where the segments overlap sequentially. Each segment overlaps the one directly behind it, resembling the way roof tiles are laid. This sequential overlap restricts the prawn’s ability to curl its body tightly. Prawns often feature longer legs than shrimp.
Market Labeling and Culinary Use
Despite the clear biological separation, commercial and culinary practices frequently disregard the scientific taxonomy, which is the primary source of public confusion. In North America, the term “shrimp” is the default name for nearly all small-to-medium varieties, regardless of their actual infraorder. Conversely, “prawn” is often reserved for larger crustaceans, sometimes referring to oversized shrimp species, irrespective of whether they possess branching gills or sequential segment overlap.
Regional naming conventions further complicate the issue. In countries like the United Kingdom and Australia, “prawn” is the dominant term used for almost every variety of edible decapod crustacean. This means a customer buying a “king prawn” may be purchasing a species a marine biologist would classify as a true shrimp. Commercial labeling is driven by size and local tradition, not by the scientific classification of Caridea or Dendrobranchiata.
From a culinary perspective, the biological distinction often becomes negligible once the animal is cooked. Both shrimp and prawns are highly interchangeable in most recipes, offering similar flavor profiles and textures. However, the prawn’s straighter body form and generally larger size can make it preferred for certain presentations, such as grilling whole on a skewer, while the curved shape of a shrimp is more suited for dishes where it is mixed into a sauce.