The search for the largest shrimp often leads to confusion in crustacean biology, as the popular term “shrimp” is frequently used interchangeably with “prawn.” However, the true record-holders for size are technically prawns. This exploration reveals giants that defy the common perception of a small, curled marine animal.
Shrimp Versus Prawn
The distinction between a true shrimp and a prawn is based on anatomical differences, despite the common culinary confusion. Shrimp belong to the suborder Pleocyemata, while prawns are classified under the suborder Dendrobranchiata. This biological separation primarily affects their body structure and gill arrangement.
Prawns possess branching, tree-like gills, while shrimp have plate-like gills that are flatter against the body. A prawn’s abdominal segments overlap uniformly, making their bodies relatively straight and unable to curl tightly. In contrast, a shrimp’s abdominal segments overlap in a way that allows them to maintain a characteristic curled posture.
Further differentiation exists in their appendages. Prawns have three pairs of claw-like legs, with the second pair being the largest. Shrimp typically have claws on only two pairs of their legs, and the front pair is usually the most prominent. Understanding this classification is important because the largest species worldwide are technically prawns.
Identifying the Largest Species
The title of “biggest shrimp” is generally awarded to two species, depending on whether the measurement is for total length or weight, and if the habitat is marine or freshwater. The Giant Tiger Prawn (Penaeus monodon) is consistently cited as the largest marine example. Females of this species can reach a maximum length of over 33 centimeters (13 inches) and can weigh close to 0.45 kilograms (one pound).
The Giant Freshwater Prawn (Macrobrachium rosenbergii) is the largest found in freshwater habitats, often rivaling the marine record-holder for sheer length. Record male specimens have been documented to reach total lengths of up to 34 centimeters (over 13 inches). While the Giant Tiger Prawn typically holds the weight record for marine species, the freshwater giant is a formidable contender.
The substantial size of the Giant Freshwater Prawn is particularly noticeable in its massive claws, or chelipeds, which are disproportionately large in mature males. These blue-clawed males are the dominant individuals in their social hierarchy and use these large appendages for combat and mating. Their large size makes both species highly valued in global aquaculture and fisheries.
Where They Live and Why They Get So Big
The Giant Tiger Prawn is native to the Indo-Pacific region, spanning from the coasts of Japan down to Australia. They inhabit a wide range of environments, including coastal estuaries, lagoons, and mangrove swamps, often burrowing into the muddy or sandy bottom during the day. This species is highly adaptable, tolerating a broad range of salinity levels, which aids in its success across various coastal environments.
The Giant Freshwater Prawn (Macrobrachium rosenbergii) has an interesting life cycle that contributes to its growth. Although the adults live in tropical freshwater rivers and streams, the early larval stages require brackish water to survive. The female migrates to the estuary—where the salinity is lower than the sea but higher than the river—to release her eggs, which then hatch and develop.
The immense size achieved by both species is linked to their life history traits, including a relatively long lifespan for a crustacean. Both species can live for several years, and crustaceans exhibit indeterminate growth, meaning they continue to grow throughout their lives with each molt. The warm, tropical environments they inhabit allow for a consistent food supply and frequent molting, enabling them to reach record sizes.