Shrimps & Prawns

Shrimp and prawns are small, ten-legged crustaceans that live in oceans, estuaries, rivers and lakes all over the world. The two names are often used for the same animals, but scientists see some real differences between true shrimp and true prawns.

Shrimp and prawn Quick Facts

Common name	Shrimp and prawn
Scientific name	Decapoda
Kingdom	Animalia
Phylum	Arthropoda
Class	Malacostraca
Type	Decapod crustacean with 10 legs
Diet	Mostly omnivores; some scrape algae or filter food
Habitat	Sea and fresh water, often near estuaries
Special feature	Sharp rostrum; snapping shrimp make loud clicks

Shrimp or Prawn?

Which word people use depends a lot on where they live. In the United Kingdom, Ireland, Australia and other Commonwealth countries, “prawn” is the usual word, especially for larger kinds sold as food. In the United States, “shrimp” is used for almost all of them, and “prawn” usually just means a very big shrimp, such as the “jumbo” or “king prawns” sold at about 15 or fewer per pound.

Scientists divide them a little differently. True prawns belong to a group called Dendrobranchiata, and true shrimp mostly belong to a group called Caridea. Here are some differences:

• Gills: Prawns have branching gills, while shrimp have flat, plate-like gills.
• Claws: Prawns have claws on three pairs of legs, while shrimp have claws on two pairs.
• Eggs: Prawns release their eggs into the water, while female shrimp carry their eggs under their tails until they hatch.
• Shape: Shrimp often have a sharp bend in the body, partly because of how their shell plates overlap.

In seafood farming and shops, the names get mixed up again. Freshwater giant river prawns are actually caridean shrimp, while many “shrimp” sold in the US are really prawns. Both are decapods, meaning “ten legs,” and both taste much the same.

Description

There are thousands of species of shrimp and prawns, and they vary a lot in size and color. Most share the same basic body plan. The front part, called the cephalothorax, is the head and chest joined together and covered by a hard shield called the carapace. Behind it is a long, muscular abdomen, or tail, which ends in a fan-shaped tail fin.

A pointed, beak-like spike called the rostrum sticks out from the front of the head and helps protect the eyes. Shrimp have stalked eyes, long antennae for sensing, walking legs under the cephalothorax and small swimming legs, called swimmerets, under the abdomen. Their gills sit under the carapace and take oxygen from the water. When startled, a shrimp can flick its tail to shoot backward in a flash.

Life Cycle

Shrimp and prawns usually mate soon after the female molts, while her new shell is still soft. The male transfers a packet of sperm to her, and the whole thing is over quickly.

Many prawns produce huge numbers of eggs. A large female tiger prawn can release hundreds of thousands of eggs at once, and they hatch within a day or so. Caridean shrimp lay fewer, bigger eggs and carry them under the tail for several weeks.

The young hatch as tiny larvae that drift with the plankton, molting many times as they grow. Huge numbers are eaten by fish and other animals, which is why producing so many eggs is important. Most shrimp live for one to two years, though some species live longer.

Habitat

Shrimp and prawns are found almost everywhere there is water and food. Most species live in the sea, from shallow tide pools and coral reefs to the deep ocean thousands of meters below the surface. Many gather in estuaries and coastal waters where food is plentiful, and about a quarter of known species live in fresh water. Each species is adapted to its own home, whether that is a sandy seabed, a reef or a muddy river.

Behavior and Diet

Most shrimp are omnivores and scavengers that eat algae, plankton, small animals and dead material. Some scrape algae off rocks, and some filter food from the water using bristly legs.

• Pistol shrimp, also called snapping shrimp, have one oversized claw that snaps shut so fast it creates a bubble that bursts with a loud crack, stunning prey. Large groups of them are among the noisiest animals in the ocean and can even interfere with sonar.
• Cleaner shrimp set up “cleaning stations” on reefs, where fish visit to have parasites and dead skin picked off. The shrimp gets a meal and the fish gets cleaned.
• Emperor shrimp ride around on sea cucumbers and sea slugs, hopping off to grab food and hitching a lift to new feeding spots.

Shrimp are an important food for many animals, including fish, seabirds, squid and whales, so they are a key part of ocean food webs.

Farming

Shrimp farming has grown from small ponds in Southeast Asia into a huge international industry. Most farmed shrimp are penaeid prawns, and two species, the giant tiger prawn (Penaeus monodon) and the whiteleg or Pacific white shrimp (Litopenaeus vannamei), make up the large majority of the world’s farmed shrimp.

Large farms raising just one species at high density are vulnerable to disease, and outbreaks have wiped out farms across whole regions. Some farms have also been built by clearing mangrove forests, which are important nurseries for fish and protect coastlines. Since the 1990s, governments, scientists and conservation groups have pushed for cleaner, more sustainable farming.

Intensive Farming

As demand from the United States, Europe and Japan grew, small family ponds were replaced by large farms using prepared feeds and careful water management. Researchers in Texas developed a “super-intensive” indoor system that grows shrimp in stacked tanks called raceways. The water is cleaned and reused instead of being replaced, so it saves water and can be set up far from the coast. These systems can produce far more shrimp from the same amount of water than traditional ponds.

Shrimp as Food

Shrimp are one of the most popular seafoods in the world. They are high in protein, low in fat and calories, and provide nutrients such as iodine and selenium. They are also low in mercury. Shrimp contain more cholesterol than many other foods, though they are low in saturated fat. Shellfish allergy is common, so anyone with an allergy must avoid them.

Shrimp can be boiled, steamed, grilled, fried or baked, and they appear in dishes from fried rice and curries to gumbo and pasta. They cook very quickly: once they turn pink and opaque they are done, and overcooking makes them tough and rubbery.

You might also see scampi on menus. In the UK and Europe, true scampi is made from the Norway lobster, also called the Dublin Bay prawn. It looks like a small lobster and is more closely related to lobsters than to shrimp. In the US, “shrimp scampi” is a dish of shrimp cooked in garlic butter.

Shrimp and prawn FAQs